340 Rebuild "Musts"

younggun2.0 said
If running iron heads he won't want 10.5:1 compression on the street. That is why I recommended 9ish:1 for pump gas.

yellow rose said
Really? I have been running measured 10.5:1 and higher on iron heads and pump gas since 1982. My personal car is 11.08:1 (actual measured) on iron heads, on pump gas. If I change the head gaskets it will be 11.25:1 and still run on pump gas.

The compression ratio/iron head/street car/pump gas myth deal should have been long dead but evidently, it's still alive and well.

It's like we are stuck in 1986 again.

DOWN WITH THE MULLET.

I hate general statements like "oh if you got iron heads you can't run more than 10:1" or something. There is so much more that goes into it. You have to know your cam specs, IVC mainly. You have to know your chamber type. Head material. Spark plug. Distributor/coil strength. How good is your tune. And the one thing everyone seems to forget, elevation. There's so much that goes into it. Telling someone "oh don't run more than 10:1" when they got a cam in there with say 300+ advertised duration and an IVC in the mid 70's is a great way to make a dog engine.

At my elevation, 10:1 compression, even with a mild cam with 60* IVC and mild overlap of 54 degrees. Give's me a whopping 145-150 psi cranking pressure. When really max "safe" cranking pressure on an iron head motor is closer to 185 psi on 91 pump. And yes. 35-40 psi is a ton of power. So there is soooo much more to it than "you can't run more than". In fact I'm looking at going solid roller. And if my cam ends up where I think it will, I'll probably end up running close to 11.5:1(static) on an iron head motor. And be very safe on 91. I could even run more, we got 94 pump gas around here.