HELP - Intake Manifold to Cylinder Head Gap

[chengny]

Thanks for looking.

At final assembly of a stock 350 rebuild. Everything is coated, lifters pre-loaded so it's time to close the valley.

Dropped the intake manifold down onto the block and this was immediately apparent (please see the images):

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The gap is huge. Those are standard Sawzall blades in each corner. Even with a cast steel manifold stacked on top, they are not even pinched. I'm guessing maybe a 3/32" gap.

The gasket set is a Mr. Gasket 5820 Ultraseal (nothing unusual, same thickness all around as a Felpro set).

The heads are remans from Dover in Georgia - they always supply a great reman. So I can't imagine the faces are short. Matter of fact, this particular set was on another engine I rebuilt and the fit was normal. Pulled them after only 200 miles or so and stored them till now.

I know that it has become standard procedure to discard the rubber gaskets (that ones that seal the manifold to the block) and just use silicone. But I have never had to eliminate them to get a good fit and always use them. It looks like this time they are not getting used.

I will be cutting them out with an x-acto knife to see if that closes the gap.

But first, I will wait and see if anyone has any thoughts as to why that gap exists.

 

[350runner]

Looks like those heads were milled... Did they sell the heads as performance heads?

 

[chengny]

No, they were nothing special - just a standard remanufactured head.

Also, I've mounted them between another stock block/manifold group before (and run them for a couple hundred miles).

They fit up with normal clearance and had no leakage issues, so I feel confident they haven't had much if anything taken off the faces.

I don't know - we'll see if the gap closes up without the block gaskets.

This the first time I have used Mr Gasket Ultra Seal intake set - usually I use Felpro - but they seem to be the same thickness. And the block end gaskets are about the same as well.

 

[HotRodPC]

DOH !!! Yep, I'd have to be thinking the block was decked or the heads were shaved.

 

[89Suburban]

Aww

Maybe you can dig up some measurements somewhere so you can tell if the block has been milled without having to take anything apart.

 

[Tyger13us]

DOH !!! Yep, I'd have to be thinking the block was decked or the heads were shaved.

both...

 

[Tyger13us]

No, they were nothing special - just a standard remanufactured head.

Also, I've mounted them between another stock block/manifold group before (and run them for a couple hundred miles).

They fit up with normal clearance and had no leakage issues, so I feel confident they haven't had much if anything taken off the faces.

I don't know - we'll see if the gap closes up without the block gaskets.

This the first time I have used Mr Gasket Ultra Seal intake set - usually I use Felpro - but they seem to be the same thickness. And the block end gaskets are about the same as well.

id never use the end rubbers anyway,, they always leak....black silicone on the ends.....

 

[crazy4offroad]

If you have an extra set of completely stock heads you could compare to see if the reman shop recon'ed a set of 1 degree angle mill heads without noticing. What's the casting numbers?

 

[Tyger13us]

If you have an extra set of completely stock heads you could compare to see if the reman shop recon'ed a set of 1 degree angle mill heads without noticing. What's the casting numbers?

that is possible?,, but i really dont think so,, he said he ran them heads before with the same manifold...

on my motor the block was decked and the heads shaved,, "thats how i got 11:1 with flat top pistons",, with a dry fit,, no gaskets all the angles were right,, but the space at the ends were only around .120,, so there was no way ya could use end gaskets of any kind,, not even the ole cork ones which id use any day,, but ya cant get um anymore... this was on my motor!!

so black silicone is about the only thing that will work for the ends......

the other thing that was a PITA was the bolt holes for the intake wouldnt line up right,, so had to use a drill bit the next size bigger than the OEM hole size,, cant remember what it was,, but i had to bore the intake holes out to the next size to get the intake bolts started...

once i got um all started and tightened up a lil bit then torqued,, it fit perfect...

 

[chengny]

Thanks for the feedback - and sorry about not getting back right away.

Summary for those who may be interested:

Using an X-acto knife, I carefully separated the rubber end seals from the IM/CH gaskets and removed them from the block.

Using a good Brown & Sharpe vernier caliper the thickness of the rubber - at the pads - was gauged.

Found that the end seals provided with the 5820 Mr. Gasket Ultra Seal Intake Manifold set are considerably thicker than normal.

The Mr Gasket seals miked out at .0040 - .0043" thick at the pads.

A Felpro end seal was miked. It was found to be .0023" -.0025" thick at the same pads.

After the rubbers were pulled, the manifold was set back down. The head/manifold gaskets remained in place. The clearances were again observed.

There was no gap at all between the manifold face and cylinder head. The gap between the bottom of the manifold and the block was gauged with feelers.

It was minimal - about .0040" - .0050" - depending on the point of measurement.

The Felpro end seals were installed as normal, and the manifold was set back down (with no weight on top).

Clearances were observed:

The bottom of the manifold rested firmly on both the front and back seals.

There was a gap of about .0015" at the cylinder head to manifold. This was possibly due to the design of the Ultra Seal Gaskets. Unlike regular gaskets, they have a raised silicone bead around each air intake port and the coolant passages.

The intake manifold was then torqued down to spec and checked for seal - seemed tight. It was not possible to insert a .0001 feeler anywhere along the manifold to head interface.

It would appear that the added .0015 thickness of the Mr Gasket rubber seals at the block was causing the excessive gap at the manifold to head clearance.

Whether this would have closed up when the manifold was torqued down remains unkown.

 

[HotRodPC]

Thanks for the feedback - and sorry about not getting back right away.

Summary for those who may be interested:

Using an X-acto knife, I carefully separated the rubber end seals from the IM/CH gaskets and removed them from the block.

Using a good Brown & Sharpe vernier caliper the thickness of the rubber - at the pads - was gauged.

Found that the end seals provided with the 5820 Mr. Gasket Ultra Seal Intake Manifold set are considerably thicker than normal.

The Mr Gasket seals miked out at .0040 - .0043" thick at the pads.

A Felpro end seal was miked. It was found to be .0023" -.0025" thick at the same pads.

After the rubbers were pulled, the manifold was set back down. The head/manifold gaskets remained in place. The clearances were again observed.

There was no gap at all between the manifold face and cylinder head. The gap between the bottom of the manifold and the block was gauged with feelers.

It was minimal - about .0040" - .0050" - depending on the point of measurement.

The Felpro end seals were installed as normal, and the manifold was set back down (with no weight on top).

Clearances were observed:

The bottom of the manifold rested firmly on both the front and back seals.

There was a gap of about .0015" at the cylinder head to manifold. This was possibly due to the design of the Ultra Seal Gaskets. Unlike regular gaskets, they have a raised silicone bead around each air intake port and the coolant passages.

The intake manifold was then torqued down to spec and checked for seal - seemed tight. It was not possible to insert a .0001 feeler anywhere along the manifold to head interface.

It would appear that the added .0015 thickness of the Mr Gasket rubber seals at the block was causing the excessive gap at the manifold to head clearance.

Whether this would have closed up when the manifold was torqued down remains unkown.

End gaskets can certainly do that. As suggested, problem handled by using Black RTV on he ends for a universal fit. So it's all good now. Up and running yet???

 

[chengny]

Haha, thanks for asking but, no - it's not in yet. It's still on the stand.

This is a long term project - and I work slow.

I'm converting a base Sierra to a Sierra Classic. One required change is the grill and headlight assembly. I have a NOS grill and the proper radiator support on hand.

I thought I'd pull the old grill and rad support - then drop the motor in while they were out of the way.