timing issues

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midlife89

midlife89

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I have a 360 that I'm having trouble getting the timing right.Have it set at 18 at idle,all in by 2500 set @ 35.When I hook up the vacuum advance and rev it up it starts missing and is showing 60.Tried adjusting the canister but it doesn't change it.If I back the timing back to 8 BTC the car wants to stall in gear,it really idles sweet @18 BTC.This is driving me nuts,I like to do as much as I can myself,kills me to take things in.Just has no balls off idle,after I get going in pulls hard,won't even turn the tires. Here's a little info on the engine,76 360,30 over,KB 107s,J heads,block wasn't decked,heads just shaved slightly to true them up,figure 9:1,xe274 cam,2500 stall,3:55 gears,670 holley carb,the distributor is a reman w/heavy spring changed to light and orange ign box.haven't heard any pinging,just starts missing.I've thought about trying Changing other spring in distrib to light all in by 1400,no vacuum adv,but I hate to do this since it's a street car.This car has always been a pig off the line ever since I bought it.One more thing,previous owner put on 3" exhaust,why I don't know since motor was stock when I got it,could this be hurting my bottom end torque? Any help would be appreciated.
 
The screw inside the vacuum servo doesn't change the total travel, only the resistance between vacuum and its return spring.
Only way I know to get what you're after is with a recurved mechanical advance.
Thats why myself and others just leave the vacuum advance disconnected.
 
oh yeah I checked Vacuum canister with vac pump and it starts advancing at about 12" of vacuum,could it be bad?this thing is driving me nuts, all I think about.please help before I lose it.
 
Should i change other spring in distrb if i do that? Instructions for springs say to do that if 4 speed or all race auto.Should I reset timing to take all she can without pinging/hard starting?
 
I'd really like to get it working as it should,going to try putting heavy spring back in and change light spring to lighter spring to bring mech advance in later so hopefully it will be all in by the time vacuum advance is losing vacuum,going to order mopar spring kit if I can't get it working better w/springs I have.Wish me luck,I'm going to need it.Gonna figure this out if it kills me
 
Are you connecting your vacuum advance to ported or manifold vacuum? Should be connected to manifold for more advance under no load (idle/cruise). Run about 8-10 degress static timing and connect the advance can to manifold vacuum. I know you'll get lots of opinions against this....just my .02
 
Disconnect the vacuum advance and see how it runs at 17° initial timing and 35/36° total.

That is how I had to set up my 68 340 S motor. It had 10.5 compression and a MP .484"/284 cam with Rhoades lifters. It didn't like having the vacuum advance hooked up.

Try "mapping" your timing advance. If you have an "advance" timing light. Start at idle and check RPM and advance at idle (what RPM is idle) then every 250 RPM until you get to 2500 or 3000 RPM (It should be maxed out by then). Try it with and without the vacuum advance hooked up and see what the difference is. Get a pad of paper and a pen and record it.

If you have some advance in when idling, you need to add stiffer springs for the low end (the smaller spring). Then you want the advance to kick in as close to off idle as you can get it and have it all in by 2500 if possible or 3000 at the latest.

Now keep in mind that if you have a high idle, you will need stiffer springs for the low end to keep the advance from kicking in before idle. So an engine that idles above 1000 RPM should have stiffer springs than an engine that idles at 800 RPM.

The stiffer spring (that comes in the distributor originally) is for top end advance only. If you notice that is why it has a bigger loop on the end of it, as it does not kick in till later. You don't want that, take it off and try using different "light" springs until you find the right combination. If you use the two light springs from the MP recurve "kit" they will kick in sooner than if you use one from the recurve "kit" and the original stock light spring that came in the distributor originally. The goal is to not have any advance used up at idle and then get it to kick in as soon as you can when you get off of idle.
 
Just put a new dist in mine it did the same thing turned out it had bad advance canister Plug it off and run without it doesnt make a big diffrence unless your driving 10000 miles a year.
 
Making some head way,put the factory spring back in dizzy,backed initial timing back to 12 BTC,now getting 50 all in @ 2500.Think I just have to play w/canister some more,gonna try giving it a little more timing,no pinging where it's at now.
 
I wouldn't back off initial so you can hook up vac advance. Figure out why the vac advance is messing with your timing so badly.

You may need a different vac can that has less advance in it.
 
I'm going to try taking it back to 18 since I got no pinging.Does it matter if I'm over 50 as long as no pinging/miss?
 
can u get cans with less advance?or is everyone a little diff. Thought about staightening out the bend in arm to make it longer=less travel or am I thinking wrong?
 
Doesn't surprise me it ads 25 degrees of timing when you hook up the vac adv. cause a lot of adv. cans add a lot of timing and yes you can get them with less timing advance. If you look at the underside of the arm coming out of the vac adv. you should see a # stamped. That # is the # of degrees of advance it has (multiply it by 2 for crank degrees). I used to have a list of vac adv. can part #'s that you can get at O'Reilley's/Autozone/NAPA with the ammount of degrees each can puts in but I just got a new computer and don't have everything transfered over. You might try looking on O'Reilley's, Autozone, or NAPA's websites and look up vac. adv. cans for different applications (has to be for an electronic dist. as ones for points had a different shaped arm) and see if they have pics that shows the stamped # on the arm. See if you can find one that'll replace the one you have with less advance. I always try to get the one with the least advance which will usually give you approx. 9 at teh dist (18 at thecrank). One other thing, have you checked the rotor phasing and reluctor gap with the vac adv. pulled in? If the rotor is out of phase too much or the reluctor gap changes too much it can cause it to misfire. I always set them up with the dist. lightly clamped in my vice and the Mity-vac hooked up to the vac adv. to check the phasing and reluctor gap when the vac. isn't pulling in and apply vac. and make sure it's still acceptable with it pulled in. The reluctor gap is easy to deal with but to change rotor phasing much you have to elongate the hole on the vac. advance locating pin to move it around. Since you said it's a reman'd dist. check to make sure they installed the reluctor correct. It has 2 locating notches for the roll pin. One is for use on a small block and the other for a big block. I've even ran into isues with a cheap (Chineese) dist. cap being made so that it throws the phasing off.

Bending the arm on the adv. won't do much but cause binding issues.
 
Thanks for the info,I reset gap on pick up while advanced,rotor was hitting pick up while advanced.Looked on line for canister w/less reach but none of the diff cans stated reach specs.One pic of one showed bottom of arm,8.5r,but don't trust that pic of part is that actual part.Wondering if you could post parts #'s of lowest reach only.Need about 15deg at crank to get my total to 50,or as close as I can get to that.Most part stores don't carry them,and the guys working there don't always know alot.Going to try a Mom nPop store today,who have found me parts that the chains couldn't.
 
midlife89 said:
Thanks for the info,I reset gap on pick up while advanced,rotor was hitting pick up while advanced.Looked on line for canister w/less reach but none of the diff cans stated reach specs.One pic of one showed bottom of arm,8.5r,but don't trust that pic of part is that actual part.Wondering if you could post parts #'s of lowest reach only.Need about 15deg at crank to get my total to 50,or as close as I can get to that.Most part stores don't carry them,and the guys working there don't always know alot.Going to try a Mom nPop store today,who have found me parts that the chains couldn't.
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I doubt you'll find one lower than 17 degrees which is the one you found that says 8.5 on the arm. I've had pretty fair luck with them being what it shown online and when I've ordered them in the past and they aren't what I needed they didn't make any big deal about me not taking it. Sorry I don't have any part #'s yet. Been having issues transferring things over to my new computer because it runs on 64 bit and all my old stuff was 32 bit so it won't run. Still working on it. Mom and Pop stores are the best so you might have good luck there. Wish we still had some around.
 
I did find one @advanced w/6.5 on it which is close to the 15 I need.Many places don't stock them anymore since they are a thing of the past,prob 10 yrs or more.Old timer at one place said he remember guys digging thru them looking for the right #,but that was when they pretty much stocked them all.I just hope the pick of it is what I'm going to get.It looks like it will fit but not positive,can't seem to back check what it fits by part#.Keeping my fingers crossed that it will work. Part # BWD v192 if anyone knows how.If all else fails going to play w/trying to limit the travel on the one I have by straightening 90 in arm to a 45/adding a xtra stop on housing.
 
I am watching this thread because I have a stock 1979 360 that HAD a/c and a 2 barrel from a 79 cordoba. It is now still stock but with a/c deleted and now a 340 intake with a 600 cfm edelbrock and headers. Without vac advance, its a dog off the line, with vac advance hooked up-no changes in timing- I can power brake it pretty good. Idle was at 1000 or so. Lowered that to about 800 last night. Havent taken it out yet, need to do a rear brake job first. But I am learning stuff with this thread- thanks!
 
midlife89 said:
I did find one @advanced w/6.5 on it which is close to the 15 I need.Many places don't stock them anymore since they are a thing of the past,prob 10 yrs or more.Old timer at one place said he remember guys digging thru them looking for the right #,but that was when they pretty much stocked them all.I just hope the pick of it is what I'm going to get.It looks like it will fit but not positive,can't seem to back check what it fits by part#.Keeping my fingers crossed that it will work. Part # BWD v192 if anyone knows how.If all else fails going to play w/trying to limit the travel on the one I have by straightening 90 in arm to a 45/adding a xtra stop on housing.
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I hate to tell ya but I bet the V192 won't work. I looked it up on O'Reilley's and Autozone's sites and they both show it fitting a points style dist. which has a different bend on the arm to accomodate a points style breaker plate. Hopefully I'm wrong but they show a clear picture and it sure looks like it has the straighter arm. If it doesn't work I wouldn't try to bend the arm on yours. It's pretty critical that it's the right shape or it'll pull the pickup plate out of kilter and the gap will change a bunch when the advance is pulled in. Adding a limiter/stop of some sort would be the thing to do as that wouldn't affect the geometry. I haven't tried it but a guy told me he wrapped a piece of stiff wire around the arm where it contacts the dist. housing to limit it's travel.
 
I found one w/6.5 at napa's site and was able to see what it fit.It was a truck 225.But it showed 68 thru 77 so I'm hoping it might.If not thought of using 1/4 20 slit lock washer around arm shaft.I'll keep u posted,part coming in Fri.Thanks for your help/info
 
midlife89 said:
I found one w/6.5 at napa's site and was able to see what it fit.It was a truck 225.But it showed 68 thru 77 so I'm hoping it might.If not thought of using 1/4 20 slit lock washer around arm shaft.I'll keep u posted,part coming in Fri.Thanks for your help/info
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If I'm not mistaken anything that fits a dist. older than a 73 won't work because they were points type distributors and as I mentioned earlier the bend on the vac. adv. arm is different. And that's odd that it shows it fits a 68-77. I thought by 75 everything was electronic but maybe slant 6's were different. Haven't had much exp. with them. Could also be a mis-print in the listing.
 
Thanks for all your help Fishy68,you were right it didn't fit.I was able to use it to determine how much travel the arm had,then returned it.Was able to get my total of 50 by splitting 2 1/4" washers and putting them on shaft to limit the arm travel.The car runs like a different car,especially at part throttle.Can't imagine running a street car with out it.
 
Glad to help and glad you got it sorted out. Sure makes a big difference when you get them dialed in. Good idea of using washers to limit the travel.
 
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