I'm sure this question has been asked before but my thread searches have come up empty. Anyway, has anyone tried 351C 4V heads on a 351M or 400? I know that there are spacers available to make this swap work. My question is how well do they work. The reason I'm considering is I have a set of quench 4V heads just sitting around. Rather than spend more money on a set of Aussie heads, I thought I'd look into putting these heads to use. Will the factory dished pistons clear the big 4V valves?

 

Look up port stuffers. The 4V heads are not real good for low RPM operations. They are great for a high RPM mud bogger engine.

 

It helps to know the application before giving advice. Depending on the cam, factory pistons should clear just fine but I would recommend aftermarket replacements.

 

Yeah, there was only a dribble of info: Low compression "factory dished pistons", A "351M -OR- 400" kind of pointed to the low end arena... He sure won't get any quench with the 4V heads and factory slugs.

Finding threads with "port stuffers" will find a lot of info re 4V heads here. Kind of a back door search.

 

The old Hot Rod magazine article about building a 400 said that a supercharger would be needed to fill the 4V heads on a 400. Of course a custom manifold would have to be built.

 

For years magazines have been printing bogus info about Cleveland 4V heads, I guarantee a supercharger is not required to make good use of these ports.

 

The added displacement and long rod length of the 400 motor makes better use of the 4V ports, than a 351C. I ran a set of D1AE-GA 4V closed chamber heads on my 400 several years ago. I had flattop pistons and about 10.3:1 static CR. I used Weiand adapter plates and an Edelbrock Performer Intake for the 351C. I had a Crane H278-2 cam, that had an Intake Valve Closing angle of 72 degrees ABDC to help keep the compression down.
This motor ran good on 91 Octane in California.

The Weiand spacers are no longer available, but Tim Meyer sell spacers from Price Motorsports.

The other thing that is required is a distributor extender, or a Mallory Unilite Distributor which will allow the distributor to clear the raised manifold.

So to add everything up, you need a 351C-4V Intake Manifold, a set of spacer plates, and a distributor extender, or Mallory distributor.

The CR with factory dished pistons will be about 9.4:1. This should be OK with a stock or similar cam, even without quench. It will require at least 91 Octane fuel.

Port stuffers will help the head flow at low lifts. There is no problem with valve/piston clearance at reasonable lifts.

 

Tim Meyer has 1.72 CH Hyper pistons that would work well with 62.8cc quench chambers. They are made for Aussie heads, but will be great for 4V heads. These will produce the quench effect.

 

danlee,

What did you use for exhaust?

 

I used a set of Sanderson shorty headers made for a 351C in a '53 F100.