68 Olds 350's had the desirable #5 heads with small chambers. If still equipped with factory pistons and heads,
compression ratio for a 2 bbl engine was 9:1 but for a 4bbl engine was 10:1
1968 SBO tuning
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68 Olds 350's had the desirable #5 heads with small chambers. If still equipped with factory pistons and heads,
compression ratio for a 2 bbl engine was 9:1 but for a 4bbl engine was 10:1
Exactly what I was after. I bet it is the two barrel version, if stock inside, running on mid grade gas.
Unfortunately it had to be bored 30 over and at the time we grabbed the cheapest pistons we could I don’t have the details on them but based on my guess they were likely Keith black cast and then to my knowledge the heads weren’t milled either so I lost compression there as well from what I’ve read.
It came to us as a 4bbl I believe.
The advance is non adjustable so it will stay at 10 unfortunately until I can buy an adjustable one. The timing in my limited testing that I have now seems ok once I of course am able to get this carb tuning squared away.
Totally changes everything. You want at least 10 more, if not 20 more degrees of vacuum advance. I would almost swap around initial and mechanical as well. 38 to 40 without vacuum advance. I ran nearly 60 degrees part throttle with manifold vacuum advance. Using those garbage pistons means you are probably under 8 to 1 compression. Low compression Olds V8's improve performance with a lot of part throttle timing.
Really that’s interesting because I tunes timing via the vacuum gauge and best vacuum was at 30 initial and then I had 21 in the distributor with 10 on the can and as crazy as it sounds I don’t remember any pinging though the idle is so much smoother with the current timing and my vacuum is only about 1 lower and my idle is actually somewhat within range so i wasn’t sure what the heck tuning non computer controlled is strange to me considering no matter what I research or try it never does what I expect [emoji52]
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No, that sounds about right. Only problem with that much mechanical timing is top end performance. It could cause detonation at higher rpm. With vacuum advance, that timing going away as you open the throttle, mechanical doesn't.
Ok cool I thought it was crazy next time I have time I’ll have to play with the timing more I thought the most total timing I should run was about 38 you’re saying I could run into the 40’s without vacuum advance and grab better performance?
Is there anyway to figure out my compression without pulling the heads maybe numbers from a compression test or something?
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Is there anyway to figure out my compression without pulling the heads maybe numbers from a compression test or something?
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