This is a hypothetical question.

If a car has a kit with a 8# pulley (or psi if it's a turbo) with stock heads, what would happen if the ported heads (or lets assume larger heads) were installed. The boost psi should drop (maybe to 6psi).

Wouldn't that be easier on the pistons (hypereutechtic)?

If someone kept the bottom end stock and got some 210 AFRs with 76cc's and 8-10#s, wouldn't that be more 'forgiving' on the stock pistons?

Obviously forged is the only way to go, but if the boost pressure drops... isn't that easier on the ringlands?

I hope this question isn't to lame, just a conversation picked up in a bar.

 

It would not be any easier on the pistons. It would be worse because you would be making that much more power. You are still making alot of boost but your getting it out quicker so it is not showing the extra pressure. It is kind of hard to explain, but the hypers are a weak point in the lt1. You would still be stressing them beyond what they can take. You are making your motor a more efficient air pump, but you're still pumping in the boost.

 

With the turbo you will still be making 8 psi with the ported heads.

 

This is hard to accurately answer.

Actually by increasing the efficiency of the induction/exhaust system, you are thereby increasing power. This may decrease boost due to the lessened flow restriction.

Less boost should mean less chance of detonation, but the increased power is still adding stress to the engine. With this being said, the bottom end may not live any longer. Cast & hypereutectic pistons are not necessarily weak (HP wise), but will not survive detonation. This configuration may help a stock LT1 or LS1 live a longer life on a stock bottom end, but is not a guarantee.

In reference to boost, keep in mind that a supercharger pulleyed to make 8# boost on a mild 350 motor may achieve around 450 hp. Put it on a built 500hp motor & it may not make any boost (with the same pulleys) due to the increased pumping efficiency of the better motor.

A turbo, unless undersized for the motor, will likely still make boost as it is being driven harder by the added exhaust volume, Also the boost was likely regulated by a wastegate, not physical turbo size.

 

(Bill) BlownBird01 - That is a crazy (and very long) story you have on your website! Unbelievable you have gone through all of that. Do you still have the turbo? Your website indicates the 'old turbo set-up'.

Special thanks to all for your help. I figured I'd ask the people who know there stuff!

So the cylinder pressure is constant regardless of efficiency, but the boost pressure (indicated) will drop. As you said, 8#s will be 8#s (cylinder pressure) but the boost gauge will not indicate 8#s due to an increased intake efficiency and will indicate a reduced pressure.

 

think of the heads as a regulator. when you port them, you're letting more air through, which drops the pressure in the "pre-regulator" side. That much more air is entering the cylinders, which makes more power, which in-turn puts MORE, not less, stress on the pistons.

 

That was my old turbo tech stuff. The "old turbo setup" was the original as it came from the factory turbo stuff. I then spent a bunch of money trying to improve the turbo tech system, like a larger turbo, new intercooling system, and downpipe, but I always ran into problems with the system. I wa forever chasing exhaust leaks, especially on the header to head gaskets, then when I tried to up the boost, which resulted in high exhaust manifold pressure, and even more exhaust leaks, I netted a blown head gasket at the track. I ended up stretching all the lower head bolts, they were loose upon dissassembly, they were replaced with ARP hardware. Then I went at it again, but this time both head gaskets (Felpro 1074) were seeping coolant from the ends.

I never got any good times with this kit, even though it put some decent numbers on the dyno. I decided to sell and am working on a twin setup that should be done in a few months before spring. I'm hoping this twin setup will be the turbo system that I had been hoping to have on the car for the last 4 years.

Bill

 

Oops, sorry SmoknZ, it was very late last night when I commented on the tough trials. My eyes must have been crossed with Blownbird01. Nonetheless, I really feel for your pain. I really wish I could fab my own set-up but Cali will not permit it and will not give it CARB approval. There is no way I could engineer something (even with less valve overlap) and have it pass smog. I'm so glad the politicians can do the thinking for me so I don't have to Can't wait to get Feinstein and Boxer out of office!!!