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On the heads that are mismatched on my 69 cutlass 350. The vehicle sn is 336879M163895. That does not seen to match either of the head # 5A397 742 or # 3A554 716.The block # is 3955582 located top front of block next to oil the tube. I was wondering if I would be able to use one of the heads and get another to match it. If so which one? Thanks
To precisely and completely answer this,we need the block VIN derivative from the block stamped just below the #1 spark plug on the BLOCK not the head. The number next to the oil fill tube is casting/part type # not the VIN derivative. Matched heads will work and probably the 5A is the best choice but get us the block VIN derivative.
One more time. Head casting number 397-742 is a #5 small block from a '68-'69 350 engine and has 7/16" head bolts. It is NOT a 5A head. A 5A head fits '80-'84 307 engines. The 3A head with casting number 554-716 fits a '77-'79 350 with larger 1/2" head bolts. As SugarBear and others have stated, the VIN derivative number stamped on the block is needed to fully ID your engine.
To precisely and completely answer this,we need the block VIN derivative from the block stamped just below the #1 spark plug on the BLOCK not the head. The number next to the oil fill tube is casting/part type # not the VIN derivative. Matched heads will work and probably the 5A is the best choice but get us the block VIN derivative.
pgalioto1:
Your block is a '79 350, it has windowed main journals which are not are strong as the earlier (pre '77 blocks). It also has 1/2" head bolts. If you want to run earlier (pre '77) heads you will need to drill out the bolt holes in the head to fit the 1/2" head bolts. If you already have one '69 #5 head, it's had the bolt holes drilled out to fit the 1/2" bolt holes in the '79 block. You still have a compression ratio mismatch between the earlier #5 head and the later 3A head.
That's good news that it is a '69 block. At least it is the correct year for the car. Now if 5A and 5 heads are identical he just needs one head preferably a 5A if not a 5. Depends on how correct he wants the car.
The difference is the size of the A. On the early engines the A is small, about 1/2 the size of and offset downwards and away from the number/letter. On the later engines the A is the same size as the number.
Here's a pic of 1972 heads with the small A and 1980s 307 head with the large A:
Last edited by Fun71; September 7th, 2020 at 03:04 PM.
The difference is the size of the A. On the early engines the A is small, about 1/2 the size of and offset downwards and away from the number/letter. On the later engines the A is the same size as the number.
Here's a pic of 1972 heads with the small A and 1980s 307 head with the large A:
The A is large not small...the reason I know is because I have the 5A heads with the casting number from 1969. Believe what you see not what you hear.
they are 69 heads. not 80;s..I posted the casting number on the heads...the casting number is from 1969.
I realize that, other than die hard Olds guys, no one knows two varieties of 5A heads exist. Put some grease over the block casting number and everyone else will think it is a Vin 9 307 under the hood. I wonder why they changed where the A went on the 72 7A heads?
I realize that, other than die hard Olds guys, no one knows two varieties of 5A heads exist. Put some grease over the block casting number and everyone else will think it is a Vin 9 307 under the hood. I wonder why they changed where the A went on the 72 7A heads?
I guess I can use it to my advantage next time I lift the hood.
March 31st, 2020, 08:39 AM
