converting crx hf to si with hf block.....?

i have a 91 crx hf d15b6 i recently swapped out the old [hf] head and intake for the si head and intake. i have a dc header, and cold air intake ,msd ignition.i gained a lot of compression since the hf block is 9.6.to1 and the head i used is ported polshed and decked so ended up with about 10.2 to 1 . next i swapped the hf ecu for a si pm6 ecu. my question is should i "chip" this ecu for even more gains???and also the tranny for the hf is more for highway drivin' i would like to swap it out for a si tranny?? what #numbers should i look for to make sure its a si tranny??? thanks jacer63 91 crx hf converted to a si >>>>>

so you had no problems with the Si valves hitting the pistons? HF pistons dont have the second set of valve reliefs, so its always been a belief that the valves would hit the pistons, but since you did this swap, its good to know it isnt true.?

If you want maximum acceleration, swap out that puny HF 5 speed for an Si tranny, or atleast a DX. it will make a HUGE difference.

the vavle reliefs made me a little wery but i mocked the head on the block and clayed the pistons with no gasket and had no interference so i set the cam gear at 2 deg advance and seem to work fine.. 100 hard miles and going since swap. no numbers on si tranny what help alot??? thanks

you *advanced* the cam gear? advancing the timing has the effect of lowering your powerband. IMO, if anything, you would want to retard the cam a couple degrees (6 degrees retard with a 59300 zex/comp cam in d16z6 is my best finding) to help out with power up top.

Ill Try A Little Tinkering With It!! So 3-6 Degrees Retard Is Good For Upper Rpm's ??whats Good For Lower Rpms ,say If Thats What Im After ? Should I Swap Out Cams With Something Other Than Stock Si? Thanks FOR ANY INPUT!! IM TRYING TO MAKE POWER WITH A LITTLE DIFFERRENT SET-UP THAN USAUL i.e D15B6

thats odd you had no probs with valve to piston contact....back when i didnt know much i put a dx head on my hf block and even with cam timing set right i bent 4 valves. as far as cams....if your short on cash, delta can do a 272 regrind on your si cam for roughly $100 total. ive ran this cam for about 6 months and i really like it. as far as cam timing....you would have to tinker with it and see where it best suits you.

if you're looking for lower rpm power, then buy a v6 or v8.

honda small displacement engines HAVE to rev high to make power by design.

Just Was Asking Questions Mr 15 Sec.... He He

and what do you run with your HF... 17.8? :rolleyes:

Havent Ran The Crx Yet... NOT DONE WITH ALL THE MODS YET ,IM SURE IT WILL RUN HARD THOUGH...But Have A Low 10 Sec Nova That I Drive On The Street On Ocassion.. 1.43 60 Foot [email protected] SO I KNOW WHAT IT TAKES TO GO FAST ...REAL FAST

and what do you run with your HF... 17.8? :rolleyes:


A 15.5 isn't too good considering you have an LS swap bro... I was running quicker than that with my D16A6+I/E.

I haven't gotten to run mine with the LS swap but i'm expecting to be in the 14's for sure, your 60' times suck BTW :)

uh huh, my stock DX runs 14.9 :rolleyes:

Are you waving that BS flag at me 91civicDXdude?
I can give you an exact list of everything I had done when I ran a 15.3 if you'd like.

Stock D16A6
no air conditioning
NGK V-Power spark plugs
NGK plug wires
Slipping Clutchmasters clutch
Ghetto used Stromung (sp?) exhaust
Used no-name short ram intake w/no filter
removed passenger side headlight
no rear interior
Potenza's aired down to 17psi up front
Potenza's out back aired up to 55psi
rear shocks set to stiffest setting (5)
front shocks set to medium stiff (3)

All that combined with a 2.085 60' time gave me a 15.3 @ 88mph. If you had a better 60' time than your 2.388 in your sig you could have run a high 14 possibly, or atleast a very low 15.

gotta have the slipping clutch.. cant post a time without "slipping ass clutch"

gotta have the slipping clutch.. cant post a time without "slipping ass clutch"


I actually think that the clutch slipping helped my time, I was able to knock out consistently low 60' times thanks to it engaging rather smoothly and keeping wheelsping to a minimum. It wasn't untill i'd made a few runs that it started to slip bad enough that my trapspeeds started to suffer.

Figure it out.