Timing Question

I am going to be breaking in a rebuilt LA 318 soon - it's going in a 3800# car and now is zero deck w/ magnum heads. I intend to use the head gasket to set quench distance at .038" - my question is what to do with the distributor & timing? I have an FBO vacuum advance distributor I got from them years ago and have been running with a factory electronic ignition before the rebuild (all stock LA318)with no issues set at factory timing specs. I also have a stock factory electronic ignition distributor I can use. What should I set timing at and do I need to swap vacuum cans now that I'll have the high-quench/closed chamber heads? I really want to avoid detonation as the pistons are now hypereutectic KB197s...

I have a 410 stroker (0.040 360 w/4" crank) running closed chamber RPM heads, Icon d-dish forged pistons (true 10:1) and Voodoo 276/.513 cam with MP ignition. I have my initial set at 18 deg and 36 deg total all in by 2500 rpm. It runs GREAT and starts with a bump of the key.

Not sure about the vacuum canister, I actually had similar thoughts as to if I need to swap it out due to the larger cam/choppier idle...not quite sure how different canisters affect the engine at cruising speeds. As far as running and starting though, it's spot on where I have it set.

I would proportion some race gas in there to elim the potential of any pinging for the breakin to get that over and done with with no issues. I would set the initial at 15 & use the FBO dist with the total at 35 (15+20 in the slots) with the can plugged in which will add more and springs selected to max at ~2500-3K, roughly the range that your breakin RPM will be at. or the OE dist with the heavy spring with the elongated loop one one end, toss it & keep the light spring in there & if you have a parts dist (2) light springs would be even better & can plugged in also. #1 #1 splurge on the octane to elim any possibility of pinging during the breakin. we can fine tune the dist later for your choice of lesser octane gas for your app.

With a unique combination like that you will need a dyno or track time to dial in your total timing.

I had a 5.9L Magnum engine with a 670 Holley, M1 dual plane intake and headers. Same combustion chamber as you. I set my total timing to the fastest pass at the track which ended up being 31 degrees for total.

Magnum is dead on, with CC heads I would limit the total to 31 instead of 35

I'm running CC heads at 10:1 with 36 total timing and ~0.039" quench and mine doesn't ping with 93.

The exact number is irrelavent. Its only a starting point. A modern chamber will generally run a lower number.

If I recall correctly I too was able to go above 31 but the truck did not go any faster. Since it was a stick and a truck I ran not too close to the edge.

Every engine is different. You should start with near-stock specifications and adjust from there. Track testing is the best or another choice is floor it up-hill with the A/C on (old-school) and listen for a ping.

I've had very good luck with stock electronic distributors, but if you have a better one, you can use that too.

The stock vacuum advance canisters are adjustable with a small allen wrench in the hose nipple on the vacuum can.

Thanks for the replies! What's the total advance with the stock electronic distributor? By retarding the initial, does it also retard the total?

Yes, unless you go back and fix that. How you fix it depends on what distributor you are running. Stock ones involve filing slots.

Regarding the vacuum adjustment, that only adjusts the vacuum required to engage it, not the amount of advance.

2 common slot length are stamped 11 and 17 (22 and 34 on the crank you see with your light), way too much. the FBO $22 plate is the easiest reasonable fix for this (& has slots for 10/12/14/16 and 18 crank degrees)

Regarding the vacuum adjustment, that only adjusts the vacuum required to engage it, not the amount of advance.

Good tip... I didn't know that.