1966 L79 Thermostat hold down, bolts or Studs?

[Nick Mesich]

I have pulled my Thermostat housing as it is rusted badly.

going to Bead Blast it and then paint it with Aluminum Paint.

Currently, there are two studs coming out of the Intake Manifold for the thermostat Housing and the Thermostat Housing is held down by two nuts that get threaded onto these two Studs.

Is this correct?

Also would anyone be able send me some pictures of a correct restored 350Hp engine and engine bay. Close ups would be appreciated.

Slowly Grinding away one piece at a time. Speaking of time.... not much of that free these days.

Thanks,

Nick

[Bill W.]

Re: 1966 L79 Thermostat hold down, bolts or Studs?

Nick,

Your description of your thermo housing is correct. Try to find some Krylon Dull Aluminum paint for it. Check Adams book for pictures of 1966 350 horse motors. Happy painting! Bill

[Nick Mesich]

Re: 1966 L79 Thermostat hold down, bolts or Studs?

Bill in the T & J it states bolts are used and not studs to hold down the Thermostat Housing.

Is the T & J manual incorrect?

I know I have read here that this is the case for some of the info. in the book.

Well I Bead blasted the Thermostat Housing and found that the one ear has a crack in it. I guess I am off to the welders to have that fixed.

Always something.

[Mark P.]

Re: 1966 L79 Thermostat hold down, bolts or Studs?

I had a '65 L79 and studs, not bolts, were correct. Perhaps there was a change from one year to another....

Mark

[Jeff S.]

Re: 1966 L79 Thermostat hold down, bolts or Studs?

Hex head bolts -- special, non-standard lengths (3/8-16 UNC thread) so they won't bottom out in the manifold blind holes.

[Gary S.]

Re: 1966 L79 Thermostat hold down, bolts or Studs?

Is your thermostat housing cast aluminum or steel? I haven't had my 66 327/350 for about six years but, for some reason, I am thinking that my housing was aluminum. Can anyone reference a 66 judging manual?

Gary

[Jack H.]

Re: 1966 L79 Thermostat hold down, bolts or Studs?

The '66 JG calls for bolts instead of studs & nuts on ALL cars (SB and BB) with the description changing based on SB/BB, HP, and aluminum/cast iron intake. Specifically for the L79:

"The thermostat housing is cast iron, painted silver, with the part number 3827369 across the top of the housing. Known original cars use bolts with headmarks of 'TR' 'M' 'CP' and 'NAT' with three radiating lines. Others may exist."

Note the JG does NOT say judges should deduct for the use of stud/nut vs. bolt! The text does a 'crawfish' with the disclaimer 'known original cars' which to an experienced judge is a red flag warning that we haven't seen ALL of the original cars produced in '66 and there may be deviations from the guidelines given in the JG text.... That makes it a judgement call by the indivual judges assigned to Mechanical at that meet.

[Michael H.]

Re: 1966 L79 Thermostat hold down, bolts or Studs?

I think the "others may exist", and "known original cars" refers to the bolt head markings, not the type of fastener. (studs/bolts) I believe just about all of the 66 judges know that there were bolts, not studs, in this location. The 369 housing was used at least as early as 63 and all were retained with bolts. If I were judging, I would only allow full credit for bolts in this location.

[Nick Mesich]

Re: 1966 L79 Thermostat hold down, bolts or Studs?

My Thermostat Housing is Cast and Painted Aluminum color.

The car is the 905th car build for the 1966 model year and the build date is September 8, 1965. A very early car....

Could this be why I have studs and nuts instead of bolts?

[Michael H.]

Re: 1966 L79 Thermostat hold down, bolts or Studs?

Nick,

I suppose anything is possible, and we've all seen some very strange things on Corvettes over the years, but I would have to guess that it's unlikely. If the same housing was retained with bolts for the three previous model years, and for the balance of the 66 model year, it would be odd that some early 66 cars used a different method.

The only difference I can think of for 66 is the fact that it was the first year that the 369 housing was used on a small block aluminum intake manifold. For 63-65, it was only used on iron intake 327 engines and the aluminum intake manifold of the 396. All 327 engines with aluminum intake manifolds used a different housing with two short studs, not bolts.

I once owned a very original 66 coupe that was built in the first week of production. (VIN under 100) While I can't say that I specifically remember that bolts were used, I know I would have noticed and remembered if studs were.

Hopefully, we'll hear from other owners of early production 66 cars.

[Jack H.]

I agree with Michael...

It's very unlikely that your car shipped from the factory with studs and nuts holding the thermostat cover in place vs. hex-head bolts. That system (studs and nuts) WAS used way back however on C1 cars with aluminum intake....

[Nick Mesich]

Re: 1966 L79 Thermostat hold down, bolts or Studs?

Thank you to all for chiming in on my question.

I will be ordering the correct bolts from LIC and change out the Studs.

I hope everyone has a wonderful 4th of July and your celebrations are filled with happiness, lots of Family and Great Friends.

Nick

[Bill W.]

Re: 1966 L79 Thermostat hold down, bolts or Studs?

Nick,

I must have been asleep when I told you studs were correct for your L-79, sorry about that! I would have corrected my mistake sooner, but have been on vacation. Bill