SBC Thermostat housing bolt Pattern question

I have a strange question. I was prefitting the Mr Gasket thermostat housing on my Fenton 3 deuce SBC manifold and it doesn't fit. The bolt pattern on the housing is just a little bit to narrow by about 1/64". I don't understand it. I thought Chevy used the same size thermostat and housing for many years from the W motor to the Gen II blocks. Am I wrong?

Anyone ever encounter this before? Is there a simpler answer to this or should I just oblong the housing bolt holes? I want to make sure i am not missing something.

Thanks for your help on this guys.

 

Kwalatee, with a capital K! File the holes gently.

 

Only the finest Chinese parts...

 

I do not think it is the housing. I compared the bolt pattern on the manifold to a Fel-Pro gasket and saw the same thing. The housing and the gasket bolt patterns are identical. I think the housing is OK, I think the quality issue is with the NOS late 60's manifold, unless there is another thermostat housing out there with a wider bolt pattern.

 

Read my sig...

 

Try a Chrysler gasket!
I have a generic "remote T-stat housing" with Chevy bolt pattern on my intake.
I can't use a Chrysler gasket for that one...
Don't know why yours would be but...?

 

My money is the housing. is your manifold GM?

 

My Manifold is a NOS Fenton 3 Deuce manifold. It was something my neighbor bought for his small block back in the late 60s but never used it.

 

1/64 th of an inch ?

Take the manifold to the best welder in town and have them weld the holes up. This us very complicated and requires the planets to be perfectly aligned within several days of the summer solstice. DO NOT TRY THIS AT HOME, you could possibly cause irreparable damage ti yourself and the environment. Them take it to a machine shop that has HAS CNC MACHINES, have them face the manifold and redrill the holes. They will also need to be tapped using ancient traditional tools or the new bolts will cause your manifold to crack and send your engine to the depths of the abiss.


Three strokes of my magic file would fix it.

All joking aside, it very well could be a manufacturers "second" sold 40-50 years ago. Does it matter ?

 

I know that would be the perfect solution, but for as little as it is off, oblonging the holes in the housing might be the easiest solution and still allow for proper sealing of the gasket.

Someone on the HAMB has offered to let me try an original housing. That will tell me if it is the housing or the manifold.

Experimenting on a $13 housing is a lot easier to handle than experimenting on an NOS Fenton manifold.

 

My experience with the cheapo die cast chinese housings is that they tend to corrode through and start leaking. If they ever seal at all.

 

What he said, and they start leaking in about three months!
I had one and heard about them turning into the sacrificial zinc of the system and when I took it off all that was left of it was the chrome shell!
Send it back and go get a cast iron/or OEM factory one.

 

The bolt pattern is 3.25 "

But since its made in communist China by children who are using the metric system, look at how they may have rounded .

3.25 is 82.55 mm

1/64 is 0.015625

0.45 mm is 0.01772

0.55 mm is 0.02265

They rounded up to 83.00 mm

 

That particular housing may last one summer,then sitting next winter it will be leaking because it warps.Sorry,but it is a pos.

 

Fair enough. I have never used a cheap one like this. I will be spending the extra $$ to get a cast iron one as long as I know it will work. Will be comparing what I currently have to an original one soon. Will report back what I find. I really hope the housing and the gasket I have (sold separately) both have the wrong bolt pattern.

31 Vicky: Thanks for the measurements. Will take a look at it tonight.

 

Your welcome !

But, Good Gravey brother, its only a 1/64th of an inch. File the freaking thing and bolt it together.

 

Bingo!!! This happened to me recently with a two year old Mr. gasket T-stat housing, I am lucky I was close to home because the engine lost most of the water. Absolute junk. Buy a cast iron one and be on your way.

 

That's 1/64th divided by 2 or approximately .0078 per hole !

 

Here's what happened to one I had on my T. The hole is on the top section. This housing was less than a year old. I still use one, but I carry a spare. You can also see an area where the chrome scrapped off. The housing is plastic! Mr. gasket product. Sorry for the crappy pic.

 

i have never had an o-ring one not leak, now i save the stock GM ones for when i need them.

 

Well I thought this was pretty funny.

 

I have one its new nice and shiney in my tool box and that is were it has been for awhile, never use them they are no good ....but they are shiney, LOL

 

I will be buying a proper OE type of housing, one that has enough material around the bolt holes to open them up a little. You guys have convinced me not to use the Mr gasket or anything like it. I have a billet specialties one with an o-ring on another motor and it has been great. No leaks and it has been on and off several times. They are just too big to go under the 3 deuces. Thanks for all the opinions I appreciate the help.

 

1/64th (.0156") , or .0078" per hole, really? Most of them the bolt holes are sloppy enough that they could be off by 1/16 and it would still bolt on. Just hard to imagine that it would be that precise!

 

I barrowed an OE housing and it too was too narrow. It is without a doubt the manifold. I used some calipers and got a real measurement. The manifold bolts are 0.28" too wide for the housing. Just ujnder 1/64 on each side. I am just going to oblong the bolt holes until it fits. Going to order a cast iron unit. Thanks everyone.

 

What kind of measuring is that?

.280"

1/64" equates to .0156" what is this .280"

Tig

 

That's not 1/64 there hamber.
That's over 1/4 inch
Big difference

 

Oops. The measuring was fine, it was just shitty typing . That should ahve been .028".

 

Use the magic file.

 

There is always the possibility that Fenton didn't use a Chevy thermostat housing on the intake for some reason or another including that the Chevy housings of the period didn't have the right angle to clear something.
I've bought more than one chrome Chevy thermostat housing over the years that had elongated slots in it new. Over time I threw most of them away too a they almost always have the issues that the other guys mentioned above. Personally I'd use a good factory cast iron or aluminum one, take the rat tail file to it to make it fit and be done with it. My ot truck with it's Perforemer, fabricated welded valve covers and what not has the ugliest thermostat housing you ever saw but it doesn't leak.