The engine is on a stand. New heads on it. ARP Head studs. (and the top row of studs and nuts do not stick up above the intake mounting surface, verified with a straight-edge.)

'98 block. New LS6 intake. New LS6 valley cover. Knock sensor wiring is not installed yet.

When I set the intake down onto the heads, the passenger front and driver rear don't quite touch down. I can rock it between those two corners. Maybe an 1/8".

It might just have a bit of a warp to it, and it might torque down flat. But I suspect that a rib underneath the intake is riding on one of the valley cover bolt heads.

Anybody run into this? Where is the contact point and how do I fix it?

TIA.

 

Mine fits snugg.. check and make sure the knock sensor wire isn't in the way some where.. Also.. did change the coolant tubes? The x style one from the 98 motor won't work, you'll need a 01 & up set.

 

Yep, it's just a bare set-up right now, because I just put the heads on last night.

No coolant pipes (although I have the new style ready to go on)
No kr sensor wires
No nothing....
Just intake and heads. (and valley cover)

 

did u have to notch out the block so the new ls-6 valley cover fits in flat ?

 

Does it look like it sitting on something underneath? or is the intake twisted? Are all the runner gaskets firmly in their groove?

 

I had that problem last night while doing my intake swap to the ls6 manifold. I found my problem to be the knock sensor wire routed over the coolant pipes. I know you said that you don't have these on the motor right now, but maybe the method I used to find the high spot might work for you too. I sprayed the bottom of the intake with some bright orange spray paint that I had, and carefully set it in place. Then once it was sitting where it should be I pressed down on the intake all over and carefully lifted it back out. What I was left with is a nice bright orange spot where my obstruction was. Hope this helps you out.

 

Yep, I had to make that notch in the block. Twice, because the first time wasn't quite enough...

When I finished, the valley cover would sit flush against the block even with the gasket removed. So it's got plenty of clearance with the gasket in place.

 

I can't tell yet, about underneath, because of that foam on each end. I'm thinking about taking that off, and shining a light under there.

The intake doesn't look twisted, but I don't know how you could look at it and tell...

This is without the runner gaskets even on it yet. That may be letting it sit down low enough to ride on a valley cover bolt head. But I don't think the gaskets are going to hold it up enough to eliminate the rocking. I may give that a try and see if it helps.

 

That's a good idea!

I may put a little blob of the kids' playdoh on each of the middle bolt heads (on the valley cover), and mash the intake down and see if one of the blobs gets cut in half....

 

Ok, I found out where the problem is.
It was not touching anything on the valley cover.
Where the hold-down bolts go into the heads, is the problem...

Each hold-down is a plastic tube that the bolt goes through. The tube mates to a shallow hole in the head. All of them except 2, on those there is a small brass tube on 2 opposite corners for positively locating the intake. The holes in the head are smaller on those corners too, because the brass tubes are smaller. That part is ok.

But some of the plastic tubes were scraping their sides on the matching hole in the heads. The hole in the heads is in the intake surface. Looks like where the intake surface was milled, it left a little burr on one side of most of the holes. That's only part of it. The other part is 2 of the tubes are scraping by a little less than a 1/16", there is a flat scraped off the side of those 2 tubes from putting the intake on and off and rocking it. Where the flat was scraped, it left some of the material bunched up a little up toward the intake.

So the holes and/or the tubes need just a little clearancing for the right fit, and I should be good to go.

 

Glad to see that you found the problem. Good luck with the rest of your project.

 

Well.....

I thought I had it figured out. I deburred the openings in the heads. I relieved the mounting posts where they were rubbing. Now the rocking is worse.

Checking the intake with a straight-edge, the center ports stick out just a bit more than the ones on the ends.... Maybe it's made this way so that the bolts will pull it flat. I'll have to check the old one and see if it's the same way.

 

 

The old one is perfectly flat. Measuring across the gasket surfaces. And measuring across the posts.

The new one is bowed. On both side. The center ports stick out more. And the posts stick out more by a similar amount. I'm going to change over the gaskets and try to bolt it down anyway. Hopefully the bolts will pull it down flat and hold it there. I'll test it by trying to slide a feeler gauge under the front and rear port gaskets when I'm done....

 

I torqued it down with no gaskets as a test. It seemed to pull flat.

I was able to slide a .0015 feeler gauge under only one spot, but not far enough in to reach an intake port. So I think it will seal up ok with the gaskets on it.

 

hope it works out for you

 

Thanks.