Frankenstien engine.. worried about R/S

ok i have been reading up some…

i kno the stock B18a R/S is 1.74:1

but, im puting a B18B1 head on my block

now, they’re supposed to be the same as our stock head, just a lil better flow. but will my R/S change, and if so, do u guys have any estimations on how much??? the answer to this question will determine if im going to sleeve the block or not.


The r/s ratio is the ratio between the rod length and the stroke. If you are not changing the crank or the rods you will not change the ratio.

Frankenstien is a term that is used to describe a ls block with a Vtec head. You stated a B18b1. This is also an ls head so it is a direct swap for your stock head. If you meant B18c1 then that is a vtec and is a frankenstien. Either way it will not affect your r/s.

Not all B18a motors have the small ports so your B18b might not flow any better. But I think they do have better stock cams.

ah ok thanks!!! yeah i bought a b18b1 just cuz. i needed another head to build up while i can still drive the car so why not ya kno?

i dont think im gonna sleeve the block. i’ll have a shop look at it to be sure, but i’ll be runnin the drag turbo kit and some n2o. i figure, its already got a good R/S and its only going to be revved to 6.7k… shouldnt need sleeving

thanks for the info!!! if anybody has anything to add, please do!:slight_smile:

R/s for the B16 is 1.74. B18a/b is 1.54.

ahhh yes. you are correct. i got their numbers flipped. hmmmmm. sleeving wont still be a problem would it??

whats the rs on an s2k? they rev to 10k rpm. yea anyways b18a and b18b are identical except the b18b has a wilder cam and polish job stock. i would honestly rev up to around 7-7.5k rpm if i was gonna put the money into a turbo kit. either that or run a smal turbo so that it finishes spooling well before i shift. btw i would have your bottem end balanced, crank polished, rods shot-peened, new pistons rins and bearings. talk to your local machine shop they will assemble a full engnie for a decent price normally. peace