Help! Power loss but car runs fine.
04-20-2010, 08:20 PM
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Help! Power loss but car runs fine. Need some help. Here is the story. Supercharged Mallett 435 Vette. Had overheating issues. Replaced block for casting defect, crack.
New block, reassembled same parts. Made 570 RWHP before. After putting back together, ran like crap. Didn't drive it really, just starting up and idling, reving, etc. Found intake tract leak after MAF and PVC problem. Fixed those and ran OK. But shooting pieces of Cat brick out exhaust. Cats were apparently melted. Drove it and not making power it should be.
Assumed Cats are bad and plugging exhaust. Replaced shorty headers, cats, etc to the catback with LG Pros with cats. Put together and is better, but still 200HP down on power. No Codes and idles good. Car is really loud and seems the exhaust is really hot.
Concerned that the people that assembled the shortblock may have messed up the install of the timing chain and that is the cause. It has a Cloyes Hex-adjust timing chain.
Is there a way to measure/diagnose if the timing chain is off a tooth or something? I have EFI Live and I was wondering if there is some way to see the cam sensor signal matched against the crank timing signal to show if this is the case? How would that be done.
Thanks,
G
New block, reassembled same parts. Made 570 RWHP before. After putting back together, ran like crap. Didn't drive it really, just starting up and idling, reving, etc. Found intake tract leak after MAF and PVC problem. Fixed those and ran OK. But shooting pieces of Cat brick out exhaust. Cats were apparently melted. Drove it and not making power it should be.
Assumed Cats are bad and plugging exhaust. Replaced shorty headers, cats, etc to the catback with LG Pros with cats. Put together and is better, but still 200HP down on power. No Codes and idles good. Car is really loud and seems the exhaust is really hot.
Concerned that the people that assembled the shortblock may have messed up the install of the timing chain and that is the cause. It has a Cloyes Hex-adjust timing chain.
Is there a way to measure/diagnose if the timing chain is off a tooth or something? I have EFI Live and I was wondering if there is some way to see the cam sensor signal matched against the crank timing signal to show if this is the case? How would that be done.
Thanks,
G
04-21-2010, 03:57 PM
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It was lean initially but I don't think it is now. That is what ruined the cat. That was the intake leak after the MAF.
We ran WOT runs and the O2s read around .925 volts which is the rich side of things right? If they were less then .900 I would guess it might be lean.
We are going to check the rockers torque. Maybe the lifters were drained and when the rockers were torqued down they went too far. Then when the lifters pumped up it is holding the valves slightly open? Is that possible?
Still is there any way to verify that the timing chain is set correctly short of taking the timing cover off? That is a huge amount of work.
We ran WOT runs and the O2s read around .925 volts which is the rich side of things right? If they were less then .900 I would guess it might be lean.
We are going to check the rockers torque. Maybe the lifters were drained and when the rockers were torqued down they went too far. Then when the lifters pumped up it is holding the valves slightly open? Is that possible?
Still is there any way to verify that the timing chain is set correctly short of taking the timing cover off? That is a huge amount of work.
