Hi I am wondering about the timing for my engine. I know there are so many factors involved but I am curious what most are running for timing? No advance, just crank trigger and no advance in the distributor. 605 BBC 14.5 compression. The cam is 287/306 @ .050 824 lift.

My 582 seems to run best at 34 degrees.

Most all of my motors are Small Blocks but same applies to BBC. We have always been told to run 38* timing. Well I have spent a bunch of time on Dyno and I can tell you best performance and runs cooler to is around 30* + or - 2*. It runs better, cooler and easier on motor.

On most of mine the "Sweet Spot" is 28-32* and in that the performance is same. If I go below about 26 or above 34* it starts losing power. It does not lose as much power with more timing but it loses a little and runs hotter and harder to start so I like to keep it in sweet spot.

One other thing many people are running way too fat and if you are then you can get away with more timing with out hurting it as much. So if it is fat then you may run 38* timing and plugs look good and performance good but you can pick up a few ponies by leaning it down some then bringing timing in lower.

Some time on dyno is well worth the money if you have a good Dyno Dude. With out a Dyno I would go to the track and start at 36* and pull 2* timing every run until it slows down then go back up 2 or 3*.

One other thing many people have their timing pointer off a few degrees and do not know it.

34* on my 15.1 565 with Rons alky injection seems to be the happy spot

598 and 632 were happy at 38** with the 385 head on Q16.
Never a problem. Buts that my combo's

All relative. No answer is right too many factors. Ive seen balancers changed and they are marked 2* different.

Start at 30*, make run, add 2* and compare MPH. Keep doing that until MPH drops off. best MPH is the timing you should be running (for that tune) Change carb, start over. Can fine tune from there.

My 632 likes 34, the 468 likes 36.

The method ski suggests is pretty good, adding 2* per pass or dyno pull until it flattens out/tips over.

The last tires/rims I put on my dragster before I sold it shook so bad I had to leave at 28* then bring it back to 36* .5 second into the run. It was still set-up like that when I sold the car with those tires/rims....

Gas or alky changes things too.

Investing in Digital ignition is an easy way to quickly move timing and I find it accurate. Start with timing set to maximum and retard to desired value.

A few factors that effect timing, A/F ratio, speed of the combustion chamber, type of fuel and the piston dome (shape).

If it were me and i had not put the engine on the dyno, If I KNEW the A/F was right, I would put new plugs in it around 34 (gas) make a pass and read the ground strap and adjust from there.

to answer your question, most BBC leave the dyno between 36-38 degrees.

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Originally posted by sr4440:A few factors that effect timing, A/F ratio, speed of the combustion chamber, type of fuel and the piston dome (shape).
If it were me and i had not put the engine on the dyno, If I KNEW the A/F was right, I would put new plugs in it around 34 (gas) make a pass and read the ground strap and adjust from there.
to answer your question, most BBC leave the dyno between 36-38 degrees.

You being a dyno operator, probably seen much and has gained great knowledge of combinations. What is your opinion on what EFI likes in timing compared to carbs, EFI on methanol vs race gas? Less, more, same?

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Originally posted by markemark:

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Originally posted by sr4440:A few factors that effect timing, A/F ratio, speed of the combustion chamber, type of fuel and the piston dome (shape).
If it were me and i had not put the engine on the dyno, If I KNEW the A/F was right, I would put new plugs in it around 34 (gas) make a pass and read the ground strap and adjust from there.
to answer your question, most BBC leave the dyno between 36-38 degrees.

You being a dyno operator, probably seen much and has gained great knowledge of combinations. What is your opinion on what EFI likes in timing compared to carbs, EFI on methanol vs race gas? Less, more, same?

Timing between methanol and gas, assuming that the A/F is correct for both, you will have less timing with methanol. Timing come down to A/F distribution to each cylinder, you have to tune to your leanest cylinder, once that cylinder goes lean enough to not support a stable flame, you lose power. EFI is better at fuel distribution. All things being equal a well-tuned carb will usually make more power due to the cooling of the intake charge making a denser mixture.
For timing between EFI and A carb, they are real close to the same, maybe a tick less for EFI because you usually end up with a slightly leaner A/F ratio.

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Originally posted by sr4440:Timing between methanol and gas, assuming that the A/F is correct for both, you will have less timing with methanol. Timing come down to A/F distribution to each cylinder, you have to tune to your leanest cylinder, once that cylinder goes lean enough to not support a stable flame, you lose power. EFI is better at fuel distribution. All things being equal a well-tuned carb will usually make more power due to the cooling of the intake charge making a denser mixture.
For timing between EFI and A carb, they are real close to the same, maybe a tick less for EFI because you usually end up with a slightly leaner A/F ratio.

Do you think using TB EFI could be same (cooling of the intake charge) as carb and be better at maintaining the desired AFR with the ECU?

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Originally posted by sr4440:
Timing between methanol and gas, assuming that the A/F is correct for both, you will have less timing with methanol.

My 665" 9* headed deal is happiest and fastest at 38* on methanol. As to the timing being less on methanol than on gas, my experience and pretty much everybody I know is quite the opposite. Every methanol engine I've been around wanted more timing for best performance than it did when on gas, mine included.

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Originally posted by Alaskaracer:

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Originally posted by sr4440:
Timing between methanol and gas, assuming that the A/F is correct for both, you will have less timing with methanol.

My 665" 9* headed deal is happiest and fastest at 38* on methanol. As to the timing being less on methanol than on gas, my experience and pretty much everybody I know is quite the opposite. Every methanol engine I've been around wanted more timing for best performance than it did when on gas, mine included.

What A/f ratio are you running?

The reason I ask is I have had maybe a dozen people come in with a known good methanol combination, we run it, get dyno numbers, find out they are running a rich A/F ratio. Then pull a bunch of timing, start leaning the engine out until it stops making HP, then add timing back in until it stops making HP. Always end up with less timing and more HP. Usually add a little more fuel just for the engine to not be as weather sensitive.
But your engine may be different, I don't believe I have done a 9* head engine.

Here's something fun Google "At stoichiometric air/fuel ratio which fuel burns faster gas or methanol."

This message has been edited. Last edited by: sr4440,

Cute (true) story about timing problem.

Someone recently contacts me about a Grid problem. Sends me a pic of the timing channel in a Data Acquisition and asks why it always reads 21* in a flat line when he has Launch Retard programmed. I have him take a pic of the Grid General Settings and Ignition Timing/ Engine RPM. The Max timing Reference is set to 36* and Max total Retard is 15*. This is normal. The Ignition timing is programmed to 0.1* at all rpms. Obviously programmed incorrectly, hence the always 21* output as Grid is in full 15* retard all the time.

They stated that they had the crank trigger pick-up moved to the far end of the prior adjustment window and got the timing set to 24* with a timing light and was running it this way. He said if they moved it further it wouldn’t run right.

Get everything corrected and running full 36* at idle and Launch Retard working as programmed. This is a carb sbc on methanol. The difference in et from being stuck at 24* all the time to running full 36* after Launch Retard timed out was 0.02 faster. The car was much more consistent after correction. Hard to believe how little the et improvement but saw the et results and true.

Thanks for the replys! My timing was at 36, turned down to 30 to try and kill the lower end for a slippery race and have to turn it back up for this weekend. I was just curious as to what most are using. Conventinal 24* head BBC engine, C14+ fuel and a simple 7AL2 ignition.

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and a simple 7AL2 ignition.

MSD Grid 7730 interfaces excellent with the 7al2 analog ignition…just saying.

SR4440, thanks for the meaningful input. It is great to have an actual Dyno operator in this forum for questions like this.

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Originally posted by markemark:
Cute (true) story about timing problem.
The difference in et from being stuck at 24* all the time to running full 36* after Launch Retard timed out was 0.02 faster. The car was much more consistent after correction. Hard to believe how little the et improvement but saw the et results and true.

I can confirm a nearly identical result from testing with my steel-headed BBC 10 years ago. Was trying to kill 4 tenths to run an index race, (no throttle stop), and kept backing my timing down from 36* in 4-degree increments. Took it all the way down to 24* and it still ran within .02, on a stable weather test day. Dropped it down to 20*, and it sounded very unhappy, so I decided not to make that pass. This was 1/4 mile on Methanol, and since the 32* pass was within .002 of my normal 36* timing at every increment, I left it set there at 32* after that day.