I have what appears to be a 455 Big Block, casting number 398021Fa with partial VIN on the block of 33m335268 which indicates it should be a 1973 but it has A heads. Does anyone have any ideas on this or is it as simple as someone has installed A heads on a newer engine.

 

There’s your answer. It’s not unusual at all for J heads to be replaced with earlier heads that flow better.

 

Thanks for the response, would you have any idea what this engine came out of based on the partial VIN?

 

I don't think it really matters. Anything could have been changed or nothing could have been changed since the A heads show it's not original. If you are trying to make more HP then most important would be the Compression Ratio. If it matters, get a boroscope and look at the pistons through the sparkplug hole. If the block is really a 1973 and has original pistons then you have low compression. A 1973 block is just fine. It's what you put in it that matters.

 

3 Olds Division,
3 1973,
M Lansing,
335268 the last 6 of the VIN of the car that rolled off the line with that block.

I don't think you can devise any other information with any degree of certainty from that number.

 

Thanks for the information, the engine came in a 1970 Cutlass parts car so it was obviously not original to the car.

 

The engine most likely came out of an A-body car. Lansing assigned blocks of sequence numbers to each platform. Typically the A-body cars got sequence numbers between 100001 and 400000 in that year, but there have been documented exceptions.

 

What models were in the 600000 range.

 

Top of the line Oldsmobile.

The Toronado.



https://toronado.org/public/FAQs/GenII/vin.htm

 

Big port A heads