66 427/425 Starter Mounting Bolts

[Bob A.]

How many bolts were used to mount the Starter. There are three mounting holes in the Starter and three three tapped holes in the block. It appears that one of the holes would use a shorter Bolt. The two bolts that I removed from the Starter appear to be special as they have something near the threaded end that looks similar to a knurl. Where can these bolts be purchased?

Regards,

Bob Adams

[Joe L.]

Re: 66 427/425 Starter Mounting Bolts

How many bolts were used to mount the Starter. There are three mounting holes in the Starter and three three tapped holes in the block. It appears that one of the holes would use a shorter Bolt. The two bolts that I removed from the Starter appear to be special as they have something near the threaded end that looks similar to a knurl. Where can these bolts be purchased?

Regards,

Bob Adams

Bob------


Can you post a photo of this starter nose? I'd like to see it. I have heard before of these "3 hole" cast iron starter noses, but I just don't recall ever seeing one.

The 1966-E1969 cast iron starter housing (nose) was GM #1965721. I do not have an NOS example of that housing which was discontinued in October, 1969 and replaced by GM #1969309. However, I have NOS examples of the 1969309 and every supercessive starter housing (and, there were quite a few) and NONE of these has a 3 hole mounting configuration.

In any event, even if your starter housing actually has 3 holes, I think that only 2 would be actually used. These would be the outer forward hole and the inner rear-most hole. Attached is a photo of an NOS GM #1969309 housing which replaced the 1965721 for PRODUCTION and SERVICE. The mounting holes present in this housing are the same ones that should be utilized on yours. I don't think that the 3rd hole on yours will even line up with a block tapping.

The starter mounting bolts are special bolts and these MUST be used for starter mounting. The "knurling" ensures that the bolts are properly aligned in the housing and, in turn, the housing properly aligned to the block.

The bolts for your starter are GM #3733289 and they're still available from GM. This bolt is 3-5/8" long. Many auto parts stores will have an equivalent bolt but it MUST be the special starter bolt and not just a "plain, ordinary bolt".

[Rich P.]

Re: 66 427/425 Starter Mounting Bolts

Here is a picture of an original pair. Most aftermarket bolts have a line through the centoer of the O in the headmarking. These bolts were used on 66-74 big blocks and 67 -up small blocks with 11" clutches.

Rich

[Joe L.]

Re: 66 427/425 Starter Mounting Bolts

Here is a picture of an original pair. Most aftermarket bolts have a line through the centoer of the O in the headmarking. These bolts were used on 66-74 big blocks and 67 -up small blocks with 11" clutches.

Rich

Rich-----


The manufacturer's ID headmarking of the "bifurcated circle" is seen on many GM bolts of the 80's and later.

[Rich P.]

Re: 66 427/425 Starter Mounting Bolts

Rich-----


The manufacturer's ID headmarking of the "bifurcated circle" is seen on many GM bolts of the 80's and later.

Joe,

thats correct and the earliest known mid year application is for the axle flange bolts (only they are grade 8).
The O was used on all GM cars I find them all over the place in junk yards, like you said up to the mid-late 80's.

Bob this bolt is usually in the HELP section of the auto parts store if you don't mind a different headmarking than original. They also pop up here and there on e-bay.

Rich

[Bob A.]

Re: 66 427/425 Starter Mounting Bolts

Joe:

You are correct. The three holes in the Starter Nose do not line up with the three tapped holes in the block, only two can be used.

Regards,

Bob Adams

[Joe L.]

Re: 66 427/425 Starter Mounting Bolts

Joe:

You are correct. The three holes in the Starter Nose do not line up with the three tapped holes in the block, only two can be used.

Regards,

Bob Adams

Bob-----


I'd still like to see a photo of the starter nose you have if you can post one.

[Bob A.]

Re: 66 427/425 Starter Mounting Bolts

Joe:

I will take a picture of the Three Bolt Starter Nose on Wednesday and post it shortly thereafter.

Regards,

Bob

[Joe L.]

Re: 66 427/425 Starter Mounting Bolts

Joe:

I will take a picture of the Three Bolt Starter Nose on Wednesday and post it shortly thereafter.

Regards,

Bob

Bob-----


Great. I think I know what the configuration of these noses is but I'd sure like to confirm it with some photos. The thing I can't figure out is why they were designed that way. Plus, they were replaced by the 2 hole noses, meaning that every application that originally used the 3 hole nose could use the 2 hole nose. So, I just don't understand what applications originally used the 3 hole nose and why. It could not have been an application that originally used a different pair of the 3 holes than that used for every Chevrolet application I know of because if that were the case, the 2 hole nose could not have replaced it.