Timing advance question
10-22-2014, 11:57 AM
#1
Melting Slicks
Thread Starter
Timing advance question
Im compiling all of my car info and I came across my ignition advance numbers for my 327/340 in my 63. (it doesnt have the Duntov cam, some other solid lifter cam)
It runs pretty good as is BTW.
According to my notes, I have 11* initial timing
Mechanical adds another 14* all in my 3200 (IIRC)
Vacuum can B26 provides 16* with 12" vacuum at 700 RPM.
Would I be better of to have more intial, and less vacuum can?
What would anideal combo be? I note that the B28 canis recommended, but its 16* advance also.
Will I gain anything If I epoxy or weld the Advance can to limit advance to 11*, and advance the initial to 16*?
This is the same dizzy that I will be using on my 383, so Id like to plan ahead to dial it in correctly.
Thanks!
It runs pretty good as is BTW.
According to my notes, I have 11* initial timing
Mechanical adds another 14* all in my 3200 (IIRC)
Vacuum can B26 provides 16* with 12" vacuum at 700 RPM.
Would I be better of to have more intial, and less vacuum can?
What would anideal combo be? I note that the B28 canis recommended, but its 16* advance also.
Will I gain anything If I epoxy or weld the Advance can to limit advance to 11*, and advance the initial to 16*?
This is the same dizzy that I will be using on my 383, so Id like to plan ahead to dial it in correctly.
Thanks!
10-22-2014, 12:08 PM
#2
Team Owner
I would think your centrifugal would.add a lot more than that to get you near the magical 36* "all in" number.
10-22-2014, 12:12 PM
#3
Im compiling all of my car info and I came across my ignition advance numbers for my 327/340 in my 63. (it doesnt have the Duntov cam, some other solid lifter cam)
It runs pretty good as is BTW.
According to my notes, I have 11* initial timing
Mechanical adds another 14* all in my 3200 (IIRC)
Vacuum can B26 provides 16* with 12" vacuum at 700 RPM.
Would I be better of to have more intial, and less vacuum can?
What would anideal combo be? I note that the B28 canis recommended, but its 16* advance also.
Will I gain anything If I epoxy or weld the Advance can to limit advance to 11*, and advance the initial to 16*?
This is the same dizzy that I will be using on my 383, so Id like to plan ahead to dial it in correctly.
Thanks!
It runs pretty good as is BTW.
According to my notes, I have 11* initial timing
Mechanical adds another 14* all in my 3200 (IIRC)
Vacuum can B26 provides 16* with 12" vacuum at 700 RPM.
Would I be better of to have more intial, and less vacuum can?
What would anideal combo be? I note that the B28 canis recommended, but its 16* advance also.
Will I gain anything If I epoxy or weld the Advance can to limit advance to 11*, and advance the initial to 16*?
This is the same dizzy that I will be using on my 383, so Id like to plan ahead to dial it in correctly.
Thanks!
The original 1963 distributor has a 24* centrifugal advance and you should try to get it all in by 3000RPM.
This set up provides,
1, 27-29* idle advance, (12-14* initial + 15 vacuum)
2, 36-38* WOT advance, (12-14* initial + 24 centrifugal)
3, 51-53* total cruise timing, (12-14* initial + 24* centrifugal + 15 vacuum)
10-22-2014, 12:27 PM
#4
Melting Slicks
Thread Starter
Ok, so perhaps I was mistaken beliveing that 41-42 was the absolute max with vac.
You are saying 52* cruise is ok? I have the Lars paper here somewhere...
Ill have to look inside the dizzy and see why Im only getting 14* advance.
I doubt its the original distributor as well.....Id be surpised anyway..
You are saying 52* cruise is ok? I have the Lars paper here somewhere...
Ill have to look inside the dizzy and see why Im only getting 14* advance.
I doubt its the original distributor as well.....Id be surpised anyway..
10-22-2014, 12:35 PM
#5
Team Owner
48* at cruise is quite safe; 52* is "on the edge". My '61 handles 52* at cruise quite nicely but you have to be careful -- you don't want detonation or "trailer hitching"...
10-22-2014, 05:26 PM
#6
Ok, so perhaps I was mistaken beliveing that 41-42 was the absolute max with vac.
You are saying 52* cruise is ok? I have the Lars paper here somewhere...
Ill have to look inside the dizzy and see why Im only getting 14* advance.
I doubt its the original distributor as well.....Id be surpised anyway..
You are saying 52* cruise is ok? I have the Lars paper here somewhere...
Ill have to look inside the dizzy and see why Im only getting 14* advance.
I doubt its the original distributor as well.....Id be surpised anyway..
What carburetor are you using? If it's a tach drive Corvette distributor you can set the centrifugal advance curve without to much trouble.
10-23-2014, 11:10 AM
#7
Melting Slicks
Thread Starter
I have 12" vacuum at idle. Gm dist. Maybe original. AFB carb. 340hp car
10-23-2014, 05:18 PM
#8
If you have 12" vacuum you need the B-28 that's pulled full at approx 8" vacuum, that will keep the idle stable.
The original Carter AFB is part #3461. If you have this carburetor take good care of it because they are hard to find. Start there and target your timing like I posted above.
The original Carter AFB is part #3461. If you have this carburetor take good care of it because they are hard to find. Start there and target your timing like I posted above.
10-24-2014, 08:55 AM
#10
The 3721 will work just fine. If you have the original aluminum intake manifold consider wiring the heat riser open use a thick gasket between the carb and intake.