What's up guys. I got a gen3 lude and I wanna go N/A with it. Anyway, not important, my question is why is a Prelude with F20B such a rare thing? With the research I've done, the head is basically off a H22A and the block is iron sleeved. It seems to me that this would be the best engine to build, especially for N/A. Why do more people not use them? Is it a big deal to swap an F20B into a Gen3? I just want some opinions on it.

So nobody asks, im wanting stage3 Skunk2 head, basic block work, matching fuel/air upgrades etc. etc. im not going into all of that right now.

 

Because a heavily built NA 2-liter's an expensive route to be slow.

F20s were designed for laws and racing league rules limiting displacement to 2.0 liters. In the "real world" Preludes are heavy and with stock gearing options a 2.2 or 2.3 liter will ALWAYS be faster than a 2.0. More displacment generates greater average torque and thus more average power. So in a straight line more average power over the applicable RPM range will be faster.

Additionally F/H VTEC heads don't make much power over 8000 rpm so additional revs from a short stroke motor won't win you much over a torquier motor at a slightly lower RPM.

Put in forged pistons and turbo an F20 and then you might have an edge with the broad RPM range but not in NA form.

 

I think the biggest reason is plain supply, there are less of them around compared to the H22, so you don't see them as often. The same could be said for the H23A bluetop engines, but they have become more popular as a swap engine in recent years, so the importers are bringing more of them over.

 

I need to ask because you avatar looks like a 4th gen. The true 3rd gen Preludes share nothing in common with any of the other gen preludes, and the years are 88-91.

So what year and body style is your 3rd gen specifically?

Because a H/F swap was re-poineered by me and I know more about this swap than most on this forum.

And my avatar shows what my old and current lude show what a 3rd gen is.

 

Whoa yea I was definitely wrong on that, mines a fourth gen my bad

 

F20B's are not popular for N/a just because of their displacement, also because it has typeS cams and still makes what a stock h22a makes. So going hug lift cams will still be disappointing power wise.

They are sleeved and of the builds you see i bet 99% are boosted for that very reason. Cams arent as important unless you are going for big numbers, they are very important for n/a. F20b's are meant to be high rev motors with their short stroke which boosted cars like.

 

So i'd be better off with boost eh? How much boost could you throw to a stock blocked F20?

 

boost or psi is only relative to the size of the turbo itself. Two different sized turbos at different psi's could give you the same results.

Figure out you're set up before you set you're mind to a particular psi. Im taking a guess here because I dont know, but I would assume similar to b series stock sleeves maybe in the 400-500 whp range. But this is merely an educated guess.

Forged internals is what you need next with a stock bottom end F20B. You probably wont get past 300whp or so with factory internals.

 

Ok cool and as far as forged internals, what exactly is cross compatible? I cant find a whole lot for the F20B so would pistons for a B20B also work? Or maybe a different engine

 

That is where this motor starts to lose its luster, there really is no aftermarket for it. Its a special motor designed to be in the 2.0ltr class, and was not as mass produced for the entire world like the H23abluetop and H22a motors, which have more interchangeable parts.

 

See whats getting me with the F20 is the fact its got a sleeved block, I don't wanna go drop 10k on an H series just to run 15psi to it and still have reliability issues you know what I mean? I guess I always could just figure out the bore of the F20 and just order pistons direct for that same cylinder bore. I'm not trying to make this thing an ultra-mega super fast drag car, I just want 300-400hp to play with. This car is just a toy, not something I wanna drop a ton of $$ on and beat everybody out there with.

 

Yeah you are going to have to order custom pistons for it and rods if you are wanting to push that kind of power.

 

I know Bishimoto has a few aftermarket parts for the F20b engine. They have forged piston/rod kits in the stock compression as well as lower compression (8.6:1 i believe). I am doing this swap into my 3rd gen and have been looking around a lot as well. My selling points were the high rev and iron sleeves for boost in the future.

 

Nice dude thanks for that info! Not to bad of a price for that either. But yea, I agree with you thats why I wanna do a F20B they seem like a solid platform