Street timing recommendations
#2742568
02/13/20 01:05 PM
02/13/20 01:05 PM
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Joined: Apr 2006
Posts: 4,220 West Plains, MO
DrCharles
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OP
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Joined: Apr 2006
Posts: 4,220
West Plains, MO
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I'm looking for advice on ignition timing of my pump-gas 451 with big cam (272@.050), currently iron headed 10.3:1 but soon to be aluminum 10.6:1. Currently I have 22 initial (starts to fight the starter hot at 24-25). Total is 36, trying to remember the curve but think it's all in by 3000. FBO adjustable limiter plate on a stock Mopar distributor. Also running ported vacuum advance. FBO likes manifold vacuum, but it only idles around 7-8" at 1100-1200 which won't pull the can in much if at all. FBO can sell me a can that is all in at 8". Since it's mostly street driven (3.91 gears), locked-out timing will not only be too advanced at low speed part-throttle cruise, but also create a hot-start problem. Cam definitely wants more than 22 to idle the best. What I'm thinking of is one light spring and one heavy spring with a loop. So I can crank it at about 12 degrees, and have it immediately advance once running to the start of the heavy spring, 26 or 28 degrees maybe? And re-position or remove the limiter plate so total is still 36, of course. Or, leave the distributor where it is, but get the light-spring vacuum advance canister and hook it up to full vacuum, which will raise the idle timing into the 30's but drop when I start off. Thoughts?
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Re: Street timing recommendations
[Re: DrCharles]
#2742571
02/13/20 01:22 PM
02/13/20 01:22 PM
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Joined: Jan 2003
Posts: 17,840 S.E. Michigan
ZIPPY
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 17,840
S.E. Michigan
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On my 10.75:1 451 with 262/266 @ .050 camshaft, I have a regular mopar perf/OE style distributor and all I did was use one spring from the Mr Gasket 925B kit. No tricks are done with the advance plate, etc. I run 34 to 38 total all in at idle which is typically 1100+ for valvetrain oiling purposes, and there is about 20 or 21 degrees in the plate so the advance mechanism which only acts as a start retard.
I've been doing this since the '80s on most with big cam combinations and it seems to work fine for me for street/strip purposes.
There is probably additional driveability improvement to be found in working with the vacuum advance, but I never took the time to experiment with it.
Rich H.
Esse Quam Videri
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Re: Street timing recommendations
[Re: ZIPPY]
#2742581
02/13/20 02:30 PM
02/13/20 02:30 PM
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Joined: Dec 2013
Posts: 4,664 Wichita
GY3
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master
Joined: Dec 2013
Posts: 4,664
Wichita
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On my 10.75:1 451 with 262/266 @ .050 camshaft, I have a regular mopar perf/OE style distributor and all I did was use one spring from the Mr Gasket 925B kit. No tricks are done with the advance plate, etc. I run 34 to 38 total all in at idle which is typically 1100+ for valvetrain oiling purposes, and there is about 20 or 21 degrees in the plate so the advance mechanism which only acts as a start retard.
I've been doing this since the '80s on most with big cam combinations and it seems to work fine for me for street/strip purposes.
There is probably additional driveability improvement to be found in working with the vacuum advance, but I never took the time to experiment with it.
Pretty much identical to what I have done on mine. 38 is the limit with good 91 no ethanol I'm at 10.6:1 CR. I now have an add-on timing adjustment knob from MSD that allows me to take timing out from the drivers seat for varying levels of nitrous.
'63 Dodge 330 11.19 @ 121 mph Pump gas, n/a, through the mufflers on street tires with 3.54's. 3,600 lbs. 10.01 @ 133mph with a 250 shot of nitrous an a splash of race gas. 1.36 60 ft. 3,700 lbs.
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Re: Street timing recommendations
[Re: DrCharles]
#2742677
02/13/20 09:08 PM
02/13/20 09:08 PM
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Joined: Jan 2003
Posts: 1,482 Lake Orion, MI
goldduster318
pro stock
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pro stock
Joined: Jan 2003
Posts: 1,482
Lake Orion, MI
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Before I went to EFI I had the heavy spring with the loop totally removed and took one coil off the light spring. This made all the timing come in by approximately 2200. I have done this to several cars and it's worked very well.
'70 Duster 470hp 340/T56 Magnum/8 3/4 3.23 Sure-Grip
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Re: Street timing recommendations
[Re: goldduster318]
#2742702
02/13/20 11:28 PM
02/13/20 11:28 PM
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Joined: Apr 2006
Posts: 4,220 West Plains, MO
DrCharles
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West Plains, MO
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What was the idle speed on those engines? If the weights are starting to move (advance) at idle, it'll never be stable. Best idle for my cam is around 1100, although I may be able to lower it to 1000 once I get done tuning.
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Re: Street timing recommendations
[Re: GY3]
#2742834
02/14/20 12:36 PM
02/14/20 12:36 PM
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Joined: Dec 2019
Posts: 138 Sweden
Mopar493
member
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member
Joined: Dec 2019
Posts: 138
Sweden
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On my 10.75:1 451 with 262/266 @ .050 camshaft, I have a regular mopar perf/OE style distributor and all I did was use one spring from the Mr Gasket 925B kit. No tricks are done with the advance plate, etc. I run 34 to 38 total all in at idle which is typically 1100+ for valvetrain oiling purposes, and there is about 20 or 21 degrees in the plate so the advance mechanism which only acts as a start retard.
I've been doing this since the '80s on most with big cam combinations and it seems to work fine for me for street/strip purposes.
There is probably additional driveability improvement to be found in working with the vacuum advance, but I never took the time to experiment with it.
Pretty much identical to what I have done on mine. 38 is the limit with good 91 no ethanol I'm at 10.6:1 CR. I now have an add-on timing adjustment knob from MSD that allows me to take timing out from the drivers seat for varying levels of nitrous. Is there actually any pump gas without ethanol today? Here in Sweden you cant get any pump gas without it, we have 5% in all gas, 95 and 98 octan, i belive its same your 91 and 93 octan and the rest of Europe have 10% Ethanol, maybe you are lucky in the states. I have a 493 cui stroker, 10,04:1, xe275hl camshaft 231/237@050, dynamic comp 8,03:1 with Edelbrock e-street 84cc heads, i drive it on 98 octan( same your 93) without pinging with a Fbo distributor 18 initial and vacuum takes it to almost 30 at idle on 900 rpm( manifold vacuum) and 34 full advance at 3200 rpm. The engine running great with a huge low end, really nice on the street and without any pinging what so ever.
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Re: Street timing recommendations
[Re: DrCharles]
#2742859
02/14/20 01:44 PM
02/14/20 01:44 PM
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Joined: Nov 2003
Posts: 36,040 Lincoln Nebraska
RapidRobert
Circle Track
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Circle Track
Joined: Nov 2003
Posts: 36,040
Lincoln Nebraska
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The 3 spring Crane kit included in the chart is no longer available but the rest of it might be useful
live every 24 hour block of time like it's your last day on earth
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Re: Street timing recommendations
[Re: Cab_Burge]
#2742873
02/14/20 02:18 PM
02/14/20 02:18 PM
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Joined: Apr 2006
Posts: 4,220 West Plains, MO
DrCharles
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West Plains, MO
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Thanks Cab, but my cam will not idle that slow. After tuning I may be able to get it down to 1000, but it's happier at 1100 or 1200. Notice in my original post I have 22 deg timing initial already, and it definitely wants more than that for a better idle, and an FBO limiter plate which is how I end up with 34-36 max starting at 22... The other problem with your suggestion is that the advance MUST start above idle speed or it won't be stable. It might be difficult to start advancing at 1200 and be all in by 1500 Probably simplest (if not absolutely best) to just have it all in at my idle...
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Re: Street timing recommendations
[Re: DrCharles]
#2742881
02/14/20 03:34 PM
02/14/20 03:34 PM
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Joined: Aug 2003
Posts: 43,112 Bend,OR USA
Cab_Burge
I Win
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I Win
Joined: Aug 2003
Posts: 43,112
Bend,OR USA
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I learned a lot pump gas tuning on my Duster, once I installed the Mr. Gasket 925B advance springs and shorten up the mechanical advance could make it idle at 850 in gear, 1000 RPM in neutral I think those spring let all the advance come in by 1200 RPM, maybe a little slower or faster I was running a Comp Cams custom ground solid roller cam in that motor that was 260@.050 on the intake lobes and 266@.050 on the exhaust lobes ground on a 108 LSA installed with 2 degrees advance on the intake lobes, 106-107 intake lobe center. My message is you can get the performance you want but you will have to try, test, different combinations until to find the one combination you like
Last edited by Cab_Burge; 02/14/20 03:35 PM.
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
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Re: Street timing recommendations
[Re: DrCharles]
#2742894
02/14/20 04:03 PM
02/14/20 04:03 PM
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Joined: Jan 2003
Posts: 17,840 S.E. Michigan
ZIPPY
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 17,840
S.E. Michigan
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Probably simplest (if not absolutely best) to just have it all in at my idle...
If interested, maybe temporarily give it a try and see what you think, first set up a vacuum gauge, warm it up and just crank the distributor to 30+ at idle, then close the throttle blades and adjust the idle mixture to keep the rpm in the same ballpark. You might find improved vacuum at the same idle rpm as previously, and better overall idle quality. It might even be possible to lower the idle rpm, I can idle mine down to 850 if I want to but I keep it higher to oil the valvetrain. Don't rev it or drive it this way as the total timing will be way too much + it will probably not crank when hot. It will just give you an indication of how the idle may or may not be improved. (I'm pretty confident it will help but have an open mind/would like folks to find this on their own). If you hate it, you can always retard the timing back to where it was.
Rich H.
Esse Quam Videri
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Re: Street timing recommendations
[Re: lewtot184]
#2742927
02/14/20 06:18 PM
02/14/20 06:18 PM
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Joined: Nov 2003
Posts: 36,040 Lincoln Nebraska
RapidRobert
Circle Track
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Circle Track
Joined: Nov 2003
Posts: 36,040
Lincoln Nebraska
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On the stock car I pinned the top/bottom plates together with a small bolt/spacer to elim the vac adv & this let me get the rotor phasing dead on
live every 24 hour block of time like it's your last day on earth
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Re: Street timing recommendations
[Re: lewtot184]
#2742990
02/14/20 09:18 PM
02/14/20 09:18 PM
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Joined: Apr 2006
Posts: 4,220 West Plains, MO
DrCharles
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Posts: 4,220
West Plains, MO
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Why not just disconnect and cap off the vacuum advance and leave the original hardware in place? My fuel mileage is non-existent anyway, but I still would like to run vacuum advance while cruising, if possible. May make it easier on the cooling system in summer. Also wondering if there's anyone out there who can set up my distributor to provided specifications... probably another dying art.
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Re: Street timing recommendations
[Re: DrCharles]
#2743008
02/14/20 09:58 PM
02/14/20 09:58 PM
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Joined: Jun 2008
Posts: 3,916 usa
lewtot184
master
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master
Joined: Jun 2008
Posts: 3,916
usa
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Why not just disconnect and cap off the vacuum advance and leave the original hardware in place? My fuel mileage is non-existent anyway, but I still would like to run vacuum advance while cruising, if possible. May make it easier on the cooling system in summer. Also wondering if there's anyone out there who can set up my distributor to provided specifications... probably another dying art. it would be very simple to just put the light race springs in and disconnect the vacuum advance. there aren't any rubbing parts so the plate is stable. setting up a vacuum advance/aggressive centrifugal isn't difficult, I do it, but it's finding the parts. tuning is a dying art, and that's why people spend thousands of dollars on the latest gadget that they still have issues with.
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