F23 Frankenstein help... PLEASE!

 
Old 10-28-2018, 11:28 PM
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Default F23 Frankenstein help... PLEASE!

Hi guys, first time poster here, long time lurker. (Skip to the bullets if you just want my goals with no backstory). New to the honda world, long time classic wrench monkey for my dad (tri-five Chevys since 8y.o.). Just turned 21 and bought a super straight and solid 1991 cb7 accord coupe that I'm planning on building into a true 90s japanese street car. And after driving it for about a month, I'm starting to have motor issues, so it's time to start digging into this sucker. Since these things are so cheap and I want to challenge myself I have decided to jump into a mild engine build/swap, with more affordable forged or OEM parts.
I'm slowly restoring the car as well so form is right next to function, so know not all of my goals may "make sense" to you number chasers. First being, I really love the classic look of the SOHC engine, and I feel it's vital for the true 90s appeal, so immediately my choices are limited. For this reason I'm thinking going with an f23a1 block (already purchased). The cylinders have some grooves so it will be bored to 87mm. NOTE: This is not my daily and will mostly be a show car and canyon cruiser in the summers (salt lake local). The motor will be turboed, with the biggest goal being response and feel vs actual hp/tq. numbers. Small, quick turbo; 10-11:1 compression; very moderate boost. For this reason I'm looking for a very high revving motor with light rotating assembly that can *touch* 9.5k rpm, and sound absolutely ridiculous. This is where I need help. Fitting those goals in the f23a.
Gunna shorten the stroke to help with the violence of 8k. So far I have seen that my only real options for "destroking" the F23a is with either a H22 crank with 87 or the F20b crank. I really don't think the H22 crank will be much of a difference, so the 88mm stroke and 4lb weight reduction seems the best fit. IF, I can find decently priced pistons for the thing... I'm hoping to use k series pistons over F23 or H22 custom parts because of their better design and weight savings of around 100g... Now I used the zeal calculator and with k24 flat top pistons I'll be just below at about a 8:5:1 ratio with longer h22 rods, which pretty low for my liking. But this is where I'm getting lost, I can't find enough info on the H22 rods and k series pistons... Will these rods clear everything on the F20b crank? I'd like to use the longer rods to accommodate for compression loss, but I'm not sure if they'll clear... Secondly, does anyone have any info on 11:1 K series dome heights?? Will these pistons push my compression too high? Can't find anything so I can't calculate compression for myself... Are a .040" head mill job and thin gasket the answer to my problems with the lower comp. piston?

*Summarized version*:
-F23 block, bored 87mm
-F22a1 head, port n polish, 272 grind, s2000 ti springs, b series retainers...
-F20b or H22 crank, balanced n polished
-H22 Rods, KStuned x beam
-K24 pistons
Will it work, even if it's not what you would do??? Will be my first honda engine build, so not 100% confident in the parts. Mostly forged, balanced, polished and assembled properly of course...

Thank you for coming to my Ted Talk.

Last edited by xxogpoohandzxx; 10-30-2018 at 02:26 PM.
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Old 10-30-2018, 11:11 AM
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Default Re: F23 Frankenstein help... PLEASE!

bump... really just curious now if the h22 rods will work with the f20b crank....
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Old 10-30-2018, 02:20 PM
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Default Re: F23 Frankenstein help... PLEASE!

ok did some irl research and talked to a local... basically was told its totally doable, i would just need to have the crank turned and run a .020 over bearing and everything should go together just fine.... I may just use a later h22 crank however, depends on if i can hit that magic 9500rpm number... updates to come if still no one feels like helping... I KNOW YOU'RE OUT THERE, DAMN YOU!!!!!!
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Old 10-30-2018, 03:12 PM
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Default Re: F23 Frankenstein help... PLEASE!

H22 rods will not work with an F20B crank. F20B crank uses a B series rod journal. It's also ill advised to turn a Honda crank. The journals are specially treated to harden the metal. Removing material will compromise the integrity of the crank.

For all you're trying to do, you would be better off just starting with a DOHC VTEC platform. The F22 head will ultimately be limited because of the single cam. The X Beams are also wildly unnecessary. Stock F20B bottom end will do 9500+ no issues, assuming the head has upgraded springs and retainers. You can also bore a stock F20B to 87mm and use H22 pistons if STRICTLY staying NA.
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Old 10-31-2018, 10:23 AM
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Default Re: F23 Frankenstein help... PLEASE!

Aradin,
thanks...
why do you say the sohc head won't get to that rpm? i know it might not be as easy, and might fall off power wise in comparison to a dohc, but would it be doable without blowing the thing? whats the potential of the f22a head?
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Old 10-31-2018, 03:37 PM
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Default Re: F23 Frankenstein help... PLEASE!

The F22A head actually flows pretty well. It's one of the better flowing single cam heads. You're just limited by how much you can do with the single cam doing all the work. A 272 regrind isn't going to allow you to make power to 9500 rpm anyway. There's only so much you can do when you're working with a single, non-VTEC cam like you're wanting to. I can tell you now that if you do manage to find a cam profile that will make or carry power to 9500rpm that it will be dead below 5000rpm and likely have horrible idle/street manners. 8000rpm or so may be more attainable but it would still require serious work. Even then the H/F series transmissions are so long geared you would really want to consider a final drive swap.

With a DOHC VTEC setup you can have the low cam for street manners/idle, and then a nasty high cam for power. That's what VTEC is for after all. Plus you open a lot more doors with the additional ability to fine tune both cams.

I think if you want to stick with the single cam you should lower your expectations a little and not worry about an arbitrary RPM number. There are some nasty SOHC setups out there that usually use an F23 bottom end with F22A head + aftermarket valvetrain. If you really want a high RPM screamer then consider switching to a DOHC platform.
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Old 12-03-2018, 12:25 PM
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Default Re: F23 Frankenstein help... PLEASE!

I agree with pretty much everything Aradin has said.

with what you described you're probably spending enough to afford a K-series swap.

focus on the strengths of the F-series. availability, decent torque and low running and repair costs. just tweak it to be more fun. do the top end work you're talking about, but stick with a pretty mild bottom end. (FYI stock K20A3 pistons fit great and give about 11:1 comp) only simple rebuild type machine work needed. there are some adapters available now that let you run the K-series intake on the F-series heads to really let it breathe.
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Old 12-04-2018, 01:49 PM
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Default Re: F23 Frankenstein help... PLEASE!

if i wanted to boost a f/h series id buy a automatic f20b from a importer for $500 out the door here in orange county. 5-10lbs of boost with your basic t3/t4 turbo would be more than enough power for someone driving a stock f series. If you going N/a buy a h23a bluetop with a tri y header and a 3" intake with a tune and you can acheive 200 whp very easily. With a ported stock intake manifold and 70mm tb 220whp can he acheived with a good tuner. No reason to try to reinvent the wheel and go all out with a build when your new to tuning honda/acuras. Keep it simple and listen to what works. For someone new keeping the block stock is very safe. Your local machine shop or engine builder cannot replicate the extreme close tolerances and accuracy of what honda does from the factory. Especially if you want to spin to 9500 rpm, honestly you need a huge cam with a lot of lift to rev that high and your definitely going to spin a rod bearing. It all just sound like a bad idea. Keep it 8,500 rpm with skunk pro1s and your engine will last much longer. Good luck hope your project turns out well.
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Old 12-05-2018, 05:16 AM
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Default Re: F23 Frankenstein help... PLEASE!

Originally Posted by Entheogen View Post
...Your local machine shop or engine builder cannot replicate the extreme close tolerances and accuracy of what honda does from the factory.
They absolutely can and should. it's a mass-production engine, not a particle collider.
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