I'm looking to buy a 79 Ranger F150 with a 351m. Seller can't tell me much about this engine except that it "runs good" but does have an oil leak. I'm looking for an engine with decent MPG but don't want to sacrifice all of the performance. The specs on crate motors seem pretty good vs the specs of a 30 year old engine. Anybody have opinions on this subject? The truck is a short bed with C6 tranny.

Thanks,
Shawnyboy

 

A truck motor of that vintage will be a complete dog.. low compression heads and a useless camshaft the barely lets the motor breath. But if you swapped on earlier heads and upgraded the cam it would kill a 302.. even a crate motor, there is no replacement for displacement.

 

Well there aren't that many good candidates for replacing the 351M heads. They are practically identical to the 2V Cleveland head except for a small difference in chamber volume (351M/400, all: 78cc; 351C-2V: 76cc). The smaller chamber 351C-4V heads aren't very good candidates due to the huge ports which will mismatch the intake manifold and not be suited for anything but high end power.

One interesting possibility is using the imported Australian Cleveland heads, these have smaller chambers and the 2V ports.

People typically add an aftermarket aluminum 4V intake to these engines with a mild performance camshaft. Check the 335 series Forum.

Here's a link to a company importing the Australian cast iron heads:

Aus Ford Parts - Aussie 351 Cleveland Specialists

And the same company's super nice aluminum version:

Aus Ford Parts - Aussie 351 Cleveland Specialists