Hello, I posted a question about my problem a few months ago and finally got a chance to investigate. I have a 351 Cleveland block (year unknown) and 400 heads from a '74 Cougar which bolted together fine.
As soon as I tried to install an Edelbrock 2V Performer the bolts would go into the holes at just enough of an angle that the bolt hits the top of the manifold on the outside edge, but the threads "bite into" the inside edge where they exit the bottom of the intake. In other words the heads seem to be sitting on the deck at an odd angle. I can finger tighten them halfway on before they get stuck, and the force required to go much further would likely crack the manifold.
Tonight a buddy and I tried lots of things. We first measured deck height, spot on at 9.206". We then tried HIS 4V heads and intake, perfect fit. His 4V heads even lined up with my 2V manifold bolt holes, the runners were obviously mismatched but the bolts went in very easily. We also measured the 400 heads against my original 351M heads which we know are unmilled. They were identical, so I assume they weren't milled either.
It seems to me then that this head/block combo is incompatible, even though everyone I've read about or talked to said they worked fine together.
The easy thing to do will be to find a pair of 2V Cleveland heads and have them machined, take my Crane springs, locks and retainers from the 400 heads and be happy. Before I do that, does anyone have any experience that might be helpful to me here?

Thanks in advance,

Bob
'78 F-150 Explorer
Arlington, TX

 

Are you trying to install a manifold for a 400 on the Cleveland?

Have the Cougar heads been milled excessively? A machine shop may have some dimensions to check. When you mill off the head you have to mill the manifold to fit. A machinist will have these specifications.

The head surfaces are at right angles (90d) from each other on all 351M/C/400 heads.

 

Thanks. No I'm aware that I'd be off by a mile with an M motor intake, it's definitely an Edelbrock 351-2V Performer. It came out of the box unmilled and lines up straight with the my buddy's 4V heads. My heads don't seem to have been milled, but it's almost as if they were milled at a slight angle?
From what you say, the M and C heads are seamlessly interchangeable. I'll take them to the machine shop for measurement, I do have a reserve pair to have machined...

As always, thanks for the help!

Bob

 

You are using old gaskets between all those parts (block/head, head/manifold) when testing the fit, right? Just checking.

Sounds like those 400 heads might have been milled incorrectly (i.e., not square). If the head is milled correctly, the bolts will be offset toward the inside edge of the intake holes (center of the engine), but straight.

Two more tests to verify the problem:

1. Try a stock iron 351C 2V manifold on the 400 heads on your block.

2. Try both the stock and Edelbrock manifolds on the 351M heads on your block (if you are absolutely sure they have not been milled).

Also, even though the Edelbrock manifolds are usually good pieces, I have seen a few that exhibited larger-than-OEM tolerances.

 

Yes the heads are interchangeable. I have a '72 400 and a '78 351M head on my '71 351C as we speak and everything bolts up fine. Your heads have been milled.

 

Thanks Bubba. I'm with you on all that. My aquisition of that C block is a long story, but basically resulted in me not having the ford intake or the C heads that came with it. The second test you mentioned is key then, I need to clean up my nasty 250,000 mile 351M heads and bolt them on for alignment. Everything points to those 400 heads being crooked.
Yes, we are using the (crushed) gaskets and test torquing the head bolts to do these experiments. I'll put new ones in when we feel we have a better fit.

Again thanks for your ideas,

Bob

 

just pointing out the obvious but have you cleaned the threads on the bolts and run a tap into the holes? and the bolts go into the "tough" holes without the intake in place?

 

Success! Thanks to Eric, Bubba, grclark & 67 F250 for the suggestions. I got up nice and early and wire brushed, scraped and air blasted the grimey M heads I had on the scrap metal heap. After test-torquing them on the block, I set the manifold in place...perfect. The 400 heads were certainly the problem, someone milled them (crooked as far as I can determine!). I'll be at the machine shop tomorrow after work to drop these off and get them machined.
I'll undoubtedly be back with more questions, thanks again!

Bob

 

just because they've been milled doesn't make them bad. even if they have been "angle milled". there are those who know more about it than i do that "angle mill" the heads for various reasons, mostly to gain HP. does the inake bolt to the 400 heads off of the block? like in a mock-up situation? if they do bolt up are the bolts looking like they are straight in the holes of the intake? is it possible with a small mirror to see how the ports are matching up? or maybe take the valves out and feel from the bowls? what i'm getting at is that you can have the intake matched to the heads if you want to go that way.