hammertime

Im working on a 71 with a 350 in it. The engine was apart when i picked it up.I have two good sets for heads , a set of 5 s and a set of 7 s i want to run a 4 barrel carb headers cam and a shift kit in the trans. Witch heads would be best to use .

80 Rocket

Run the set of heads that are in better shape. Performance wise, very little difference. Nothing the *** dyno will feel.

redoldsman

The 7's have hardened valve seats while the 5's don't.

MDchanic

Actually, I think the 7As have hardened valve seats, but the 7s don't.

The only meaningful difference between the two is that 7s had valve rotators, and deeper spring pockets to accommodate them, and the 5s did not.

- Eric

hammertime

Thanks for your input . The 7 s are on a running engine that im going to slip into the car untill i get the extra money to rebuild the original block and do the heads. Im going to have it going down the road by new years day ! Im going to start the new year off the my way.

redoldsman

I know the 7a's have hardened seats but for some reason I thought the 7's did too. If I was putting money on one of us being right, I would put my money on you.

1969w3155

Didn't the 7's debut in '71, the first year for hardened valve seats?

67 Cutlass Freak

According to this chart, the #7s were introduced in '71 with non-hardened seats, but the '72 version did have hardened seats.
001.jpg
I have talked to a lot of Olds engine builders, and racers, that feel hardened seats are not needed. Some of the #5 heads came with 2.00" intake valves. I agree that you should use which ever set was in better condition.

MDchanic

I would agree.

- Eric

joe_padavano

And yet, at one time Mondello also claimed that headers don't fit Supremes...

Sorry, but all Oldsmobile heads from the 1971 model year onward have factory induction-hardened valve seats. I was alive and reading the car magazines at the end of 1970 when this was reported on. There is no basis for the "little A means hardened valve seats" rumor - otherwise, why don't we have JA heads??? The induction hardening only goes a few thousandths of an inch into the cast iron, so the first time you have the valves cut, it's pretty much gone. To the OP's original question, any 4, 5, 6, 7, or 7A heads are virtually identical from a performance standpoint.

MDchanic

That reason would probably be because you saw Joe mention it before, and I didn't.

- Eric

Lars

Use the ones with better valve guides. Keep an eye out for uneven spring pockets.

hammertime

Thanks for all you help . Im thinking i will use the 7s that i have on the running engine after i get them redone. I just want to have fun make some noise burn off some of those tires and to hell with those dam hybrid P.O.S. ! ! !

Macadoo

When I had my 7s in for milling and refreshing, I was told they had hardened seats. That doesn't necessarily mean they do but I thought I'd add to the confusion.

hammertime

Im looking for a factory HEI dist. to put in my 71 cutlass 350
, does any body know what will fit without getting a new one

don71

Hammer, you could get a factory used one from...1974-1979. Any 350,403, or 455. I call these "four pin module" units.

The first one I used was from a 77 403. The one I'm currently using came from a 75 455.

You might want to install a re-curve kit or a adjustable vacuum advance. But this could be done at any time later down the road, just to tailor/tune it to your combination.

Easy to do.

joe_padavano

Any factory Olds HEI with a vacuum cannister will work. Avoid the CCC distributors from the 307 that do not have a vacuum cannister.

hammertime

Thanks once again i hope to have the car running on this saturday. All i have to do is find that hei dis. and it will be running down the road, This has been a good father son project we have learned so much about the car and each other.Thanks again.