rustytoolss
Well-Known Member
The 5/16" threads for my thermostat do not feel good/ might strip. Can I enlarge the thread size to 3/8" without creating a problem ? Will they have enought material to tighten correctly ?
rethreading thermostat holes from 5/16 to 3/8 ?
- Thread starter rustytoolss
- Start date
-
Alaskan_TA
Well-Known Member
Buy a Heli-Coil kit and do it right.
pishta
I know I'm right....
Heli-coil or worst case, stud with red lock tite.
What intake manifold is it?
Yeah. I've never seen that before.
Ofcourse he doesn’t say what the hell he is working on. We can only guess it’s a modern Mopar. Kim
rustytoolss
Well-Known Member
Sorry I did not say ...but I'm working on a 1962 318 Poly
rustytoolss
Well-Known Member
stock 318 poly
Doesn’t it already have 3/8s bolts? Kim
rustytoolss
Well-Known Member
No 5/16 NC
As stated, before Heli coil it!
AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
- Joined
- Jan 19, 2014
- Messages
- 24,918
- Reaction score
- 12,272
I studded my 360LA which already were 3/8ths. and used some torque-spreading conical washers, like as are on the slanty manifolds.
if your stat house is flat and the receiving area is adequate, it won't take much torque to keep it from leaking. To make it even easier, I run a 7pound cap. The hoses and stuff last forever.
If you need a sealer, you can't beat "the right Stuff." but it's a PITA to remove later.
if your stat house is flat and the receiving area is adequate, it won't take much torque to keep it from leaking. To make it even easier, I run a 7pound cap. The hoses and stuff last forever.
If you need a sealer, you can't beat "the right Stuff." but it's a PITA to remove later.
Last edited:
ir3333
Well-Known Member
To answer your question...i have done that and it worked fine.Are there other options...absolutely.
rustytoolss
Well-Known Member
Thanks, I just checked a Drill Tap chart, 5/16" is the correct drill size for a 3/8"-NC thread. Did a test with a 5/16 nut, you can tap it to 3/8-NC no problem.
You will probably have to drill your thermostat housing and enlarge the gasket holes. What a pain.
Alaskan_TA
Well-Known Member
3 minutes tops.
No pain killers required.
I would take the extra time to do it right with a Heli-Coli set though.
Exactly. What a pain modifying everything to make it work where a thread insert will fix it right.
pishta
I know I'm right....
thread inserts are huge. I doubt they would have the room on a poly, as the drill is a .488 for this.
Helicoil would be the smallest OD repair or drill and tap for next oversize....(gasp) metric!
I used these for a LA pump housing on the bottom 2 holes from the oil pan. They worked great but the initial hole is huge.
View attachment 1715879667
Helicoil would be the smallest OD repair or drill and tap for next oversize....(gasp) metric!
I used these for a LA pump housing on the bottom 2 holes from the oil pan. They worked great but the initial hole is huge.
View attachment 1715879667
So, again, why not "just" use the next SAE size- 3/8 if you are already going to drill a hole that's almost the correct size to tap for 3/8?
I'd almost bet you could drill the existing holes flush and be able to tap them to 3/8.
I'd almost bet you could drill the existing holes flush and be able to tap them to 3/8.
MAke sure the threads are clean all the way down the hole. It's a cast iron manifold so it's pretty tough and forgiving. I use a pocket screwdriver to loosen the gunk in the bolt holes then blow them out with compressed air than follow up (carefully) with a thread chaser. I don't use a tap. You might have enough good threads for a stud and some Locktite. (might) Clean the threads on the bolt if you are reusing that.
Last edited:
harrisonm
Well-Known Member
I agree with @Alaskan_TA and others; do a Heli Coil. I have done a bunch of them, and they work great. In the time we have been discussing other options, you could have gone to a store, bought them, and had it installed. They work great and are easy to install. You won't be sorry.
-
