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vacum or mech. advance distributors

Bob Burnside

Bob Burnside

Well-known member
What do more run on their boats? what are the advantage of each. Stock or aftermarket distributors what do you like?
 
The vacuum advance has only 1 purpose, for fuel economy under LIGHT loads. Sorry but airboats are never under light loads. I wouldnt use one just set up to mechanical curve to come on fully before 3000 rpms. You can use a distributer with and advance and just dont hook it up.
Tim
 
Forget about your vacuum advance and disconnect it. Buy a $7 Mr. Gasket spring kit and install the weakest springs. Don't worry about your initial timing either. If you have a SBC 350 or a motor with a 4.00 bore set your total timing at 34 degrees around 3000rpm and if you run a 400 or a large bore motor set your total timing to 32 degrees.
 
Vacuum advance is for Grandmothers in Lincoln Towncars.
Your airboat is definitely in the hotrod category. Disconnect it, plug it, and like Thunder said set it up with some light springs.

olf
 
Now I'm confuse, what do I do????

I have a Chev Marine small block engine, 1996, vortex 255/294 HP? @ 4400 rpm.
Iron heads and iron block, alum high-rise intake.

I got it from Marine power model B350P, 350 Premium
Marking on engine 10243880, V03117MH, & C0700013

Edelbrock model 1405 600 cfm

This is not a hot rod engine, but a Marine engine like a Kodiak less the water intake. It came with a 3/4 1 inch thick fly wheel.

The book said initial timing 8* @ 500 rpm, total timing 26* @ 4000 rpm.
What do I set the timing to?
Do I remove the vacuum advance?

Tom
 
I recall working on medium duty GMC HEI equipped engines that had a plate that replaced the vacuum advance can and had a rod to secure the outer ring of the pickup. I was just wondering if anybody had the part number? I'm sure I can find one in a wrecker around here but I thought others might like to know as well. Good chance it's NLS (no longer serviced) but I like the look better than a unused vacuum can hanging off the distributor. 8)
 
Rutting Moose":2wow02i0 said:
Now I'm confuse, what do I do????

I have a Chev Marine small block engine, 1996, vortex 255/294 HP? @ 4400 rpm.
Iron heads and iron block, alum high-rise intake.

I got it from Marine power model B350P, 350 Premium
Marking on engine 10243880, V03117MH, & C0700013

Edelbrock model 1405 600 cfm

This is not a hot rod engine, but a Marine engine like a Kodiak less the water intake. It came with a 3/4 1 inch thick fly wheel.

The book said initial timing 8* @ 500 rpm, total timing 26* @ 4000 rpm.
What do I set the timing to?
Do I remove the vacuum advance?

Tom
Click to expand...

I'm sorry to be a pest, could someone give me a reason to why on your engines you recommend, "no vacuum advance" and the manufacture of my engine recommends to use "vacuum advance"?

Are your engines a racing engine like a 383 Stroker and mine is like a truck engine?
My engine was designed to push a water prop not a air prop, is that why?
The water prop having more of a constant load.
My cruising rpm is around 2800 rpm.

Tom
 
Your centrifugal advance with a HEI is good for 20deg. That is the only way I like to set up an airboat motor by a curve kit only using mech advance and set total timing I don't care about initial timing.
 
This is the way most people set up motors. Street, strip, boat about everything Unless it's a full competetion then they usualy lock the timing down!
 
Mine is locked down on this one and my last one as well. My msd box does use a start retard until certain rpms then its full advance. my box also takes out timing when I hit the bottle switch. I gotta get that bottle hooked up soon and see if it comes in handy.
 
Some applications you can lock it down and your boat will perform better. The main issue is the motor is harder to start. What I do is run my ignition on a toggle and spin the motor over once it's turning hit the switch and she start's every time. Locked timing is usually the way to go however in certain combos it can hurt a motor so I don't like recommending it to most people.
 
This is right from classic airboats site.

Preinstall Tips After Starting Engine
1. Do not attach vacuum advance.
2. Timing should be set so it never advances past 32 degrees total advance when the engine is wide open, full throttle. This check can be made when the airboat is on the trailor, in an open field. Make sure your airboat is securely strapped to the trailor and that the trailer is secured to a vehicle.
If this is confusing, please call us so we can assist.
3. Check oil pressure to make sure it is adequate.
4. Set RPM's at 800 to 900.
5. Engine water temperature should be 160 degrees. If greater than 160 degrees call factory. If less than 140 degrees call factory.
 
That's good advise! I tell people 32 with a 4.125 bore and 34 with a 4.00 bore and if your boat is heavy or large then 32deg!
 
I have a Mopar buddy that was an early do it yourself crank trigger guy. One pickup at something easy to start and flip the switch and another pickup for locked down advance. I am just thinking that I have seen engines bucking with 30 degrees at idle so for an outrageous light high HP boat I could see locking down but the guy with 2 coolers, light plant, friends on the boat. :lol: The MSD timing computer sounds interesting, I wouldn't want to get a lap top out and adjust every cylinders timing so the basic one would do the trick. or I have nothing against the basic HEI mechanical platform as well. With a gear drive I think the idle gear clash noise would be worse locked down just as I think I read on here where noticeable gear noise reduction with larger L.S.A. Gets back to harmonics as well. :?
 
Correction, he used the factory pickup in the distributor for starting and the crank trigger for running. :wink:
 
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