906 heads have slightly oversize end holes for studs

[sprice]

Correct me if I am wrong, only front and rear exhaust manifold studs are in the water jacket? My problem is those holes for the studs are quite loose. I was having problems with timing and seepage at those bolts so tore it down to fix. Went through 3 different kinds of thread sealer with varying success. However with the engine at operating temp, the pressure in the system pushes out antifreeze on three out the four points. I have chased the threads, cleaned and dryed the holes which is when I noticed the front and rear are very loose. I know that I didn’t dry the holes before applying thread sealer, and that’s one reason it didn’t work.

It’s not 7/16”. Seems to be in between 3/8 and 7/16”. Heads are on and in the car. Was hoping not to have to tap out to 7/16” as the filings will likley end up in the cooling system.

Anyone had this problem and is there such a thing as slightly oversize bolts or studs or other solution?

 

[Davea Lux]

Try putting some hard drying Permatex (the stuff in the tube) on the threads and let it sit overnight, with the coolant drained.

Dave

 

[mopar440]

Teflon tape and permatex?

 

[sprice]

I tried the Permatex twice however first time didn't let it dry and then didn't knead it in the tube. I did get a new tube thinking mines was old but I don't think I let the hole dry enough. I'm a little shy on Permatex right now. I went and got some Loctite 545 Hydraulic Sealant to try. After writing this post I am wondering if they are slightly larger to allow for the sealant material back in the day.

 

[Big_John]

Why don't you just drill/tap/install Heli-coils and be done with it?

Pretty easy to do... Goop the new stud up with Permatex and you are done.

 

[sprice]

Why don't you just drill/tap/install Heli-coils and be done with it?

Pretty easy to do... Goop the new stud up with Permatex and you are done.

Will give that a try. Just don't like the sloppiness in the hole.

Thanks.

 

[68PK21 440.6bbl]

Are you double nutting them or just installing the studs in finger tight?

 

[sprice]

I didn't have studs however am installing now and double nutting.

 

[narnone]

We just had the same issue with 906 heads going on a 1978 440.
There is plenty of meat around those holes.
So here is what we did:
Ordered Dorman ST-39 studs.
These are 7/16-14 x 3/8-24. They come 12 in a box. We only needed one, so gave the rest to my builder. $20.00
Dorman-Rockford Catalog
Drill bit: You need a letter bit: "U" which is 0.3680. If you don't have one, go a little smaller.
Here is the chart:Tap and Drill Size Chart - American Fastener Technologies Corporation
Because it was in the water jacket, we used J-B weld Extremeheat. 3oz is 10.00
https://www.jbweld.com/product/j-b-extremeheat
We should have the engine running next week, but it's tight and I doubt it will leak.

 

[5wndwcpe]

As far as metal shaving in the coolant go, you can slip a piece of panty hose over the inlet neck on the radiator, then install the hose. Bring the car up to temp, shut it off and let it cool down. Pop the hose off and all of the contaminants will be trapped in the panty hose.

Then go out and buy your wife a new pair.
...or, yourself if you're into that sort of thing.

 

[mopar440]

As far as metal shaving in the coolant go, you can slip a piece of panty hose over the inlet neck on the radiator, then install the hose. Bring the car up to temp, shut it off and let it cool down. Pop the hose off and all of the contaminants will be trapped in the panty hose.

Then go out and buy your wife a new pair.
...or, yourself if you're into that sort of thing.

Dang thats a good idea!

 

[70bigblockdodge]

Pop the hose off and all of the contaminants will be trapped in the panty hose.

That's better than my lint trap screen, thanks.
All of those holes go to water on a big block. I would retap to next larger size, heli-coils are great, but sealing against pressure is not their strong suit.

 

[5wndwcpe]

That's better than my lint trap screen, thanks.
All of those holes go to water on a big block. I would retap to next larger size, heli-coils are great, but sealing against pressure is not their strong suit.

Agreed