Went to a friends house as he asked me to give him a hand install a nitrous kit . Got there got things hooked up and asked what pills he was putting in it . He said 175, i said ok , we probally need back off the timing alittle . He laughed and said to what , i said a few degrees anyways . He laughed again and said , i've never had a timing light on this motor .. ever . Humm

I had mine with me , wanted to see what the total was . So i looked and vac advanced hole on the hei was blocked off . I had him bring the rpm's up to 2,500 turned the dial on the back of the timing light and had the balancer at zero it read 41 , i did it at 2,800 and 3,000 rpm , that read 43 on the back with the balancer at zero . Pulled number one plug TDC and the balancer hadn't slipped.

I was at the track the weekend before with him and the car went 12.18 at 112 mph . He said he usally runs 93 octane , the block is zero decked , has forged flat tops and 58 cc heads . Wouldn't this motor ping with that timing ? I thought i recalled most small blocks like 34 to 36 maybe 38 .

I suggested after checking with another timing light ( same readings )to back the timing off and forget the bottle for now . Now if the car loses et and/or mph , should it be set back to where it was or is something else off to check ? Did i do something wrong ?

Hows it run with the timing backed off? Try it,,,Dave

I've always believed that once the car starts to detonate, it will loose power and MPH. You will not have to hear it, you'll see it on the time slip.

I always started tuning with less timing than I knew the car wanted. Then I'd keep advancing it 2 degrees at a time and make a pass. If the mile an hour keeps picking up, I'd give it another 2 degrees. If the car fell off, I'd back it up 2 degrees and leave it. One afternoon of tuning at the track and you'll find exactly what it likes.

Hope that helps.

PS - My last SBC ran best at 40 degrees. Despite what I just stated, I was always scared to give it more. Never did try 42.

So much for the set it to 36 theory, mine runs the best @ 29, go figure.

Timing is just a number. The correct timing is what the engine runs best at. Lots of factors play into what the number will be. I have two 383's, one runs best at 32 and the other at 35.

So much for the set it to 36 theory, mine runs the best @ 29, go figure.

My friend who bought my dyno builds engines for a local short track. They are 355", use Vortec heads with the marine manifold, and timing is 27 degrees.

My APBA World Record Breaking hydro ran a 427, and on the dyno, lost power above 34 degrees. It held two world records when I sold it.

That much spark lead to me shows the engine could use less octane. Yes less octane. You can over octane a engine to the point that you have to advance the timing so far in advance to start flame propagation earlier to get a more complete combustion cycle. Is the camshaft to crankshaft timing retarded severely? Perhaps try some 91 octane? Fiddle around with a slightly lower octane and different spark leads. Let us know what you find. What heat range and type spark plugs? You want just enough octane and spark lead to support complete combustion without detonation. Makes for the most effcient combustion cycle.

I can see how 43º would make the bottom end feel stronger but it's also likely that it's resulting in less power once it's all in. With 43º a lot of energy is being wasted trying to overcome the combustion trying to push the piston back down the cyl on the compression stroke. I made the same mistake years ago. I kept adding advance and it kept feeling stronger. I was certain that my next trip to the strip would yield the best time slip yet but it didn't turn out that way. It ran almost .3 sec slower! One of the more experienced racers put a light on it and it was at 44º. Backed it off to 38º and got my .3 back on the next run.

Interested to see what the next track time slip looks like.

I have my nova locked out at 38-40. Its been that way for a good 4 years now and no problems with melted aluminum. when i spray it i back it down to 32-34

Lets not forget about the accuracy(or lack thereof) of many dial back timing lights.......

Are you sure that the "zero" on the timing tab is correct?

Well , he decided to run it on nitrous ( no motor passes ) the 125 kit and timing at 36 degree's , it went 11.21 @ 122 . Still would like to have him run it no nitrous and mess with timing . I'll let him fiqure out what he wants to do , as he got 3 passes and had no issues .

Keep in mind that HEI systems will retard timing aproximately 1.5 degrees per 1000RPM after max mechanical advanve is achieved. This is due to the way the magnetic triggering grounds the module on the back side of the sine wave. as the pole piece spins faster the magnetic wave grows larger and the trigger event is later.
The HEI has a built in retard function!!! Kinda cool huh

If his timing is at 43 at 3000, going through the lights at 6000 you would have to deduct 4.5 degrees so he is ony at 38.5.....

Milan