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.
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.
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.
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
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,