Timing...what should I run

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wheelman21

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Hey all. I'm going to re-time my 340 so I wanted to see what everyone thinks for timing. It is a 340 with 10.5-1 compression, J heads with 2.02s, 508 lift cam with 248 duration and 108 lsa. Intake is an M1 with a mighty demon 750 on top. 3.91 gears in the rear. What's everyone think for initial and total?
 
You talking cam timing or ignition timing? Id go 106* maybe even 104* on intake centerline w 15* initial and 35* total as a starting point. My 10.2:1 340 w a MP .484 centerlined @ 104* actually runs best around 18* initial w closer to 38* total
 
That's a lotta cam for 10.5 compression. It's probably gonna need a lotta timin. I would start with 16 initial and keep bumpin two degrees and see how it feels. Probably needs around 34-36 total.
 
I run a slightly conservative 14 initial and 34 total in my 318. Very similar spec.

Bowl blended 2.02 J heads. Solid cam 254/254 @.050 on 108. 10.3:1 compression. (.018 lash)

It runs pretty good, never pings and never overheats. It idles a lot nicer at about 18 initial though. May get the curve changed one day.

I wouldn't recommend anymore than 36 total.
 
Distributor is a customer curved mopar unit that came with the motor. I had swapped it out for a unit with a vacuum advance but it was a rookie move and I didn't realize at the time that the distributor wasn't correct for the motor being built the way it is. So I swapped it in tonight. It seems like at least at idle, it really likes about 18-19. Looked like I was getting about 35* at 3k. What do you think gents?
 
wheelman21 said:
Distributor is a customer curved mopar unit that came with the motor. I had swapped it out for a unit with a vacuum advance but it was a rookie move and I didn't realize at the time that the distributor wasn't correct for the motor being built the way it is. So I swapped it in tonight. It seems like at least at idle, it really likes about 18-19. Looked like I was getting about 35* at 3k. What do you think gents?
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If it likes 18-19/35 I would do with that. You can mess with the curve with different springs but you might get detonation. You never know until you try.
 
wheelman21 said:
Distributor is a customer curved mopar unit that came with the motor. I had swapped it out for a unit with a vacuum advance but it was a rookie move and I didn't realize at the time that the distributor wasn't correct for the motor being built the way it is. So I swapped it in tonight. It seems like at least at idle, it really likes about 18-19. Looked like I was getting about 35* at 3k. What do you think gents?
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I'd ditch that distributer but your curve sounds spot on.

Most here will tell you to speed that curve up and bring it in faster but then again most people here ***** about detonation and tell you you'll want a low compression engine. I run 15/35 and it's all in at 3500. With a 3500 convertor that works just fine for me and it runs on 91octane pump fuel.
 
Is it a street car? If so, keep the timing light in the tool box. Simply pull the timing up to where it rattles on acceleration, then back it off till it stops. That will probably run better than you would ever imagine.
 
RustyRatRod said:
Is it a street car? If so, keep the timing light in the tool box. Simply pull the timing up to where it rattles on acceleration, then back it off till it stops. That will probably run better than you would ever imagine.
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i would still want to use a light to see where it is now (base line) and where it ends up just so i know for future reference. plus the light is good to see what rpm total comes in at.. :)
 
here are a couple good articles for figuring it all out..


timing1.jpg


timing2.jpg


timing3.jpg


timing4.jpg
 
RustyRatRod said:
Is it a street car? If so, keep the timing light in the tool box. Simply pull the timing up to where it rattles on acceleration, then back it off till it stops. That will probably run better than you would ever imagine.
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Good article

What if you can't hear the rattle?

I had detonation and couldn't hear it. When I ditched the POS MPP unit which was set at 22/32 all in by 1800ish and went to my MSD I had it re-curved with 20 degrees in the dist all in by 3500 vs. 1800 or so. Car ran way better and it ran cooler with noticable power increase in the mid to top and and it revved much freer.
 
The biggest problem you're gonna run into is limiting the amount of mechanical advance. There's no easy way to do that, unless your Mopar distributor is after about 2004 and made by Mallory. If you set the initial where it needs to be, you'll end up with too much total. Conversely, if you get the total right, you'll not have enough initial advance. The only way to do it with the distributor you have is to remove and disassemble the distributor and shorten one of the advance slots by welding it up. Welding up about 1/3 of the slot usually gets it perfect. If you have the later Mallory made distributor, it's much easier as you can get the Mallory plastic advance keys and adjust it that way, without removing the distributor.....but it's easier if you do.
 
RustyRatRod said:
The biggest problem you're gonna run into is limiting the amount of mechanical advance. There's no easy way to do that, unless your Mopar distributor is after about 2004 and made by Mallory. If you set the initial where it needs to be, you'll end up with too much total. Conversely, if you get the total right, you'll not have enough initial advance. The only way to do it with the distributor you have is to remove and disassemble the distributor and shorten one of the advance slots by welding it up. Welding up about 1/3 of the slot usually gets it perfect. If you have the later Mallory made distributor, it's much easier as you can get the Mallory plastic advance keys and adjust it that way, without removing the distributor.....but it's easier if you do.
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The slots have been adjusted. Maybe I can get a picture of the inside of if it just so you guys can confirm that the slots have been modified. It certainly seems like a heavily modified mopar unit. It is only mechanical advance. Should I be running vacuum? Is vacuum advance worth the trouble?
 
wheelman21 said:
The slots have been adjusted. Maybe I can get a picture of the inside of if it just so you guys can confirm that the slots have been modified. It certainly seems like a heavily modified mopar unit. It is only mechanical advance. Should I be running vacuum? Is vacuum advance worth the trouble?
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No vacuum advance
 
Seems like a lot of the answers here are based on the MSD Bushing that you have. Initial low enough not to go over the total by the bushing you have installed……. Buy or make some custom bushings! Lol

I have 10,12,14,16,18 & 20++ bushings. I use or make what works best for the combo.

Someone on here has the part numbers for Mcmaster Carr bushings that you can get on the cheap. I will not mention names though. haaaa
 
and when you get done and plan on driving it on the street don't forget to plug the vacuum advance back up. It hurts nothing. it will help engine burn cleaner and may get mpg when hooked up. The no vacuum is a drag racing thing. Hook it up. It drops out as soon as you get into the throttle.
 
C130 Chief said:
Vacuum advance won't make it any faster on the track, but will help with fuel economy and street manners.
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la4spd said:
and when you get done and plan on driving it on the street don't forget to plug the vacuum advance back up. It hurts nothing. it will help engine burn cleaner and may get mpg when hooked up. The no vacuum is a drag racing thing. Hook it up. It drops out as soon as you get into the throttle.
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How will the vacum advance help street manners?

Also, if you have 38 total and now add in vacum advance, i'm not liking the end result. I want to know what my timing max is and when it will happen.

Same with my carb, mech secondaries.
 
roccodart440 said:
How will the vacum advance help street manners?

Also, if you have 38 total and now add in vacum advance, i'm not liking the end result. I want to know what my timing max is and when it will happen.

Same with my carb, mech secondaries.
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read the second article i posted above.
 
I read it..

While it makes sense, it's not my way of thinking.
 
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