Thermostat housing bolt head marking

[Kenneth H.]

The bolt and stud on my 1970 LT1 thermostat housing are incorrect. I was wondering what the correct bolt head marking is (TR, M or RSC are my available choices), and also the specs (i.e. length, thread, etc.) for both the bolt and the stud.

Any help would be appreciated.

Thanks.

[Kenneth H.]

Re: Thermostat housing bolt head marking

Can anyone help me with this?

[Kevin G.]

Re: Thermostat housing bolt head marking

Ken
Here are two pictures from my 72. Hope it helps?

[Kenneth H.]

Re: Thermostat housing bolt head marking

Kevin, thanks for the pictures. They help a lot. It appears that the bolt and stud that I'm looking at are correct for the application. I'm wondering, though, whether the bolt head marking was the same for the '70 as for the '72. The bolt heads I'm looking at are "TR", "M' and "RSC" bolts. If the bolt head configuration isn't judged then it doesn't matter, but if it is judged, I'm sure that one of the judges will probably chime in at some point.

Thanks.

[David S.]

Re: Thermostat housing bolt head marking

Ken,

Any chance you have a measurement on both the thermostat housing bolt and stud? I have a couple bolts (different head marks TR, RSC) but they are different lengths. Trying to determine what's original. I have a June built 70 LT1.

Thanks,
Dave

[Joe L.]

Re: Thermostat housing bolt head marking

The bolt and stud on my 1970 LT1 thermostat housing are incorrect. I was wondering what the correct bolt head marking is (TR, M or RSC are my available choices), and also the specs (i.e. length, thread, etc.) for both the bolt and the stud.

Any help would be appreciated.

Thanks.

Ken------



The short "bolt" is actually a flanged stud.

The long bolt was trimmed (i.e. non-indented head) bolt of SAE grade 5 (3 radial lines). The one pictured with a "C" headmarking is quite common. However, many others were probably used. This was a VERY common size bolt, was probably used by the MILLIONS during the period, and undoubtedly had several suppliers. "M" is another widely seen headmark for this bolt. I'm sure "TR" and "RSC" are other possibilities. I think any period-correct headmarking should judge OK. So how do you know what bolt was originally supplied on your engine? The only way to know, for sure, is to have the known-orignal bolt.

[Kenneth H.]

Re: Thermostat housing bolt head marking

Joe, thanks for the info. It answers most of my questions. I was wondering if the bolt and stud pictured below look correct.



thermo housing bolt and stud 1.jpgthermo housing bolt and stud 2.jpg

Sorry about the out of focus on the second image.

Thanks.

[Joe L.]

Re: Thermostat housing bolt head marking

Joe, thanks for the info. It answers most of my questions. I was wondering if the bolt and stud pictured below look correct.



[ATTACH=CONFIG]58570[/ATTACH][ATTACH=CONFIG]58571[/ATTACH]

Sorry about the out of focus on the second image.

Thanks.

Ken------



Yes, they appear correct to me.

[Kenneth H.]

Re: Thermostat housing bolt head marking

Thanks, Joe. I'll go ahead and get them.

[Gary B.]

Re: Thermostat housing bolt head marking

First and second picture is 1970, C02 build date, it is a "C" bolt and stud.
Third picture is a 1970, G07 build date. It is a "D" bolt.
Fourth picture is a 1969 Nova, 350, 2-barrel sitting there. It's a "C" bolt.
Gary Bosselman

70-C05-Build.jpg70-C05 Stud.jpg70-G07 Build.jpg69 Nova 1.jpg

[Kevin G.]

Re: Thermostat housing bolt head marking

First and second picture is 1970, C02 build date, it is a "C" bolt and stud.

Gary Bosselman

[ATTACH=CONFIG]58579[/ATTACH]

Hi Gary, Looking at this picture I notice some silver paint on the stud/nut area. It, the upper part of the stud, appears to have been masked or covered prior to the silver manifold touch up. Is there a reason for leaving this one stud natural?

[Gary B.]

Re: Thermostat housing bolt head marking

Short answer is yes. Early 70 LT-1 engines were painted differently, more hand work, touched up with brushes, etc. As the years went by, they were not so critical. But, I think the real reason, (my theory) was on other engines, this stud was used for the battery ground terminal and alternator mounting bracket. So, I think the factory masked the stud, regardless if it was a LT-1 engine or a Nova engine. It was probably easier telling the line workers to mask all studs, than to do this series of engine, but not this series. Again, my theory.

Photo is the 69 Nova, really an nice low mileage original car. Sits in good company with about a dozen other low mile C3 Corvettes.
Gary

DSCN5018.jpg

[Joe L.]

Re: Thermostat housing bolt head marking

Short answer is yes. Early 70 LT-1 engines were painted differently, more hand work, touched up with brushes, etc. As the years went by, they were not so critical. But, I think the real reason, (my theory) was on other engines, this stud was used for the battery ground terminal and alternator mounting bracket. So, I think the factory masked the stud, regardless if it was a LT-1 engine or a Nova engine. It was probably easier telling the line workers to mask all studs, than to do this series of engine, but not this series. Again, my theory.

Photo is the 69 Nova, really an nice low mileage original car. Sits in good company with about a dozen other low mile C3 Corvettes.
Gary

[ATTACH=CONFIG]58627[/ATTACH]

Gary------


The stud was painted on my original owner 1969 300/350. It's also been painted on every other cast iron intake Corvette small block I've seen.

[Rich P.]

Re: Thermostat housing bolt head marking

Did not see any lengths given, The long bolt is 2" measured from under the head and the short bolt/stud is 1" measured from under the head

[Kenneth H.]

Re: Thermostat housing bolt head marking

Rich, thanks for that info. I completely forgot that I also asked for the specs on the bolt and stud.