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contraption22
05-27-2014, 10:42 AM
Hello all.

The later DOHC heads have a divorced thermostat housing. It is a separate casting from the intake manifold, vs the early heads having the thermostat housing integrated into the intake manifold.

Does anybody know if the thermostat housing from a late head will bolt on to an early head?

Thanks,

Mike

Pat
05-27-2014, 12:32 PM
In for answer...

turbo84voyager
05-27-2014, 01:46 PM
My guess is yes because you can bolt up the old manifold with the integrated housing to the new head but I can confirm tonight I have a later thermostat housing and a early DOHC intake with the integrated housing. I also might have a solution to eliminating the coolant cap on top of the housing for those who are using a stock radiator. I have a aluminium outlet sitting on my door step so when I get home I will compare that as well.

Justin

contraption22
05-27-2014, 01:59 PM
On a suggestion by an ingenious friend of mine, I am going to pick up a housing gasket for a later head to see if it matches the face of the early head.

84omni
05-27-2014, 07:23 PM
They do bolt to the early head but the late style intake has a different bolt pattern and will not work with the early head.

turbo84voyager
05-27-2014, 07:31 PM
I just verified by laying a new style thermostat housing gasket on a early intake where the thermostat is and it all lines up.

contraption22
05-27-2014, 07:36 PM
Thanks all!

wallace
05-28-2014, 07:05 AM
So you can cut the housing off of the old manifold and use the newer tstat all on the older head?

contraption22
05-28-2014, 08:12 AM
That's my plan.

Well kinda. It looks like I will be needing a custom manifold for my car. So using the later tstat housing would eliminate the need to cut off and re-use that portion of the original manifold.

rbryant
05-28-2014, 01:09 PM
That's my plan.

Well kinda. It looks like I will be needing a custom manifold for my car. So using the later tstat housing would eliminate the need to cut off and re-use that portion of the original manifold.

I think the 420a t-stat housing can also work but I would have to check.

I actually have a full custom t-stat housing that I had made if you are intersted. It uses a standard GM waterneck so you have lots of options with it.

Overall I decided to weld a flange on the #4 freeze plug so that I don't have to deal with the interference between the manifold and the housing. I also don't have to run a coolant line over the intake manifold. I changed the headgasket to match the T3 coolant flow pattern to compensate for the coolant going across the head.

-Rich

contraption22
05-28-2014, 01:28 PM
Thanks, Rich.
I already ordered used later model Tstat housing for it. If it doesn't work out, I will certainly explore other options.