Oval Track Dizzy… Locked Advance or Not?

[sanfordandson]

In restricted classes, such as circle track where everybody has the same size 2-bbl carb, using this curve with the initial set to wherever makes the best power, depending on carb size 350, 500 or 390, etc. but typically advancing from 36 at 3000 to maybe 44 at 8000, is almost an unfair advantage in a field of engines which are “all in at 2500” because the locked or all in early timing retards as RPM increases (because the electronics in modules or CD boxes have a constant slew rate) and engines actually need more timing because of the high intake vacuum at high RPM. This curve compensates for the retard and allows timing for best torque and then advancing to best power at high RPM.

you wont see anywhere 8000rpm with a 2bbl combo..especially the OP's combo. we have tried a similar setup and while it does help at higher rpm the loss of power at lower rpm from decreased timing was not worth it in the end.

[ZEROMAN91]

Don't forget to check the rules, at my track they take the cap off and see if the advance mech move 10* they use a gauge to measure. We use GM HEI by rule.

[Krooser]

Don't forget to check the rules, at my track they take the cap off and see if the advance mech move 10* they use a gauge to measure. We use GM HEI by rule.

Here's the rules…

"Distributors. Stock O.E.M. distributors only. Billet distributors allowed. No multiple-spark
boxes. No magnetos or dual-point distributors allowed. Any coil used must fit in stock
cap and must use stock coil cover. GM H.E.I. Distributor can be interchanged with Ford
and Mopar engines. Adapt-A-Cap is allowed"

WISSOTA has some of the dumbest rules ever… so many contradict themselves. But that's what you get when you have rules by committee…

[billet]

With all you and your son are going to have to learn (it's a ton), Keeping things simple and not worrying about the engine part of it will be a big help. Concentrate on the driving and chassis side of it, an adaptive driver and/or well handling racecar will overcome large %'s of horsepower. That is part of the reason, I'd just lock the dissy.

Just look at the IMCA modified guys complaining about the crate engines, lol. These are the guys that have 700HP+ 430's and complaining it ain't fair they get to run a 400HP 604 crate engine. These crate engines for the most part are the dominate combo on all but the really big or hooked up tracks.

I can tell you from over 20 years into circle track racing, it takes time to learn everything you need too least to a reasonable level. Also keep in mind who you get advise from, one of the hardest things you will have to figure out is whether there is a car issue or a driver induced issue and also whether the problem the car has (per what driver says) is even a correct diagnosis. When you watch your son race, don't get caught up in the moment and just watch the race like a spectator; you need to be watching the attitude of the car along with a ton of things to double check what the driver says is happening with the car. I will give you a big clue and something that is pretty easy to watch that will help you out: Watch the front wheels as is what direction they are pointed at all times. This will help you figure out if the car is tight or loose.

Good luck

[Krooser]

With all you and your son are going to have to learn (it's a ton), Keeping things simple and not worrying about the engine part of it will be a big help. Concentrate on the driving and chassis side of it, an adaptive driver and/or well handling racecar will overcome large %'s of horsepower. That is part of the reason, I'd just lock the dissy.

Just look at the IMCA modified guys complaining about the crate engines, lol. These are the guys that have 700HP+ 430's and complaining it ain't fair they get to run a 400HP 604 crate engine. These crate engines for the most part are the dominate combo on all but the really big or hooked up tracks.

I can tell you from over 20 years into circle track racing, it takes time to learn everything you need too least to a reasonable level. Also keep in mind who you get advise from, one of the hardest things you will have to figure out is whether there is a car issue or a driver induced issue and also whether the problem the car has (per what driver says) is even a correct diagnosis. When you watch your son race, don't get caught up in the moment and just watch the race like a spectator; you need to be watching the attitude of the car along with a ton of things to double check what the driver says is happening with the car. I will give you a big clue and something that is pretty easy to watch that will help you out: Watch the front wheels as is what direction they are pointed at all times. This will help you figure out if the car is tight or loose.

Good luck

That's all good advice…

I never ran with the most HP back in my younger days but tried to rely on my driving ability and set-up. My last dirt sportsman car had a major snafu in the front suspension that caused a major league push on a heavy track… but it was on a rail on the dry slick. So I set it up like a pavement car (big sway bar and a ton of left side weight) and did pretty well with it.

My last driving was done during the old IMCA Florida Series that was held during Speed Weeks during the 80's. I think we had five or six tracks scheduled a ten day period. Our first date was at Lake City but we rained out. The next week I blew my junkyard 351-C at New Smyrna and I befriended another Ford racer from Gainesville and used his shop to switch motors. We put in my "good" motor… a stock 351-C with an old set of NASCAR iron heads and a Chet Herbert reground cam.

The last Saturday before the 500, IMCA rescheduled that rainout so we snuck up to Lake City again. The track had run an All-Star late model/sprint car show the previous night but the promoter never graded or watered the track before our gig. Running against cars with 700 HP late model power (the claim rule was suspended for the series) we started last in our heat and managed to transfer thru the consi and B-main to the big show. I think we grabbed 4th or 5th in the main and those big time guys with those down south motors were amazed we could pass 'em on that crappy track. I didn't have enough HP to spin the tires! That's the only way I did as well as I did…

This season will be a fun deal… I hope. My son has raced several times in borrowed cars when I was promoting dirt tracks back when he was a teenager… he has a good head on his shoulders and should do well. We aren't looking for big wins but I think having him start out at a few small venues will allow him (and I) to learn a lot this year.

[Tuner]

In restricted classes, such as circle track where everybody has the same size 2-bbl carb, using this curve with the initial set to wherever makes the best power, depending on carb size 350, 500 or 390, etc. but typically advancing from 36 at 3000 to maybe 44 at 8000, is almost an unfair advantage in a field of engines which are “all in at 2500” because the locked or all in early timing retards as RPM increases (because the electronics in modules or CD boxes have a constant slew rate) and engines actually need more timing because of the high intake vacuum at high RPM. This curve compensates for the retard and allows timing for best torque and then advancing to best power at high RPM.

you wont see anywhere 8000rpm with a 2bbl combo..especially the OP's combo. we have tried a similar setup and while it does help at higher rpm the loss of power at lower rpm from decreased timing was not worth it in the end.

I’m sorry you didn’t understand I was referring to the advance curve RPM, not the engine RPM. If whatever advance curve you tried before didn’t work for you, I suggest you try it again using the parts and specifications I mentioned in this thread. I think you will be pleased.

The principle is to provide the best timing for best power at the lower RPM where the intake vacuum is not so much and also provide more timing at high RPM when the intake vacuum rises to a high value, as if you had a large carburetor and were closing the throttle.

If you do much dyno work, surely you have noticed nearly all engines, restricted intake or not, want more timing as the RPM increases above peak torque RPM up to peak power RPM. Obviously, the restricted carb engines benefit most. I have tuned 2 bbl engines that wanted 12° more at 7000 than 4000.

[Keith Morganstein]

In restricted classes, such as circle track where everybody has the same size 2-bbl carb, using this curve with the initial set to wherever makes the best power, depending on carb size 350, 500 or 390, etc. but typically advancing from 36 at 3000 to maybe 44 at 8000, is almost an unfair advantage in a field of engines which are “all in at 2500” because the locked or all in early timing retards as RPM increases (because the electronics in modules or CD boxes have a constant slew rate) and engines actually need more timing because of the high intake vacuum at high RPM. This curve compensates for the retard and allows timing for best torque and then advancing to best power at high RPM.

you wont see anywhere 8000rpm with a 2bbl combo..especially the OP's combo. we have tried a similar setup and while it does help at higher rpm the loss of power at lower rpm from decreased timing was not worth it in the end.

I’m sorry you didn’t understand I was referring to the advance curve RPM, not the engine RPM. If whatever advance curve you tried before didn’t work for you, I suggest you try it again using the parts and specifications I mentioned in this thread. I think you will be pleased.

The principle is to provide the best timing for best power at the lower RPM where the intake vacuum is not so much and also provide more timing at high RPM when the intake vacuum rises to a high value, as if you had a large carburetor and were closing the throttle.

If you do much dyno work, surely you have noticed nearly all engines, restricted intake or not, want more timing as the RPM increases above peak torque RPM up to peak power RPM. Obviously, the restricted carb engines benefit most. I have tuned 2 bbl engines that wanted 12° more at 7000 than 4000.

Tuner, great info as usual. I always read your posts and learn something. We run our 2BBL engines to 7400 RPM. Could easily run them higher, but 7400 seems to work and have some longevity. I've always run locked out advance on these engines, but will be trying out your suggestions.

[Tuner]

For obvious reasons the 350 2 bbl enjoys this the most, but it works with 4 bbl and compression engines too, each engine simply wants more or less as suits it. The most trouble I have ever had with this setup was at a big short track event, 350 2bbl, people from every corner of the country, and the scrutineers who just couldn't find how (they thought) we were “cheating air in somehow” and wouldn't leave us alone looking for it, such that it cut into the practice and setup time the driver and crew needed. Didn't matter, stood on top of the podium anyway. It was gratifying to have the only car that wasn't just stuck in harness in the pack. The cylinder walls were polished with 1000 grit paper too (maybe 2000, LOL), so we had less friction and more timing where it counted. I can't (don't want to) believe that was more than 20 years ago. Time flies.

[Hectori]

[quote="Tuner"][/quote]

I have allways been strong believer on advance curve. But never thought of using mechanical advance to so high RPMs, but it makes sense. Maybe i play around with it on my next build.

I can see how lockin advance can have advantages in some applications. But it has allways seem to me more easy way out.

[les327]

Is thair an advantage in using a vac adv. In a dirt oval street stock 358 500 holley application ??

[Tuner]

Is their an advantage in using a vac adv. In a dirt oval street stock 358 500 holley application ??

It will run cooler on yellows. Take care to use a vacuum can with a strong enough spring it is fully retarded at 10” Hg. For HEI’s there was a vacuum can on late 70’s 454’s that was 10° crank between 10” and 15” Hg. Either use one of those or modify a can so it has no travel below 10” vacuum. I have set up lots of them with the curve I described above and with a 10° vacuum advance like this. In the last 40 years, many times I have heard the words, “That is the first time it ever cooled on yellows, instead of getting hotter.”

[les327]

Is their an advantage in using a vac adv. In a dirt oval street stock 358 500 holley application ??

It will run cooler on yellows. Take care to use a vacuum can with a strong enough spring it is fully retarded at 10” Hg. For HEI’s there was a vacuum can on late 70’s 454’s that was 10° crank between 10” and 15” Hg. Either use one of those or modify a can so it has no travel below 10” vacuum. I have set up lots of them with the curve I described above and with a 10° vacuum advance like this. In the last 40 years, many times I have heard the words, “That is the first time it ever cooled on yellows, instead of getting hotter.”

Thank you for that advice.

[Krooser]

I also asked this same question at a circle track forum. One member there posted this answer to my question… very tuff to read and understand but….

"After using a vacuum advance and only the best spring controlled weights to aid in hooking up with less horses for a few feet in order to be able to floor the car while sideways and it moving, I addressed the potential of hotter fire and more fuel! While burning twice the fuel that most use all night just in a 20 lap race with the plugs still snow white, I figured out that hotter fire allows for a boost in horses if you can put enough fuel in to match! Sure we wasted a few parts getting to that point but the horses was out of the gate! You can't turn back after being hooked and everyone is looking for the Nitrous on the car! Intakes were pulled! Fuels were sent off for testing! Tachs were disconnected! A stock GM module and coil with a tan cap and rotor that puts out more than you can believe! More than we could buy! A 10 degrees block on both vacuum and weights giving a 20 degrees advance total was used! Bench testing on 12 volts it would jump from pin to pin with out any plug wires on the cap easily! Test yours and it most likely just clicks inside or jumps to ground at the coil! Getting it to the plugs does require a good set of tan parts and wires to say the least! A Rocket 350 GM OLDS coil from a early year with a .080 plug gap was used! Jets must be changed before hot lapping and a constant check on the wet oil of at-least 3 threads on number 3 cylinder to keep from going lean and melting plugs, head gaskets or burning the block and heads in three laps! Proceed with caution as not to be shocked or trampled in the process of these extra horses! Set the timing with the engine at 5,000 rpms without vacuum hooked up! Be sure to use a live vacuum port or it will not fall back to the weights while on the throttle! I run no power valve in my carbs ( blocked and up 5 jet sizes more, 83-86s on a two barrel) and a cool 150 degrees engine temps to allow more air to flow as well! Work your way up on timing and fuel to get more horses with the extra fire power! No racing fuel used, just 93 pump gas! Hope you find more than you expected and then some!"

Read more: http://thedirtforum.boards.net/thread/4 ... z2yxY8L4sf

[rce4csh]

Where the "unlocked' distributor really shines is when things go wrong!1 Like recovering from an engine stall after a spin or when two cars get together to end in a stop and the motor dies. Moments like this make having a dizzy with and advance curve that allow easy starting even when the car is bound up in gear and too restricted by something else like another car(s). This has saved my bacon to be able to roll the starter on with the car in gear,no clutch release and get it to light and drive away. Try this same stunt with a locked out dizzy and you may be buying a new crank as result.

[Tuner]

I've freshened up a few Prestolite distributors that were in 426 Hemi engines in Petty prepared cars. They all had the advance curve Mopar published in their engine books for such engines in that sort of racing. The primary spring has so little tension it starts to advance at about 200 RPM (crankshaft) and is on the second spring at about 400 RPM. The second spring is so strong the advance only increases 4 or 5 crank degrees from 400 RPM to 8000. Those distributors have 24 crank degrees. Any time the engine is running it is on the second spring somewhere in that 5 degree slope. If the engine stops the primary spring pulls it back so it will crank over easy if the engine is hot.

Those distributors are a real piece. Cast iron housing, tapered roller bearings upper and lower, you pack them with grease and set a little pre-load like a pinion bearing, a heavy sort of flywheel above the upper bearing with the weight pivot pins in it, and a double tongue and groove constant velocity coupler engaging the intermediate shaft.