Formula934

iTrader: (4)

The heads are right out of the box, no work done.

Also sorry for the confusion but the PTV issue is not just an issue of lift but duration. After the setup was put together with 1.6 on both intake and exhaust, one of the pistons on one of the cylinders showed signs of printing from the exhaust valve, so 1.5s went on instead of 1.6s. The SR setup would allow preciseness in terms of where my clearances are.

BizZzatch350

iTrader: (33)

I agree with Pat, I have a set of Dart Pro-1s on my LT1, and out of the box they weren't very impressive, nice casting but I would say a ported stock casting like Pat or Joe runs would be a better head. I had the Dart's ported and they turned out to be a decent set of heads, I plan to reuse them on my 398. I bet those AFRs are a really nice casting but the car could yield some really great results if those heads were gone back over by a competent head porter. I agree swapping heads at this point wouldn't be worth it for you, but the money for the solid roller may be better invested in to those heads you already have to reach your power goal with hydraulic roller set up you already have. I think there is a lot of power left in the heads of that car.

joelster

You say that one of the pistons showed signs of printing from the exhaust valve. Did you check that one spring? A weak spring can become unstable at high rpm and lose control of the valve. Typically it happens on the exhaust side. As the engine wears down and the timing chain begins to stretch the valve events lag behind from when the chain was tight. That can play a role as well, especially if it was on the tight side to begin with.

The only way to properly check ptv clearance is to mock everything up and use checking springs and a dial indicator. When I checked my motor every cylinder was different, every valve was different. Not by a lot, but when you are going out to the thousandth of an inch tiny variances come into play. You may have had one cylinder that was just on the tight side and one overrev caused it to kiss a piston. If you have an adjustable timing set try it with the cam advanced 2 degrees and see how much the ptv clearance opens up.

What springs are you running? What are the cam specs?

Formula934

iTrader: (4)

Cam specs are on the first page of post. As for the springs, I have to check on that, they are a dual spring rated to .700 lift.

You could be onto something about advancing the cam 2 degrees.

joelster

You can only do so much by moving the cam around. If you advance it to open up the exhaust clearance it will tighten up the intake clearance. Make sure that both are acceptable when you move it.

BADHAWK51

iTrader: (1)

I'm running a similar cam as the op :249/257 .612 107LSA HR. I spoke with AI awhile back and they told me the gain would be minimal of switching over to a solid since I was already running a large HR and still running the stock pcm with it's 7,000 rpm limit.


The cost of switching would not justify the gain.