351 block numbers

[don4331]

Ok so you just answered the question I got on here to ask lol. I got a set of 351 heads, guy said they were clevelands, but they ended up being 351m or 400 heads. Which is fine, but I have to get a special intake to make those work on my 351w block right?

Yes, you need a 351 Clevor intake e.g. https://www.speedwaymotors.com/Edelbrock-7183-351-Clevor-Ford-RPM-Intake-Manifold,23646.html

There are also adapters to go from Windsor manifold to Cleveland heads, I've never use them so I can't comment on how well the work.​

And you will need to do some minor machine work:

The water jacket hole in front of the head needs to be filled:​

The cheap way is to machine (drill) the square hole round and then insert a Welch plug (aka freeze plug).​

Slightly more expensive is to tap for a pipe plug. Then install pipe plug (using loctite red) and machine the pipe plug flush with the surface of the head.​

Next, you tip the head up and machine (drill) a hole in the head on the intake side to match the Windsor water jacket style - most people use an intake manifold gasket to scribe the shape onto the head and cut to that.​

Lastly, lay a head gasket (Windsor) on the head and make sure all the oil holes line up. If they don't a little "porting" needs to be done to ensure oil drains back from heads to oil pan.​

You need Cleveland rockers, custom push rods.

Good luck.

Note: 351M/400 heads were from the days of 8.0:1 CR ('76 351M had 145hp, 400 a whopping 160) and have some pretty open chambers so you want pop up pistons in most cases. They like a good set of headers as the exhausts are far more restrictive than intake.​

Back in '80s, the Street Boss was good for ~50hp on my 302 Bobcat Wagon.

 

[pjtoledo]

some info on the water passages that need modified.
scroll to the last page.

EngineBuildingTipsSpecs.pdf (ford.com)