Stripped intake holes in Champion aluminum heads

[tminer]

I bought them used around 2003 from a serious racer and pretty sure they'd been off and on a few times. Had to have them cleaned up from latest turbo dinner. I'm inclined to helicoil (.562") all 10. Once done, OK to use 32 ft-lbs? I don't remember and don't have in my notes what I used when I built motor back then.

 

[CS99]

Get some stainless thread inserts.

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[bison]

I bought them used around 2003 from a serious racer and pretty sure they'd been off and on a few times. Had to have them cleaned up from latest turbo dinner. I'm inclined to helicoil (.562") all 10. Once done, OK to use 32 ft-lbs? I don't remember and don't have in my notes what I used when I built motor back then.

Pics of stripped holes?


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[tminer]

I think maybe part of my problem may have been a bad torque wrench. I noticed yesterday that the ratchet is kaput. I also may have galled the threads based on recent research. I used a cordless 1/4" impact driver to remove the bolts.

I did drill and tap the passenger side head for Helicoil yesterday, but here are pics of front 2 driver's side. I did chase threads and used ARP moly lube with 1.5" 18-8 allen head cap screws and extra .125 thick washers.

 

[tminer]

Not extra washers. I also did some research on torque, most of which seems to be geared to when bolt snaps, but looks like 32 ft-lbs is reasonable, slightly more than the 30 figure I found to be the proper number. Bearing in mind that I generally know just about enough to be dangerous!

 

[earlbrown]

Heli-Coils will be fine. Just install them straight and correctly. The bolts are 3/8" so they aren't the least bit stressed holding down an intake.

The end result will be better than when the heads were new.

 

[tminer]

Thanks.

 

[tminer]

Even without gaskets the intake will not sit low enough to get bolts on both sides. Even eyeballing it's obvious it's not low enough. No obstructions that I can find and just a bit off. I have Cometic head gaskets if that's a factor as to loosening head nuts if that's an option. But thinking of enlarging manifold holes to 9/16 since they are already oversized at ~1/2.

Does anyone know the angle of the bolt holes in head relative to the manifold mounting surface?

 

[captndave737]

Sounds like the mating surfaces on the intake need to be milled.

 

[tminer]

That reminds me that I forgot to look at port alignment before drilling out holes. The manifold was recently removed and no changes made except drilling and tapping holes for vacuum lines.

 

[Pronto]

That could very well be why they stripped.

 

[Warp6]

Use a fixture to drill and install helicoils, if you can. This will help prevent crooked holes.

 

[tminer]

Yes, I do now believe that this mismatch and my failure to recognize it led to my cross threading the bolts. And also that eyeballing the tapping and relying on tap to follow the hole was not sufficiently accurate.

They are so close and the way they install pulls them down due to the bolt angles. It's the final resting place that matters. Everything was machined to align ports. Machinist used a 1200 gasket set in the process. Can't swear to it, but pretty sure that I installed the heads and intake as a set, which I suspect may be part of my issue. I did have to rap on it with a rubber mallet to break it loose.

So today I'm stripping the plenum and injectors to take a look at port alignment. Have an angle gauge on the way and an old iron head to measure and compare bolt angles. Try and find engineering diagram with factory spec and see what I can find, make or have made to use as a drill/tap guide.

 

[earlbrown]

45* on the flange.

 

[tminer]

The flange is 45 from end rails, but bolt is 15 from being square to flange. Big Serts kit plus their tap guide on way. Just need to make a jig to hold the guide.