1969 350/350 Rochester Carburetor Questions

[Steve M.]

Doing a frame-off on a 1969 convertible with 350/350. Received the engine back after blue printing/balancing and painted. The studs on the manifold for the back of the carburetor are painted orange. Is this correct? The long bolts for the front and the nuts for the back should be black or plated? Thanks for any information. Steve

[Joe L.]

Re: 1969 350/350 Rochester Carburetor Questions

Doing a frame-off on a 1969 convertible with 350/350. Received the engine back after blue printing/balancing and painted. The studs on the manifold for the back of the carburetor are painted orange. Is this correct? The long bolts for the front and the nuts for the back should be black or plated? Thanks for any information. Steve

Steve-----


The studs were supplied with the engine from the engine plant. However, I believe they were covered in some way when the engine was painted (or, they were installed after painting). So, there should be no paint on them. Of course, it's possible that some paint got on the very bottom of the exposed portion of the stud. If so, it would not be visible with the carburetor installed.

The carburetor retaining long bolts were zinc plated. The nuts used on the studs were also zinc plated.

[Terry M.]

Re: 1969 350/350 Rochester Carburetor Questions

Steve-----


The studs were supplied with the engine from the engine plant. However, I believe they were covered in some way when the engine was painted (or, they were installed after painting). So, there should be no paint on them. Of course, it's possible that some paint got on the very bottom of the exposed portion of the stud. If so, it would not be visible with the carburetor installed.

The carburetor retaining long bolts were zinc plated. The nuts used on the studs were also zinc plated.

Joe,

In judging we frequently see engine orange paint on the top of those studs. I would agree with Joe that they should have been covered. You wouldn't want paint to get to the interior of the intake manifold, but way many original engines tell us the top of the studs were exposed.

I look at more 1970-72s than 1969, but most of those long bolt heads are dark colored. Perhaps they deteriorate to a dark color, or more likely they are dark to begin with.

[Joe L.]

Re: 1969 350/350 Rochester Carburetor Questions

Joe,

In judging we frequently see engine orange paint on the top of those studs. I would agree with Joe that they should have been covered. You wouldn't want paint to get to the interior of the intake manifold, but way many original engines tell us the top of the studs were exposed.

I look at more 1970-72s than 1969, but most of those long bolt heads are dark colored. Perhaps they deteriorate to a dark color, or more likely they are dark to begin with.

Terry-------


The carb studs on my 1969 had no paint on them.

The bolts on my 1969 were zinc plated. For 1969 GM says the bolts were GM #187147 and GM also says that these bolts were zinc plated and 3-1/2" OL. Things changed for 1970. For 1970 the bolts were GM #3967476. I don't have finish information on this bolt but, from what you've observed, I'd say they were black phosphate-finished. These bolts were 3-5/8" long, probably to account for the thicker gaskets used for 1970 and later.

[Terry M.]

Re: 1969 350/350 Rochester Carburetor Questions

Terry-------


The carb studs on my 1969 had no paint on them.

The bolts on my 1969 were zinc plated. For 1969 GM says the bolts were GM #187147 and GM also says that these bolts were zinc plated and 3-1/2" OL. Things changed for 1970. For 1970 the bolts were GM #3967476. I don't have finish information on this bolt but, from what you've observed, I'd say they were black phosphate-finished. These bolts were 3-5/8" long, probably to account for the thicker gaskets used for 1970 and later.

Interesting information Joe. Thanks for digging deeper into the bolt data.

[Joe L.]

Re: 1969 350/350 Rochester Carburetor Questions

Interesting information Joe. Thanks for digging deeper into the bolt data.

Terry-------


Also, 1971 and 72 were different. In addition to using short bolts instead of studs for the rear carb fasteners, they used different long bolts than 1969 or 1970 as follows:

E1971-------GM #9432450---phosphate finish, unknown length

L1971-72----GM #9419047----phosphate finish, 3-3/4" OL

[Terry M.]

Re: 1969 350/350 Rochester Carburetor Questions

Terry-------


Also, 1971 and 72 were different. In addition to using short bolts instead of studs for the rear carb fasteners, they used different long bolts than 1969 or 1970 as follows:

E1971-------GM #9432450---phosphate finish, unknown length

L1971-72----GM #9419047----phosphate finish, 3-3/4" OL

Thank you again Joe. You are remarkable in your diligence.

[Mark E.]

Re: 1969 350/350 Rochester Carburetor Questions

I have a collection of these bolts, some zinc (cad?) plated, others dark phosphate. Lengths vary too. Now I know some of their applications.

Another front bolt difference: Some have a flange hex head, some a regular hex head, and some (early Q-Jets, maybe before their application on Corvettes) use a round, slotted head.

Rear nuts (pre-'71) I've seen were all zinc plated, regular hex. While rear bolts ('71- newer) were dark phosphate. Have others seen differently?

And it's my understanding the factory typically did not use washers with any of these fasteners. That's curious since it makes sense to use lock washers to help maintain torque and avoid damaging the soft metal of the air horn.

[Joe L.]

Re: 1969 350/350 Rochester Carburetor Questions

I believe the rear nuts (pre-'71) were all zinc plated, and rear bolts ('71- newer) were dark phosphate. Is this true?

Mark-----


Yes.