Cutting Out and No Power above 4000 RPM

[JamesLinder]

Recently my 2000 SS Camaro has developed problem where it loses power and cuts out above 4500 RPM when trying to get to 6500 RPM redline. I replaced plugs, plug wires, air filter, and crank sensor last week and still have the problem.

Since we do not have fluctuating MAP readings when this occurs we are pretty certain the valves are not floating.

I installed a Racetronix Fuel Pump Kit about 6 months ago and it ran fine with the existing injectors (36 lb/hr) where my motor has about 520 hp at the flywheel (383 LS6 stroker).

Two days ago we strapped a fuel guage to the windshield and it turns out fuel pressure drops from 60 psi to 55 psi at WOT.

My car has the fuel pressure regulator in the gas tank with the fuel pump assembly instead of a return line from engine compartment.

My question is whether or not this drop in fuel pressure is to be expected or if this means the pump is not performing correctly?

I did not test pressure at WOT when the pump was new, only after the high RPM issues began recently.

Thanks, Jim

[edcmat-l1]

A 5 psi drop won't do that. I would have to drop much more than that. Need to post a data log of it doing it.

Can you determine when it started doing this? Was it all of a sudden? How does it feel when it does it? Like someone turning off a switch, or like it noses over?

[JamesLinder]

It is not like turning off a switch, but sort of like it is missing out, but no back firing. Engine keeps running but no power and exhaust does not sound normal. You would think valves are floating but mechanic says the MAP would not hold steady if it was the valves floating out. The comp cams dual valve springs only have about 10K miles on them.

[edcmat-l1]

Could be valve springs, could be a miss, without a data log it's all a guess.

[tune time]

Recently my 2000 SS Camaro has developed problem where it loses power and cuts out above 4500 RPM when trying to get to 6500 RPM redline. I replaced plugs, plug wires, air filter, and crank sensor last week and still have the problem.

Since we do not have fluctuating MAP readings when this occurs we are pretty certain the valves are not floating.

I installed a Racetronix Fuel Pump Kit about 6 months ago and it ran fine with the existing injectors (36 lb/hr) where my motor has about 520 hp at the flywheel (383 LS6 stroker).

Two days ago we strapped a fuel guage to the windshield and it turns out fuel pressure drops from 60 psi to 55 psi at WOT.

might be a stupid question but does the car still have catalytic converters on it if so you might have hurt 1 and the back pressure is too much above that rpm and will not
Let it rev. Just a thought not seeing the car its hard to know

My car has the fuel pressure regulator in the gas tank with the fuel pump assembly instead of a return line from engine compartment.

My question is whether or not this drop in fuel pressure is to be expected or if this means the pump is not performing correctly?

I did not test pressure at WOT when the pump was new, only after the high RPM issues began recently.

Thanks, Jim

[tune time]

Might be a stupid idea but dos it still have cadilitic
Converters on it, you may have hurt one of
Them and it is makeing to much back pressure
Above that rpm and wont let it rev. And that
would also change the exhaust sound

[JamesLinder]

Please see if you might notice what is causing the problem; I'm thinking the new fuel pump (6 months in service) is not delivering volume at high RPM now.

2nd log attached is closed loop run with my usual settings whereas the first one attached was experimenting with open loop with MAF meter zeroed out and long term fuel trims disabled.

[JamesLinder]

several broken valve springs; evidently the comp cam springs were not up to the task; we are going with some "Extreme" valve springs supplied by Patriot Performance, now Promax Performance, out of Alabama. Should have car back on road Saturday afternoon. One cylinder had no compression at all, but thank God the only damage was to the springs. Since these were dual springs the inner springs kept the valves from hitting the pistons on the cylinders affected.

[LSxpwrdZ]

BTR springs... only springs on the market without a single failure!

[Badassbird]

X2 for BTR. The patriots will only hold correct pressure for 5-10K miles on an aggressive cam.

[JamesLinder]

They admitted that their gold springs would not last long so we went with their Extreme Springs this time, which are supposed to be good to 7000 RPM on higher
lift cams. I did take a serious look at those offered by Texas Speed but have not
read anything yet on BTR. Sounds like I will need to look at these next time around.
Thanks.

[bigfatls6]

who makes the BTR springs?

[DrLoch]

http://www.briantooleyracing.com/springs.html

[KLUG'S SS]

who makes the BTR springs?

Brian Tooley Racing. He's a sponsor over on LS1Tech.

[KLUG'S SS]

I was a little late on that. lol.

[DrLoch]

I was a little late on that. lol.

Beat ya... Passing on info is always a good thing

[LSxpwrdZ]

Brian designed his own spring kit. I personally tested his retainer design for it's strength and the lock/keepers broke in half and the retainers never broke!

His retainers locks/keepers are the lightest on the market for superior valve control and precision machined so that the seat and the retainer actually fit the inner and outer springs! You didn't get that with PRC or Patriot spring kits! Worth it to take a look at his kits as there really are NONE on the market that compete with the attension to detail that he has put into them!

[JamesLinder]

Thanks James. I was in a rush and bought mine before I received your advise. Patriot Performance went under and was bought out by ProMaxx Performance (still located in AL); their rep said their "Extreme" springs I bought are manufacturered by Triple B. Are you familiar with them? When mine need replacing next time I will definitely go with your recommendation; I realize you know LS motors quite well. Oh, I have a tune that is finally starting well. I had to open up the throttle body butterfly more so that at warm idle in park my IAC now runs between 30 and 40. Appears I was running out of range before opening the butterfly more.

[JamesLinder]

The new springs have more space between the coils and therefore do not coil bind at lifts above 0.6. I believe the compcam springs my original builder used were always border line acceptable since I was running slightly over 0.6 lift even before I switched cams. I learned a costly lesson about valve springs and that knowledgeable builders for LS motors are not that easy to come by. Seems like there a quite a few differences in building a solid LS motor versus the old style motors.

[LSxpwrdZ]

Awesome sounds good!

I am not familiar with Triple B. I had heard Patriot went under as well and were emerging as a different brand but didn't know that brand name.