#21  
Old 12-03-2019, 03:53 PM
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I'm going to put some thought into a easy way to move the nipple ... something that doesn't involve trying to braze on a tiny nipple. Although it would probably be easy to solder for someone soldering skills. Original hole could just be plugged with epoxy.
I think about getting creative, I thought about just trying to heat it and bend it without crimping it. Which would probably get me the 3-4 degrees I want. But then I also think, "You have a cheap distributor you put a DUI module in. Why don't you just buy a better distributor with a small cap and not try to play master fabricator"

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Old 12-03-2019, 04:31 PM
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Yep you could stick something like a welding rod or coat hanger in it and bend it. Internally the spring is out on the edge of the small end of the cone, so bending the nipple wouldn't hurt a thing.

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Old 12-03-2019, 08:19 PM
Sun Tuned Sun Tuned is offline
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If I were gonna mess with it at all I'd tap the nipple, find a Allen head screw like you used, add some threads to it maybe up to the underside of the head, gun drill the whole screw.

Figure out what length it needs to be and get that set. Maybe cut down id of the head just a bit and put the hose over all of it.

You could make several different lengths and have at it.

There are still 3 of the 5 HEI advances easily obtainable. And there's 1 good point advance left. Far far easier to just use the right one and dispense with the erector set Mr wizard theatrics. But then I know what your doing and have at it, you're having fun. I used to live on Practical Machinist years ago.

One day somebody gonna have to show everyone else how to use the erector set, it won't be an option
then.

As far as brazing on the vac can... I got that perfected about a year ago. I can now take 3/16 stainless brake line bend it in a tight tight 90 degree elbow. I figured out how to silver braze that to the can hat without wrecking the diaphragm. Works very nicely for those that really want the elbow they used to have on their original units and don't want to reclock or use that stupid plastic 90 I've seen so much.

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Old 12-04-2019, 01:53 AM
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Jeez, those guys on Practical Machinist can be rough, I really do my homework before I ask a question there

I'm going to look for a VC680 B1, or a VC1675 B13 ... both have a high vacuum start point and max advance that's not ridiculous. Both max out at a vacuum 3-4 hg below my idle vacuum ... so I'm thinking they would work for me.

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Old 12-06-2019, 03:44 PM
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Now that I've pretty much settled on my requirements for a VA unit.

I still have this question in my mind ... what is the fundamental reason behind not using the factory specs for initial timing and VA specs? What is the flaw in Pontiac's original reasoning that warrants these changes? Modern fuels? Modifications? Bear in mind I ask this question weighted towards everyday driving as opposed to performance. As I'm sure any factory spec can be altered to increase power at the cost of something else.

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Old 12-06-2019, 04:15 PM
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Quote:
Originally Posted by dataway View Post
Now that I've pretty much settled on my requirements for a VA unit.

I still have this question in my mind ... what is the fundamental reason behind not using the factory specs for initial timing and VA specs? What is the flaw in Pontiac's original reasoning that warrants these changes? Modern fuels? Modifications? Bear in mind I ask this question weighted towards everyday driving as opposed to performance. As I'm sure any factory spec can be altered to increase power at the cost of something else.
The answer is modern fuel.

The fine art of tuning on here is some state of de-tune from factory specs.

Clay

FWIW I prefere better fuel and tuning up instead of down. But I do have my own car crippled right now to run on pump chit

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Old 12-06-2019, 04:30 PM
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Not necessarily.

A lot of the factory initial settings were 6 degrees.
I pretty much toss that out the window and set em up for 10 minimum. At that point the factory had too much vac adv in em and it always works out better to pull that back some.

Gotta remember factory set em up for a wide variety of drivers and a wide variety of fuel possibilities. Cause there was that thing called warranty they were trying to get to the other side of. So they crutched em, and to their advantage. Their game and their ball.

What did Royal and Knaefel do?
As the articles said they “crank in a terrible amount of initial and centrifugal advance” now if you had the fuel to support that it worked. And they did jump off the planet when you leaned on the gas.

Try this with regular grade gas and now you got a recipe for large metallic objects in the bottom of the oil pan.

So you increase one you gotta decrease something else somewhere. Since the vacuum advance is 100 percent load sensitive, this was the most sensible thing to limit. Initial never goes away and centrifugal is there dependent upon rpm. Vacuum is dependent upon how far you got your clodhopper stuffed in the radiator fins.

  #28  
Old 12-06-2019, 05:27 PM
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It depends on the engine setup you have Dataway. Factory distributor settings weren't very good for performance or fuel mileage, then or now. The initials were low, the curves were slow, very slow in some cases, and the vacuum advance was excessive.

You're going to have to experiment with what your engine likes and the conditions you're going to put it through. There is no one size fits all.

If it helps at all, my RAIII is probably the closest thing to what you have. With the possible exception I've spent a lot of time on details of the build, for example such as deck height and cam install position among other things, but it's assentially stock. Has 10.13:1 compression. It loves 14 degrees initial timing, I have 34 total timing in it and it's all done around 2800 rpm. The vacuum advance is an adjustable unit I modified, welded the slot to limit it to 10 degrees. It comes in at 6-7 inches of vacuum and it's done around 12 inches of vacuum. The engine makes 13-14 inches idle vacuum up here at 5,000 feet elevation.
I've run this thing on 91 octane cat pea for years, daily drive it in the freezing cold up here as well as the 100+ summer heat, and I beat the snot out of it at the track. It's been perfectly fine. I've even jacked the timing around at the track. 36 did nothing for it, and 32 slows the car down.

  #29  
Old 12-06-2019, 06:01 PM
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I made a limiter of flat aluminum sheet that goes under the end screw head and its slotted so I can adjust as required

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Old 12-06-2019, 06:34 PM
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If you're limiting from the screw end and actually pushing the rod into the canister, that's the incorrect end to limit from. That actually also moves the breaker plate and advances your initial timing, and doesn't limit the total vacuum advance.

You want to limit the vacuum advance from the pull side, leaving the rod in it's original resting position, and stop it's movement towards the canister.

Unfortunately the Crane instructions are incorrect at explaining this.

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Old 12-06-2019, 06:51 PM
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Nope what I do is limit travel at end of travel I don't keep the VA from extending fully

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  #32  
Old 12-06-2019, 08:29 PM
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Formulajones has it right.

Sure you can limit the vac can from either side, but only one way (the pull side) is the best correct way. Reason being is that by doing it on the push side, although you technically have limited the total travel of it allright, what has now been done is drastically alter the tension of the spring inside the can. For sure it raises the vac in hg on the no advance side and I can’t remember trying it what I ended up with on the max advance side but I’m pretty sure it skewed it some couple of vac in hg too. Effectively like shimming valve springs. It works in that it limits the advance numbers but for sure there is a more correct way.

So instead of a starts at 7” and max advance at 12” you end up with something like starts at 9” and max advance at 13 something. It should be the same max advance as what the can was originally but it don’t want to work out quite right setup on the push side.

Also like he said I can’t believe crane never addressed that either. I will say I have seen vac adv units sent in here that were done in this way and they had been used a number of miles. Almost all of them had this characteristic “dead spot” that you could hear loudly when the advance took up the tension as vac was applied. Several jerked very pronounced when the advance began to operate and was not smooth in application as it should be. You don’t want any jerky movements.

Properly set up they should ALL be limited if modified at all on the pull side. Always. Just a better deal that way and only takes a moment to move it if it’s done on the push side.


What no one wants to say that sets up distributors, is that for certain engine families, certain cylinder head chambers, etc for the most part they all end up set up pretty much the same. Now sure there will be differences for fuel, if it has nitrous etc. But pretty much most of this stuff all ends up setup the same within a degree or 2 when it’s all optimized. So when you get it pretty close there’s never much need to goof with it or reinvent the wheel on it.

That’s what nobody wants to say and you take guys that set these things up for a living and you’ll play hell getting them to admit it. There are 50 things that need to fall in place and this timing deal is in my opinion the first and most important. But at the end of the day it all has to work together or none of it works worth chit.

The factory set em up right and they did pretty good with that given the game they had to play. But we don’t have to play that game anymore, so we can do better.

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Old 12-07-2019, 06:07 AM
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Excellent, thanks for the input folks .... what I'm seeing in the big picture is that ...ehhh... 3-6 more degrees initial, 5-10 less degrees VA, factory MA and it will put you in the ball park depending on your particular engine.

Interesting that there is so much opinion on such a fairly narrow range of specs. And interesting that depending on a particular engine that 3-4 degrees can make a noticeable change.

As a kid I ran my GTO for a while with straight 36 degrees of initial, and nothing else. It actually ran OK, that was in the 70's. Mallory dual point I think.

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Old 12-07-2019, 03:54 PM
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Think I read somewhere.....that the engine will be at its best efficiency at 50-52 BTDC at steady cruise. So that's with Centrifugal and VA maxed out. Any truth to that idea? I suppose you want that at your designated cruise rpm, so that could vary and you could adjust for it.

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  #35  
Old 12-07-2019, 05:56 PM
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Yes Ted there is some truth to that.

Honestly though I tend to keep it around 44-46 degrees and I find that to work really well on the current pump fuel on engines that have some compression in them, good quench etc,,,,, and the results have been very good MPG return at steady cruise, usually in the upper teens if everything else is right.

  #36  
Old 12-07-2019, 06:02 PM
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As has been said before in this thread and several others. There are a few things that will dictate what you can get away with.

Type of fuel and quality of it. Combustion chamber design. Camshaft and where (how) it’s installed. Compression ratio.

Two engines with a couple of these above drastically different will alter that. When I said the distributor setup will all be pretty much the same, i was talking about in a fairly general sense. Example of this is say just about all 390 hp 428 setups running on 1970’s premium fuel... gonna be setup fairly damn close to the same when optimized. Unless you start trying to do goofy chit. Like a 5 degree limited vac adv and dictating 5 degree initial setting and getting the rest out of the centrifugal. Sure you can do it that way but it won’t be optimal.

Another example is old style small chevies. The question is... “ how much total can you run in those?” Most will answer in the range of 36-38 degrees. Not if you have changed to a set of vortec cylinder heads with the fast burn kidney bean modern chambers you don’t wanna try that especially on 87 unleaded.

So within reason, on like setups, the stuff ends up with about the same setup. I believe that may have been Cliff that said the 50-52 number. I know I’ve said it years back, as have a couple of others.

Take my 89 R3500 chevy for instance. Dead stock 454 tbi engine. Now I’ve ripped all that tbi junk off it, and put on a 800 cfm cadillac QJet I had. Edelbrock 2-0 intake I got cheap, and HEI. Now I’ll tell you this. Initial setting on this is at 14. Centrifugal is right on 22. And I’m running a 15 degree vac can from Delco that I put an aquarium tube sleeve over the pull pin and knocked down from 15 to 12 degrees.

That’s where ‘this thing runs the best across the entire range of what I’ve done with it. It’s pulled just itself, a boat, a 16 ft flat deck trailer, and a 28’ gooseneck loaded with 22,000 lbs. yes that’s not what it should be pulling but it does it somewhat frequently. Point being, I screwed with this thing so constantly one summer trying to “chase” that magical magnificent certain number I damn near wore out a set of hood hinges and the distributor holdown bolt doing it.

When all the hoopla cleared. That one, with its 7:75:1 Gatorade gas compression ratio ended up running where I’ve had it for the last 3 years. It don’t make a bit of difference where else you set it up differently, it will start having issues such as hot restart if you try and limit the centrifugal and go to bumping initial. It ended up where it is thru much trial and error. And I’ve got a friend that bought one and he wanted to try all these new ideas and such and within reason I’d fix him what he asked for on his and when we were done it ended up like mine.

Now, all that said that don’t mean from this day forward all those setups need to run 14 initial
22 centrifugal, and 12 vac adv. your experience may differ such as if your in colorado. But here at sea level I’ve proven if your gonna dunk around with it... that’s a good place to start and save a bunch of labor messing with all the other we’ve already tried.

Now the old 454 is tired. So when it warms up, im gonna put a fresh engine in it. This next one won’t be 7:75:1 compression. I wanna see what one of these will do at 10-10:25 max. I expect it won’t want 14 degrees initial and that will get dropped back some as will the vac can maybe some 2 degrees each to start with and see where we end up.

Other setups will mimic the same scenario.

All these distributor setup places will tell you they set up everything to match “your” requirements to “your” specific setup. Most will. Some just do what they do. Without mentioning any names and several people on this board run them. It’s curious that if you flip them upside down and look at the specs engraved under the cap base, I think if you guys got to comparing notes you’d find that all the street/strip distributors reach full advance at exactly 3000 rpm. I think if the same folks looked a little further they’d also see that they also ended up with 22 crank degrees at that same 3000 rpm. I can almost guarantee that if they ordered them with a vac adv that they in fact would ALL find they got the same number 15 degree vac can bolted on there also. I can almost promise you that.

I would also tell you they run well and the people are satisfied with these products. Ignition stuff in particular is and always has been a salesman’s smoke and mirrors shell game, but the engine itself kinda cuts through the bullchit, and is the final judge of what it really wants.

Hmmm.... 14 initial, 22 centrifugal, and 12 vac advance

Looks like 48 degrees to me. Could pull that sleeve off and 12 vac adv goes to 15 and that makes 51.
It’s low compression allright. I’d bet 10:1 might need to be pulled back a bit.

I’ll get it done and report back shortly.

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Old 12-07-2019, 06:08 PM
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And for the record I always enjoy reading Cliffs , formulajones, and several others thoughts. Unless you have numerous cars with which to gather results from hands on it’s nice to see more than 1 or 2 folks that are actually on the same page.

I’ve got mine at 48 cause I didn’t want any paper weights, so I went what I consider conservative for where I’m at. And I bet I could pull a couple more out and not notice any difference too.

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Old 12-08-2019, 03:25 AM
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14 initial, 22 centrifugal and 12 vac advance. Exactly what I ended up with on my ElCo's 350 HP 396 with a stock points distributor from the junkyard. Crane vacuum advance with limiter installed per David Ray. Dumped the MSD distributor that came with the car and went from 9 to 14 mpg highway with nothing more than a good distributor rebuild, plugs and wires and a days worth of install, test, remove, install, test, remove until I was happy with the results. Didn't touch the QJ at all beyond lowering the idle. Engine has early closed chamber heads and a stock cam. No pinging at all on 91. Just goes to show that a little time and effort goes a long way.

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  #39  
Old 12-08-2019, 09:41 AM
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Basically the more efficient your engine is the LESS timing and FUEL you will need to get the needed work done.

Low compression smog era engines with pathetically low compression, crappy combustion chamber shapes, tons of squish area plus retarded cam timing/pathetic little cams in them are going to like, want and need the most timing everyplace to see best efficiency.

Higher compression, tight squish, better cam choice and improved engine breathing will want much less timing, all else being equal.

For set-ups I do here we typically shoot for around 10-12 degrees initial as this makes for easy hot restarts. I typically put around 10-12 degrees in the mechanical curve (20-24 at the crank) and have it start right off idle and all in around 2800-3200rpm's. For the VA 10 to about 14 degrees will get it done for most set-ups.

So when you do the math on all that were in the 40-50 degrees range for most set-ups. Of course it should go without saying that the higher compression engines with smaller well chosen cams and better combustion efficiency will be on the lower end of that scale and the opposite on the higher end.

Robert, the big 454 Chevy is a great engine with excellent potential, they are just sitting there waiting for someone to come along and make the needed changes to get them to run like they were meant to. I read recently where someone/someplace took a plane of mid-70's low compression motorhome engine and exploited it a bit and made some great dyno numbers with it, as they should have. I still remember WAY back when John Lingenfelter showed us the potential of the 454 with "peanut" port heads, and the builders that took notice quit using them for "doorstops".......FWIW......Cliff

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Old 12-08-2019, 10:30 AM
69 Limelight 69 Limelight is offline
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That's all fine and dandy if the way your car is geared you have a 2800-3200 rpm cruise. Throw in an overdrive with an 1800-2200 rpm cruise like Formulajones (and a lot of others including myself, is the way to go if you're going to drive these cars any distance) and the 40-50 degree cruise advance goes out the window.

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