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  #1  
Old 08-12-2008, 02:50 PM
buick350 buick350 is offline
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Default 50 degrees BTDC?

I have just installed a MSD6AL and distributor, I set the initial timing by ear and with a vacuum guage, it was running the best it ever had with 19" of vacuum, I put the light on it and it read 50 BTDC I retarded it back to 20 degrees, is this due to too much cam or have I done something wrong? I didnt think it would run with that much advance! how do you know when the overall timing is correct, I have got a bush kit on order
350 mid eighties chevy
performer intake
600cfm Holley
1 5/8 headers
Duration @ .050" lift: 222/222 (int/exh) Crane 114201
I guess 8:1 C/R
mech advance only
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Old 08-13-2008, 07:56 AM
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msdtech1955 msdtech1955 is offline
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what distributor are you using ?>
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Old 08-13-2008, 10:26 AM
buick350 buick350 is offline
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#85561 slip collar
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Old 08-13-2008, 10:45 AM
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msdtech1955 msdtech1955 is offline
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it almost sounds like the when the balancer turns ! you can check this by putting the motor on tdc ( compression stroke) and see if the tdc marks line up ....

or the wrong timing cover mark for that balancer .your are currently using
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Old 08-13-2008, 01:31 PM
buick350 buick350 is offline
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Quote:
Originally Posted by msdtech1955
it almost sounds like the when the balancer turns ! you can check this by putting the motor on tdc ( compression stroke) and see if the tdc marks line up ....

or the wrong timing cover mark for that balancer .your are currently using
tried a piston stop and its within a degree cannot figure out if 50 degrees is a dud reading or genuine.
someone suggested my low compression and cam duration could make this happen
I have been looking for a mechanical reason but I am baffled
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Old 08-13-2008, 01:54 PM
Andrew Starr Andrew Starr is offline
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I don't believe there is a problem at all. For no load at idle it is very possible for an engine to have 50 degrees of timing and run smooth with high vacuum. It all depends on the dynamic of the engine including cam, compression, combustion chamber design, piston dome and exhaust system. At the same time I wouldn't keep it there because as soon as you put load on the engine it will be way too much.

When we tune an EFI system it isn't uncommon for us to use timing in the 40 to 45 degree range to increase engine efficiency at no load part throttle.

If I was timing your engine I would set total timing between 35-38 degrees and put the largest bushing in the distributor then play with the springs for part throttle timing.

Hope this helps.
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Old 08-13-2008, 02:33 PM
buick350 buick350 is offline
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Quote:
Originally Posted by Andrew Starr
I don't believe there is a problem at all. For no load at idle it is very possible for an engine to have 50 degrees of timing and run smooth with high vacuum. It all depends on the dynamic of the engine including cam, compression, combustion chamber design, piston dome and exhaust system. At the same time I wouldn't keep it there because as soon as you put load on the engine it will be way too much.

When we tune an EFI system it isn't uncommon for us to use timing in the 40 to 45 degree range to increase engine efficiency at no load part throttle.

If I was timing your engine I would set total timing between 35-38 degrees and put the largest bushing in the distributor then play with the springs for part throttle timing.

Hope this helps.
Thanks Andrew, its not something I have experienced before, I have now got 22 initial and the silver bushing for the mechanical advance, I need to fine tune when I get MSD spring and bush kit, I didnt notice any detonation with this setup, should I keep it like that or increase/ retard initial timing
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Old 08-21-2008, 06:20 PM
1972elcaminoss 1972elcaminoss is offline
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i experienced a very similar problem with a similar application. i ended up locking the advance mechanism and setting the timing @ 34 degrees. i have had 0 problems with this set up, and it idles better than ever. if this is not enough timnig for your idle your could always use your vacuum advance unit (hooked to manifold vacuum) to achieve more timing at idle, but you might detonate under low throttle heavy load situations, but at least you wont have all that timing at wot. i ended up not using the vacuum.
hope this helps you,
ryan
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Old 08-26-2008, 02:33 PM
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msdtech1955 msdtech1955 is offline
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buick 350 , email me your number so i can talk to you about this.
have alot of questions to ask...and it would be easier on the phone.

msdtech@msdignition.com
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