408 not making power
#1
408 not making power
Need some ideas ya'll.... I recently installed an iron 408 in my CTS-V with L92 heads, L76 intake and 236/238 cam with ~.600 lift and 114 LSA. It's not perfectly tuned but is right at 13.0:1 AFR at WOT according to Wideband and is running about 28 degrees Total advance. It's putting 435HP and 405 lbs./ft. of torque to the wheels. This seems WAY low to me according to what else I've seen out there. The motor makes pretty good oil pressure (around 30 lbs. at idle and 52 lbs. at 5000 rpm). It seems to run fine, nothing that would indicate compression or leak down issues... just not what I expected. Any ideas why it could be so off on power?
It does consume about a quart of oil every 1000 miles or so, but with no visible oil smoke out of the exhaust except at WOT high rpm...even then very little.
It does consume about a quart of oil every 1000 miles or so, but with no visible oil smoke out of the exhaust except at WOT high rpm...even then very little.
Trending Topics
#14
The heads have not been milled. They are stage II ported by port pros. Harold does great work...don't think the heads are an issue. I use HP Tuners...do you want me to post the .htp file?
#15
TECH Addict
iTrader: (22)
Join Date: Sep 2004
Location: tennessee
Posts: 2,639
Likes: 0
Received 0 Likes
on
0 Posts
the l92/76 combos seem very picky about cam profiles. even with that cam (which probably needs 8-10 more * of duration on exhaust side) the power seems way low,especially on the tq side. what does your exhaust setup consist of ?
#16
Launching!
iTrader: (44)
Join Date: Aug 2007
Location: Greensboro, North Carolina
Posts: 286
Likes: 0
Received 1 Like
on
1 Post
l92's came with 70cc chambers, I was getting an idea of your compession.
With a flat top piston and a l92 head you could only be @ +/- 10.0 to 1.
#17
exhaust is 1 3/4 kooks full lengths and cats with cords cat-back. The chambers are stock size and piston has a small dish but my math puts this near to 11:1 compression with a 408.