So I see a lot of chatter on here about "G" heads. My 72 Cutlass Supreme has "GA" heads. What does this mean, and why are they so desired?

Thanks, Dave

 

G are 71, Ga, are 72.Not much difference in them, both have harden seats.

 

Hardened seats...that has to do with leaded and unleaded fuel, right?

 

Yes can use unleaded gas, which is all you can buy now.

 

Dave,
G heads are 455 heads produced for 1971 Oldsmobile

GA heads are 455 heads produced for 1972 Oldsmobile

The main difference is the 71 heads have just the exhaust valve seats induction hardened, while the 72 heads have both the intake and exhaust valve seats hardened.

 

 

X2. The induction hardening only goes a few thousandths deep.

 

Not necessarily so. I had a 67 400E that my son and I drove over 70,000 miles. Tore it down for another reason and there was absolutely no valve recession. Unless you are going to drive long trips at sustained higher RPM, hardened seats are not needed. Flame at me away now.

 

 

Is there any high performance associated with the GA heads?

 

No, they came in came in both small vale and large valve versions, and as far as flow they are on par with the other big block heads. Nothing special other than they are 1972 specific.

 

Any way to know small or large valves?

 

Not unless you pull the heads.

 

Ain't trying to do all that...what if it's the U code?

 

Specifications of Olds F G Ga H J heads.
six digit number = casting #,
cc = combustion chamber

*F 404438 80cc Intake 2.072", Exhaust 1.625", 1970 455's with W-30. Large valves, 2.072 and 1.625". Maybe have hardened exhaust seats. Valve rotators on all valves, therefore deep spring seats. One center exhaust port blocked off from the intake heat crossover port for better power. 'Improved port configuration for better flow"- according to Supercars Unltd. book 442 by the Numbers. Very rare and valuable. *THE* head to get, if cost is no object, or for an investment. Watch out for an E ground to look like an F; check the 6-digit casting number and the 3 digits on the underside as well (should not be 686). Always look for the two raised ribs on the end of the head that are nearly impossible to duplicate, even with JB weld. Only F heads had these ribs, never E's.

G 409100 80cc Intake 2.000, 2.072", Exhaust 1.625" 1971 455's, except W-30 [see H]. Valves commonly 2.000 and 1.625", but Toronado and 442 heads had the larger 2.072" intakes. Common heads use valve rotators on all valves, but 442 [and Toro?] heads used rotators on exhaust valves only- according to 442 by the Numbers. Wherever rotators are used, the thick rotator/retainer required the use of a deep spring seat. Maybe hard exhaust seats. The A is like 'A'. Some are large, some are small in size.

Ga 409100 [same number as G head] 80cc Intake 2.000, 2.072", Exhaust 1.625, 1.685" 1972 455's, including W-30. Valves almost universally 2.000 and 1.625", even 442's had small intakes, if auto trans models. Even the Toronados were relegated to small intake valves this year. Only 442's with W-30 or MT had the larger 2.072" intakes. No way to tell valve size without measuring a valve. Strange combinations of exhaust valve sizes and angles, depending on application. Weird combination of valve sizes and seat angles that no other heads matched. This might make finding valves more fun, should you need them. Exhaust valve with a unique 1.685" diameter and 30 degree face. All Ga heads use valve rotators on all valves, therefore have all deep spring seats. Hard exhaust seats.

*H 409160 80cc Intake 2.072", Exhaust 1.625" 1971 455's with W-30. Large valves, 2.072 and 1.625". Valve rotators on all valves, therefore deep spring seats. Maybe have hardened exhaust seats. One center exhaust port blocked off from the intake heat crossover port for better power. 'Improved port configuration for better flow"- according to Supercars Unltd. book 442 by the Numbers. Improved *over what* they don't say. Very rare and valuable.

J 411783 80, 82cc Intake 2.000" exhaust 1.625" 1973-76 455 "smog" motors. Standard [small] valves: 2.000 and 1.625", even Toronado, 442, etc. [presumably]. Exhaust port is choked off to about 1" diameter just under the valve. No blocked heat crossover. Rotators, deep spring seats, hardened exhaust seats. Very common. Avoid.

 

Not bad enough to go digging Norm😀. And the rear diff and axle housing are #'s matching. The only thing that isn't stock are the boxed LCA's

 

I don't know what you mean by this. There are no VIN numbers on either of those, so you can't say they are "number matching" to any particular vehicle. The only parts that are "numbers matching" are the block and transmission if their VIN derivative stampings match the vehicle VIN.

 

If it runs like the proverbial violated simian, no need to do anything other than be happy.

 

Ok...maybe not "#'s matching", but the date code and the option code stamping line up, so that's close enough for me😀