90.70mm vs 95mm vs 97mm Stroke

[djcaz_aom]

I am wanting a little input from those in the know.

I'm planning my new F build and have all of these cranks to choose from:

- H22 (90.70mm/ 50mm and 55mm mains)
- H23 (95mm/ 50 mm mains)
- F23 (97mm/ 55mm mains)
- F20A (88mm/ 50mm)
- F20b (55mm mains)

Build:

- 12.1:1 Compression Pistons 86mm
- Forged Rods (size depends on crank choice)
- Fully built A6 Head (Port and polish, over-sized valves, upgraded valve train good to 11,00RPM, 326CFM)
- 272 Cam (or whatever is necessary to achieve my goal)
- 52mm ITBs

Goals:
As close to the 300WHP mark as possible.

I love me some torque, but have grown found of the revving capabilities of the H22. Please don't come on here telling me to just swap in an H22, I have three sitting in my garage.

I have been and always will be a fan of the F series motor.

I would like some pros and cons and why.

Your input will be greatly appreciated.

[91cb7h22poss]

do the f22 block.. due to your liking. 86mm pistons, and the forged rods like you said, and depending on your money situation, a fully balanced and polished crank out of an f23, you wont rev as high. but with the 2.3 crank, theres your stroke at 97mm. this is actually what i plan on doing with my build actually, minus the ITBs, little sketchy around my area, too much shit falling from trees...

[F20A CB7]

Smaller the crank the higher the rpm will b? Less tq rite

[92smokeaccord]

your bottom end depends on your top end.like for instance if your delta 272 cam can rev to 8k rpm but a power band from 4k to 8k.then you wnt to build your bottom accordingly.you want your bottom end to kinda match how high your max rev limit your cam will put out.if you have a custom cam that alows power past 10k then you want a short stoke to be able to accommodate the high reving capabilitys.

[MortsAccord]

Honestly man 300WHP isn't going to happen on a N/A setup without some extreme money invested in a 2.2-2.5L . Seriously everyone on the internet always overshoots their build goals. I've seen some of the dyno graphs people have for their cracked out "300 whp" builds and their TQ curve looks like shit.

Lightweight aluminum rods and pistons will be needed, 1 ounce of reciporcating weight is equal to 1 lb of rotational weight, so saving weight on rods and pistons will make a large gain in the top end. The problem is that aluminum rods fatigue easily, pretty *** if its not a track car.

Higher RPMS' make the rings work harder to evacuate oil from the piston walls, and will lead to more burnt oil than a lower RPM build.

If you did build a head to those ballpark stats, then you would wan't a small crank. like the 90.7 I don't think I would go to a 88mm crank. You'd lose too much displacement and probably not be happy with it.

Let me shed some light onto the general idea of revving to the moon.
go here.
http://thefirstgensite.com/code/maxrpm.htm
88mm stroke = 3.46456693 = 8650 rpm
90.7 = 3.57086614
95.5 = 3.74015748
97.0 = 3.81889764 = 7850 rpm

Even for racing componets an 88mm stroke should only go to about 8650.


If the above doesn't sit with you well then: Your only cost effective option for that kind of power is to boost it. Only another 800 rpm out of an 88mm stroke vs the 97. F that. stroke and turbo FTW IMO


It also depends on your ability to do your own work which makes the cost even less. Welding exhaust isn't hard at all people blow it out of proportion on its difficulty. If you got that then its probably a much better route.

Turbo engines typically last longer than an equally powerful N/A setup, since the turbo isn't always producing those static high compression ratio's, it allows for the engine to not be over-worked when your not on the pedal hard.

Turbocharged engines are quieter.

For a turbo head all you really need is port and polish the intake with some oversized exhaust valves. - the challenge for turbo engines is getting all that extra exhaust volume out. If you do head work, tackle the exhaust side first before the intake. It will reap rewards much more efficiently. As a general rule, when building an engine and considering the air flow it sees, you should engineer the cars system in reverse. This will make sure you dont have a choking point because you ran out of funds on a intake job and did nothing for the exhaust.

I'll edit more later.

[djcaz_aom]

Okay, pistons are bought, head work has long been done. All cranks listed, I have in my possession.

As for a turbo, that is out of the question. My goal of 300WHP is a goal I am okay with even if I don't hit it.

I also do a lot of my own work and save a bit there.

Thanks for your input, but I am set on building this NA.

[thepowderblue]

The f23 will make the most torque so I vote f23. The only thing is the f23 has the thin rods so I would upgrade them.

[MortsAccord]

Thanks for your input, but I am set on building this NA.

its cool, just trying to give you a realistic outlook on the build.(lol most build threads are of someone without any idea on what they want) I was unaware you had already gotten some investment in there yet.

Other ods and ends.

I wouldn't take out power steering to get a pony out of it, since the car was designed with power steering. You might want to look into some lightweight pulleys, they aren't much, but I'd leave the balance shafts in there. Lightweight flywheel and aluminum pressure plate would be nice.

You could balance the crank to the rod's and pistons you chose. knife edging it would help a little with windage. Use a slightly closer tolerance on bearings and run 20W oils could help with some peak hp as well.

Honestly I don't see ITB's as a much of a benefit unless you get a scoop and intake setup that helps feed them ambient air instead of engine bay air. - it would probably be the very last thing I'd do.

There are places that will modify an OEM water pump to cavitate less/operate more efficiently, which can save you on some power. If you got the time, might as well camfer/debur anything in the radiating system that meets up. Same thing with intake/exhaust, any seemless connections in those systems will keep your VE% up.

Coil on plug wouldn't hurt, but at the cost and headache of doing it you might as well buy a standalone management system, such as SDS-EFI's equipment.

Are you still going to run AC? I'd gut that stuff out

[SOHC-FTW]

H22 crank or use the stocker, either or will need to be polished, balanced, and blueprinted for such a build.

I would however suggest you look into a better cam for such an application. The 272 is great for a mild build, but for your build i would go with a custom hardweld and grind of your choice.

[SNOOZE]

I vote for the H23A crank because it's in the middle, and because it makes more torque. Like mentioned above some of these NA builds lack torque so I think the 95mm is the perfect match because you will have power and torque. Your kinda in the middle and not choosing between either high end power or torque.

[Jarrett]

There's more to building an engine than simply deciding what bore and stroke you want. You incredibly compound this issue when you order pistons without the entire build planned out.

Let me shed a little light on this. Assuming those pistons are the off-the-shelf variety from Bisimoto then they're only going to make a 12.1:1 compression ratio in an F22A that's been over bored 1mm. Anything else and that changes.

Assuming you decided to go with a 90.7mm stroke then you'd likely pair those with the 143mm rods as well. Coupled with those pistons you're looking at a compression ratio around ~10.84:1. This could be elieviated by having custom rods made that are 143.5mm or milling .5mm off the block.

An 88mm stroke would improve the compression issue if used with the accompanying 145mm rods to about 11.28:1. But if the crank isn't an F20A or '97 F20B with 50mm mains then you'll need a different block.

The same issue in regard to the main diameters applies to the F23A crankshaft as well.

All I've really brought up is compression ratio and the mains diameters. There are countless many more variables involved but it looked like right off the bat you weren't considering some of the most basic dimensions.

Good luck!

[98vtec]

you are going to need a big motor, big cams, race gas compression and a whole bunch of money.

believe me i know.

sucks you already bought pistons. with the crank and rod combinations possible with the H/F series, you can have high compression pistons that paired with a short stroke, will drop the compression considerably or you can jack the piston up so high it hits the head....all with the same pistons.

personally, i start with the camshafts and build around that. That way you know what compression you need, you know the displacement needed to really make some power and you know what you are getting yourself into.

[djcaz_aom]

Just to answer a few points, I have blocks with both 50mm mains and 55mm mains.

I started this build years ago and have no problem getting custom sized rods for the build.

The 272 cam is a suggestion more than a definitive. My head is already fully built. I never had the bottom end built due to the shop doing the work shutting down.

Thanks to everyone posting and giving some input.

I am really looking to see if my plans are on par with the knowledge that others have from experience. I have considered my different combinations and that's why I have so many blocks and cranks to choose from.

Keep it coming. Thanks.

** I also updated the original post with the crank dimensions I have available.

[Jarrett]

That's quite the collection.

[Joey GT-R]

I thought I'd just throw it out there, but the K24A2 crank at 99mm can be machined to fit H22s and F22s. They rev to 8K stock so paired with the right rods and pistons you might can have the longest stroke of all and still rev fairly high. Or if you're just after the most torque possible, any of the other K24s would do. If I was to go back to an F22A build, I would consider this.