Not making the power I want/expected - check my setup, anything wrong?
05-17-2012, 06:04 AM
#1
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Not making the power I want/expected - check my setup, anything wrong? I was expecting this to make AT LEAST in the 450-465whp ballpark or even a little more and it didn't, was wondering if people can look over my mods and see what's missing if anything...
The car is a 99 Corvette 6MT with 4.10s. I will check the compression today and see if its ok, but the bottom end was freshly built (I crushed a valve spring, dropped a valve on my last motor and it crack the block, etc) so I don't think that's the issue.
Bottom End...
-stock 346 with new gaskets, all new bearings, etc.
-2.5cc reliefs fly cut in pistons
-Magic stick 4 camshaft
-Ported oil pump
-Powerbond 25% reduction pulley
Top End...
-TEA Stage 2 heads with PAC 1521s, stock lifters, rocker trunion upgrade with stock rockers - .040 milled = 60.9 cc chamber size = should give approx SCR of 11.1-11.2 to 1
-.040 headgaskets
-FAST 102mm intake mani ported by Vengeance Racing
-LS2 OEM fuel rails
-Cobra 39lb injectors with EV6 pig-tails wired in
-LS2 90mm T-body ported with tb harness adaptor
-Breathless intake and airbridge
-Truck MAF - Tuned with MAF only - MAP is shut off after 400rpm
-1 3/4 headers of unknown origin, got em with the car - has an x-pipe replacing where the cats would be, but its cut short and the factory h-pipe is welded to it with the factory cat-back
The car made 411whp with 26 degrees of timing in it up top, no knock at all with that, but it knocked with 27 degrees and didn't make any more power so we put it at 26 and left it. A/F was a smooth 12.5 throughout. We thought it might be the exhaust being a bit restrictive so we unbolted the X-pipe and made 431whp with the headers dumped open. Like I said I was expecting more and was wondering if there's something I'm missing.
The car is a 99 Corvette 6MT with 4.10s. I will check the compression today and see if its ok, but the bottom end was freshly built (I crushed a valve spring, dropped a valve on my last motor and it crack the block, etc) so I don't think that's the issue.
Bottom End...
-stock 346 with new gaskets, all new bearings, etc.
-2.5cc reliefs fly cut in pistons
-Magic stick 4 camshaft
-Ported oil pump
-Powerbond 25% reduction pulley
Top End...
-TEA Stage 2 heads with PAC 1521s, stock lifters, rocker trunion upgrade with stock rockers - .040 milled = 60.9 cc chamber size = should give approx SCR of 11.1-11.2 to 1
-.040 headgaskets
-FAST 102mm intake mani ported by Vengeance Racing
-LS2 OEM fuel rails
-Cobra 39lb injectors with EV6 pig-tails wired in
-LS2 90mm T-body ported with tb harness adaptor
-Breathless intake and airbridge
-Truck MAF - Tuned with MAF only - MAP is shut off after 400rpm
-1 3/4 headers of unknown origin, got em with the car - has an x-pipe replacing where the cats would be, but its cut short and the factory h-pipe is welded to it with the factory cat-back
The car made 411whp with 26 degrees of timing in it up top, no knock at all with that, but it knocked with 27 degrees and didn't make any more power so we put it at 26 and left it. A/F was a smooth 12.5 throughout. We thought it might be the exhaust being a bit restrictive so we unbolted the X-pipe and made 431whp with the headers dumped open. Like I said I was expecting more and was wondering if there's something I'm missing.
Last edited by RideZX-6R; 05-17-2012 at 07:35 AM.
05-17-2012, 10:18 AM
#7
The type of dyno does IS a factor. With no changes, a local guy went and dynoed on 2, made 40hp more on one than the other.
Sounds like the exhaust is holding it back, since it gained 20hp from it. Might be a little left on the table since it has less timing than usual and the AFR is on the safe side.
Go make a pass at the track, see what it traps. Stuffing a big cam with some nice heads isn't always a recipe for success.
Sounds like the exhaust is holding it back, since it gained 20hp from it. Might be a little left on the table since it has less timing than usual and the AFR is on the safe side.
Go make a pass at the track, see what it traps. Stuffing a big cam with some nice heads isn't always a recipe for success.
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05-17-2012, 10:25 AM
#8
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The type of dyno does IS a factor. With no changes, a local guy went and dynoed on 2, made 40hp more on one than the other.
Sounds like the exhaust is holding it back, since it gained 20hp from it. Might be a little left on the table since it has less timing than usual and the AFR is on the safe side.
Go make a pass at the track, see what it traps. Stuffing a big cam with some nice heads isn't always a recipe for success.
Sounds like the exhaust is holding it back, since it gained 20hp from it. Might be a little left on the table since it has less timing than usual and the AFR is on the safe side.
Go make a pass at the track, see what it traps. Stuffing a big cam with some nice heads isn't always a recipe for success.
AFR is on the safer side, 27 degrees started getting 1/4 to 1/2 degree of knock and added no power - so we put it back to 26. if the exhaust is restrictive, that could possibly explain it a little - same with poor header design.
I'd expect more than 430whp with this setup even with open headers tho, can't imagine header design is THAT poor that it stifles the motor THAT much.
10-14-2012, 09:13 PM
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This is crazy. I have a 383 with patriot heads and the ms4 cam. I am only making 411 as well. My rear end is a 3.90. this is in a 1975 280z. I have ls6 intake and 3/4 headers. My baby cammed 346 made 405 hp/tq on the same dyno and same car. no with the bigger engine and cam im only making 6 more hp/tq. I have been looking everywhere to try to find a similar incident for a solution. Did you ever find out what was going on?
10-14-2012, 10:53 PM
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I really hope you aren't using injectors made for a DOHC engine... Could be a huge issue there...
Just saying
Also gearing kills some hp because your doing the same amount of work in less time. The more time you have to the work (power) it will usually be about 10 to 15hp higher with a taller gear. So don't worry about the dyno too much. Run it at the track.
Just saying
Also gearing kills some hp because your doing the same amount of work in less time. The more time you have to the work (power) it will usually be about 10 to 15hp higher with a taller gear. So don't worry about the dyno too much. Run it at the track.
