Now I have no Exhaust, how far can I go without burning a valve?

[KYJ10]

I just have the manifolds on, and need to get a couple of miles to the exhaust place. If I take it real easy, will I be OK. This engine has 0 miles as I just rebuilt her. Dennis

[AMC258]

if absolutely nothing else, I'd find a junk rig matching yours, pull the pipes down, and cut yourself some shorties, even that may be a little risky.

[89grand]

I don't see there being any problems.

[RWC]

I've done it.

RWC

[mark]

ive got open headers on my bb chevy.gonna be that way till i get it legal.i still drive it around the shop and in the woods in the back.am i in danger of burning a valve too?
why does this happen?

[dnixon]

I think the big thing is when you shut if off to keep the cold air from hitting the hot valve. I think this is the biggest problem. A kid at my high school used to run straight headers and when he would shut his engine off he would jump out and put coffee cans on the ends of them to keep the cold air out. Just an idea.

[mark]

that makes sense.thanks

[Stuka]

You can drive with long tube headers with no problems really. But straight exhaust manifolds is a bad thing.

From what I know cold air doesnt hurt them. Its the lack of backpressure that causes it. It makes the engine run much leaner in carb'ed setups. EFI isnt effected so much. When the engine runs lean it will cause the combustion temps to get much higher. This is what causes exhaust valves to burn. If you step up your jets in the carb to make it run back in stoich it should be ok. Long tube headers have tuned back pressure for each cylinder (unless they are the cheapo tri-y ones). So If you plan on doing it for a while, I would definately jet the carb to run correctly.