40 degrees initial!

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JG1966

JG1966

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Hello, FABO. As you can tell by my avatar I'm normally over at the sister forum but I run a 340 in my 72 RR and figured there are more small block experts over here. I run my 340 now at 20* initial, 38* total all-in at 2400 rpm or so. Hughes 2832 cam .228@50 .530 lift. I wanted to see where she "wanted" the timing. I turned distributor to highest, smoothest idle. I was at 40 initial!! Lowered idle back to 850-900 (that's where I need idle) and kept going. Again, she was happiest at 40 initial. I don't run any vacuum advance (I only have manifold port on my AED 750DP and can't get rid of off-idle stumble with vacuum hooked up. I make 9hg at idle in gear. Tried many times. So vacuum advance may not be an option). I'm trying to avoid a locked down distributor (plus, hot starting I'm sure would be an issue at say 38 or 40 initial). Hot starting is no issue at all at 20* initial. Any suggestions to make motor its happiest with this situation? Thanks
 
You can get a start retard.

Put a little less advance in the dizzy and try that. I.e 10 degrees and run 28/38 etc
 
roccodart440 said:
You can get a start retard.

Put a little less advance in the dizzy and try that. I.e 10 degrees and run 28/38 etc
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Thanks Rocco. That's definitely one option. I might not get kickback at 28 initial, too. We'll see. At least that gets me closer to the sweet spot. Can start retard hook up to any ignition system? Does it have to be MSD? I have mopar electronic
 
If it was mine, I would pull number 1 plug and verify TDC with a piston stop, to confirm the balancer hasn't slipped. That's a lot of initial timing. It could also be that the engine has really low cylinder pressure and simply wants that much. I've never seen one want THAT much initial, but I guess it's possible. I would be checking for "other" issues. Maybe find true TDC with a piston stop and run a compression test and see where the cylinder pressure is.
 
Have you driven it like that yet? It may idle nice, but.........
 
RustyRatRod said:
If it was mine, I would pull number 1 plug and verify TDC with a piston stop, to confirm the balancer hasn't slipped. That's a lot of initial timing. It could also be that the engine has really low cylinder pressure and simply wants that much. I've never seen one want THAT much initial, but I guess it's possible. I would be checking for "other" issues. Maybe find true TDC with a piston stop and run a compression test and see where the cylinder pressure is.
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Thanks Rusty. I've checked No. 1 TDC. It's spot on correct and balancer hasn't slipped. I did compression test recently and got these numbers
No. 1 -- 160
No. 2 -- 158
No. 3 -- 159
No. 4 -- 155
No. 5 -- 165
No. 6 -- 162
No. 7 -- 166
No. 8 -- 160
 
flyfish said:
Have you driven it like that yet? It may idle nice, but.........
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No. I would never drive it like that. I've got 18* mechanical advance so I moved it back down to 20* initial. Engine runs strong. Just wanted to see what she liked (also got highest vacuum at 40 initial). I know some small blocks love a lot of initial but I wasn't expecting that high of a number
 
You advanced it till it hit 40 then backed off the idle? Or it was at 40 after you backed down the idle?
 
JG1966 said:
Hello, FABO. As you can tell by my avatar I'm normally over at the sister forum but I run a 340 in my 72 RR and figured there are more small block experts over here. I run my 340 now at 20* initial, 38* total all-in at 2400 rpm or so. Hughes 2832 cam .228@50 .530 lift. I wanted to see where she "wanted" the timing. I turned distributor to highest, smoothest idle. I was at 40 initial!! Lowered idle back to 850-900 (that's where I need idle) and kept going. Again, she was happiest at 40 initial. I don't run any vacuum advance (I only have manifold port on my AED 750DP and can't get rid of off-idle stumble with vacuum hooked up. I make 9hg at idle in gear. Tried many times. So vacuum advance may not be an option). I'm trying to avoid a locked down distributor (plus, hot starting I'm sure would be an issue at say 38 or 40 initial). Hot starting is no issue at all at 20* initial. Any suggestions to make motor its happiest with this situation? Thanks
Click to expand...

Its most likely you are too lean at idle and transfer so you have to advance the timing to improve the fire events at idle to create enough vacuum. What do you have for IFR's and IAB's? You can partially block the IAB's with your fingers and see how it responds to a richer mixture at idle and on the T-slot as you bring the revs up while out of gear.

IMO you do not have enough compression with 160. I would aim for 185.
 
318willrun said:
You advanced it till it hit 40 then backed off the idle? Or it was at 40 after you backed down the idle?
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I advanced it from 18* initial and idle went steadily up from 850 to about 1000. I was at 40. I turned idle back down to 850 and advanced it more but idle went down at that point.
 
JG1966 said:
I advanced it from 18* initial and idle went steadily up from 850 to about 1000. I was at 40. I turned idle back down to 850 and advanced it more but idle went down at that point.
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I guess my thought was if it idled up and the mechanical advancement started to add timing, you could get to 40* pretty quick if you had weak springs. But I doubt at 1000 rpms.
 
Hysteric said:
Its most likely you are too lean at idle and transfer so you have to advance the timing to improve the fire events at idle to create enough vacuum. What do you have for IFR's and IAB's? You can partially block the IAB's with your fingers and see how it responds to a richer mixture at idle and on the T-slot as you bring the revs up while out of gear.

IMO you do not have enough compression with 160. I would aim for 185.
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My idle air bleeds are .070 and my IFRs are .035. I've never messed with them. That's what came on carb. As far as the compression numbers, I'm good with them. I don't really need 185 and have to worry about needing tp run race fuel. Right now I use 15 gallons 93 and five gallons 110.
 
JG1966 said:
Thanks Rusty. I've checked No. 1 TDC. It's spot on correct and balancer hasn't slipped. I did compression test recently and got these numbers
No. 1 -- 160
No. 2 -- 158
No. 3 -- 159
No. 4 -- 155
No. 5 -- 165
No. 6 -- 162
No. 7 -- 166
No. 8 -- 160
Click to expand...

It should spark knock like a beeotch with that much initial timing. No way would I run it that high....and I would double and triple check everything regarding the timing. I know you say you have, but it sounds like something's not right there.
 
318willrun said:
I guess my thought was if it idled up and the mechanical advancement started to add timing, you could get to 40* pretty quick if you had weak springs. But I doubt at 1000 rpms.
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Ok. Now I understand. I definitely never got mechanical advance involved.
 
RustyRatRod said:
It should spark knock like a beeotch with that much initial timing. No way would I run it that high....and I would double and triple check everything regarding the timing. I know you say you have, but it sounds like something's not right there.
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Thanks Rusty. I never drove it like that, obviously. Just idle and there was no spark knock at all. Maybe my springs are so light I'm drawing mechanical at 1000 RPM but I just can't believe that. I use two blue light springs. I'll double check and make sure my springs didn't bust or come off. But I really doubt that happened
 
Invest in a FBO advance limiter plate, a very good investment.
Set initial timing to 20 -22 degs and limit mechanical advance to 36. Enjoy !
 
fishmens67 said:
Invest in a FBO advance limiter plate, a very good investment.
Set initial timing to 20 -22 degs and limit mechanical advance to 36. Enjoy !
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Thanks Fishmen. I have a FBO limiter plate but I have adjustable distributor so really don't need it. A very smart guy who lives near me and used to race pro stock hemis took a look at the motor last month and took car for spin and said it ran very nice. But first thing he said was to run 38 total. I was at 35 at the time. I'm gonna try 22-24 initial (maybe more if I can get away with it) and 38 total.
 
JG1966 said:
Thanks Fishmen. I have a FBO limiter plate but I have adjustable distributor so really don't need it. A very smart guy who lives near me and used to race pro stock hemis took a look at the motor and took car for spin and said it ran very nice. But first thing he said was to run 38 total. I'm gonna try 22 initial, 38 total.
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Lemmie ask you if you remember.....does one of the springs you have have a slot in one end? If it does, that might be your problem. That requires almost no RPM at all before you get some advance. If you have that, you need to throw it in the ditch and put one in there that does not have the slot. That was a leftover from the emissions days when these engines were anemic and needed all the help they could get.
 
fishmens67 said:
38 is big block territory. small blocks 34-36
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Yeah. I wondered that, too. Seeing as it was a "big block" guy telling me this. And he is kind of old so maybe he was confused :). Seriously, he's a great guy but 38 did seem high to me. But this guy knows more about Mopars and motors in his pinky than I will ever know. I didn't want to question him
 
RustyRatRod said:
Lemmie ask you if you remember.....does one of the springs you have have a slot in one end? If it does, that might be your problem. That requires almost no RPM at all before you get some advance. If you have that, you need to throw it in the ditch and put one in there that does not have the slot. That was a leftover from the emissions days when these engines were anemic and needed all the help they could get.
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Rusty, I'm ignorant and don't remember but what is a slot? What's it look like? If I recall both ends of the springs are "circles", if that makes sense.
 
JG1966 said:
Rusty, I'm ignorant and don't remember but what is a slot? What's it look like? If I recall both ends of the springs are "circles", if that makes sense.
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It's the hook on the end of the advance spring. Sometimes, you see them with a slotted hook that allows some almost instant advance.
 
RustyRatRod said:
It's the hook on the end of the advance spring. Sometimes, you see them with a slotted hook that allows some almost instant advance.
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Ok. I'll double check. So I want the full circle type (bottom photo) not hook (top photo)?.
distributor-spring-set-t3-sp-cali-2-etc.jpg
 
JG1966 said:
Yeah. I wondered that, too. Seeing as it was a "big block" guy telling me this. And he is kind of old so maybe he was confused :). Seriously, he's a great guy but 38 did seem high to me. But this guy knows more about Mopars and motors in his pinky than I will ever know. I didn't want to question him
Click to expand...

Actually, big blocks like about 34 or so and it's the small blocks that like around 36.
 
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