What could be wrong? dyno issues
01-21-2008, 10:40 PM
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What could be wrong? dyno issues Well i took my car to Alvin at Pcmforless to get a dyno tune. First off the car runs great now and is very smooth to drive but to get to the point, on my dyno runs the car wouldnt pull past 5800rpms. We have no idea why I readjusted the valves after the dyno and nothing seems to have change. If you have any ideas that may help please let me know.
The car is a 93 Trans Am
It has: 355 rebuild
Comp 503 cam
Mild ported heads
Msd opti
2600 stall
373 gears
and here is the dyno graph. the air/fuel stayed around 12.4 until it started to fall of at 5800 rpms
The car is a 93 Trans Am
It has: 355 rebuild
Comp 503 cam
Mild ported heads
Msd opti
2600 stall
373 gears
and here is the dyno graph. the air/fuel stayed around 12.4 until it started to fall of at 5800 rpms
01-22-2008, 01:13 AM
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What is your rev limiter set at? My buddy did that. The car was tuned to shift at 6100rpm but the person that built the motor set the rev limiter at 5800rpm. Something to check
Last edited by onephatZ28; 01-22-2008 at 01:20 AM.
01-22-2008, 02:33 AM
#5
I agree it could be in the spring, but I would also look into your "mild ported heads". Who did the porting and what are they flowing, are they flow matched etc.
Those numbers are pretty low especially given the fact it was a dynojet and not a mustang dyno.
Those numbers are pretty low especially given the fact it was a dynojet and not a mustang dyno.
01-22-2008, 08:59 AM
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thanks for the responses, the valve springs are CCA-987-16 (comp 987 springs), to tell you the truth im not sure of the install height, the head were puchased off of member on here and they were the ones that come on golden engines 383 longblock.
About the rev limiter, thats what i thought it may have been but since alvin was dyno tuning at that time we would have been able to control that, we also bypassed the msd box thinking that may have been the problem but that didnt fix it either.
could it be that i just have week lifters or would that not cause this problem?
About the rev limiter, thats what i thought it may have been but since alvin was dyno tuning at that time we would have been able to control that, we also bypassed the msd box thinking that may have been the problem but that didnt fix it either.
could it be that i just have week lifters or would that not cause this problem?
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01-22-2008, 01:34 PM
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I thought we were all pretty much in agreement that Golen engines kinda sucked ****... So those heads may just be crapily ported.
Also, I'm sure Alvin would've changed it, but the stock Rev Limiter is set @ around 5850rpm.
Also, I'm sure Alvin would've changed it, but the stock Rev Limiter is set @ around 5850rpm.
01-22-2008, 02:07 PM
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I know you have a MSD opti but it could be bad, It happens. how old is it ? and if it is a 93 it is a non-vented opti. do you drive in the rain? Just a thought
01-22-2008, 02:10 PM
#11
Alvin here,
It definately wasn't a rev limitor. The PCM rev limitor was 6500 and the MSD box didn't have a chip in it so infinite. He said he used the lifters that cam in the rebuild kit (cheap) I'll put money on htats where the problem is.
It didn't pull a vaccum on the intake at WOT so the intake was nice and healthy.. ON top of that he had beautiful exhaust so theres not much else it could be. The peak appeared also to be in the right area so I would bet that the cam timing is also right.
It definately wasn't a rev limitor. The PCM rev limitor was 6500 and the MSD box didn't have a chip in it so infinite. He said he used the lifters that cam in the rebuild kit (cheap) I'll put money on htats where the problem is.
It didn't pull a vaccum on the intake at WOT so the intake was nice and healthy.. ON top of that he had beautiful exhaust so theres not much else it could be. The peak appeared also to be in the right area so I would bet that the cam timing is also right.
01-22-2008, 02:11 PM
#12
I thought we were all pretty much in agreement that Golen engines kinda sucked ****... So those heads may just be crapily ported.
01-22-2008, 03:02 PM
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thanks for the replys... Alvin i belive you are right im going to get the lifters tomorrow and see if that helps any. hopefully it will and i can get this thing straightened out. If not ill try the valve springs.
01-23-2008, 05:44 PM
#18
Any spring can get tired. Without testing spring pressure and looking at installed height, hard to say on the springs. Cheap lifters might be an issue too.
Folks, when you buy used heads, spend the bucks to get them flowed and freshened at a competent speed shop! Yup, it'll cost you, but valves that don't seal well don't make power!
Folks, when you buy used heads, spend the bucks to get them flowed and freshened at a competent speed shop! Yup, it'll cost you, but valves that don't seal well don't make power!
I'll proceed to 