Another bolt size needed

[Lippyp]

Sorry guys, yet again I am struggling with finding a bolt size. Can anybody tell me what size the engine mount bolt (the big single one that goes from the tower on the frame to the rubber mount) is on a 69 350 SBC. I had to take the entire tower out to remove an old bracket whilst changing out my P/S pump at the weekend and the old motor mount bolt is looking pretty chewed up and the rubber is a little old and covered in paint overspray, so I am going to replace the mount and need a new bolt. I have found a good supplier for UNC bolts now in the UK but need to know what size it is.

Thanks

[TROYLV]

will check the length today. it is a 5/8th dia, but don't know length off hand. you could measure the length. why not just use metric? everthing over here is going to that.

[JimKshortstep4x4]

It is a 7/16-14x1 1/4" long. You may have to go with 1 1/2" and use spacers or use a 1".

Jim

[crazy longhorn]

7/16 -14 NC thread......not sure on the lenght, but close to 1 ". 5/8 is the head size of the bolt.....crazyL

[Lippyp]

Thanks for the info guys, as speedy and helpful as ever. Troylv, I try to keep with original spec bolts as much as possible as it's a royal pain having a mixture of metric/imperial bolts. Also this goes into a captive nut so it has to be right.

Thanks

[COBALT]

Make sure you buy a grade that matches the grade in the stock bolt, or something that won't cause damage to your mount over time. You don't want your bolt to be harder than the threads in the mount or the bracket, or you'll end up with the same problem I have: a loose mount that allows my fan to bang against my fan shroud on right turns.

0 marks: 2-grade
3 marks: 5-grade
6 marks: 8-grade
stainless: ~5-grade

I'd go with either stainless or 5 grade. It's a bit more ductile than 8-grade, and will flex a bit with the movement of the mount due to cyclic loading. Just some Materials Engineering for the day.

[flyingcubby]

Does anyone know the bolt or screw size that holds the parking brake bracket to the dash for support. Without the bracket bolted every time brake is applied the bracket moves / wiggles. Thanks in advance....Mike

[DeadheadNM]

Originally Posted by flyingcubby

Does anyone know the bolt or screw size that holds the parking brake bracket to the dash for support. Without the bracket bolted every time brake is applied the bracket moves / wiggles. Thanks in advance....Mike

Can't recall size off hand but here's what it looks like: http://67-72chevytrucks.com/vboard/s...4&postcount=14

[flyingcubby]

Thanks deadhead, found one laying around, Solid again.....Mike

[davepl]

Just in case someone stumbles across this thread searching for keywords, a quite note on the reproduction of the 1970 big block mounts out there:

- The center bolt is METRIC
- The center bolt is TOO LONG and needs to be cut down lest it poke the block

[ck5566]

Originally Posted by COBALT

Make sure you buy a grade that matches the grade in the stock bolt, or something that won't cause damage to your mount over time. You don't want your bolt to be harder than the threads in the mount or the bracket, or you'll end up with the same problem I have: a loose mount that allows my fan to bang against my fan shroud on right turns.

0 marks: 2-grade
3 marks: 5-grade
6 marks: 8-grade
stainless: ~5-grade

I'd go with either stainless or 5 grade. It's a bit more ductile than 8-grade, and will flex a bit with the movement of the mount due to cyclic loading. Just some Materials Engineering for the day.

Question on if going to build a block from ground up then how do you know what grade of bolt to use not having any thing there to start with in the first place? Does the motor mounts say any thing about what needs to be used?