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1976 Honda CVCC engine Turbo swap Project: To "B", or not to "B"?

1976 Honda CVCC engine Turbo swap Project: To "B", or not to "B"?

 
Old 05-04-2019, 09:38 AM
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Icon3 1976 Honda CVCC engine Turbo swap Project: To "B", or not to "B"?

So, I own a 1976 Honda Civic Wagon and it needs a new powerplant. The original CVCC engine sat with the head off for more than 2 years and the pistons are frozen in the block. I might be able to salvage it or replace it with another one like it, but I have always wanted to put something larger in it anyway. I have never boosted a car before, but I have done a ton of research over the last 6 years and I think this is the direction I'd like to go. My goal is to have a 265-300HP engine that can run on 91 Octane 95% of the time and maybe 93 Octane on occasion. This needs to be a reliable daily driver that lasts for years to come as I have no desire to crack the engine open every 3 years to rebuild something.

My options seem to be as follows, but I'm open to other ideas:

1) A stock-ish B18C with low CR pistons boosted
2) A stock-ish B16B with low CR pistons boosted
2) A {D-series Frankenstein} D16 head/D17 block some aftermarket internals and boost - Sleeve and overbore to 75.5mm, use a D16 crank for shorter throw, longer rods, and low CR pistons so I have more displacement, higher r/s ratio, higher revving, and decreased sidewall pressures.
2) A {B-series Frankenstein} B16 or B18 head/B20 block some aftermarket internals and boost - Sleeve and overbore to 84.5mm, use a B16B crank for shorter throw, longer B16B rods, and low CR pistons so I have more displacement, higher r/s ratio, higher revving, and decreased sidewall pressures.


I know that:
1) People have put a B/D/K-series engine in one of these cars before, but the B was tight and the K required lots of modification and a new subframe...plus that sucker is heavy (So, K-series is out)
2) B-series engines tend to be about 90-100lbs heavier than a D-series engines so there is that too...power to weight ratio would be dramatically different
3) B-series engines have about 39% more power stock (on average) vs. D-series engines...so I start closer to my goal from the beginning
4) The D-series engines (for the most part) are cheaper and have less aftermarket parts available than their B-series brethren
5) DOHC vs. SOHC has its advantages

So, my big issue is that no one can seem to tell me which of these options with be the most cost effective...I also have not just opened the discussion up to "any other option" like I am now. If this was your project, and you had my goals (please don't say sell it...and buy X thing instead) what would you feel is the best path to achieve them?
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Old 05-05-2019, 06:28 AM
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Default re: 1976 Honda CVCC engine Turbo swap Project: To "B", or not to "B"?

Originally Posted by 1stGen76 View Post
So, I own a 1976 Honda Civic Wagon and it needs a new powerplant. The original CVCC engine sat with the head off for more than 2 years and the pistons are frozen in the block. I might be able to salvage it or replace it with another one like it, but I have always wanted to put something larger in it anyway. I have never boosted a car before, but I have done a ton of research over the last 6 years and I think this is the direction I'd like to go. My goal is to have a 265-300HP engine that can run on 91 Octane 95% of the time and maybe 93 Octane on occasion. This needs to be a reliable daily driver that lasts for years to come as I have no desire to crack the engine open every 3 years to rebuild something.

My options seem to be as follows, but I'm open to other ideas:

1) A stock-ish B18C with low CR pistons boosted
2) A stock-ish B16B with low CR pistons boosted
2) A {D-series Frankenstein} D16 head/D17 block some aftermarket internals and boost - Sleeve and overbore to 75.5mm, use a D16 crank for shorter throw, longer rods, and low CR pistons so I have more displacement, higher r/s ratio, higher revving, and decreased sidewall pressures.
2) A {B-series Frankenstein} B16 or B18 head/B20 block some aftermarket internals and boost - Sleeve and overbore to 84.5mm, use a B16B crank for shorter throw, longer B16B rods, and low CR pistons so I have more displacement, higher r/s ratio, higher revving, and decreased sidewall pressures.


I know that:
1) People have put a B/D/K-series engine in one of these cars before, but the B was tight and the K required lots of modification and a new subframe...plus that sucker is heavy (So, K-series is out)
2) B-series engines tend to be about 90-100lbs heavier than a D-series engines so there is that too...power to weight ratio would be dramatically different
3) B-series engines have about 39% more power stock (on average) vs. D-series engines...so I start closer to my goal from the beginning
4) The D-series engines (for the most part) are cheaper and have less aftermarket parts available than their B-series brethren
5) DOHC vs. SOHC has its advantages

So, my big issue is that no one can seem to tell me which of these options with be the most cost effective...I also have not just opened the discussion up to "any other option" like I am now. If this was your project, and you had my goals (please don't say sell it...and buy X thing instead) what would you feel is the best path to achieve them?
we're familiar with Gillespie's '76 b-series and L15 Dakota, and compassion shouldn't be low compression at all. 10.0:1 or better, and keep it b- series
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Old 05-05-2019, 06:45 AM
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Default re: 1976 Honda CVCC engine Turbo swap Project: To "B", or not to "B"?

With such low numbers, I hate to admit it, B will be alright with stock internals. D will not need sleeving, even with daily ABUSE at that level, at that bore. Source a full D16Z6, no need to Frankenstein unless you ABSOLUTELY have to. Internals on a D at that level are required for safe keeping, you'd really be pushing the envelope on stock but, I have seen close to 300 on stock internals. I wouldnt risk it though. Lol!

I'm hoping this turns into a legit build thread because this is a build I'd love to see!
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Old 05-05-2019, 12:01 PM
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Default re: 1976 Honda CVCC engine Turbo swap Project: To "B", or not to "B"?

I think you'd have even more fun with a L15B7 from a wrecked 2017 civic
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Old 05-06-2019, 09:04 AM
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Icon3 re: 1976 Honda CVCC engine Turbo swap Project: To "B", or not to "B"?

Originally Posted by Txdragon View Post
With such low numbers, I hate to admit it, B will be alright with stock internals. D will not need sleeving, even with daily ABUSE at that level, at that bore. Source a full D16Z6, no need to Frankenstein unless you ABSOLUTELY have to. Internals on a D at that level are required for safe keeping, you'd really be pushing the envelope on stock but, I have seen close to 300 on stock internals. I wouldnt risk it though. Lol!

I'm hoping this turns into a legit build thread because this is a build I'd love to see!
I had my suspicions that both the engines might tolerate 300Hp without any change to internals, but I don't want it to be a risky build...I want rock solid You think I can push a D to 75.5mm bore safely, boosted, w/o sleeves? - I've heard/read mixed thoughts on that. Any thoughts on which engine B or D suites the vehicle and performance level better? I have a feeling that the extra 100lbs of a B may not be worth the weight trade-off in such a light car. Larry from Endyn strongly encouraged me to use a D16 to maintain agility. I have been working on this project on and off for years...heck I wrote threads about the original engine rebuild and another one about stripping it down to the shell, but alas I kept taking breaks and now I cannot even remember which of the many forums I used to be on that I posted those on so I cannot consolidate everything...maybe I will get a bug one day to hunt it all down...but for now, I am back and I am going to try and do something with this 1st Gen.

Originally Posted by TheShodan View Post
I think you'd have even more fun with a L15B7 from a wrecked 2017 civic
I have to admit, the L15 is tempting...I say a great overview at vtec academy (The New L15B7 Turbo from Honda - VTEC Academy). In fact he mentions in the video that it might be a good fit for a 1st or 2nd gen civic because it requires a taller engine bay. That said, I am not a fan of all the plastic parts(intake manifold, valve cover, etc), especially the valve cover, that thing is not sexy at all. I have a feeling I would struggle popping the hood and seeing that Tupperware engine no matter how good a fit it may be for my goals. I really appreciate the suggestion though.
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Old 05-06-2019, 09:22 AM
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Default re: 1976 Honda CVCC engine Turbo swap Project: To "B", or not to "B"?

If you go with a D-series and don't want to do full sleeves, you can do CSS like I did on my build (75.5mm D16Z6 - should be near the top of the Forced Induction forum if you want to take a look). I'd recommend a set of rods and some forged pistons, and not YCP cast pistons. CSS is supposed to be good for up to 600 whp, which is way above my target of 300-400 whp. I'm hoping this will be a solid build for my desired power goals. I'm not sure on whether B-series or D-series would suit the car better - B-series definitely has more aftermarket support, but again, for your goals, you should be able to get the parts you'd need to pull it off with a D-series. If the engine bay is small and you're worried about the weight, go for a D-series.

It's a beautiful car man, and I think a resto-mod on it would be badass. I have a soft spot in my heart for the classic Hondas - I had 3 N600's about a decade ago that I was planning to combine into one running vehicle, but sold off the project to fund the next one.
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Old 05-06-2019, 09:32 AM
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Default re: 1976 Honda CVCC engine Turbo swap Project: To "B", or not to "B"?

Yeah...I fell in love the moment I saw it. Driving it was a ton of fun. I got attention from old timers who had their first date in one as well as young bloods tuning ricers. Everyone seems to enjoy it. I am hoping people who have done B and D swaps can give me some estimated cost(s) to hit my goal...my feeling is the D will be cheaper when it is all said and done, but I'd like to price both. My other concern is torque...I don't want to build an engine and mount it only to find out that it could/will twist the chassis...I know the last B I saw swapped ran custom mounts, and the only K I have ever seen used required a custom subframe/mounts.
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Old 05-06-2019, 10:08 AM
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Default re: 1976 Honda CVCC engine Turbo swap Project: To "B", or not to "B"?

I can't speak to the actual swap, but if you are curious I can give you some $ numbers for what I've spent building the D16Z6.
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Old 05-06-2019, 10:30 AM
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Default Re: 1976 Honda CVCC engine swap - To B, or not to B?

Originally Posted by 1stGen76 View Post
I have to admit, the L15 is tempting...I say a great overview at vtec academy (The New L15B7 Turbo from Honda - VTEC Academy). In fact he mentions in the video that it might be a good fit for a 1st or 2nd gen civic because it requires a taller engine bay. That said, I am not a fan of all the plastic parts(intake manifold, valve cover, etc), especially the valve cover, that thing is not sexy at all. I have a feeling I would struggle popping the hood and seeing that Tupperware engine no matter how good a fit it may be for my goals. I really appreciate the suggestion though.
Seriously, Don't knock it until you try it and see one. The fact that you have a water cooled exhaust manifold, efficient turbine set package, and water cooled turbine housing ALONE make it sexier than just some metal intake manifolds or other plastic parts. As an owner of this engine, I can honestly, say, I was just as skeptical as you sound right now.. Owning this now for two years, I can realistically say, I was wrong about Honda when they developed this..

*Note: There is no VTEC in this engine, just VTC. The video was mislabeled*

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Old 05-06-2019, 10:39 AM
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Default Re: 1976 Honda CVCC engine swap - To B, or not to B?

Originally Posted by 1stGen76 View Post
I had my suspicions that both the engines might tolerate 300Hp without any change to internals, but I don't want it to be a risky build...I want rock solid You think I can push a D to 75.5mm bore safely, boosted, w/o sleeves? - I've heard/read mixed thoughts on that. Any thoughts on which engine B or D suites the vehicle and performance level better? I have a feeling that the extra 100lbs of a B may not be worth the weight trade-off in such a light car. Larry from Endyn strongly encouraged me to use a D16 to maintain agility. I have been working on this project on and off for years...heck I wrote threads about the original engine rebuild and another one about stripping it down to the shell, but alas I kept taking breaks and now I cannot even remember which of the many forums I used to be on that I posted those on so I cannot consolidate everything...maybe I will get a bug one day to hunt it all down...but for now, I am back and I am going to try and do something with this 1st Gen.
I bored my Z6 to 76mm and the engine builder said there was still enough of the sleeve left to handle well. I have had a bad stroke of luck with head bolt holes, so I haven't been able to run said 76mm build yet. I'm hoping to get my other block back soon so I can.. lol! I've read up on quite a few builds on stock sleeves at 76 taken to the 450 range; just depends on the block health I suppose. .5mm over is gonna be no sweat though at the level you want. As for B vs D.. Single cam can only go so far (current record is 794whp by Speedfactory, and it is built to the friggin sky) and the B can see some amazing numbers but, for sake of ease, I'd stick with D. The B has a larger market but, you will have no problem sourcing what you'll need for about all your single slam can give ya.
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Old 05-06-2019, 10:41 AM
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Default Re: 1976 Honda CVCC engine Turbo swap Project: To "B", or not to "B"?

That car looks really clean. I'm assuming that is not factory paint?

Either way if you intend to build this I am subscribing!
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Old 05-06-2019, 06:52 PM
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Default Re: 1976 Honda CVCC engine Turbo swap Project: To "B", or not to "B"?

Originally Posted by TheShodan View Post
we're familiar with Gillespie's '76 b-series and L15 Dakota, and compassion shouldn't be low compression at all. 10.0:1 or better, and keep it b- series



Your saying I should keep a 10:1 CR while boosted? I assume that is possible with a great tune in a B series, and I assume Gillespie and Dakota are builders?...have you heard of or seen any D series swaps to compare to by any chance?




Originally Posted by DaX View Post
I can't speak to the actual swap, but if you are curious I can give you some $ numbers for what I've spent building the D16Z6.






I would be very interested in your parts list, prices and success (hp/tq)




Originally Posted by DaX View Post
If you go with a D-series and don't want to do full sleeves, you can do CSS, I'd recommend a set of rods and some forged pistons (YCP cast pistons)...you should be able to get the parts you'd need to pull it off with a D-series.




If the engine bay is small and you're worried about the weight, go for a D-series.




It's a beautiful car man, and I think a resto-mod on it would be badass.



I have already committed to changing out all the internals if I go D series. That said, I am glad people are willing to provide real world advice based on experience. Thatís why Iím here, Thanks. I was going to do a D16/17 Frank because if Iím gonna buy internals I liked the idea of stroking the build with extra long rods to change my r/s ratio.




The engine bay is small-ish, more like narrow. The bay/front clip on this is 4Ē longer than the two-door version, which is one reason I bought it. I weight is a concern. I believe the car weighs about 2400lbs with me in it (stock), or less so the engine will be adding weight no matter what as compared to stock.




Thanks for the kind words about the car




Originally Posted by TheShodan View Post
Seriously, Don't knock it until you try it. The fact that you have a water cooled exhaust manifold, efficient turbine set package, and water cooled turbine housing ALONE make it sexier than just some metal intake manifolds or other plastic parts.


It is interesting, I will dig in and maybe it will become an option to compare against, cheers.




Originally Posted by Txdragon View Post
I bored my Z6 to 76mm and the engine builder said there was still enough of the sleeve left to handle well...I've read up on quite a few builds on stock sleeves at 76 taken to the 450 range; just depends on the block health I suppose. .5mm over is gonna be no sweat though at the level you want. As for B vs D...for sake of ease, I'd stick with D. The B has a larger market but, you will have no problem sourcing what you'll need for about all your single slam can give ya.



Knowing that makes life a bit easier...The fact that I can probably use stock sleeves is valuable info.




B vs D: Iím leaning D, thanks for your ďvoteĒ.




Originally Posted by Caoboy View Post
That car looks really clean. I'm assuming that is not factory paint? Either way if you intend to build this I am subscribing!



History of the car:

I am itís third owner. The first owner bought it new and had it converted soon after to pull as a dinghy behind his RV in and around the mid west. It then was bought by a gentleman near Cape Cod, Massachusetts...I then bought it off his friends car lot where it was sold on consignment. At some point along the way it got dents and dings, there was rot and rust in a few places, it was patched and ďrepairedĒ...seats got re-wrapped and it got a respray. I drove it for about 6 months before water started shooting out of my carb...I rebuilt the engine...did it again after a little longer than the first time. So, then I decided to start from scratch. I stripped it down to a bare steel shell, found some issues, had steel work done, and then a primer sealer was sprayed on to save my progress while I saved money and attending to other projects.


Some before shots

The first engine rebuild

Stripping the paint

The issues revealed

Most of the steel work is done, and quick primer sealer is applied

Finally got it home, stored it, and everyone is currant...

Last edited by 1stGen76; 05-06-2019 at 08:17 PM. Reason: Answering more than one post in the same reply...
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Old 05-06-2019, 07:48 PM
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Default Re: 1976 Honda CVCC engine Turbo swap Project: To "B", or not to "B"?

Originally Posted by 1stGen76 View Post
Your saying I should keep a 10:1 CR while boosted? I assume that is possible with a great tune in a B series, and I assume Gillespie and Dakota are builders?...have you heard of or seen any D series swaps to compare to by any chance?
My previous Z6 build was 10.5:1 boosted.
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Old 05-06-2019, 08:20 PM
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Default Re: 1976 Honda CVCC engine Turbo swap Project: To "B", or not to "B"?

Originally Posted by Txdragon View Post
My previous Z6 build was 10.5:1 boosted.
Keep in in mind I am planning to run 91 octane most of the time and it will be a daily driver. Sometimes I may run 93 octane when I wanna have some fun...but not often.
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Old 05-07-2019, 01:46 AM
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Default Re: 1976 Honda CVCC engine Turbo swap Project: To "B", or not to "B"?

Originally Posted by 1stGen76 View Post
Keep in in mind I am planning to run 91 octane most of the time and it will be a daily driver. Sometimes I may run 93 octane when I wanna have some fun...but not often.
91 is fine for that CR.
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Old 05-07-2019, 03:25 AM
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Default Re: 1976 Honda CVCC engine Turbo swap Project: To "B", or not to "B"?

Here's some rough numbers for the block, head, and transmission. Don't forget fuel, cooling, engine management, and other supporting modifications for the turbo. I can dig more and find some numbers on that as well if you want, but here's a start for the basic engine/transmission:

Eagle Rods - $320
CP Pistons - $570
CSS and all block machine work with shipping - $830
ARP head studs - $120
OEM oil pump - $160
ACL bearings - $100

Ferrea 6000 valves - $240
Ferrea valve locks - $80
Supertech springs/retainers/stem seals - $300
Comp 59300 cam - $200
OEM head gasket - $70
Head machine work - $230

Competition Clutch - $330
Mfactory LSD - $650
Carbon synchros & new sleeves - $180
Bearings & seals - $200
HASport mounts - $300

Probably about another $1,000 in small stuff that adds up. That's about $6K before getting into the "fun" stuff. Granted I'm over built for my goals, but it sounds like that's where you want to be too.
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Old 05-07-2019, 03:53 AM
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Default Re: 1976 Honda CVCC engine Turbo swap Project: To "B", or not to "B"?

Originally Posted by DaX View Post
Here's some rough numbers for the block, head, and transmission. Don't forget fuel, cooling, engine management, and other supporting modifications for the turbo. I can dig more and find some numbers on that as well if you want, but here's a start for the basic engine/transmission:

Eagle Rods - $320
CP Pistons - $570
CSS and all block machine work with shipping - $830
ARP head studs - $120
OEM oil pump - $160
ACL bearings - $100

Ferrea 6000 valves - $240
Ferrea valve locks - $80
Supertech springs/retainers/stem seals - $300
Comp 59300 cam - $200
OEM head gasket - $70
Head machine work - $230

Competition Clutch - $330
Mfactory LSD - $650
Carbon synchros & new sleeves - $180
Bearings & seals - $200
HASport mounts - $300

Probably about another $1,000 in small stuff that adds up. That's about $6K before getting into the "fun" stuff. Granted I'm over built for my goals, but it sounds like that's where you want to be too.
Gotta add any potential labor charges if you dont do the work, or don't have a little tyke to do all the work for ya!!

There are some things done that may not be needed or just for future proofing, but this is a good example of a SOLID D build meant to get you pretty far goal-wise. You can easily cut this price down by 1/3 if not by 1/2, without sacrificing quality parts!
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Old 05-07-2019, 04:55 AM
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Default Re: 1976 Honda CVCC engine Turbo swap Project: To "B", or not to "B"?

I vote Z6 turbo


Follow dax and txdragons build advice, they know their stuff.


Amazing car!
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Old 05-07-2019, 06:44 AM
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Default Re: 1976 Honda CVCC engine Turbo swap Project: To "B", or not to "B"?

Originally Posted by DaX View Post
Here's some rough numbers for the block, head, and transmission.
Thank you DaX, I broke it up into sections, and I would appreciate any other thoughts additional members have in regards to the items already on the list, and/or new items to add to it. It is as follows:

Top End
- ARP Head Studs - $120
- Ferrea 6000 Valves - $240
- Ferrea Valve Locks - $80
- Supertech Springs/Retainers/Stem Seals - $300
- Comp 59300 Cam - $200
- OEM Head Gasket - $70
- Head Machining - $230

Bottom End
- CP Pistons - $570
- Eagle Rods - $320
- ACL bearings - $100
- CSS & All Block Machining (+s/h) - $830

Bolt-ons
- OEM Oil Pump - $160

Transmission
- Competition Clutch - $330 <<<<<<< Brand?
- Mfactory LSD - $650
- Carbon Synchros & New Sleeves - $180 <<<<<<< Brand?
- Bearings & Seals - $200 <<<<<<< Brand?

Misc
- HASport Mounts - $300 <<<<<<< These will have to be custom, or semi-custom on my car because HASport does not have any mounts on their website for Civics built earlier than 1984

Originally Posted by DaX View Post
...another $1,000 in small stuff...Granted, I'm over built for my goals, but it sounds like that's where you want to be too.
I would like to slightly overbuild, but not because I think I will want to reach even further after achieving my initial goal of 265-300HP, more for safety/peace of mind. I have no desire to invest this much blood, sweat, tears, time and cash into a build that blows up...ever. I aspire to build it clean, build it right, and most of all - build it once. If possible.

Originally Posted by DaX View Post
...Don't forget fuel, cooling, engine management, and other supporting modifications for the turbo. I can dig more and find some numbers on that as well if you want...
Originally Posted by Txdragon View Post
There are some things done that may not be needed, or were added just for future proofing, but this is a good example of a SOLID D build meant to get you pretty far goal-wise. You can easily cut this price down by 1/3 if not by 1/2, without sacrificing quality parts!
DaX, For the sake of myself and those that find/read this thread in the future it would be awesome if you could dig deep. A comprehensive thread is a good thread, and out of respect to anyone else contributing, yourself included, I will do my best to document my progress.

TxDragon, Money, as it often is, will be the only true bottleneck on my progress. That said, I will not let that kill this build - but I can only invest so much all at once. If you know ways to help me achieve my HP/Drivability goals that would cost less "without sacrificing quality" I would love to hear all about them.

Originally Posted by Txdragon View Post
Gotta add any potential labor charges, if you don't do the work, or don't have a little tyke to do all the work for ya!!
I have done every once of the work, so far, with the exception of the weld-work as I have never learned how...and I have 4 tykes, but I would only trust my eldest daughter to be safe in the workshop and she is a teen now so hanging out with Dad is getting less cool everyday...but that is ok. I need a hobby I can go do and have some Zen ME time. On a related note, unfortunately, machining and fabrication require tools I do not yet own...so there is also that.

Originally Posted by Txdragon View Post
...91 is fine for that CR...My previous Z6 build was 10.5:1 boosted.
I have to admit, all the engine theory, geometry, and math I have learned taught me that a static CR that high will be equivalent to something dramatically higher when you look at the dynamic CR numbers under boost...how do you get around knocking on 91 with a peak dynamic CR (under 10psi) of 17.6:1? (Refer to https://www.rpmoutlet.com/images/eff...sion-ratio.jpg as a resource/example). Maybe I am way off, but I was under the impression that going over 12:1 CR at any point especially under boost, even for brief periods increases your chance of knocking/early detonation to crazy levels. Since you were successful with such a high CR build, please, help me understand how, when, and why it is ok to run such a high static CR in a FI build?

Originally Posted by 2x0 View Post
I vote Z6 turbo Follow dax and txdragons build advice, they know their stuff.Amazing car!
Thanks for the 2 cents 2x0, I appreciate you taking the time to show some love and build my confidence in DaX/TxDragon. It is great to hear that these two guys are steering me in the right direction.

**** Side Note: Sooooo, to those just finding this thread, or subbing - stick with me. Unless my life dramatically changes (more than it has twisted and turned for the last 6-7 years) then I am finishing this project, period. It has been a long time coming.
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Old 05-07-2019, 06:52 AM
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Default Re: 1976 Honda CVCC engine Turbo swap Project: To "B", or not to "B"?

10:1 or higher compression for turbo Honda builds has been the norm for a decade or more. It simply means that you will not have to run as much boost to reach a given power level as you would with low compression, but you also get the added benefits of a more responsive engine when not in boost.

The limiting factors for detonation will be the fuel you use and how much power you are making. The power you make will be a result of your compression ratio, amount of boost, turbo size, and a host of other things. You simply adjust those factors to make the power you want that is within the safe limits of your fuel and build.
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Old 05-07-2019, 07:01 AM
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Default Re: 1976 Honda CVCC engine Turbo swap Project: To "B", or not to "B"?

Originally Posted by 2x0 View Post
10:1 or higher compression for turbo Honda builds has been the norm for a decade or more. It simply means that you will not have to run as much boost to reach a given power level as you would with low compression, but you also get the added benefits of a more responsive engine when not in boost.

The limiting factors for detonation will be the fuel you use and how much power you are making. The power you make will be a result of your compression ratio, amount of boost, turbo size, and a host of other things. You simply adjust those factors to make the power you want that is within the safe limits of your fuel and build.
Of course we can cross-reference other sources but according to the chart that I linked previously if I kept a native 9.2:1 CR then I would only be running about 3.5 psi of boost before I hit a dynamic CR over 12, and if I ran a different piston with 10:1 CR the dynamic CR at 2 psi would do the same... am I able to push past the 12:1 CR dynamically (for short bursts, Iím guessing) safely?
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Old 05-07-2019, 07:10 AM
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Default Re: 1976 Honda CVCC engine Turbo swap Project: To "B", or not to "B"?

Originally Posted by 1stGen76 View Post



I have to admit, all the engine theory, geometry, and math I have learned taught me that a static CR that high will be equivalent to something dramatically higher when you look at the dynamic CR numbers under boost...how do you get around knocking on 91 with a peak dynamic CR (under 10psi) of 17.6:1? (Refer to https://www.rpmoutlet.com/images/eff...sion-ratio.jpg as a resource/example). Maybe I am way off, but I was under the impression that going over 12:1 CR at any point especially under boost, even for brief periods increases your chance of knocking/early detonation to crazy levels. Since you were successful with such a high CR build, please, help me understand how, when, and why it is ok to run such a high static CR in a FI build?
I'll be flat honest and say I don't know the physics and engineering behind it but what I can say is that through tuning, there is such a minimal difference between 91 and 93 octane. Your tune in the end is what's going to count. My first tune was with John Vega of Pherable dot net and that was the first question I asked because I have 93 readily available, I do travel to areas that ONLY have up to 91. He said no worries.. I tuned on 93 and initially netted 332whp; this was a datalog based street tune, I verified later and tweaked at a local dyno to hit 347whp. I used 91 occasionally and even datalogs did not show me any difference 1 pull to the next.. Keeping it conservative, you could essentially run 11:1 CR on pump fed boost. That's pushing an envelope, but doable.
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Old 05-07-2019, 07:48 AM
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Default Re: 1976 Honda CVCC engine Turbo swap Project: To "B", or not to "B"?

Originally Posted by 1stGen76 View Post
Of course we can cross-reference other sources but according to the chart that I linked previously if I kept a native 9.2:1 CR then I would only be running about 3.5 psi of boost before I hit a dynamic CR over 12, and if I ran a different piston with 10:1 CR the dynamic CR at 2 psi would do the same... am I able to push past the 12:1 CR dynamically (for short bursts, I’m guessing) safely?
I'll side with txdragon and say I do not have any scientific knowledge about this subject. All I know is what I've learned over the years by what has worked for others and myself.

He did make a big point about how critical tuning is. Part of the reason that we can run boost and high compression without detonation is that we retard the timing when in boost to compensate. But the better the fuel, the more timing it can handle. E85 is very forgiving

The chart that you referenced with the dynamic compression doesn't make much sense. First of all, boost pressure is irrelevant without knowing the size of turbocharger. It might make more sense for guys who do not have the ability to tune like we can, I'm thinking like old school, carbureted V8's with blowers on them. Thankfully we have precise engine management systems and can fine-tune to safely get the most out of our builds.
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Old 05-07-2019, 07:56 AM
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Default Re: 1976 Honda CVCC engine Turbo swap Project: To "B", or not to "B"?

Originally Posted by Txdragon View Post
... through tuning, there is such a minimal difference between 91 and 93 octane. Your tune in the end is what's going to count...I tuned on 93 and initially netted 332whp...and tweaked at a local dyno to hit 347whp...Keeping it conservative, you could essentially run 11:1 CR on pump fed boost. That's pushing an envelope, but doable.
Very interesting. If you have a chance, check out the Zeal AutoWerks website for some very cool calculators. What the advanced CR calc tells me is that with a 10:1 CR, at my average elevation (690FT), running a stock D16Z6 (except pistons, I input -5.4 dish vs -10.10 stock to increase the CR, and match your 10:1 for math purposes), you can run 3.19 psi before hitting an "effective" or dynamic CR of 12:1. How much boost were you running, and do you know your piston specs? Maybe I can use those details to create a model and figure out how high you were able to push your dynamic CR.

Originally Posted by 2x0 View Post
I'll side with txdragon and say I do not have any scientific knowledge about this subject. All I know is what I've learned over the years by what has worked for others and myself. He did make a big point about how critical tuning is. Part of the reason that we can run boost and high compression without detonation is that we retard the timing when in boost to compensate. But the better the fuel, the more timing it can handle. E85 is very forgiving
I am not arguing the fact that it can be done, and a good tune means everything...without it a build is just a bunch of metal trying to move, but I am trying to break it down a bit so I can understand where the "envelope" really is and ow I can better maximize the engines potential. As for retarding or advancing the timing - I have heard/read that one is worse for/more dangerous for the engine than the other. Do you know anything about that? If not, I am sure I can go back and dig around in some of the links I was reading last month. Is there a cam that can compensate for that by design so I can avoid dramatic retard/adv of my timing?
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Old 05-07-2019, 08:15 AM
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Default Re: 1976 Honda CVCC engine Turbo swap Project: To "B", or not to "B"?

Originally Posted by 1stGen76 View Post
As for retarding or advancing the timing - I have heard/read that one is worse for/more dangerous for the engine than the other. Do you know anything about that? If not, I am sure I can go back and dig around in some of the links I was reading last month. Is there a cam that can compensate for that by design so I can avoid dramatic retard/adv of my timing?
All things that your tuner will understand intimately and will be able to answer for your specific setup, when on the dyno. Their job is to find the "sweet spot" for timing that will be unique to your build, and safely yield the amount of power you want or within the limits of your setup.

In general, we start with the stock timing map for our engine, such as a D16Z6 factory tune for example. When you add more modifications, such as cams, they will like more or less timing at different RPM, which again only a tuner with a dyno will be able to figure out by seeing how the engine responds to changes. The sames goes for when you add forced induction. In general the engine will want the timing to be retarded a certain degree per amount of boost pressure, but again in order to optimize this, the performance has to be recorded on a dyno as the adjustments are made.
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