Recently acquired a 1969 Cutlass S. Vehicle runs well. Has the original 350 motor but I see where someone put 5A heads on it. Research tells me that these are from an eighties 307.
My question is how much power loss is there with these heads compared to the original #5's ? The car has about 90 K miles on it so I plan to eventually pull the motor for a rebuild & replace heads with the #5 heads.
Just curious to know what people think of this application.
Thanks !

 

Take a picture. Is the A, the same size? I believe there was a rare 69 5A head where the A is smaller and slightly off to the side like the 71 7A head. If those are the heads, they will be as good as any 350 factory head. Also the 307 heads had 1/2" vs your factory 7/16" head bolts.

 

Olds 307 & 403: the heads definitely have stamped "5A" on them. The numbers stamped on the block (395558 2) suggest that it is a 350 motor.

 

Yes there is evidence of 5A heads in 69. BTW, the 7 heads are 71 350 and 72 is the 7A 350. Difference is 71 only had hardened exhaust seats, 72 had both intake and exhaust hardened seats.

 

395558 2 is a common 350 block from 68-76.
Your heads (5A) should have a casting number of 397 742

 

Allen, will check my casting numbers. Thanks. So what you are saying is that these "5A" stamped heads could be the original heads that came with this 350 motor (68-76).
If so, would they be the same as the #5 heads in respect to CR, size of valves, & flow ?
I know that a 5A head was made for 1980"s Olds 307's also but what I am hearing from forum members is that head would not fit on the (68-76) 350 motor. Is that correct ?
Thanks !

 

Allaan, the 72 heads are 7a, not 7A. The 7A heads were later smog heads.

 

Yes, they could be original to the car and yes they were for 350 engines. Yes, they would have the same CR valves and flow as the 5 head.



Glennnn?, The 72 heads are 7A. I know this for a fact, and they are OEM on my 72 Cutlass. 7 heads were 71. 8 heads were smog heads (73) 350 engines, and J heads for 455. Better have another cuppa coffee my friend.

 

Note: Although the 395558 2 was a standard 350 block for those years, the heads changed almost yearly. The 5A were only 68/69

Do you know where to look for your head casting (6 digit) number?

 

Allan, my understanding is that 6 digit number is located "around" the center valve cover bolt on driver's side ?

 

Allan, I have had two 72 Cutlasses with 350's. My point I was making is the heads are 7a (note lower case a) and not 7A (note upper case A). In post #4 you were saying 72 was 7A (upper case).

 

First, the block number doesn't "suggest" that it's a 350, it PROVES that it's a 350. Unfortunately, that is irrelevant. What is the HEAD casting number, above the center two exhaust ports. That's what matters.

 

The head casting number is 6 digits, broken into groups of 3 on each of the heads, not just the VCs.
They'll be similar to this

 

OK. Checked under several layers of grime & found the heads to be stamped: 397 742A
Nice to know they are at least period correct. I am planning to have this engine/heads rebuilt in the near future.
Thanks to all who responded.

 

Sorry I meant to put 7A heads were 1972, not 71. I would like a set of those 5A 350 heads to hide a bigger motor on a 83/84 Hurst/Olds or a 85 442.