62 340 hp engine pulleys

[Chris H.]

I love this group!!

I have searched the archives to figure out what pulley system I should have on my early 62 340hp.

I buy into no idler pulley (yea, less money!)

My upper pulley has p/n 3724816 stamped in it which agrees with judging manual, Paragon and this site.

However, the crank pulley per the judging guide should be 3756328, there seems to be disagreement in the archives on this. I see p/n 3858533 mentioned.

My car has the double belt 3858533. Now, I in no way want to say my engine is original. It had a 64 intake and a 63 carb. Most of the fasteners are the right type, but wrong markings.
BUT, sure would like to use my 3858533 with 6 5/8" diameter (same as 3756328?).

Any help out there?

Chris

[Joe L.]

Re: 62 340 hp engine pulleys

Chris----

The original crank pulley used on 1962-63 Corvettes with 340 and 360 hp engines was GM #3766987. This is a 2 groove pulley of 6-3/4" OD. In August, 1964, the GM #3766987 pulley was discontinued from SERVICE and replaced by the GM #3858533 which is a 2 groove pulley of 6-5/8" OD.

So, the GM #3858533 is the correct SERVICE replacement pulley for the 1962 340 hp application, but it's not the correct PRODUCTION pulley for the application.

[Chris H.]

Re: 62 340 hp engine pulleys

Joe, you are saying the judging guide is wrong? It list the crank pulley as 3756328.

Also, I remeasured my 3858533 and it is actual od of 6.75". Is 6 5/8" an effective diameter?

In my service parts book it shows 3858533 as 6.75" for my car but it also says it is stamped 3766987.

[Joe L.]

Re: 62 340 hp engine pulleys

Chris------

GM #3756328 is the 1962 250/300 hp crank pulley.

I've not measured one of the '533' pullies; GM's "official" dimension is 6-5/8". The 3858533 pulley is NOT stamped 3766987. That notation and the dimension attached to it is an anachronism in the particular edition of the P&A Catalog that you're looking at.

[Chris H.]

Re: 62 340 hp engine pulleys

OK, so I am supposed to have a double lower pulley and no idler pulley. Is there no belt in the one of the sheaves?

In looking at Nolands book there are no good pictures (that I found) of the lower pulley except for the fuel injected engine. These all have a single crank pulley unless the idler pulley is included.

It just seems strange that a double pulley was used on the crank at sop for 62 model year. Why would the double pulley be there? Was it used elsewhere at Chevy?

Chris

[Joe L.]

Re: 62 340 hp engine pulleys

Chris------

Who said that an idler pulley was not used for 1962 340 hp? Not me. I think that was a conclusion that you came to. An idler pulley assembly WAS used for 1963 with 340 hp. The assembly was originally GM #3793332. The idler pulley uses the 2nd groove.

[Chris H.]

Re: 62 340 hp engine pulleys

The AIM says that the idler pulley was added 3-7-62 to the 340 hp engine. It used to take GM a long time to carryout a change after Engineering wrote the paperwork. (still does on some of my parts even with computers!!!). By the time the plant got the directions and ordered the parts and scheduled the change it would have been 1963 model year. Therefore very few if any would have gotten the idler pulley change. Per the judging guide and Nolands book no original 62 340 hp engine has been found with the idler system. This is what has had me confused with your info.

I believe I should actually have a single sheave lower pulley (car built in 1961). p/n 3756328

What do you think?

Chris

[Dennis C.]

Re: 62 340 hp engine pulleys

Chris - I am inclined to agree with you ('328). I doubt any '62 was delivered with anything related to a double groove crank pulley or 2 belt system. DC

[Dennis M.]

Re: 62 340 hp engine pulleys

Chris,

I have not looked at the numbers on my pulley, but feel that the 340 engine in my 62 is original and it uses only one belt. If it is not too Cold tonight I will check my pulleys.

[Mike E.]

Re: 62 340 hp engine pulleys

I've been aware for 25 years that the AIM indicates a double-groove pulley set-up with idler pulley on high-horse engines late in the year. I've also documented late original-owner cars, as well as very correct cars (including 14445--article was done on that in the Restorer). NONE have shown up with double pulley or idler system. Dennis is right--328 is correct single gtoove pulley. That's why that information is in the manual--because it is absolutely correct.