Ls2 403 with L92 heads looking for improvement
01-20-2019, 03:06 PM
#62
I thought I'd bring this back up from the dead... but the L92 valves are killing you too. Swap to the LS3 hollow-stem and you'd pick up 15HP with no other changes. They weigh a lot and it's hard to control them uptop with 5/16" pushrods and just regular .660" valve springs.
The torque on the motor is still garbage though... 466 is not good. I would expect to see something closer to 500 with that cam. But, I'm willing to bet the 4" bore is hurting you. Moving to a 235-245cc Cathedral port head would probably yield more power/torque on a 402.
Because the cam is a good cam for a 4" stroke LS3-headed motor. And it's not really that large. You guys just need better tuners. But the heads don't flow anywhere near the same on a 4" bore vs 4.065" bore.
The torque on the motor is still garbage though... 466 is not good. I would expect to see something closer to 500 with that cam. But, I'm willing to bet the 4" bore is hurting you. Moving to a 235-245cc Cathedral port head would probably yield more power/torque on a 402.
Because the cam is a good cam for a 4" stroke LS3-headed motor. And it's not really that large. You guys just need better tuners. But the heads don't flow anywhere near the same on a 4" bore vs 4.065" bore.
01-22-2019, 02:17 PM
#63
I thought I'd bring this back up from the dead... but the L92 valves are killing you too. Swap to the LS3 hollow-stem and you'd pick up 15HP with no other changes. They weigh a lot and it's hard to control them uptop with 5/16" pushrods and just regular .660" valve springs.
The torque on the motor is still garbage though... 466 is not good. I would expect to see something closer to 500 with that cam. But, I'm willing to bet the 4" bore is hurting you. Moving to a 235-245cc Cathedral port head would probably yield more power/torque on a 402.
Because the cam is a good cam for a 4" stroke LS3-headed motor. And it's not really that large. You guys just need better tuners. But the heads don't flow anywhere near the same on a 4" bore vs 4.065" bore.
The torque on the motor is still garbage though... 466 is not good. I would expect to see something closer to 500 with that cam. But, I'm willing to bet the 4" bore is hurting you. Moving to a 235-245cc Cathedral port head would probably yield more power/torque on a 402.
Because the cam is a good cam for a 4" stroke LS3-headed motor. And it's not really that large. You guys just need better tuners. But the heads don't flow anywhere near the same on a 4" bore vs 4.065" bore.
Last edited by handyandy496; 01-22-2019 at 02:24 PM.
03-04-2019, 11:35 PM
#65
I don't think that's quite accurate.
I have a similar combo.
An LS2 408 with CNC ls3 heads, fast 102 intake and high compression.
I was using a camshaft with 6 degrees of overlap and made 460rwhp
When I swapped to a 12 degree overlap cam power shot up to 505rwhp
The point of no return in regards to overlap depends on combination.
On a 400-416 with those heads is around 20 degrees.
Once you go beyond that, the power increases get smaller and smaller while driveability becomes way worse.
You will see camshafts for square port stroker engines don't usually go beyond 25-26 degrees overlap because of diminishing returns.
12 degrees on mine drives almost like stock so I'm upgrading to almost double the overlap.
I have a similar combo.
An LS2 408 with CNC ls3 heads, fast 102 intake and high compression.
I was using a camshaft with 6 degrees of overlap and made 460rwhp
When I swapped to a 12 degree overlap cam power shot up to 505rwhp
The point of no return in regards to overlap depends on combination.
On a 400-416 with those heads is around 20 degrees.
Once you go beyond that, the power increases get smaller and smaller while driveability becomes way worse.
You will see camshafts for square port stroker engines don't usually go beyond 25-26 degrees overlap because of diminishing returns.
12 degrees on mine drives almost like stock so I'm upgrading to almost double the overlap.
03-05-2019, 11:16 AM
#66
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I thought I'd bring this back up from the dead... but the L92 valves are killing you too. Swap to the LS3 hollow-stem and you'd pick up 15HP with no other changes. They weigh a lot and it's hard to control them uptop with 5/16" pushrods and just regular .660" valve springs.
I would also experiment with the Mid-Length Runners very inexpensive and easy to swap in/out.
I bet it would pick up 15-20 from 5000-6500 RPM+
Is a graph available to post?