Vacuum leak around intake bolt holes

[Dieselman966]

Stock intake and heads?  Let us know if otherwise.  Are you using the cork or rubber end seals?  When you dry fit the intake, did you use the end gaskets?  When you dry fit the intake, did you use the dry intake gaskets?  How did you verify the intake to head fit?  By sight or feeler gauges?  What did the intake imprint look like on the old gaskets?  Any apparent alignment concerns, like could you see where the intake was impressing on the gasket and did it look uniform?

A longer shot, but did you carefully inspect the intake for cracks or voids?

The heads were machined down .020 and the engine deck was machined down .070. Total was .090. Then had him machine the intake side of the heads .080.  The head to intake transition is real close.  I checked the fit up of the intake while it was out visually.  Everything looked pretty even. Feeler gauges would have been more accurate though.  I am not using gaskets on the ends of the intake. Just a thick bead of silicone to seal it up there. The intake gasket kit I am using is MS 90145.

[Dieselman966]

The intake is an edelbrock ingot from a guy on Facebook. Visual it does not appear to have any cracks.

[superduty]

Is it possible the bolt are bottoming out? Try 2 flat washers on the bolts and retest.

[chris401]

Earlier you didn't see any oil usage. If that is still the case and the runners are sealed I would block off the PCV valve and see if the vacuum leak is still there.

[66FAIRLANE]

I took it for a drive yesterday and it wouldn't shift on it from 1st to 2nd until higher rpm. I'm thinking that I dont have enough vacuum for the modulator now.

Is the modulator or line to it leaking?

[Dieselman966]

Is it possible the bolt are bottoming out? Try 2 flat washers on the bolts and retest.

That's a possibility. They seem like they are turning easy still while I'm torquing them down. I'll give it a try though.

Earlier you didn't see any oil usage. If that is still the case and the runners are sealed I would block off the PCV valve and see if the vacuum leak is still there.

I still dont see any smoke out of the tailpipe yet and I did pull the pcv valve and plug it. Still have the same issue.

I took it for a drive yesterday and it wouldn't shift on it from 1st to 2nd until higher rpm. I'm thinking that I dont have enough vacuum for the modulator now.

Is the modulator or line to it leaking?

I haven't checked that yet. The line looks good but I'll get a new one and put it on there. Maybe its cracked pr split and I cant see it.

[Nightmist66]

Check the angles between the heads and intake. I caught this on my new build during mockup. I verified the block and heads were machined perfectly at 45 and 90°. I knew the problem was the intake. You could see it slightly by eye with no gaskets in place. I dry fit the gaskets and could wiggle the gasket in certain places on the bad side and was fine on the other. I pulled the intake and checked the angles and found one side fine at 45° and the other off by 1-1.3°. I had my machinist mill the angle back by that amount. The intake was used and milled in the past. After another dry fit, I snugged the intake down slightly and checked the gaskets for witness marks all around the ports. Everything looked good.

[66FAIRLANE]

Brake booster?

[My427stang]

Don’t just throw a couple flat washers on there, measure how deep the hole is with a Phillips screwdriver, The idea of bottoming bolt is good but your likely to pull the threads out of the head if you do it by experimentation. Depending on the intake every hole can be different too so be sure to measure all

[blykins]

Depending on the intake every hole can be different too so be sure to measure all

This is a good tip for every fastener used in an engine.  With aftermarket parts, new bolts, etc., it's always prudent to check every single fastener length to make sure you have adequate thread engagement.  The biggest issue I see is with some camshaft bolts, as well as cam thrust plate bolts and oil filter adapter bolts on aftermarket blocks. 

[Dieselman966]

Don’t just throw a couple flat washers on there, measure how deep the hole is with a Phillips screwdriver, The idea of bottoming bolt is good but your likely to pull the threads out of the head if you do it by experimentation. Depending on the intake every hole can be different too so be sure to measure all

I checked all of the bolt holes for length. None of the bolts were bottoming out. 

[Dieselman966]

I cleaned up my intake tonight and I decided to compare it to my stock 4bbl one. The ports are way bigger on the stock one vs. The edelbrock performer 390 one.  I wonder how much this is hurting the performance? Does the edelbrock really work better than the stock one?And could this be contributing to my vacuum leak problem? 

[338Raptor]

These tiny Edelbrock intake ports definitely can’t support very much power.  They may be good for a low RPM 360 or 390 motor but not a high RPM performance motor. Without any mods I don’t know how much power they can support but I would guess 400hp is probably not obtainable with any cylinder head. In fact, maybe 300 hp is more realistic.  Someone else who has more experience with this manifold would know more about this.
If you decide to port match the intake to your gaskets or head port sizes be aware you need to ensure the intake runner cross section (further up inside the manifold) is similar size to your port opening size.  In other words you don’t want a small runner leading to a larger port opening. This would accomplish nothing, the manifold would still be the bottleneck. 

But this still doesn’t explain your vacuum leak.
I suggest placing a straight edge on the manifold to look for warpage or low spots possibly caused my aggressive gasket scraping or a power gasket scraper. 

[Joe-JDC]

Check the bottom of the ports on the intake manifold to see if they are sitting on the head gasket, or block.  Some of the Edelbrock intake manifolds had too much material cast into the ports lower edge, and must be cut off so the intake will sit down properly.  Also, you need to make sure the oil drain back area at the front of the manifold is actually cast into the manifold, so you will not have a oil drain back problem.  As for the manifold actual flow, it is not as good as the stock -H, -F, or -J aluminum Ford intakes.  A couple of the ports only flow around 220 cfm as cast.  Joe-JDC

[Dieselman966]

Check the bottom of the ports on the intake manifold to see if they are sitting on the head gasket, or block.  Some of the Edelbrock intake manifolds had too much material cast into the ports lower edge, and must be cut off so the intake will sit down properly.  Also, you need to make sure the oil drain back area at the front of the manifold is actually cast into the manifold, so you will not have a oil drain back problem.  As for the manifold actual flow, it is not as good as the stock -H, -F, or -J aluminum Ford intakes.  A couple of the ports only flow around 220 cfm as cast.  Joe-JDC

It ended up being the head gasket in the way.  I've never had that  problem before.  Now I know to check that before putting sealant down on the gaskets.  The intake is sitting on the heads nice and even now.