Posted By: radar
I need opinions on high perf dist. tuning options - 01/18/09 06:37 AM
Howdy
I was going through hell trying to tune my carb to idle well on my 408 stroker. I got some help here and learned a lot about timing and distributors- it was a low initial advance causing my trouble.
Here's my problem- my motor wants 16-20 degrees of timing to run well off idle, but it pings when it approaches full mechanical advance around 3k. I bought the MSD pro billet thinking that their 18 degree mechanical advance bushing would work for me, but as I get the tune closer I'm finding that the motor doesn't want 34 degrees total, maybe more like 30. That leaves me with the same problem I had with the stock distributor- too much mechanical advance.
Judging by the sizes of the mech. advance bushings in the msd kit (.373=18deg, .339=21deg) each degree of timing takes up .011" of slot travel in the distributor's plate. I could weld it up .055" shorter and run 17 initial and 30 total.
I'm wondering if I might be wasting my time trying to get the mech advance down to 13degs? Maybe I should just run the lightest springs or even just one spring and retard the total advance to 30? My concept with this is to basically just use the mech advance for starting and hope it won't detonate off idle. I would want the advance to give me 15deg+ timing at 800rpm idle. I have 4.10 gears and a four speed with a single plane and a mildly rumpity cam, so I'm already not getting good power until 1700 or so.
I'm driving this in the street a lot, so I don't think a locked out advance would work for me.
This is my first v8 build and ground up tune so I need all the help I can get!
Thanks
Kevin
I was going through hell trying to tune my carb to idle well on my 408 stroker. I got some help here and learned a lot about timing and distributors- it was a low initial advance causing my trouble.
Here's my problem- my motor wants 16-20 degrees of timing to run well off idle, but it pings when it approaches full mechanical advance around 3k. I bought the MSD pro billet thinking that their 18 degree mechanical advance bushing would work for me, but as I get the tune closer I'm finding that the motor doesn't want 34 degrees total, maybe more like 30. That leaves me with the same problem I had with the stock distributor- too much mechanical advance.
Judging by the sizes of the mech. advance bushings in the msd kit (.373=18deg, .339=21deg) each degree of timing takes up .011" of slot travel in the distributor's plate. I could weld it up .055" shorter and run 17 initial and 30 total.
I'm wondering if I might be wasting my time trying to get the mech advance down to 13degs? Maybe I should just run the lightest springs or even just one spring and retard the total advance to 30? My concept with this is to basically just use the mech advance for starting and hope it won't detonate off idle. I would want the advance to give me 15deg+ timing at 800rpm idle. I have 4.10 gears and a four speed with a single plane and a mildly rumpity cam, so I'm already not getting good power until 1700 or so.
I'm driving this in the street a lot, so I don't think a locked out advance would work for me.
This is my first v8 build and ground up tune so I need all the help I can get!
Thanks
Kevin
