honkyb18c

I have seen the sticky....that CTR pistons in a b18c block with pr3 head yields about 12.5 compression with an OEM HG.


I have a b18c R block with b16 head....im pulling the motor down to put CTR pistons in. I live in The Bahamas yet I am located in Toronto at the moment.

Im trying to decide on what Head gasket to go with as I will need to buy it before i go back to the island. We do not have access to any parts like that down there.

I know that the oem HG will give around 12.5 and also cometic has a few thicker models that will lower it by .3 .7 etc.

I would just like to know how sure or correct is the sticky on here. There are so many threads that say 11.6 with ctrs in a b18 with pr 3 head etc.

I cannot afford to go above 12.5 and would ideally like to be around 12.1 etc. Yet on the other hand i do not want to buy a thciker head gasket that drops it .3 and all of a sudden im back in the 11's with compression.


Thanks for the help

ruffrhyder

iTrader: (1)

Why not use B16 PR3's then if you are worried about high CR.
A B18C R block with a PR3 head is basically a poor mans type R.

www.zealautowerks.com

honkyb18c

yea...the PCTs are already bought....just looking for clarification on compression...

b20vtec has a sticky saying that compression will be 12.0

but here on Honda tech theres a sticky with it sayin it will be around 12.6

just trying to get whats right

ruffrhyder

iTrader: (1)

Use the zealautowerks link I posted above. It's more like 12:7, even higher if you resurface the head and deck the block. Why people buy parts before researching is beyond me.

honkyb18c

research has been done....compression really doesnt matter....just wanna no what people thought was more believable....there are 2 stickys....one on here and one over on b20vtec. the compression numbers are quite a bit different.

Just trying to determine head gasket thickness now.

ruffrhyder

iTrader: (1)

Buying the right pistons to achieve desired CR is better than buying a thicker HG to achieve a lower CR. The thicker HG's are expensive and I've seen many leak fairly kickly.

honkyb18c

i guess you dont have the answer...im looking for an opinion on what comprrssion ratio is a better estimate for this application...

ruffrhyder

iTrader: (1)

You said you researched before buying the pistons, yet you're here asking if the CR will be okay for your application. Something doesn't add up. Speaking of application, how is anyone suppose to give you any help when you didn't even bother to post your build specs. What cams will you use, what fuel do you have available, what will the build be used for, etc.

hmoobhero

CR is gonna be around 12:0, get the thickest gasket and go from there. other factors influence the CR also. are you gonna use stock valves or flat-faced. flat-face will bump up CR. if you're so worried bout it sell those pistons and get itr pistons. you dont have to worry bout anything...and hopefully you get it tuned after installing them. the b16 head will lower the CR also. their combustion chambers are bigger than gsr. which allows more room for the piston to valve clearance.

BULLYAHOLIC

I have this setup sitting in my driveway. Compression will be around 12.1. Iam having a pretty hard time getting mine to run properly. I went with a oem hg. Im not saying thats the problem, because i dont know yet what is wrong with it. I wish i had went a lil more conservative on my cr. Not to mention there is very little info on this setup. I have looked high and low, and found nearly none on this setup. I know it's been done plenty of times, but i cant find sticky's, write up, or anything that would help where the ctr pistons were used. When you get yours on the road shoot me a pm.

BULLYAHOLIC

I just went to zealautowerks to see my comp and it said im at nearly 13.1

hmoobhero

did you get it tuned yet? running regular gas is not the best idea. at least 93 for this high of CR. after changing something internally you will need a tune. if you already got a tune then your tuner sucks...

BULLYAHOLIC

Im not driving the car, because it hasn't been tuned. I do run 93, but there is a local gas station around here that sells 100, so ill prolly have it tuned with 100. Depends what mt tuner thinks.

hmoobhero

you should be fine with 93, theres tons of dynos that were tune on 93 with around 12:0 CR but your tuner has to be good. get it tune and your car will run fine. also, depends if you gonna dd or drag race only.

BULLYAHOLIC

It's my d.d. And i hope your right about having it tuned, and it running fine. Im outa money, and patience. My car has been put together for 2 weeks now, and i have only drove it home from my friends house.

hmoobhero

whats your setup? i/h/e/cams/pnp/valve job/etc...? ecu as of right now? i cant guarnatee that it will run better. if you used old /cheap parts, no tuning is gonna make your car run right...

honkyb18c

I just wanted an answer on what compression ratio is more belivable for the application of PCT/CTR pistons in a b18c block with b16 head.

As stated above in my prior post, there are 2 stickys that I have been looking at.

One says the CR is closer to 12.6 while the other says 12.0

h224thgensedan

https://honda-tech.com/forums/honda-prelude-4/cr-calculations-compression-testing-438456/ There is a link to the math you can figure it out with that information.

EDIT: https://honda-tech.com/forums/all-motor-naturally-aspirated-44/diy-compression-ratio-calculation-2476094/ Sorry posted wrong link earlier

BULLYAHOLIC

bottom end was assembled by a good machine shop, all new parts(arp head studs, and rod bolts) head is a stock jdm b16a. greddy headers, cai, 2.5 custom exhaust, 310 injectors, chipped p28, in a 1991 da.

00Red_SiR

This is the best link: https://honda-tech.com/forums/all-motor-naturally-aspirated-44/pct-ctr-piston-compression-ratio-717928/

12.5-12.6:1 is roughly where you'd be at.

honkyb18c

yea...gat ya....i think i may go with a bit thicker then the stock oem gasket to drop it a bit. Like a 0.04 from cometic maybe. Also I have Pro1s which will slightly bleed off some of the compression. That should have me around low 12s for sure.

ruffrhyder

iTrader: (1)

Has the block been decked, the head resurfaced? If so, how much material was removed, a .040" gasket may barely account for the resurfaced thickness, therefore a .050 or so may be needed.

honkyb18c

the car was purchased from japan....The block came overbored 0.20mm to a 81.5mm piston...but i have no clue if the block has been decked or head milled...

I live in The Bahamas and will only be in the States for a few more weeks so I need to pick up the head gasket before i go back....which means i wont be able to measure the deck heaight etc.

I guess im going to go with 0.04 just a bit thicker then stock.

Killer4Sho

I Currently have a setup like this. B18c5 with CTR pistons. The engine will ping on regular gas if you have the timing on the distributor at standard timing (16 degrees). What i did to prevent this ping was to get a B&M FPR and up the fuel pressure to about 51 PSI along with retarding the timing to about 14 degrees with #8 plugs. My car is daily driven and runs fine. If i do decide to race i find some race gas, advance my distributor to stock timing and run open exhaust. My 2 cents. You can Pm if you like.

Killer4Sho

Based on zealautowerks your compression would be approximately 12:7 with the OEM gasket