Thermostat housing on a LD 340 intake

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Michael Siple

Michael Siple

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Went to put a thermostat housing on a intake I have and intake uses a 7/16 bolt . Housing I have to put on uses the smaller 3/8 bolts. Need a housing that uses the bigger bolt. Anyone point me in the right direction. Thought they were all the same but I'm wrong again. Thanks -Mike
 
Someone drilled & tapped your holes oversize, either drill the housing oversize, or fix the holes....
 
You must be talking about the head sizes of the bolts- bolts are sized by the shaft diameter. Unless you meant a 5/16 bolt?
Anyway, LAs had two different size thermostat housings that are not interchangeable, a larger diameter one that was used up until the mid '70s, and a smaller diameter one that was used from the late '70s onward. but to my recollection, they still used the same size bolt...
Are you sure the LD340 didn't have stripped bolt holes that were drilled out oversize?
 
Or was it drilled and tapped for a heli coil and the coil came out with the old bolt?
 
went out to double check - 3/8" bolt drops right in - 1/2" bolt will not start. 7/16" bolt threads smoothly. Other intakes I have - all 3/8". T stat area a little rough - don't laugh @ this old intake - it can clean up fine. Not likely I'll find a housing that takes a 7/16" bolt. I bought 2 intakes - performer rpm & this LD 340 from a member here - can't remember who.

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Run a stud, use a washer and bolt under it, thermostat housing should for over it and have enough stud to start a nut. Work it from there.

Red neck fix.

Or you can weld it shut and start the hole over again…..
 
rumblefish360 said:
Run a stud, use a washer and bolt under it, thermostat housing should for over it and have enough stud to start a nut. Work it from there.

Red neck fix.

Or you can weld it shut and start the hole over again…..
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My thoughts. Aluminum intake, studs aren't a bad idea.
 
With anti seize. He’ll have to run a long (odd looking) stud should it need to be serviced.

Weld in an aluminum stud?
 
Aluminum is easy to repair. A good welding/machine shop could fix that thermostat area right up with no problem and make it good as new. That's a great intake and is worth fixing RIGHT.
 
RustyRatRod said:
Aluminum is easy to repair. A good welding/machine shop could fix that thermostat area right up with no problem and make it good as new. That's a great intake and is worth fixing RIGHT.
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And while they're at it, have them surface the pitted gasket area.
 
just use the bigger bolt if the threads in the hole are good. If you need to drill out the housing bolt holes you might want to get a cast iron housing available at the NAPA store. In my experience they seal better anyway because they are less apt to warp than aluminum ones.

My alternative response was: "that manifold is toast - I'll give you $100 for it."
 
Someone had some vicious tap water, and never changed it, allowing acid to build. Water and maintenance matter.
 
I'm having doubts if there'd be enough clearance to run a 7/16 bolt or stud through the thermostat housing and still have enough room to turn the hex- you're talking a 5/6 (bolt)-11/16 (nut) head size there. You MIGHT be able to use a socket head allen screw there- the heads are slightly smaller.
Rusty's correct- that manifold is worth fixing right. At a bare minimum, Loctite a couple lengths of aluminum threaded rod in there, and drill it out to the correct size. Redneck, but it works.
 
[1] Use a s/s steel bolt to prevent further problems.
[2] If the head of the bolt is too big, file/grind the head so that a 9/16" spanner fits.
[3] Or use a socket [ Allen ] head bolt.
[4] You are not anchoring the Titanic, so above simple fixes will work.....
 
Some pics after a little machine shop care. Thinking it'll be alright. Helicoil bolt holes & epoxy t-stat housing surface.

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str12-340 said:
IMHO - get rid of the bolts and use studs to reduce future issues
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Easier on the threads in the intake. Most stripped threads on aluminum intakes are from bolts. Thermostats are terrible for it and many carb base threads strip because of it too. I like to use studs.
 
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