Manifold & Head Fitment

[Wolverine]

I actually started this post in relation to another regarding intake manifold and carb replacement.

It seems to me there are at least a couple of important intake manifold to head fitment issues:

1. Matching angles of the heads to the manifold. Not sure what the angles are SUPPOSED to be, or how much of a tolerance there can be taken up by the gaskets.

Also, the heads also have to be square to the manifold.

2. Placement of the manifold when placed onto the heads. It seems to me the bolt holes should be virtually perfect.

Do you guys have tips/rules to follow to assure there is a good fit between manifold and heads before everything is tightened up and the RTV is dry on the front and rear of the block?

 

[eddyw]

Hi,

Recently changed on my 351C (2V heads with 4V manifold (cast iron original Ford manifold removed).

Replaced by (purchased from Mustang Unlimited):

Edelbrock intake manifold "performer-4V" EDL2665 (at 40Nm torque)

Carb.Street Avenger 670CFM 4V (electric choke) H80670

Intake manifold gasket set MS96012 70/73-351C 4bbl

It fits very well, only a small adjustment to do with the carburetor lever (it hit just to the manifold, you can also resolve this with a thin spacer).

Engine running at 04/2013, car is now for the paintjob and soon totally built up, hoping for an end at 05/2013.

Eddyw

 

[c9zx]

I actually started this post in relation to another regarding intake manifold and carb replacement.

It seems to me there are at least a couple of important intake manifold to head fitment issues:

1. Matching angles of the heads to the manifold. Not sure what the angles are SUPPOSED to be, or how much of a tolerance there can be taken up by the gaskets.

Also, the heads also have to be square to the manifold.

2. Placement of the manifold when placed onto the heads. It seems to me the bolt holes should be virtually perfect.

Do you guys have tips/rules to follow to assure there is a good fit between manifold and heads before everything is tightened up and the RTV is dry on the front and rear of the block?

A lot of things need to be considered. Was the block decked, were the heads milled, has the original intake been milled, what the finished dimensions of a new intake are compared to original. With the heads bolted on, test fit the intake and measure the gaps at the front and rear and at the port at the top and bottom of the runners/ports. This will give you an idea about the need to mill the intake to fit the engine or if the intake has already been cut to much to fit properly (usually the first case). In some cases both the sides and the ends of the intake will need to be milled. While the mating surfaces of the head and intakes do not have to be perfectly parallel the do need to be within the crush distance of the intake gasket or a vacuum leak will occur, usually at the bottom where it will draw vaporized oil from the lifter galley. It is all a geometry exercise. If you want to grasp what is happening mak a large, rudimentary scale drawing of the block and heads. Measure the distance between the top and bottom of the ports and bolt holes from left head to right head. Then take an exaggerated amount off the deck of the block or the face of the heads. Now take the measurements again and compare them to the first set of measurements. It will be clear what happens. Chuck

 

[Wolverine]

It will be clear what happens. Chuck

I understand what will happen.

I am looking for a document that tells me:

1. What to measure.

2. What to measure with.

3. Do my measurements tell me:

a) I should have a good fit.

a1) What size head and manifold gasket should I be using.

b) Manifold needs to be milled this much.

c) Block is not decked...do not pass go, except go back to machinist.

d) Heads need work...do not pass go, except to machinist.

e) Whatever else needs to be done.

As we use older and older parts, from a variety of sources(especially those of us with thin wallets, or just plain cheap) we are trying to match up heads, blocks and manifolds that may have already been touched by at least 2 mechanics each.

I read TONS AND TONS of "THE BEST 351C" tech guides, but have not found anything on this...old complaint.

 

[c9zx]

It will be clear what happens. Chuck

I understand what will happen.

I am looking for a document that tells me:

1. What to measure.

2. What to measure with.

3. Do my measurements tell me:

a) I should have a good fit.

a1) What size head and manifold gasket should I be using.

b) Manifold needs to be milled this much.

c) Block is not decked...do not pass go, except go back to machinist.

d) Heads need work...do not pass go, except to machinist.

e) Whatever else needs to be done.

As we use older and older parts, from a variety of sources(especially those of us with thin wallets, or just plain cheap) we are trying to match up heads, blocks and manifolds that may have already been touched by at least 2 mechanics each.

I read TONS AND TONS of "THE BEST 351C" tech guides, but have not found anything on this...old complaint.

I did not intend to annoy you. Since you understand, I won't bother you with further unhelpful explanations. May the force be with you. Chuck