allyolds68

I'm having issues with my 455 pinging. It seems to be getting worse with time. I never had the problem until I put the 7042250 Q-Jet on it. The Q-Jet is off a 72 350 and it was rebuilt with a kit from Cliff Ruggles. Over all the Q-Jet runs much better than the Holley did. When I first put the carb on it had CG secondary rods (.0744 tip) and it was pinging badly. I changed the secondary rods to CV's (.052 tip) at Cliff's recommendation. It eliminated the pinging. I initially pushed the timing to 9 degrees initial and 27.5 degrees all in at 3000 rpm's (vacuum plugged) and noticed that I started getting pinging a couple months ago so I backed my timing off to 7.5 degrees initial which made the pinging better but it hasn't gone away at WOT. My distributor is the original stock one from the 70 455 and I'm running points. I run 93 Octane. The latest is from Sunoco but I use whatever 93 I can find so I don't think it's a gas issue.


My build specs are:


Stock large valve E-heads with stock valve train
Stock points distributer
Edelbrock Performer intake
Open element air cleaner
Speed Pro SPE 369P + .030 over
Comp Cams DE 42-208-4


I don't have the build paperwork in front of me but I don't think the block was decked any more than enough to make it true. I had requested a stock rebuild that I could run on pump gas. I get 16"+of vacuum at idle as measured by my 1966 console mounted vacuum gauge. My initial feeling this this has something to do with vacuum advance but I don't know much about it.

brown7373

Did you do anything with the primary jets & rods? The 72 would be leaner than an earlier engine (70 455 distributor) and I don't have my books in front of me, but I would think a 350 is jetted leaner than a 455 on the primary side. And while not the main fuel supplier at WOT, the primaries still contribute significantly to the overall mixture.

allyolds68

I know I said a lot about the carb because that's the major change in the last year. When I originally changed the secondaries to CV's I wasn't getting pinging at WOT. I was getting a bogging off the line though so I adjusted the secondary door opening to hold it closed longer and it eliminated the bog. This pinging has developed over the last couple months leading me to believe it's a vacuum advance issue

oldcutlass

At wide open throttle the vacuum advance drops out, so I doubt that's it. I'm wondering if your timing is coming in too fast at the lower Rpms.

Oldsmaniac

I am thinking todays monkey pizz that they call gas is part of they problem. Have you tried octane boost.

Del70

..I would verify that the vacuum advance is working, that it is not sticking. It is easy to check....

edzolz

I had the same problem with one I used to own. I solved the problem by installing an adjustable vaccum advance and tuned it in to that. Jeg's or Summit has them.

CutlassDad

Is it possible that the timing ring (vib dampener) has shifted?

allyolds68

I set the timing at 9.5 a year ago and it hadn't changed until I backed it down to 7.5 two months ago. If the damper shifted the timing doesn't change, just the location of the mark changes (and the balance of the engine will be effected)

grampy

Pull the cap see if a spring fell off or broke ck the travel of the weights.try adding one heavier spring to slow down the curve,run it without vacume advance see if it stops.what dose the plugs look like. What's the cranking compression.

cutlassefi

No it won't. The weight is in the hub, not the outer ring, for that reason.
Have you tried a cooler plug and/or removing combustion deposits by using the water or trans fluid trick?

allyolds68

Mark,

You're correct, I should have realized that.



I haven't pulled the plugs or done anything except drive it (& messed with the timing last year). I probably need to go through everything. Plugs, points, etc. The car's got about 10K miles on it since it was finished. I don't own a dial back light, just borrowed one last year. I probably should pick up a new damper with full timing marks too.


There's a lot of good advice about where to start. Hopefully I'll have time to mess with it this weekend and let you all know how I make out.

allyolds68

I sucked on the vacuum advance this AM (no, I don't have a vacuum tool) and it holds and I'm fairly certain it moved (heard it click). I don't know squat about vacuum advance but I assume at idle and normal driving the vacuum retards and then when you get on it and the vacuum drops out and the distributor advances. I disconnected the vacuum advance (and plugged everything) and I don't get any pinging. It's not as warm today at about 60 degrees out but Sunday it was about 75 so it wasn't much warmer.


I pulled the cap and rotor off and the springs are intact and nothing's binding with the weights.

I don't know if this matters but its always had an issue when warm starting that feels like vapor lock. You have to hit the key and then hit it again to start. The first hit of the key won't turn the motor more than a 1/4 turn. When you hit it the second time it spins freely.

I'm starting to think the balancer may have spun. I had my neighbor (he's got a repair shop) do a new front timing cover seal for me a month or so ago and I specifically asked him to look to see if the balancer spun. He told me the rubber looked cracked but it hadn't spun. The problem existed before he did the seal so I doubt he had anything to do with it. I suppose the Sunoco gas could have been extra crappy but I've had similar (but not quite as bad) pinging with other brands.

I pulled #1 & #5 this morning. I didn't have time to do more. Here are the pics. I don't know the first thing about reading plugs:


#1





#5

CutlassDad

There should be a mark that looks like a chisel hit that marks the pulley hub and damper ring straight across the rubber ring. If the outer ring has shifted that mark (those marks) will no longer be aligned straight across the rubber.
If the ring has shifted there is no way to realign the ring and hub.

If the ring may have shifted, the first step is to verify the ring vs. hub position.

oldcutlass

Heres what I think you need to do, borrow or buy a setback timing light and a tach/dwell. Verify your dwell is at 30, no more-no less. Then verify your total timing with the vacuum disconnected and where it's all in (basically how much and what RPM it stops advancing). Then repeat with vacuum advanced connected.

allyolds68

That's what I asked my mechanic to do and he said it hadn't moved. Isn't the chisel mark on the inside of the damper, so I won't be able to check it unless the damper is off?

Fun71

Not exactly. The vacuum advance provides additional timing advance during typical engine operation: as the engine's vacuum signal increases, the timing advances. When the carb is at WOT, the vacuum signal drops out and the additional advance from the vacuum canister is removed.

You can make your own marks on a factory style dampener. Just measure the circumference then divide by 360 (for 360º in a circle) to get how many inches for each degree. Then multiply that by 10 and you have a linear measure of 10º that you can mark onto the dampener. I have a line painted on mine at 10º, 20º, 30º, and 40º, then I use the timing tab, that goes form 0-12º, to make up the in-between numbers. For example, if I want the timing at 34º I turn the distributor until the 30º line is even with the 4º mark on the timing tab.

allyolds68

So it's basically backwards of what I thought. I've got the vacuum advance connected to the carb vacuum port (per the assembly manual). Should it be connected to manifold vacuum? Maybe it's still getting vacuum at WOT????. I know the manifold vacuum goes to zero because I can see it on the vacuum gauge I've got on the console (It's connected to manifold vacuum)



I'll probably do that. In the mean time I'm borrowing a dial back light (I hate borrowing other people's tools) and I'm going to screw with it this weekend

pmathews

I'm using the same 265DEH cam, and I'm running manifold vacuum. I'm running a 330HC, so not an apples to apples comparison, but I can add some insight.

I started with 8 initial, 28 total but richened my carb a little on the primaries and secondaries, and that helped. It doesn't take much (about 5% richer). Now I'm running 12 initial, 32 total, with my vacuum locked to 10 degrees max on 93 octane.

You may want to check and see if the vacuum is pulling too much advance, I wouldn't use more than 12 degrees vacuum advance if I were you. You can buy an MSD limiter for really cheap, about $8 -> http://msdignition.shptron.com/p/hei...nce-stop-plate

allyolds68

You hit it.

The dwell was at 25.


So tonight I borrowed a dial back light and I have an analog dwell meter/tach.


I adjusted the dwell to 30 (no vacuum connected, all ports and lines plugged)

Then I set the timing at 7.5 degrees @ idle. It was all in at 25 degrees at 3000 rpm's.

Next I connected the vacuum advance. No difference at idle and all in at 45 degrees at 3000 rpm's

It actually held pretty steady at 44 degrees at 2500 rpm's and then gained another degree up to 3000 rpm's

I took it for a spin and no pinging.

This is where I have my vacuum advance connected:

allyolds68

I have an MSD coil and an MSD 6AL with a rev limiter that isn't installed. I haven't installed them because I just don't want to give up the old simple system. I was going to get one of those pointless ignition modules that fit under the cap too.

pmathews

I wasn't talking about an MSD module, I was talking about the vacuum advance limiter, it's a tiny $8 piece. Crane makes one, too, but I tried it, and it was terrible. The $8 MSD piece did the trick, don't bother with the Crane one.

pmathews

20 degrees of vacuum advance is a lot. I would use 12, that way, you can bump up your initial to 12-14 (30-32 total mechanical in your case) and see much better performance without pinging. It's a common mod, and it works.

allyolds68

Will it work on a stock distributor? It seems like it's made for an MSD distributor

Fun71

All I can say is try it both ways and see which works better for your particular setup.

25º doesn't seem like enough total advance - most folks run somewhere in the 30s (32 to 38 is typical).

Yep, that's the right spot for ported vacuum.

allyolds68

So I need to REDUCE my vacuum advance and INCREASE my mechanical advance?


I supposed I should increase my initial timing to see what I get for total advance and limit my vacuum advance.


I'm assuming by increasing initial timing to 12-14 my total mechanical should be 32-38 so I shouldn't do anything with springs or weights yet?


What should I limit the total vacuum advance to?

oldcutlass

Ok, did you set your dwell before setting the timing, gotta ask? If you ran your rpm past 3000 like to 4000 and your timing did not advance anymore, then I do the following. Advance your initial timing to 10.5 degrees and it should add 3 degrees to your total (28) and your total with vacuum(48). What octane fuel are you running?

Lets do this in baby steps, walk before you run.

allyolds68

I set the dwell first before I did anything else. After I set the initial timing at 7.5 the dwell was still 30.


My timing didn't advance anymore after 3000 rpm's


I'm running 93 octane with 10% ethanol. I can run 91 octane without ethanol but there isn't any 93 octane non ethanol around here.


FWIW my engine is a 70 455 out of a 70 442 4 speed car. The only difference is the 70 442 had A/C and I don't have A/C in my 68. (& the carb is from the 72 350)

oldcutlass

I'd keep running the 93. Is yours also a 4 speed? Try the settings that I described and if the math works out then we can limit the vacuum advance and advance the timing a bit more.

pmathews

Here's a better photo -> http://i572.photobucket.com/albums/s...SDheibolt2.jpg

I installed this on my HEI (non-MSD) distributor, and it changed the vacuum advance from 20 degrees to 10 degrees.

MDchanic

It seems we may have passed this way before.

I will repost my instructions from then, as they are no less relevant. I'd say you are still on the right track, and Eric is giving you good advice.

Here it is:

"Here's the basic layout of what you do:

• Set the maximum mechanical timing so that it doesn't ping at full throttle, usually somewhere in the 34-36° BTDC range at 3,000 to 3,500 RPM.
  Use an aftermarket advance tuning kit to set it so that it is "all in" by 3,000 to 3,500.
• Set the "bottom end" of the timing so that the car starts easily
  (that is to say, if the span of the mechanical advance unit is wide enough, the engine will be retarded enough to start easily, but if not, such as with HEI, you may need to extend the range a bit with mechanical modifications or an advance tuning kit (which may be able to increase the mechanical range).
• Set the speed of the mechanical advance with an aftermarket advance tuning kit - take it out for full-throttle runs through the RPM range - if it pings at a particular engine speed, but not once it winds out past the RPM where it reaches full advance, you may need to use a stronger spring on one side to hold it back from full advance for just a bit longer.
• Start working on the vacuum advance - you will need a vacuum gauge in the car so you can see where it pings.
  • Drive it around and listen carefully for pinging at part-throttle
    (generally at low RPMs when going up hills at 40-60 mph).
  • An aftermarket adjustable vacuum advance can is useful for this exercise, even if you later decide to use a non-adjustable can.
  • Follow the advance can's directions to advance incrementally until you hear ping, then retard a bit.
  • The vacuum gauge will tell you where it pings and where it does not.
    If it pings at the highest vacuum settings, you may benefit from reducing the range of the vacuum can (usually with an included stop), and then re-adjusting.
    These things can usually give you over 20° of advance, which, if you already have 36° mechanical, can put you way over 50°.
    It's tough to get this just right, because you're timing it at a time when it's got some load on it, and is also running at over 3,000 RPM, so it pretty much puts you on the highway, where it's hard to hear pinging - I recommend driving close to concrete barriers on your left during uphill runs with minimal throttle deflection (to keep the advance unit fully deployed), so that you can hear the sound from the engine reflected off the concrete.
  • Once you've got the highway-speed, uphill cruising pinging dialed in, you can go back and fine-tune the vacuum advance spring pressure to get the most advance under partial vacuum conditions.
  • At this point, you can measure the settings that you've obtained with the vacuum advance, and buy a non-adjustable unit that is close to those settings, if you wish."

- Eric

allyolds68

Yes, 4 speed





Thanks Eric. Two different causes but you are correct, the info at the end is the same. The procedure you describe above includes using a lot of equipment that I don't own and probably never will. I'm hesitant to bump the timing too much without having the means to really get the mechanical and vacuum advance right.

gs72

Here is a pretty good article explaining how the distributor advance systems work. I know it's a Chevy article but it is still very informative. First time iv'e posted a link, hopefully it works.http://http://www.camaros.org/pdf/timing101.pdf

allyolds68

you were close


here you go:

http://www.camaros.org/pdf/timing101.pdf


thanks