On an older Monty Barrett IO-360 with 9.5 to 1 pistons, I am seeing both mags set at 26 to 27 degrees. One mag newer, one not.
Is this deliberate for more power, or just a mistake?
Bad for the engine?
Thanks
Mark
Mike Busch says its good for high performance engines. Says he wishes he could recommend it for certified stuff but can't. ...
Some RV guys bugged him for help with temps and that is what he said will help.
Glad he's finally showing an interest in experimentals.
Mike Busch says its good for high performance engines. Says he wishes he could recommend it for certified stuff but can't. ...
Some RV guys bugged him for help with temps and that is what he said will help.
Glad he's finally showing an interest in experimentals.
I'm pretty sure Mr. Busch does NOT advocate advancing timing to help with temperature on experimentals. Increasing spark advance WILL cause higher cylinder head temps.
With that said, question for the OP:
You said older Monte Barrett engine. How many hours? Advanced timing could be an indicator of Mag wear.
I'm pretty sure Mr. Busch does NOT advocate advancing timing to help with temperature on experimentals. Increasing spark advance WILL cause higher cylinder head temps.
With that said, question for the OP:
You said older Monte Barrett engine. How many hours? Advanced timing could be an indicator of Mag wear.
On an older Monty Barrett IO-360 with 9.5 to 1 pistons, I am seeing both mags set at 26 to 27 degrees. One mag newer, one not.
Is this deliberate for more power, or just a mistake?
Bad for the engine?
Thanks
Mark
Timing with high compression pistons, which you have, is generally set at 20 degrees (check the data plate).
I reset timing if 1-3 deg off spec. and will monitor it for change, more than that and the mag needs to come off IMO.
Timing with high compression pistons, which you have, is generally set at 20 degrees (check the data plate).
I reset timing if 1-3 deg off spec. and will monitor it for change, more than that and the mag needs to come off IMO.
Timing with high compression pistons, which you have, is generally set at 20 degrees (check the data plate).
I reset timing if 1-3 deg off spec. and will monitor it for change, more than that and the mag needs to come off IMO.
The timing was set to 25 (probably) when the engine was new, what happens is if the point contacts where faster than the point cam the timing advances, if the cam wears faster than the points the timing retards, the manufacture tries to get these to wear at the same rate but that is difficult, since yours has only advanced 1 or 2 degrees I would just re time the mags.
I am asking the wrong question. Problem is not the wear on the mags changing the timing. Timing was reset recently (by someone else) and one mag new.
Question I should have asked is:
What should I set the mags at?
Data plate says it is a O-360-C1E set at 25 degrees. However it is now an IO-360-xxx with 9.5:1 pistons. Two slick 4371 mags.
So, I could set them anywhere between 20 and 27 degrees. But what should I set them at?
Thanks
This complicates things. The 4371 has a 25 degree lag in the impulse coupling. So if you time the mag to 20 degrees, then on start-up the impulse coupling will delay firing until about 5 degrees after TDC. Whether this is a problem in practice I don't know, but it could make for more troublesome starts.
The Slick 4373 has a 20-degree impulse coupling. Maybe Mahlon or someone who has experience with both these models could tell us if the 4373 should be used when timing mags to 20 degrees for high compression pistons?
Bill is right on. In any case if it where mine I would set them both at 20 degrees.
My IO-360-A1A likes 20 better then 25 (smoother) and Aero Sport built an O-320 for us a year or so ago with 9 to 1s and they set the timing to 20. The max I would go is 25.
... what happens is if the point contacts wear faster than the point cam the timing retards, if the cam wears faster than the points the timing advances
Correct. This is easy to understand if considered logically:
For the mag to fire, the points have to be opened by the cam. If the point faces are worn compared to when the mag was initially timed, then they will open to their firing gap sooner (earlier on the compression stroke) thus the timing becomes more advanced.
Conversely, if he cam is worn, then the mag shaft (and engine) has to rotate farther before the cam is able to open the points to the firing gap.
Obviously the wear of these items also affects the mag's internal timing (E-Gap) which degrades the overall performance of the mag.
