Thermostat housing / water outlet

[Sabesimpson]

Hi all!
So I’ve tried everything to get this housing. Tried all the parts stores, even ordered the “77-81 trans-am 4.9L” housing.
Anyone here have a good part number?
This $20 part is the hold up.

Every one I got the bolt pattern was to wide.

Thanks for the help!!

[BobBray]

The Pontiac housing fits 351's with the thermostat on the front of the water crossover. A 1965 should have a crossover with the thermostat on top. Does your truck use a thermostat housing with a vertical outlet or a horizontal outlet?

[jerrspud]

oh dang. So a normal SBC water outlet doesn't fit?

[Sabesimpson]

Correct it is aluminum horizontal

[Sabesimpson]

Small block Chevy does not fit it is to large. Bolt pattern is off by about 1/4” on each. And the gasket is to large to hold the t-stat in place.

[James]

I had the same problem with my thermostat housing. I had repaired it with Devcon 10760 Gray Titanium Putty, 1 lb. Can. Be sure to bead blast the housing before using it. It is the most chemical and temperature resistance version they make.

https://www.amazon.com/gp/product/B00065TM08/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

I just realized the price of that stuff really went up.

I included a before and after pictures of my housing.

[BobBray]

Can you tell me what the distance is between the bolts? Center to center.

[James]

can you tell me what the distance is between the bolts? Center to center.

3" c-c.

[BobBray]

I found this one for an older Pontiac, but the outlet is more vertical:

https://www.rockauto.com/en/moreinfo.php?pk=819081&cc=1350469&pt=10337&jsn=1638

[Sabesimpson]

Correct 3” on center

[Sabesimpson]

I found this one for an older Pontiac, but the outlet is more vertical:

https://www.rockauto.com/en/moreinfo.php?pk=819081&cc=1350469&pt=10337&jsn=1638

Hi! What vehicle did you look up for this?
Thanks.

[James]

Hi! What vehicle did you look up for this?
Thanks.

According to Rock Auto it fit:

PONTIAC ACADIAN 1968-1971
PONTIAC BONNEVILLE 1959-1970
PONTIAC CATALINA 1959-1970
PONTIAC FIREBIRD 1967-1969
PONTIAC GRAND PRIX 1962-1970
PONTIAC GTO 1964-1970
PONTIAC LEMANS 1966-1970
PONTIAC TEMPEST 1961-1970
PONTIAC VENTURA 1960-1961

With a 389 cid or the 400 cid engine.

I don't know if it will fit the GMC V6.

[BobBray]

It all depends on which water crossover you have. The later Pontiac thermostat housing with the wider bolt spacing fits my '67 351.

[Sabesimpson]

Thanks! My cross over has the housing sitting on top at this point if vertical I will try to Mach up a hose. I just need the 3” in center bolt holes

[Sabesimpson]

Here is a shot of the cross over

[Sabesimpson]

Update….. I was able to match up a housing at NPD in Ventura!
Now I found an oil leak coming from up top and running down the top of the bell housing. Smh

[Prowbar]

Update….. I was able to match up a housing at NPD in Ventura!
Now I found an oil leak coming from up top and running down the top of the bell housing. Smh

Good job on the housing.

Some thoughts regarding oil leaks:
1. Rear freeze plug in the camshaft bore... Inaccessible unless you have the motor out. Had this on my old 305E.
2. Valley cover gasket. Easy to replace.

[Sabesimpson]

Thanks! The investigation starts tonight!

[Sabesimpson]

Prowbar,
Investigation complete! You were correct rear freeze plug @ camshaft bore. Oddly, it looks like someone replaced it. Guess i will be pulling the motor sooner then i wanted.

[Prowbar]

Prowbar,
Investigation complete! You were correct rear freeze plug @ camshaft bore. Oddly, it looks like someone replaced it. Guess i will be pulling the motor sooner then i wanted.

Interesting. One check you can do before pulling the engine is to check if the camshaft drain hole is clear.

In the last cam journal, the closest one to the freeze plug, there is a small hole drilled (about .150") longitudinally in the journal to relieve the oil that gets trapped behind the camshaft galley and freeze plug. These can also get clogged with sludge and junk.

Remove the intake manifold and valley cover, then turn the engine so the drain hole is facing upwards. With a small screwdriver or drill bit, you should be able to poke it through.

Having it clogged or at least, close to clogged, build up excessive pressure causing the freeze plug to leak.

Hope this helps.

[Sabesimpson]

THANK YOU so much for that info that will save some time i hope. Any contacts on engine gasket kits? (Complete) I think i want to eventuality pull the motor any way paint the engine compartment and the engine.

[Prowbar]

Here's a set on Rockauto. Price is pretty good. https://www.rockauto.com/en/catalog/gmc,1965,1500+series,5.0l+305cid+v6,1419409,engine ,cylinder+head+gasket+set,5416

You still need a couple of additional gaskets: the oil pan gasket, valley cover gasket, water pump gasket, and timing cover gasket, as these are not included in the set for some reason.

Good luck.