What is an IDH ?

[jack alexander]

I was looking at a 1966 "396" 325 HP corvette that was for sale. When I started looking at the engine block numbers, I saw something I was unfamilar with. The front pad number started out with IDH then went to TO928F108929. It was a "961" block with 702 heads and a 948 intake which looked ok. Any feedback on the "IDH" would be appreciated. I thought that it might be a factory replacement but thought that was a "CE"
Thanks in advance!
Jack

[William V.]

Re: What is an IDH ?

The 396 325 hp engine was never factory installed in any Corvette. 1965 was the only year where a 396 425 hp engine was factory installed. The big blocks for 66 were the 427 390 and 425.

[Kevin Whiteley]

Re: What is an IDH ?

I couldn't find any reference to "IDH", but the 961 block was fairly limited in it's use. That being 65-66 Passenger and 66 Chevelle. That said, there is an "IGH" for a 396/325hp block passenger car for 1966. The "F" in the engine stamp pad indicates the car was assembled in Flint, which is the Passenger/Chevelle plant. There is a code for "ID" which is a 427/425hp Passenger, so it could be possible that the block was first assembled as and "ID" engine, remanufactured due to some fault and stamped with the extra "H" instead of grinding the original stamp off. This is all that I have. Hope it helps.

[Tom D.]

Another ...961 block - stamped TO215IVR

I understand IVR means 396 with T/H trans and a Rochester Carb in a full size Chevrolet. Casting date is A176. A fellow Michigan chapter member advised using it to hold my boat in place...

Tom D.




MI Chapter Site

[jack alexander]

Re: Another ...961 block - stamped TO215IVR

Thank yoy for all of your responses. I was aware that the block was not used in a 66 but my confusion come as to what it was exactly. If it was a 435 HP passengeer would it have those heads? The boat anchor idea is looking better.
Jack

[Tom D.]

3872702 heads could have been 325 HP

Colvin, in "Chevrolet by the Numbers - 1965 to 1969" lists the following applications for those (oval port) heads:

66 Pass 396 with 325 HP
66 Pass 427 with 390 HP
66 Chevelle 396 with 325 HP, or 360 HP
66 Corvette 427 with 390 HP

[Edward M.]

Re: What is an IDH ?

I have seen this before. The ID is the engine suffix code. The H stands for Holley. This engine was equipped with a Holley carb. I have also seen engines stamped xxR, where the R represents Rochester carburetor. The reason for the carburetor type addition to the engine suffix code was that the carburetor mounting studs in the intake manifold were different between the two carb types.
They didn't want any confusion at the assembly plants when it came time to install the carbs. I've seen this on both small and big block engines.