Starter bolts
Thread Starter
Instructor
Joined: Apr 2019
Posts: 197
Likes: 26
From: Clifton, virginia
Starter bolts
Hi Fellas,
I am going to look at a 1975 C3/Manual Tranny today and owner is telling me starter bolts keep coming loose. Car does not have original 350. It has been swapped to a 400SBC. What can cause starter bolts to keep coming loose? Would loctite fix this if threading is not stripped?
He is asking 7400 for the car with new clutch, pressure plate, radiator, brakes. Body is in pretty good condition with no rust.
Thank you all.
I am going to look at a 1975 C3/Manual Tranny today and owner is telling me starter bolts keep coming loose. Car does not have original 350. It has been swapped to a 400SBC. What can cause starter bolts to keep coming loose? Would loctite fix this if threading is not stripped?
He is asking 7400 for the car with new clutch, pressure plate, radiator, brakes. Body is in pretty good condition with no rust.
Thank you all.
Le Mans Master
Joined: Aug 2017
Posts: 8,336
Likes: 2,809
From: Cool Northern Michigan
Starter bolts are very special in that they have a knurled shank to keep movement of the starter intact. If someone were to use standard hardware bolts, they could work lose I suppose. I doubt LocTite is the answer or it would have been done before this.
If the blocks threads are damaged, I would think long & hard if you want to get involved with thread repair. That is a bad spot to get at with the exhaust, oil pan, frame, etc.
Most people have luck with helicol thread repair kit but only if you have easy access to the bolt hole.
If the blocks threads are damaged, I would think long & hard if you want to get involved with thread repair. That is a bad spot to get at with the exhaust, oil pan, frame, etc.
Most people have luck with helicol thread repair kit but only if you have easy access to the bolt hole.
Thread Starter
Instructor
Joined: Apr 2019
Posts: 197
Likes: 26
From: Clifton, virginia
oh thank you so much for the great info on the starter bolts coming loose. yeah i figured he tried loctite for sure because he has a lift in his garage. may be he used standard 9/16th bolts intead using true starter bolts. there's another guy selling his 1980 C3 and asking 6200. body andn interior is in excellent condition in his climate controlled garage and all but it has sat for 11 years and he says it car will not keep idle and needs brake line and tranny pan gasket. but i'm scare of any car sitting that long as seals are probably shot and become a massive headache and money pit.
Drifting
Joined: Oct 2020
Posts: 1,566
Likes: 574
From: Wisconsin
Couple things:
bolts, without some kind of threadlocker, rely on bolt stretch to stay tight. Yours may have been overtightened too many times. Get new bolts. Next, vibration and movement are the enemy of keeping bolts tight. Some small block Chevy starters have a small angle bracket on the back end to help carry the force of the starter. Check if you have one. Lastly, some interference between the flex plate and the starter may be causing the starter to move around and loosen up. You may need to shim the starter. Is it making any noise when starting?
bolts, without some kind of threadlocker, rely on bolt stretch to stay tight. Yours may have been overtightened too many times. Get new bolts. Next, vibration and movement are the enemy of keeping bolts tight. Some small block Chevy starters have a small angle bracket on the back end to help carry the force of the starter. Check if you have one. Lastly, some interference between the flex plate and the starter may be causing the starter to move around and loosen up. You may need to shim the starter. Is it making any noise when starting?
Pro
Joined: Jul 2021
Posts: 719
Likes: 156
No, should Not use threadlocker on starter bolts; something else is wrong.
In addition to the knurl, most correct starter bolts have a taper located between knurl and threads; block's starter threads have a tapered lead into threads.
Heavy old OE MT10 starters often have a support bracket extending from block to rear of starter housing. Without bracket, all that dangling weight works to loosen starter.
Suggest swap to late model OE type GM Permanent Magnet Gear Reduction starter (aka PG260). about half weight , very powerful, inexpensive.
'75 should have HEI dist; therefore requires NO "R" terminal. Under $100 NEW, Delivered
read it Closely 2 or 3 times; ALL of it matters
https://autoprollc.com/wp-content/up...eb2016_web.pdf
In addition to the knurl, most correct starter bolts have a taper located between knurl and threads; block's starter threads have a tapered lead into threads.
Heavy old OE MT10 starters often have a support bracket extending from block to rear of starter housing. Without bracket, all that dangling weight works to loosen starter.
Suggest swap to late model OE type GM Permanent Magnet Gear Reduction starter (aka PG260). about half weight , very powerful, inexpensive.
'75 should have HEI dist; therefore requires NO "R" terminal. Under $100 NEW, Delivered
read it Closely 2 or 3 times; ALL of it matters
https://autoprollc.com/wp-content/up...eb2016_web.pdf
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,114
From: Crossville TN
The knurling on the shanks of stock starter bolts serves to remove the 'slack' between the hole size and the shank size that fits inside it. The less 'gap' in that bolt fit, the more solid the joint.
The simplest (and best) solution is to just go buy some stock starter bolts from a GM dealer or a NAPA auto parts store. An alternative would be to buy some 'correctly made' bolts from a Chevy or Corvette parts vendor.....or a salvage yard.
The simplest (and best) solution is to just go buy some stock starter bolts from a GM dealer or a NAPA auto parts store. An alternative would be to buy some 'correctly made' bolts from a Chevy or Corvette parts vendor.....or a salvage yard.
Last edited by 7T1vette; Sep 22, 2021 at 12:56 AM.
Le Mans Master
Joined: Apr 2001
Posts: 5,941
Likes: 281
From: Was New Orleans but swam to Baton Rouge LA
Cruise-In IX Veteran
What type of starter does it have? There are actually 2 different GM starter bolts. The old style bolts are all standard thread and size. The PMGR starters used starting in the late 80's have a metric knurl with the 3/8th thread.
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Dr. Detroit
Joined: Mar 2012
Posts: 10,095
Likes: 4,022
From: New Braunfels Texas
You can buy the correct starter bolts form your local parts slinger on the "HELP" rack......or the Dorman catalog....if they do not have them, tell them to lock the doors and shut down....Lol!
Jebby
Jebby
Team Owner
Joined: Jun 2001
Posts: 23,363
Likes: 1,059
From: Virginia USA
I always use brand new starter bolts when I mess with my starter. Take a look at the knurl on a new bolt vs. the bolt taken out. You'll see the new bolts knurl is ridged and 'grabby" when you run your finger over it but the old bolts knurl will be almost smooth to the touch. It's doing something.
I've never had a new bolt loosen up on me but sure enough the couple of times I've used one over again I'm back under there changing it out. Has happened twice. Once on my brothers 1967 Ford Country Squire Station Wagon and once on my 1984 Camaro. I've used new starter bolts ever since.
I've never had a new bolt loosen up on me but sure enough the couple of times I've used one over again I'm back under there changing it out. Has happened twice. Once on my brothers 1967 Ford Country Squire Station Wagon and once on my 1984 Camaro. I've used new starter bolts ever since.
Pro
Joined: Jul 2021
Posts: 719
Likes: 156
I always use brand new starter bolts when I mess with my starter. Take a look at the knurl on a new bolt vs. the bolt taken out. You'll see the new bolts knurl is ridged and 'grabby" when you run your finger over it but the old bolts knurl will be almost smooth to the touch. It's doing something.
I've never had a new bolt loosen up on me but sure enough the couple of times I've used one over again I'm back under there changing it out. Has happened twice. Once on my brothers 1967 Ford Country Squire Station Wagon and once on my 1984 Camaro. I've used new starter bolts ever since.
I've never had a new bolt loosen up on me but sure enough the couple of times I've used one over again I'm back under there changing it out. Has happened twice. Once on my brothers 1967 Ford Country Squire Station Wagon and once on my 1984 Camaro. I've used new starter bolts ever since.
"Knurl: The knurled area of the starter bolt maintains correct pinion alignment by preventing twisting between the starter housing and the bolt. All PG starter housings are machined for a 10.1mm knurl. Most 10MT starters use a 9.7mm housing. Using the incorrect knurl will allow the starter to twist and result in pinion misalignment, noise, and premature pinion and flywheel wear" from Remy link in P#5
So, the Old starter has 9.7mm bolt hole and the New starter has 10.1 bolt hole. old skinny bolts in new floppy holes means exactly what you can predict.