To Advance or Lock?
 

Should a performance boat engine ignition timing use an advance or be locked at the total advance?

Dennis Moores books recommend using the advance on marine ignitions, but does not reference why many (or most) performance maring engines have the ignition "Locked" at total advance. All of the engine builders (marine performace builders, not automobile) recommend locking out the ignition advance.

I am running a 350 sbc, 9.8:1, thu-hull exhaust, 228-228/.320-.320 @.050 cam, performer RPM intake, 715 vacuum carb.

I have been running 34 degrees locked advance.

What are the pro's/con's of locking the ignition?

Are you running the stock Merc Thunderbolt distributor and ignition module?
If so, the advace curve is built into the module.
His book on the SBC has the curves and max advance listed for the various module part numbers.

By locking the distributor in at 34* you're limiting the maximum alowable avance.

At what rpm are you using to verify it's at full advance? It might be somewhere around 3000 RPM.

Remember, Dennis said not to use any more advance than is required to obtain maximum speed.

One reason is that the engine doesn't require that much advance at idle. By leading the combustion process that much you will probably have to richen the idle excessively to compensate.

Why not just do it right and have the timing optimized for idle and higher RPM running?

I am running MSD-6M box with an MSD billet distributer.

Presently I am locked at 34 BTDC (from idle to infinity).

I run locked at 30 so motor will not die when going into gear. I have tried different curves to start at higher rpm to solve going in gear problem but got tired of fighing the problem. Been locked for 2 years now & wish I had done before.

I like my motors locked mostly blower motors,,

PLEASE JUST BE SURE TO CHECK PAST WERE THE TOTAL IS ,MONTHLY

In my Drag race days ( Cars ) I used to run a crank trigger. I would keep the advance locked in at 40*. I also ran a triple step retard system to turn it back a touch as I went through the gears. It worked great. The only real problem was starting the motor while it was hot. I would have to get it cranking with the ignition off, then hit the ignition switch. But, this was a race only application. I think you would be better off using an advance system. My .02

No problem running locked. I have plenty of power. Just curioust if there are any drawbackes, like increased chance of detonation when accellerating from idle.

Seems to me if a locked timing advance was the right way to do it GM , Ford, Chrysler, etc., would have done it that way all along...

Because it works doesn't mean it can't work better if set up properly. I run 20 degrees of centrifugal advance all in by 3000 RPM.

I am hoping we can get someone that understands the physics to explain. Most marine race engines are set up locked. (especially blower engines.)


JohnJan,

That statement is correct if you do not increase compression, go to a more agressive cam, change the intake, exhaust, etc... The manufacturers are VERY conservative in their setups; in order to minimize any warranty contingencies.

Hello, Guys,
I ran a blower motor on the dyno some time ago and the guy helping me asked if the disibutor was welded or just pinned-it was a MSD and was pinned. He said I could pick up 6-10hp just by welding the advance solid. We tried it and gained 7hp. at the otherwise same setup!!! When we checked the timing before welding, the mark would move slightly, became rock solid after welding. If you don't have an idle problem, locked is great. If you need help with too unstable or high an idle, it will help a lot to put in some advance curve- the best, most reliable idle is about 4*. Response is better with more advance, but you don't want to cut off or break your drive getting in gear.
For the start problem, MSD and others make a 20* start retard that will take care of that prolem. Electronic advances seem to work just as well as welded ones for max power.

Give me that smooooooooooth idle :)

I have the MSD billet distributor, internals in the dist cap have been removed because I have a crank trigger system and my timing is LOCKED IN at 32* constantly. The engines can be difficult to start at times as I don't have the 20*start retard in my Crane Hi-6M ignition boxes but I was told that they can be reprogramed to start easier and at different RPM levels.

BTW, those crank triggers are pretty nice because when you go to check the timing it DOES NOT MOVE EVEN ONE LITTLE HAIR-----and I like that! :)

Who care's what the base timing is as long as it starts easy, advance the total advance 3000rpm and above till it pings or slows down mph, alot of the one's I have done will go as high as 38 before they ping but go faster and run cooler around 33-36 if it's to low or high they can run hot,and most of us know what happens to a blower motor when it's not timed right.(boom).Teague himself told me to run 36 on a motor he built and I was fixing, I got it already broken and apart so wasn't able to see what it was at,but I put it at 34, 36 just seems to high for a 588ci blower motor.You wont hear it ping just boom.

My egine builder dyno'd my engine at Keith eickert's facility and it is a MSD locked out @ 38 degrees

Running 10:25 compression pistons with 118 cc heads, allowing for head gasket thickness theorectical CR of 9:8

461 cu. peak power is 500 at 5,800 rpm,

Cam specs @ .50
624 lift int. 612 exh. duration 242 int. 252 exh, on 112 lobe centers

I have an igntion to crank the engine with no spark and flip a switch and instant start!

Locked in?
 

When you install a radical camshaft into a low compression marine engine (9:1 or less) you really kill the cranking compression and low rpm compression. With such low compression you can run a lot of timing advance at low speed without fear of detonation. Locking in the timing won't effect such a radical engine and it will start fairly well.
It you have a modest camshaft in a stock engine, the cranking compression and low rpm compression, will be much higher. The engine may detonate at low rpm and be very difficult to start (if you over advance the timing by locking it in).
Hope this makes sense to someone!
Sincerely
Dennis Moore

Well, I think all these responses were great. Heres what I think I did with the engines in my formula. They were 500 HP's on steroids, running crane hi-6's ignitions locked at 36 degrees. I was given this information from crane. The hi-6 ignitions fire +/- 20 degrees below 2000 rpm thus my first fire at idle was really at 16 degrees. If you try and use a timing light with these ignitions there are flashes everywhere until you get above 2000 rpm. BTW, My engines started immediately and ran very well.

If you lock the timing at that much advance you will never be able to turn the motor over after it warms up. Alot of ignitions are set to one timing setting at idle so that you can start the motor as soon as it go's past a certain rpm it gos to the preset timing advance.