b17 p61 piston into a b18a

I have a b18a long block laying around along w/ b17 p61 pistons and rod.
i’m goin to rebuild the b18 and was wondering if its any better to
use the p61 pistons.
what will the compression be and would there be any loss or gain?

I’m just gonna hone the cylinder, replace rings, seals, and bearings.

some input will help.

it wouldn’t hurt at all to put em in. i have p30 (jdm b16) pistons in my recent rebuild. haven’t dynoed it yet, so i have no real results, and i combined them with cams and some other stuff, so i can’t go by seat of the pants at all. but as far as compression goes, you’ll be running about 9.7:1.

Not worth the time. Step up to at least a PR3 piston if you’re gonna have the engine rebuilt…

9.92 compression.

good for turbo :shrug:

i have 2 blocks, a b17a block which i will use p30 pistons.
now the p61 pistons are just laying around, i guess it’ll be better to
use it w/ the b18a block rather than the stock LS pistons.

So 9.7.1 compression? i’ll take it over 9.2. :slight_smile:
i know b16 pistons fits on LS rods w/ out any mod, but
will the p61 be the same?

thanx for the input!

i believe they’ll fit just like a pr3 would. the only ones that need modification to the rods are crt and itrs because the wrist pins are bigger

just buy some pr3 pistons, they are like $50 max used. Thats not that much.


can i dig this up?

i have 404’s running with stock CR, and you can probably guess that the gains weren’t exactly impressive from running such big cams on 9.2 CR.

right now, i can’t afford/or justify having new pistons put in, cause i spend WAY too much money on this car, so i’m planning on having the head milled 30thou for now, to get me up to 9.8 and hopefully give the cams some life.

Now, I’m looking for a piston that I can install, say next season that will raise my CR slightly to the mid 10’s or so, and the p72 seems perfect, 10.4 or so.

Can anynone confirm they fit?

yeah they fit, but you do need to shave 1mm off each small end. thats 1mm on the right side, 1mm on the left side to fit any b18c based piston. find some p61’s (92-93 gsrs) that will bolt on perfectly.

you better check on the valve clearances with those camshafts… 30 thou off the head is quite a bit.

check your math… i would thing your compression would be higher then a low 10 with all the stuff your taking off. c-speed is not completely accurate

thx for the info!

i ran through the formula’s using the tegtip, and cspeed was pretty close, 30 thou would put me just over 9.8:1

if youre gonna go through all that labor and money to rebuild your block, why go any less than 11:1?

reliability, i figure anything over 11 isn’t gonna last nearly as long as something in the low 10’s, i mean even if it’s tuned right that’s still alot of pressure on the rods and cylinder walls that the engine was never meant to handle.

plus i think a 10.4 would be a good compression ratio for the 404’s, it’s not too low, and it’s not so high it causes major stress on the engine

but right now, i’m actually thinking i might just keep the CR around 9.8 and get a wet injection nitrous kit, then i’d have a pretty mean fairly reliable all-motor car, with some extra kick when i need it,

That compression is lower than an ITR. Honda ships FACTORY motors with higher compression…

It doesn’t matter, ITR’s are completely different motors, the fact remains that the higher the compression, the greater the stress on the engine parts, the greater the stress the shorter the life.

But anyways, I’m goin with slightly over 11:1, this post is ancient.