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Date code looks like March 17, 1969 and they were used on the 69 350 CID which was 325HP with 2.11/1.77 valves and a compression ratio of 10.5:1. may have been used on the firebird.
 

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GTO & Tempest heads found on the 1969 GTO 400 CI 350HP/366HP Ram Air III engines & the Tempest 350CI 330HP HO engines(like found in the Custom S option). Also found on the Firebird 350CI 325HP and 400CI 335HP engines.

Big valve 2.11" intakes and 1.77" exhaust. Screw in rocker studs.

The 350 version is said to be 64-68 CC's while the 400 version is supposed to be 72 CC's. You would have to have them checked to verify.

A good & desirable head to work with.
 

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Discussion Starter #4
Thanks guys. I truly appreciate the information. These are the heads on my GTO.

This is the information on the front passenger side of the block:



SOFGOAT
 

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YS code is for the 1969 400CI/350HP automatic engine. This engine calls for the #16 or #62 heads in a GTO.

Have you checked the date code at the rear of the block near the distributor hole to verify it is a 1969 block?

The #48 heads could certainly be original to the engine as Pontiac did not always follow their own rules and mixed and matched on occasion. It is possible that a previous owner purchased them when the car was "newer" and installed the #48 heads off of the 350HO IF the chambers were the smaller size and he/she wanted to raise compression for a little more kick. It could have been blueprinted for racing purposes. They could have been replaced at a dealership for warranty purposes.

So, it is hard to tell what the true story is if you do not have the car's personal history. If the engine is still original and has not been rebuilt, I would take a look at the cam. The factory cam for the 350HP automatic was the "067" cam. If someone was blueprinting it to race in a specific class, they may have upgraded to a more aggressive factory cam. Thinner head gaskets would be another "trick" to raise compression as well.
 

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Discussion Starter #6
YS code is for the 1969 400CI/350HP automatic engine. This engine calls for the #16 or #62 heads in a GTO.

Have you checked the date code at the rear of the block near the distributor hole to verify it is a 1969 block?

The #48 heads could certainly be original to the engine as Pontiac did not always follow their own rules and mixed and matched on occasion. It is possible that a previous owner purchased them when the car was "newer" and installed the #48 heads off of the 350HO IF the chambers were the smaller size and he/she wanted to raise compression for a little more kick. It could have been blueprinted for racing purposes. They could have been replaced at a dealership for warranty purposes.

So, it is hard to tell what the true story is if you do not have the car's personal history. If the engine is still original and has not been rebuilt, I would take a look at the cam. The factory cam for the 350HP automatic was the "067" cam. If someone was blueprinting it to race in a specific class, they may have upgraded to a more aggressive factory cam. Thinner head gaskets would be another "trick" to raise compression as well.
Thanks sir.

I hope to tear into a more detailed analysis of the engine sometime in the near future. I am not sure of the car's history other than how long it had been in the barn; early to mid-1970's based on plates, title, parking stickers, etc...

I appreciate everyone's feedback. I've provided less than optimal information and hope to gather more complete data in the near future.

SOFGOAT
 
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