Ls2 408 stroker
The valve springs being too soft is surprising to me personally. Valve float can be spotted on a dyno chart very easily, and your chart doesn’t look to me as if valve float was occurring. But valvefloat would explain why your tuner couldn’t throw more timing at it. Hold up on the head gaskets first. Lots of guys here run 14:1 or more with E85 as daily drivers.
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it could be a variety of things but thanks for the suggestions.
It's definitely not the injectors as they were removed and cleaned and tested good.
I will update again once I have more information.
It's driving me crazy.
It's definitely not the injectors as they were removed and cleaned and tested good.
I will update again once I have more information.
It's driving me crazy.
On The Tree
Joined: Jun 2019
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From: HTown, Texas
A buddy of mine was chasing a dead cylinder on his heads/cam GTO, it was down on power like yours. He eventually determined it was a break in the wiring to one of the injectors. He repaired the wire and gained like 60whp on the dyno. LOL
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Will mention it
Originally Posted by Che70velle
The valve springs being too soft is surprising to me personally. Valve float can be spotted on a dyno chart very easily, and your chart doesn’t look to me as if valve float was occurring. But valvefloat would explain why your tuner couldn’t throw more timing at it. Hold up on the head gaskets first. Lots of guys here run 14:1 or more with E85 as daily drivers.
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Looks like that on my torque curve
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If anything I'd go with a thinner gasket and get quench as close to the .030" range as possible.
But going to a thicker gasket is just a band-aid to cover what is likely a bigger problem.
KW
Last edited by KW Baraka; Sep 3, 2019 at 01:44 PM.
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Another update.
After a conversation with my tuner the issue is valvetrain instability.
He checked the valvetrain and the springs cannot handle the lift and the valve train is floating so we need to lower the lift.
The valves are staying open at high rpm and causing the power loss.
We feel it might be because of the heavy pro street rockers.
This is also causing the converter to act a lot tighter because engine is way down on torque too.
So I might have to change out the rockers and go back to a standard 1.71 ratio.
However the PAC1209X spring should be able to control them because they are rated to .750 lift.
I said this and I was told that's what it can handle as a maximum value but it depends on combination.
Open pressure is at 450lb and seat pressure is at 170lb
So tomorrow I should know for sure what the culprit is causing these issues.
He is also having a spring tester delivered from one of his colleagues to measure lift.
You never know the springs may be faulty.
I also looked at the dyno sheet today and with the old 236/244 camshaft, engine was actually making 510rwhp and 900Nm torque.
For some reason I am no longer pissed off.
After a conversation with my tuner the issue is valvetrain instability.
He checked the valvetrain and the springs cannot handle the lift and the valve train is floating so we need to lower the lift.
The valves are staying open at high rpm and causing the power loss.
We feel it might be because of the heavy pro street rockers.
This is also causing the converter to act a lot tighter because engine is way down on torque too.
So I might have to change out the rockers and go back to a standard 1.71 ratio.
However the PAC1209X spring should be able to control them because they are rated to .750 lift.
I said this and I was told that's what it can handle as a maximum value but it depends on combination.
Open pressure is at 450lb and seat pressure is at 170lb
So tomorrow I should know for sure what the culprit is causing these issues.
He is also having a spring tester delivered from one of his colleagues to measure lift.
You never know the springs may be faulty.
I also looked at the dyno sheet today and with the old 236/244 camshaft, engine was actually making 510rwhp and 900Nm torque.
For some reason I am no longer pissed off.
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They are already a hard spring,
If I get a stouter spring does this mean my open pressure and seat pressure will be higher too?
On The Tree
Joined: Jun 2019
Posts: 184
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From: HTown, Texas
Another update.
After a conversation with my tuner the issue is valvetrain instability.
He checked the valvetrain and the springs cannot handle the lift and the valve train is floating so we need to lower the lift.
The valves are staying open at high rpm and causing the power loss.
We feel it might be because of the heavy pro street rockers.
This is also causing the converter to act a lot tighter because engine is way down on torque too.
So I might have to change out the rockers and go back to a standard 1.71 ratio.
However the PAC1209X spring should be able to control them because they are rated to .750 lift.
I said this and I was told that's what it can handle as a maximum value but it depends on combination.
Open pressure is at 450lb and seat pressure is at 170lb
So tomorrow I should know for sure what the culprit is causing these issues.
He is also having a spring tester delivered from one of his colleagues to measure lift.
You never know the springs may be faulty.
I also looked at the dyno sheet today and with the old 236/244 camshaft, engine was actually making 510rwhp and 900Nm torque.
For some reason I am no longer pissed off.
After a conversation with my tuner the issue is valvetrain instability.
He checked the valvetrain and the springs cannot handle the lift and the valve train is floating so we need to lower the lift.
The valves are staying open at high rpm and causing the power loss.
We feel it might be because of the heavy pro street rockers.
This is also causing the converter to act a lot tighter because engine is way down on torque too.
So I might have to change out the rockers and go back to a standard 1.71 ratio.
However the PAC1209X spring should be able to control them because they are rated to .750 lift.
I said this and I was told that's what it can handle as a maximum value but it depends on combination.
Open pressure is at 450lb and seat pressure is at 170lb
So tomorrow I should know for sure what the culprit is causing these issues.
He is also having a spring tester delivered from one of his colleagues to measure lift.
You never know the springs may be faulty.
I also looked at the dyno sheet today and with the old 236/244 camshaft, engine was actually making 510rwhp and 900Nm torque.
For some reason I am no longer pissed off.
9 Second Club
Joined: Feb 2004
Posts: 818
Likes: 215
From: VA
408 has always been a lack luster performer for what ever reason. You really have to sort the combo to get them to produce. There is no reason its not capable of 500-520 at the wheels through an auto. To be making 450 with this set up it for sure has a dead hole or 3. Did you relocate coil packs? Possibly have the wiring on one bank *** backwards? Injector wiring all good? Fuel pump is keeping up on E85? At 13.5:1 it should easily be making 440-450 torque.
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From: Central Cal.
Depending on the spring, Higher open pressures don't always mean much higher closed (rest) pressures