OUTLAW EAGLE MANUFACTURING

MOriverbum · Joined: 26 Jul 2010 Posts: 51

Hey guys, I need a little input. I had some slight oil leaks on my tweaked zz502 that I decided to fix last weekend.(Valve cover and those pesky rubber seals on the front and rear of the intake)(NOTE: replaced block ends w/ black silicon) I replaced my leaky gaskets with new ones, and have reassembled the engine. I have found 32 degrees written in marker on the back of the intake by the distributor. Now my question is why would the vacuum advance port on my billet MSD distributor be capped off? Do you think I should just leave it alone and set the base timing? or hook up the vacuum? It ran excellent last year, with no hesitation. Sorry for all the questions just curious.
Thanks for the help

MOriverbum · Joined: 26 Jul 2010 Posts: 51

I bought the boat used, discovering a new surprise every day.

DOC · Joined: 17 Jun 2005 Posts: 329 Location: Whitecourt

Just set total timing, dont worry about initial timing or vacumn advance.

boosted · Joined: 04 Jun 2009 Posts: 378

The vacum advance will give you a little better fuel economy at cruise and thats it. If you do hook it up you should make sure that it does not advance too far. Any more than 10 deg of extra advance is looking for trouble but you could expect to see about 1 gal/hr better fuel economy.

MOriverbum · Joined: 26 Jul 2010 Posts: 51

thanks for the reply, I know how to set your basic timing. but this engine is a little more hi-po than I have been around. Do i set base timing around 12degrees and then check it at 3-4k for my advance? I can do stuff by the book, but this motor is above my head and has (no book). Need all the help I can get!

thanks, Mr. know nothing

boosted · Joined: 04 Jun 2009 Posts: 378

Set your intial and then verify that the total advance (without the vacum advance) is. On a factory zz502 in a jet boat 32 deg might be a tad much if your trying to run regular fuel. The guys around here have been taking out a few deg to keep thing safe. I thought they were setting them at 28 deg total. After that you can have it at idle and plug in your vacum advance and see how much the timing changes. It depends on the vacum advance but some you can adjust the total amount and at what vacum it begins to move. On my FORD I have it set to start pulling advance at around 8"-9" of vacum. I cruise at 10-11" but if I want more power then I don't want the extra advance to start detonation.

RED ROOSTER · Joined: 04 Aug 2010 Posts: 86

Is it ok to not run the vacuum advance on a boat due to the fact that they are always running above 3000 rmp ?

boosted · Joined: 04 Jun 2009 Posts: 378

You don't have to run the vacum advance. All it does is increase fuel economy and lower emissions. That being said it depends on how hrad your engine is working at 3000 rpm. A 502zz on a AA impeller is usually around 11-12" of vacum at 3000 so it will benifit from the vacum advance but I have a freind who is turning two a impellers with one motopr and it sits at 6" at 3000 rpm. It won't help there alot.

Hines · Joined: 05 Jul 2005 Posts: 304 Location: Red Deer

Just do what Doc said,plus the fact it worked fine last year,runner.Later.

ALEX · Joined: 02 Aug 2005 Posts: 176 Location: red deer

The vacuum advance improves fuel economy in light load situations in an automotive application;no factory marine engine uses a vacuum advance as there is no light load situation in a boat.
If an automotive distributor is used in a boat (please also note that it will not comply with Coast Guard/SAE standard for flame resistance) the vacuum advance should be lock or at least not connected.
The timing curve on the distributor should be set to have 10 deg initial and about 30 deg total ...as noted previously...the actual amount of timing that is safe to use will depend on fuel quality and chamber design ie compression,piston head and cylinder head shape ...vortec motors especially are timing sensitive.