Ignition Timing the Proper Way

[Paul128a]

Sirs, I am running my 21foot deep-v bottom step hull with a 350 chevy, Torker II manifold and 1 inch spacer, Holley 650 double pumper, .030 Flat-top pistons, Crower Cam, 2.02/1.60 valves, Roller Rockers, MSD Billet Distributor with MSD 6 box, 31 inch watercooled stainless headers, and a Mercruiser Alpha/MR drive.
So far, I get 4800rpm and 60mph on GPS.
I ran the boat with the MSD Billet Distributor vacuum advancer connected to the Holley carb.
This is where my NEW question is. I adjusted the ignition timing with the vacuum advancer DISCONNECTED, and set it at 36 degrees BTDC at 3000rpm. I then CONNECTED the vacuum advancer and thats how I run the boat.
However, when I was at the beach, I checked the timing with the vacuum advancer CONNECTED, and in neutral, and was surprised to see 55 degrees BTDC at 3000 rpm.
When I remove the vacuum advancer, it gets 36 deg BTDC at 3000rpm.
How should I set proper timing?
Should I run the boat with or without the vacuum advancer connected?
Thanks to you guys in advance.

[VAMI]

that is the proper way .I think that vacum pod should be ajustable, a allen wrench through the little hole where the hose hooks up to.or dont use vac adv at all . thats to much timing 55

[jkh04200]

Thats the way its supposed to work. Your initial timing is low to allow the starter to turn the motor over. Ince started the manifold vacuum advances the timing to allow for better low end. Once you lose manifold vacuum your mechanical or timing kicks in for top end.

[502 JET]

You need to back that timing way down! You have mechanical advance also which will throw the timing higher.
With the vacumme line disconnected and plugged adjust your base timing, start with 10-12 degrees. Now reconnect the vac line and rev the engine up and check total timing. Depends on your set up what the max timing you should run. Any where between 28* and 34* should be a good start.
The only way you would adjust the timing like you were doing it would be with the mechanical advance locked out with no vac advance.

[H20MOFO]

I Think We Need Ducky!! When I Timed My Engine I Come Up With 60* Total And I Know That Ain't Right Based On How My Boat Runs And The Fact I Made Reference Marks On My Dist. And Intake Manifold,
Im Timed Way Looser Now Than I Was B-4 (based On Those Marks) Needless To Say I'm All Ears. (balancer Twisted? Jap Tinimg Cover (pointer) What The?

[jbone]

Haha....he called us "sirs." Hahaahaaa. (sounding like Beevis and Buthead):D
J

[H20MOFO]

I Swearrrrrrr I Deleted That Post.

[earlbrown]

That's sounds about right. In neutral there's no load on the engine so the advance should head on up there.
Here's a pretty good read on some timing basics.
http://www.digitalcorvettes.com/forums/showthread.php?t=75830

[Paul128a]

Thanks a lot for the help!
Sorry for calling you guys Sirs, that was just in respect.
Once again, thanks!

[cfm]

Vac advance not needed or wanted for I/O applications. Disconnect it and plug vac fitting at vac source.
With your engine a good baseline will be 10°-14° initial and 34 or so total all in by 3k ± 200. Again, no vac advance.

[BDMar]

Vac advance not needed or wanted for I/O applications. Disconnect it and plug vac fitting at vac source.
With your engine a good baseline will be 10°-14° initial and 34 or so total all in by 3k ± 200. Again, no vac advance.
This is absolutely correct! Do not use the vaccuum advance. It will never have a light enough load while driving to let it advance to 55 or 60, however with the fuel thats available today and the higher loads placed on the engine in a boat you really dont want it advancing more than 34 deg.

[asch]

Responsive as hell I bet too. Then..... knock...knock...rattle....BANG!
How is the motor even turning over with 36 advance anyway. Somethin dont seem right. Surprised you haven't detonated a piston yet.
Chevys seem to like no more than 36 degrees total.
24-26 degrees in the distributor and 10 initial at the crank works for me. Easier on your starter and battery too.
And yeah, disconnecting the vac. hose to the distributor is a good idea.

[Paul128a]

Vac advance not needed or wanted for I/O applications. Disconnect it and plug vac fitting at vac source.
With your engine a good baseline will be 10°-14° initial and 34 or so total all in by 3k ± 200. Again, no vac advance.
Thanks for the great info. I will do that tomorrow as I am planning to go out this weekend if the seas are great.

[Paul128a]

Responsive as hell I bet too. Then..... knock...knock...rattle....BANG!
How is the motor even turning over with 36 advance anyway. Somethin dont seem right. Surprised you haven't detonated a piston yet.
Chevys seem to like no more than 36 degrees total.
24-26 degrees in the distributor and 10 initial at the crank works for me. Easier on your starter and battery too.
And yeah, disconnecting the vac. hose to the distributor is a good idea.
I think you have the conversation a bit wrong. You never turn your engine over with 36 degrees of advance.
I set my timing to 36 degrees AT 3000RPM, so I get about 12 degrees of initial or TURN-OVER timing.
Hope that clears things up. How do you set your 24-26 and 10 at the crank? :)

[H20MOFO]

Hi Guys. I'm Still Open For Sugestions On What Could Could Make My Timing Show That Far Off. I Have No Vacume Advance. Did Chev Have Different Pointers For Differennt Years. If The Balancer Has Spun (don't Know How Likely That Is) Is My Motor Running Out Of Balance? I've Already Bought A 2nd Timing Light. Sorry If This Is What You Guys Call Thread Jackin (its Timing Related Right). I Don't Want To Spend Any Time Finding Tdc If It's Going To Keep Movin.

[Boostedballs]

I recently learned that 50 deg BTDC while cranking will knock the outer starter bolt tab right off the block. At least this is what happened in my bud's 1996 Suburban with vortec 350 when the computer went south. We killed 4 starters, replaced the crank position sensor and finally replaced the entire short block when the 5th starter decided it was stronger than the block. Talk about being pissed at GM! They had a tech bullatin on it. Now I have perfectly good 350 roller motor with 125k in my garage. Just thinking about how to repair the block. I think some marine bellhousings use a starter mounted to them instead of the block, is this correct?
Anyway, don't mean to hijack your thread but, yes- 12deg initial and 34max total timing should be good for that setup. Ditch the vac.

[H20MOFO]

I Have No Vac. Motor Turn Over Like Butter(i Know What It Sounds Like When Compression Is Bucking The Starter) Still Open 4 Sugestions? Zero Pinging Ect.

[DUCKY]

These guys are right...vacuum advance on a boat is pretty much useless. However there is a learning experience to be had here....
There are two kinds of vacuum. Venturi vacuum, and manifold vacuum. Where do you have the vacuum line connected? My guess is that it's connected to a small nipple on the carb's baseplate, which is a source of manifold vacuum. It should be connected to a nipple on the side of the primary metering block (if your carb has one), which is "ported" or venturi vacuum. Venturi vacuum increases with carb flow (engine rpm) up to a max of say 7-10" of vacuum with very little effect by varying load. If you were going to use this as a method of advance, you would need to take the amount of available vacuum advance into account when calculating your total, or use a vacuum pump to suck the thing to full advance while setting the timing. Manifold vacuum, on the other hand, is at it's highest at idle or deceleration with the throttle blades closed, and could be as high as 30" depending on camshaft, engine condition, etc... Manifold vacuum decreases with application of throttle, down to as little 0 at WOT. If your vacuum advance is connected to manifold vacuum, you would have excessive timing at idle, that would decrease as soon you open the throttle. Engine damage could easily occur by running a mid range speed with this setup, especially if your motor is on the lean side.....
Hope his helps!

[H20MOFO]

I Have No Vacume Advance At All.just Mechanical.
I've No Black Specs On Plugs. Thinking Of Bumping Up The Timing Further.(i'm All But Positive 60* Is An Incorrect Reading )just Don't Know Why Or How It Could Be That Far Off Unless My Balancer Has Slipped Or Somethin?

[hotbo]

msd says to not use a dial back light with there boxes it inteferes with them.the biggest problem is you need more than 10-12 degress intial timing:idea: 14-16 is good and then total no more than 36-38.this can be hard to do if you do not know how much advance is in the distributor:jawdrop: .msd and mallorys billet dist,come with 20-21 bult in so14 intial would put you at 34,16 ,36.now as far as HEI dis.im not for sure but do away with the vacum pod on the thing and set your total.hope this helps later trav.:shift:

[DUCKY]

....the biggest problem is you need more than 10-12 degress intial timing...
Why?
Bottom line is that the max timing needs to be set first. All forms of advance in play and set wherever you can balance power output with reliability based on your application I know some racers that run as much as 42 degrees, but for most people, 32-35 is more than sufficient (with decent quality fuel) If you like to run crap fuel then 30-32 should be your max . Then work backwards from there. If your motor won't idle and respond well with 10-12 degrees of initial lead, there is most likely another problem somewhere.