Mopar Muscle Association UK

I would have thought you'd need dynamite to crack a standard big block manifold...I've seen the "corner" cracked off an ally manifold due to overtightening, but never a cast iron one.
...Ivor exits stage left with expression of acute ingrowing toenail while he waits for Blue or Dave to prove him wrong!

Hey I got in first and proved you wrong Ivor!
Yeah I once had a standard 440 intake which was cracked on the underneath,
it took a while to figure out what that problem was!

I wouldn't say it would be impossible to crack one but I have never heard of it happening. Exhaust manifolds yes but intake no. I think a crack bad enough to cause a major leak would be easy to see too.

Usually intake vacuum leaks are due to intake gasket problems or leaks in any hoses conneted to vacuum operated devices such as the brake booster.

My question would be "What makes you think one or more of your cylinders is low on performance?"

A manifold leak would tend to effect the whole engine. What is your problem exactly and have you done a compression test or anything?

Ah! Jon you proved us both wrong!

OK Jon, I'll just go out into the garden and eat worms...

Righto

When that happens I try switching plugs and leads around first. Then do a compression test if needed.
I assume the idle speed, timing and mixture are fine?