Hi- I'm new to this Group..any advice would be appreciated...Need some Help- I purchased my very first Classic Car .1971 442 Convertible. My Car is currently in the Shop getting some work done. I have a "Cars and Parts"Catalog that tells me my Engine should have the letter "H" on the Left cylinder Head. Mine has a "G" which my Catalog says is for SX 455. The Mechanic says its not Unusual in the 70's that manufacture would from time to time do this. is that true ? Does this hurt the value of the car ? Everything else checks out has all Original except for the Trans(TH400 ) . Thanks in Advance, Bill O

 

Hi,

Welcome.
If you have a 1971 Oldsmobile 442 and all is original, your motor will be a 455 cu in with the letter G on the cylinder heads.
If your car is a 1971 442 with the W-30 option then your motor is a 455 and will have an H on the cylinder heads.
We need a bit more info on your car as to what it is advertised as and what it really may be.
The V.I.N. will have some info along with the big tag that is on the cowl.
Pictures will help too. Any original paperwork such as: dealer invoices, build sheets or broadcast cards. An original window sticker will list the options also but pretty scarce.
List the VIN and all the codes on the cowl tag and we can start there.
An original 442 is nice
An SX is not a 442 but is still nice
A 442, w-30 is the best performance pkg they had to offer that year and if you were to have an original one of those would be the most valuable.

 

Welcome. As noted, every single 455 built by Oldsmobile in the 1971 model year came with "G" head castings except the W-30 motors, which came with the "H" castings. Your engine should have come from the factory with "G" heads.

If you really do have a 442 (VIN should start 344671xxxxxxx), then the G heads would be correct. A 442 is NOT an "SX455". That was RPO code Y79, which was only available on Cutlass Supreme cars in 1971, not 442s. A Cutlass Supreme convertible would have a VIN starting 342671xxxxxxx). All Y79 cars also came with "G" head castings in 1971. I don't know what document you are reading, but it is flat wrong.

Finally, the factory did NOT randomly swap parts as suggested by your mechanic. Every substitution by the factory was fully documented in engineering documents and dealer service bulletins. There is NO factory documentation that G heads were swapped for H heads. That did not happen.

Good luck with your car.