HELP! Top End Rebuild 78 Olds 350
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Joined: Sep 2019
Posts: 13
From: Oklahoma City
No I would leave them alone if they are ready to go. If they need the valves replaced I would consider it. No point in spending too much on factory heads nowadays with the cheap aluminum heads that are available now.
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Joined: Apr 2012
Posts: 1,606
From: Bradenton, FL
Im located in southwestern ohio north of Cincinnati. Might be worth the trip to grab those #3 heads if the #5's don't work out
Didn't the "5" heads have a smaller compression chamber than the original 3A heads therefore the thickness of the gasket minus the smaller combustion chamber equals out the same? They do, I'm talking about #3 heads, NOT #3A, they came on 330s and have ~64cc combustion chambers
Also, your saying the head bolt holes need to be drilled as well, im assuming this would be done by a machine shop. Are the angles the same? I read something about some being 39° angles rather than 45°. ALL Oldsmobile V8 head bolts are square to the deck, you're thinking pushrod holes.
I thought the 5 heads (no "A", being from 68 or 69) would be a good match? Are there any options besides 3A that are a direct bolt on? I just was to upgrade while im at it but dont really have to funds do go have something machined. I have no idea how much and of that would cost. They are, I like to use the #3 and #4 heads from 330s on the later models to make up for the massive piston dish and thicker head gasket. You will, no matter what, have to have the head bolt holes (On 2, 3, 4, 5, 6, 7, 7A, 8 heads) drilled out to 17/32 on a mill drill that has a square table that can support a 53lb cylinder head at 90* through every single hole. I have the second largest Harbor Freight standing drill press and broke through one of the outer head bolt holes on my heads because it wasn't square. No worries on the rest of the machining. At least have them cleaned, magnafluxed, and surfaced before installing.
I was just told the "5" heads were highly desirable and a good fit Correct, they are.
Didn't the "5" heads have a smaller compression chamber than the original 3A heads therefore the thickness of the gasket minus the smaller combustion chamber equals out the same? They do, I'm talking about #3 heads, NOT #3A, they came on 330s and have ~64cc combustion chambers
Also, your saying the head bolt holes need to be drilled as well, im assuming this would be done by a machine shop. Are the angles the same? I read something about some being 39° angles rather than 45°. ALL Oldsmobile V8 head bolts are square to the deck, you're thinking pushrod holes.
I thought the 5 heads (no "A", being from 68 or 69) would be a good match? Are there any options besides 3A that are a direct bolt on? I just was to upgrade while im at it but dont really have to funds do go have something machined. I have no idea how much and of that would cost. They are, I like to use the #3 and #4 heads from 330s on the later models to make up for the massive piston dish and thicker head gasket. You will, no matter what, have to have the head bolt holes (On 2, 3, 4, 5, 6, 7, 7A, 8 heads) drilled out to 17/32 on a mill drill that has a square table that can support a 53lb cylinder head at 90* through every single hole. I have the second largest Harbor Freight standing drill press and broke through one of the outer head bolt holes on my heads because it wasn't square. No worries on the rest of the machining. At least have them cleaned, magnafluxed, and surfaced before installing.
I was just told the "5" heads were highly desirable and a good fit Correct, they are.
Thread Starter
Registered User
Joined: Aug 2018
Posts: 58
Alright, ive got them. The #5 heads are mine!
Now, they came with no valve springs, retainers, or anything besides 3 spark plugs and the valves lol. Can i use my factory springs or do i need to do some measuring and order something special?
Im waiting on head gaskets from rockauto that got retuned to sender and am thinking im just going to have to go to autozone and pay double to get them to me before next year..
Also, should i have it ported when i have it checked and the head bolt holes drilled out?
Now, they came with no valve springs, retainers, or anything besides 3 spark plugs and the valves lol. Can i use my factory springs or do i need to do some measuring and order something special?
Im waiting on head gaskets from rockauto that got retuned to sender and am thinking im just going to have to go to autozone and pay double to get them to me before next year..
Also, should i have it ported when i have it checked and the head bolt holes drilled out?
Last edited by Goodoldsreliable; Oct 22, 2019 at 05:51 AM.
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Joined: Dec 2006
Posts: 10,104
From: Melville, Saskatchewan
I know the number 5 heads use regular retainers and your 3A heads use rotator retainers. You may be able to use them but it will depend on the spring pocket height on both heads. The Edelbrock Performer Plus springs are affordable but require non rotator spring retainers.
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Joined: Aug 2011
Posts: 4,109
If you are planning to install the springs and seals yourself go for it; but, no matter who assembles them be sure to vacuum test/seal check the final valve job before putting the heads on the block. This is literally a five minute procedure at a machine shop that cannot be done unless the heads are assembled, it confirms that the newly done seat grinding and valve grinding make a proper seal. Ask them to show you how it is done to learn.
Good luck!!!
Good luck!!!
Thread Starter
Registered User
Joined: Aug 2018
Posts: 58
What price range should i he looking for? I was expecting around $100 to have them cleaned and resurfaced, then a tad bit more for the drilling out of the head bolt holes. This guy just said itllbe around $420 to get them ready to bolt on. Should i grab my heads and run??
No it's not a parts car!!
Joined: Nov 2010
Posts: 438
From: NE, Illinois
What price range should i he looking for? I was expecting around $100 to have them cleaned and resurfaced, then a tad bit more for the drilling out of the head bolt holes. This guy just said itllbe around $420 to get them ready to bolt on. Should i grab my heads and run??
new Valves and springs installed. If they are doing all of that and also drilling for larger head bolts, $420 sounds reasonable.
Out of Line, Everytime😉
Joined: Dec 2006
Posts: 10,104
From: Melville, Saskatchewan
Rod or main? Strip it down and get the crank turned or find a pre 77 Olds 350 block or motor. If the rods spun, they need resized by a machine shop. The 77 and up has a windowed, weaker block.
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Joined: Aug 2018
Posts: 58
Now that weather is warming up im doing some thinking. Will any pre 77 350 and its trans work here? No other major adaptions should have to be made, correct?
im going back and forth on whether it even matters to get a 76 or earler engine since i just planon having it as a daily/cruiser. I don't want to just abandon this engine because its "weaker".
im going back and forth on whether it even matters to get a 76 or earler engine since i just planon having it as a daily/cruiser. I don't want to just abandon this engine because its "weaker".
Last edited by Goodoldsreliable; Apr 27, 2020 at 09:10 AM.
Out of Line, Everytime😉
Joined: Dec 2006
Posts: 10,104
From: Melville, Saskatchewan
Any 68 to 80 Olds 350 will work. Even a 330 would bolt in place if in good running shape. The 73 to 76 motors seem to be easiest to find in good running shape. A 77 to 80 motor will work and worth less money. Just make sure it isn't a 260, a pre 85 307 would also work. The 85 and later 307's have tiny ports and a dog reputation. The transmission depends, just leave your current one in there. Get an estimate to rebuild your current motor and go from there. Good luck.
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