just did a compression test on the race motor. i got 250 across all four does that look like a low number for my setup? block/head was decked. and machine shop told me my c/r should be around 13:1.

Block:
12:5.1 je pistons 84mm standard bore.
eagle esp rods
ge sleeved
balanced b20 crank

crower stage 3 cams
dual springs/titanium retainers
brass valve guides
multiple angle valve job
ported head


any input appreciated



edit: some old pics lol ignore the clamp coming off the intake mani.. sk2ps tb doesnt have a port for that hose so i had to T it into the heater hose. also those 25" slicks came with the bogarts. took em off and got some 23" right now.








Modified by 408wdy at 9:26 PM 7/13/2008

 

If the numbers are even all the way across then I would be pretty happy.

One question is how much lift and duration on the primaries of a stg 3 cam?

I've seen high compression motors peg a tester but they only had stockish primaries.


Modified by mar778c at 6:30 PM 7/13/2008

 

i was expecting high numbers too but all i got was 250.. glad they are even though.

for the stage 3 cams i got these numbers from crowers web site.

63413-2
Stage 3 - All-Motor Drag Race profile.
Requires #84161 spring/retainer kit with modified ECU.
Rough idle. VTEC controller recommended.
23+ hp w/other mods

Advertised Duration Duration @ .050" Gross Lift w/1.55

Int- 305 mid Int- 263 mid Int- 468 mid
Exh-305 mid Exh-255 mid Exh-468 mid



Note: Specs for secondary and primary lobes are the same and are as follows:
Secondary - 206 @ .050" 442 Gross Lift w/ 1.5 rocker ratio
Primary - 206 @ .050" 427 Gross Lift w/ 1.45 rocker ratio


Modified by 408wdy at 4:54 PM 7/16/2008

 

Those are some big numbers for a primary. No wonder the tester is reading low.
Any dyno numbers?

 

haven't had it on the dyno yet. i was trying to get it tuned yesterday but was short on funds. i'll be hoping to tune this coming saturday. will post numbers in here and my build thread.. thanks for your input, i appreciated it

 

I believe it's a common misconception that large cams "bleed off" compression.

Compression testers vary, just like all tools. Be happy that they are even.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by BMo Tuning &raquo;</TD></TR><TR><TD CLASS="quote">I believe it's a common misconception that large cams "bleed off" compression.

Compression testers vary, just like all tools. Be happy that they are even.</TD></TR></TABLE>

You are correct. The thing is the large profiles increase the overlap which lowers the amount of air being compressed.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by mar778c &raquo;</TD></TR><TR><TD CLASS="quote">

You are correct. The thing is the large profiles increase the overlap which lowers the amount of air being compressed.</TD></TR></TABLE>

I'd actually be interested in seeing how much more compression my engine pulls with stock cams in place.

OP: I have an 11.9:1 gsr that also "only" pulls 255psi at operating temp, 250psi while dead cold tho

 

I have 11.2:! Wiseco in my 85x89 and pulled 270-275 all across.

 

Just to give some ideas of what other motor do: I pulled 270 on all 4 with 87x85, 12.5 compression with toda C cams. my buddy pulled off 270-290 with buddy clubs 3 , 84x89 with 11.5 rs pistons..

 

i think my rings might have gotten washed on initial startup. car ran rich for about 15-20 mins.. oh well probably have to tear down and do new rings/headgasket.