408 not making power

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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.

Oct 19, 2007 | 11:12 PM

cherryelky305

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Its the torque numbers that bother me in that situation. Not what I'm used to seeing. I have absolutly no experience however. I know someone will chime in.

Oct 20, 2007 | 08:59 AM

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Anyone?

Oct 20, 2007 | 09:14 AM

Launching!

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Your cam is tiny. I would look at getting a cam in the 244 to 248 duration at .050 range.
Is this an auto or 6sp. ??

Oct 20, 2007 | 09:18 AM

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It's a 6 speed. I wondered about the cam too but a lot of folks seem to be making 500 rwhp with cams similar to this.

Oct 20, 2007 | 09:28 AM

WKMCD

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I'm not wild about the cam choice. I think you;ve pushed the intake duration too far out. Back that up to 230 and I think it will come up a bunch.

My $.02

Oct 20, 2007 | 09:30 AM

Launching!

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Are your l92 heads out of the box or have they been milled?

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Oct 20, 2007 | 09:31 AM

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Quote:

Originally Posted by WKMCD

I'm not wild about the cam choice. I think you;ve pushed the intake duration too far out. Back that up to 230 and I think it will come up a bunch.

My $.02

Its not as bad as some of the others. You know what I mean

Oct 20, 2007 | 09:32 AM

#10

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Optimal no, but not too bad. 230/242 would be pretty close to optimal.

Oct 20, 2007 | 09:36 AM

#11

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Hey Kevin, does the thread title sound eerily familiar?

Oct 20, 2007 | 09:48 AM

#12

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Quote:

Originally Posted by edcmat-l1

Its not as bad as some of the others. You know what I mean

My bad.....Ill leave this one to the "Experts".....???

Oct 20, 2007 | 09:51 AM

#13

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Quote:

Originally Posted by 408z28

My bad.....Ill leave this one to the "Experts".....???

No worries. They (L92s) just like a different profile. They def dont like or need a bunch of intake duration, or alot of overlap. They are a heavily intake biased head.

Oct 20, 2007 | 09:59 AM

#14

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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?

Oct 20, 2007 | 09:59 AM

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slow trap

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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 ?

Oct 20, 2007 | 10:13 AM

#16

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Quote:

Originally Posted by VDiddy

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?

I was asking in reference to your cc on the chambers, not your port work.
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.

Oct 20, 2007 | 10:18 AM

#17

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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.

Oct 20, 2007 | 10:19 AM

#18