I had recently rebuilt my n/a LS to up my CR. I was running around 11.7-12.0 and recently moved up to 13.6-13.9 CR. When I first rebuilt the engine I had Crower 62404's and my compression test came out 260psi. With my old set up of 11.7-12.0 CR and the 404's I made ruffly 170whp and 137ft lbs and the comp test was 240psi. Now with 62405-A's and the CR of 13.6-13.9 I dynoed 175whp and 135 ft lbs and the compression test came out to 210psi. I think that the came are bleeding too much compression presure.

How much compression do I need for these damn cams????
The specs are duration int-322 / ex-319
lift int-478 / ex-469


Modified by dohcter g at 4:48 PM 5/24/2005

 

those are some crazy specs... its normal for it to read lower psi numbers, you have more cam overlap with those cams...But you have to remember you have lower psi numbers but when the engines going higher into the rpm that cam overlap is working to the engines advantage and making more compression throughout the higher power band.....to answer your question, i dont think your over cammed..

the question is do you have the right fuel/headwork/ header for that compression and those cams?

 

I am scratching my head on this one!

I know the 405's do bleed a lot of compression off b/c the intake valves close at 45 degrees ABDC, as where the 404's closed at 34 degrees ABDC! That will bleed off a lot of compression(much more than the 404's), however 13.9:1 Compression should still be around12.6:1 dynamically with the 405's!


Was that dyno at P1 Auto? Did you get the tune done on a mustang dyno again or a dynojet?

1.6i may be right. You may need a better exhaust manifold for better scavenging of the exhaust gases.

 

I dont think just the exhaust will do it.

 

Just for kicks I will try my buddy's 2.5" collector. We are not even running full exh. we have them stop right under the shifters.

 

ya you should definatley hae enough compression to work well with 405s theres a few builds around of 405s and 405as with pct pistons you must have some issue somewheres in your build it may be a tuning issue

 

bump for some more advice for this guy!


I think a ventalation system for the crankcase would help alot with that high of compression.

 

I don't think tuning is the prob. either. Jack from P1 Auto tuned it and he is a well known Honda tuner in NC.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by dohcter g &raquo;</TD></TR><TR><TD CLASS="quote">I don't think tuning is the prob. either. Jack from P1 Auto tuned it and he is a well known Honda tuner in NC.</TD></TR></TABLE>


I vouch for Jack. He knows alot. I knew him back in the day when he lived in Lynchburg, VA

Is it possible that you could be under cammed?