Help with timing
- Thread starter hunt2elk
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67 B-body
Well-Known Member
Seems to me that if I hook the can to manifold vacuum, it will reduce vacuum as the throttle is depressed "fact". This is just the same time that mechanical advance is supposed to be providing more adv beyond initial. I too have heard of this "early on" method of manifold vacuum, but keep in mind lots of the early dist's had no vac advance as well. Does the suggestion that simply because it happened before emissions became a concern "which was much later in history than the early ported vac advance setups" we should concider it the "correct" method? If so, than I could argue the opposite of the statement "What about the Harry high-school non-vacuum advance polished billet "whizbang" distributors you see in the Summit and Jeg's catalogs? They're JUNK on a street-driven car"... Remember that these early distributers were also non vac advanced types too..... They weren't performance new wizbang engines....
I'm an engineer too BTW, and have a degree in Automotive Technologies / Development. A change in career paths has lead me to Robotic / electrical engineering instead, but my roots lye deep in the automotive world! I just don't agree with HIS all mighty / only way to do it mentality! One more thing,,, how quickly does your big cam large overlap high duration camshaft loss what little vacuum you have in that intake? I can probably guess that a lot of us here dont have much throttle plate movement before its all over with!
So with this being said, how long will that vac can on your dist be holding higher adv readings at anything beyond idle full vacuum? Not to long I would think.
It's up to you,,, but I have always used ported vacuum for the dist, and manifold for the brakes and PCV system. Speeking of brakes,,, it reminds me to remind those reading, that many of you have vacuum boosters "cans" hooked up into that manifold vacuum curcuit. How would this affect your ign timing if you have your potted can on the dist hooked to manifold vacuum? Not well I'm affraid.... I wish you all the luck, but sometimes people don't always agree....This just happens to be one of those times...LOL
My 2 cents
I'm an engineer too BTW, and have a degree in Automotive Technologies / Development. A change in career paths has lead me to Robotic / electrical engineering instead, but my roots lye deep in the automotive world! I just don't agree with HIS all mighty / only way to do it mentality! One more thing,,, how quickly does your big cam large overlap high duration camshaft loss what little vacuum you have in that intake? I can probably guess that a lot of us here dont have much throttle plate movement before its all over with!
So with this being said, how long will that vac can on your dist be holding higher adv readings at anything beyond idle full vacuum? Not to long I would think.
It's up to you,,, but I have always used ported vacuum for the dist, and manifold for the brakes and PCV system. Speeking of brakes,,, it reminds me to remind those reading, that many of you have vacuum boosters "cans" hooked up into that manifold vacuum curcuit. How would this affect your ign timing if you have your potted can on the dist hooked to manifold vacuum? Not well I'm affraid.... I wish you all the luck, but sometimes people don't always agree....This just happens to be one of those times...LOL
My 2 cents
1toolguy
Well-Known Member
How can you tell which location is which?
oldbee
Well-Known Member
'Ported' vacuum advance really didn't help all that much when floored(like racing), but when cruising you would get the vacuum advance to help gas mileage...Racing all the time, you wouldn't ever get it, so everyone went to pure mechanical advance.
67 B-body - The only time I unhook the vac. advance is when checking the initial timing, otherwise I have it to the left side of my Edel. 750 which is above the throttle plate. Sorry for the confusion. As far as the reluctor. I bought the electronic kit for a 383, but I didn't install it so I suppose the engine builder could have monkeyed with it. Can you explain exactly what I should be looking for. Thanks
1toolguy
Well-Known Member
I found an old Mopar Muscle article that says the reluctor rotates clowckwise for a small block and counterclockwise for a big block. Put the alignment pin next to the corresponding arrow and it's correct.
Could it be that the timing chain sprockets dots are incorrectly aligned? On my very first build I thought I had the correct dots aligned but I had the wrong dot on cam sprocket picked out and the timing readings were just as you describe.
I was hoping I would'nt have to take the front of the motor apart, but it is looking like that will be my next project. Anybody have any other ideas?
67 B-body
Well-Known Member
An old trick shared to me by Koffels,
If you run the #1 piston up to TDC compression stroke, you can take a small straight edge and lay it across the top of the lifters. You should find that they are exactly the same height compared to eachother. It takes a little less work than pulling the belts, pulleys, balancer, water pump, timing cover. Then having to re-seal the cover to the block and pan while in the car.....
Just an option for ya....
green1
Well-Known Member
Lordy, we have the same problem, which doesn't seem to be a problem. 440, just built by Dan Dvorack, we saw it run in his shop, installed it, and will smoke the tires. Following his suggestion on take it up until ping, then back off, good. If hard hot start, take some advance out of the dissy.
So, hooked up an timing light to base line what he had it at, 10 and 32, no vacuum. Advanced it, drove it, advanced more, no ping, so we wanted to know where it was at; old light dead, put 2 different dial lights on it. They read idle at 36, full advance at 15. WTF?
So we decided that it was chinese lights or new balancer; just keep going to ping. And it runs better each time. 5 more initial, had to drop carb down 600 rpm. vacuum 14. Go figure
So, hooked up an timing light to base line what he had it at, 10 and 32, no vacuum. Advanced it, drove it, advanced more, no ping, so we wanted to know where it was at; old light dead, put 2 different dial lights on it. They read idle at 36, full advance at 15. WTF?
So we decided that it was chinese lights or new balancer; just keep going to ping. And it runs better each time. 5 more initial, had to drop carb down 600 rpm. vacuum 14. Go figure
451Mopar
Well-Known Member
I have the same problem on my friends 383. Yesterday, we pulled a valve cover and the intake valve dosen't even start to open till about 10-15 degrees after TDC.
It also looks like there may be 15-20 degrees of slack in the timing chain!
This car likes alot of ignition advance and ran super rich because it only had about 5" of vacuum (no vacuum leaks either.)
I think after replacing the timing chain and getting the cam phased correctly, it will run correctly.
It also looks like there may be 15-20 degrees of slack in the timing chain!
This car likes alot of ignition advance and ran super rich because it only had about 5" of vacuum (no vacuum leaks either.)
I think after replacing the timing chain and getting the cam phased correctly, it will run correctly.
green1 - This sounds very familiar except I only have 11.5" of vac. Are you sure the sprockets are aligned correctly? Are you leaving it like it is? At least I now know I am not the only one having this problem.
67 B-body
Well-Known Member
I dont think anyone has replied to Cranky regarding "whats the compression".
He brings up a good point with this! If any of you having issues have put a large cam in your low compression engine, your just asking for trouble. It will want all kinds of base advance just to get it to run "right". By using the term "right", I don't meen it literally either.... You need to get the correct combination of parts for it to truely run right... I have a cam probably larger than anyone of yours having this trouble, and my base timing is around 15deg adv. I however have plenty of compression to help get the gasses burning!
Have any of you done a cranking PSI check with a compression tester? Just wondering where you're at on this reading?
I did a compression test and all cylinders were between 132 and 142. The pistons are listed as JPW KB162 030 from the engine builders invoice. I think this works out to about 9.5/1. Is this setup causing me the problems? The machine shop told me they called Comp Cams and were told to use this grind. I called them a year later and was told it will work, but it is not the most common cam anymore. I just want to understand whats going on before I open up the engine.
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Scatransit
Well-Known Member
Been following this thread and I waited to offer my two cents to see what more info you could provide. As you have just found out, the engine could care less what position the distributor shaft is in. Distributor alignment has been a "black art" due to confusion over just how the spark event occurs. The oil pump gear teeth, shaft gear teeth, & cap tower location are all way over emphasized. As long as there is spark at the right time, and in the right order, that is all that matters. Phasing is only needed to provided clearance for the vacuum advance unit, and to some degree the wire that exits the dist housing, all so that the dist housing can be rotated without interference...that's it. For ease of instruction, manufacture, & assembly, the diagrams in the s/m are great for reference, but not gospel. That said, it seems that your balancer is good, the engine runs good, and that your only issue is the timing marks not lining up? This could be due to the camshaft, &/or chain/gear alignment (for the sake of this discussion, lets assume the chain & gears are ok since the engine runs well and there is no backfiring, missing, etc.). I have a 268XE in my car, and timing to "spec" just doesn't cut it. I'm at about 12 initial, with about 38-40 total (vaccum advance dissconnected for these measurements) and vaccum at idle is around 15...the car screams. All I'm saying is don't pay any attention to the timing mark. The best tool for timing adjustment - in any engine of the era - is the vacuum gauge. Briefly, adjust for the highest vacuum reading at about 800 RPM and then back of 1-2 inches. This is your baseline. From here you can adjust to & fro until you arrive at the best combination of performance and easy starting. Be sure to use the gas that you'll be burning the most. Hope this offers a little help...
Thanks for your input. I am just a HVAC guy trying to learn more about these engines. I am just looking to get the readings within reason, which I think yours are. I guess maybe I am to much of a perfectionist and want things done right. Not only for my peace of mind, but some day my kids will end up with my cars and I would like them to not have any problems. The car goes like hell the way it is now and I still haven't got it to ping. The most vacuum I can get is about 11.5" at idle, so I don't want to back it down any from here.
Scatransit
Well-Known Member
No problem... Once you get it running right (which it sounds like you have) and you understand how it all works, it's a simple matter to move things around so that it all matches what is published in the S/M. Keep in mind though, that the timing marks may never line up the way you want them to. Due in part to the camshaft design as well as engine characteristics - which incidentally can still differ even between two identical engines. We all had to learn at some point how these things work, now you can pass it on! Wish I new more about home HVAC!
ArtH
Well-Known Member
Maybe this site will help with your vacuum readings.
http://www.therangerstation.com/Magazine/Summer2003/VacuumLeaks.htm
http://www.therangerstation.com/Magazine/Summer2003/VacuumLeaks.htm
Thanks for the webpage Art. My vacuum does fluctuate about 1" and I realize it is lower than it should be. I may have a issue with that, but I don't think it would cause my extremely high timing readings. I have tried two different carbs and got the same readings, so that is not the problem. Maybe an intake gasket leak?
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