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Looking for a good set of 79 olds 350 heads for my H/O...did complete rebuild then I let my daughter drive it. She got it hot & cracked heads. I will get some casting numbers this wk. Any help would be appreciated.
Bad things happened when my daughter drove my Olds as well. Those 3A Olds heads are very crack prone. There was a bunch of new replacements on Ebay a few years back. There is a couple of rebuilt 3A heads on Ebay right now.
Olds heads have a number for small blocks and a letter for big blocks near the #1 spark plug. This makes ID very easy. Different years had different heads with different flow rates, valve sizes, etc. so all Olds heads are not created equal.
You might want to consider getting some older 350 heads and having the bolt holes bored out for the ½" head bolts. Some 7 or 7A heads would be less prone to cracking and should help a bit for performance.
I completely agree on older heads. They flow better and will put your compression back 8.5 to 1 without milling. All the later #A heads have horrible exhaust ports with a small 1.5" exhaust valve. Your 3A heads have a well known cracking issue, so even replacements could do the same.
Thank you for all the info. I've already put flat top pistons in it. Are the older head have smaller combustion ports? It's already spark knocks some with the 3a heads, idk about making compression any higher...thoughts?
The best bet would be #8 heads, I have found 77 to 78cc stock, 79cc is the stock spec, your stock heads are supposed to be 75cc. With a clean up mill, you will only be around 9 to 1 compression with #8 heads. They need a bowl hog cutter under the exhaust valves to flow as well as early heads, there is a lip there but they have 1.625" exhaust valves. A 2" W31 replacement intake valve with a bowl cutter under the intake is also a good idea. What cam? Stock carb?
That carb is calibrated very lean, doesn't help detonation. What is the duration or cam model? Unless you find the 3A cheap, #8's will help your detonation and they rarely crack.
You should be able to get the #8 heads cheaper than the early heads. They need more work than earlier heads to flow well but much less than your current heads. Like I said, a bowl hog cutter under all the valves and a 2" W31 replacement intake valves are a good idea. If you have new springs and regular retainers on your current heads, factory on both heads are rotator retainers, those should transfer over. Good luck. My Daughter overheated my Dakota and cracked the Magnum heads in it, also very common. She also ran the 2004R in my 70 low on fluid, left town without telling me, cooked it. Also had a pushrod break while driving it, not really her fault. The oldest daughter fried the original V6 in the Dakota, smashed it up and the youngest daughter has smashed the Tercel twice and nearly ran it out of oil. So yes, I know a bit about both issues.
Last edited by olds 307 and 403; March 27th, 2019 at 07:20 AM.
March 25th, 2019, 05:00 PM
