Hi all,

I've asked this question in the proformance section with not much luck , I didn't know there was this section just for the M motors.

I was wondering how a stock 351M that was in good condition would do with a compression test, I did a compression test on mine which is in a 79 bronco and it only had about 115psi, is this normal for one of these motors or to low.

Ray71.

 

what's most important is that all the cylinders are within about 10% of each other. make sure you have the throttle held open during testing to allow the engine air to compress, and get about 4 pulses on each each reading. 115 isn't too low, but it's no monster either.

 

ya 115 is good my 77 f250 is reading 115-130 and runs just fine

 

Thanks for the reply, i'll give it a try with the throttle open and see how it comes up.

I'm about to bolt some Aussie 302c closed chamber heads on it, from what i've read it sounds like the best thing that can be done for a 351m.
it already has a four barrel vally cover and 650 holly carb.

Thanks again for the reply.

Ray71.

 

"I'm about to bolt some Aussie 302c closed chamber heads on it, from what i've read it sounds like the best thing that can be done for a 351m."

No, I really don't agree. The best thing that can be done for a 351M is to rebuild it as a 400. The Aussie heads are going to give you a high compression ratio that will likely not run on pump gas. Even given the 351M's low 8-1 CR, the Aussie heads will put you over 10-1.

 

the quench heads bring with them some mitigating factors, the chamber turbulence and less timing needed might help keep the planet spinning? only one way to find out. the M/400's usually have a generous deck clearance that might need to be whacked down a bit though, to realize the best effect of the quench chambers.