Author Topic: got my balancer off now............ (Read 14010 times)

1onehotTA · « **Reply #15 on:** July 13, 2006, 09:53:00 PM »

WAIT A MINUTE, the W72 gets timed at 18 degrees? I have been setting mine at 16, I thought that is what it was supposed to be? And my distributor is new, it has less than 500 miles on it, it is a pro form brand. But my car knocked even before I put this distributor on, the old one had alot of old crusty wiring and connections. I figured that distributor might of been part of my problem.

ta78w72 · « **Reply #16 on:** July 13, 2006, 10:27:06 PM »

Don't you have the emissions sticker on the radiator support? It says 18 degrees. The RPM should be 775. Now I have a manual transmission so an auto may be different.

Edit: I checked John Witzke's wonderful paper (thanks so much John...you're the best!), and you set the timing on an auto W72 at 18 degrees and 600 RPM.

But check out his paper for yourself. You can download from this site.

Could be the reason you've got knocking.

ta78w72 · « **Reply #17 on:** July 13, 2006, 10:33:54 PM »

"You can see that it's plastic, and secured by two of the front cover bolts. I think the marks are in exactly the same position. I have no idea what the round-fitting-looking-thing was intended for. Maybe the Pontiac engineers were looking ahead to some sort of crank position sensor."

Hey Wayne, that round fitting looking thing is a magnetic timing probe hole. I've never used one of those things though and my car doesn't have one.

whwright · « **Reply #18 on:** July 14, 2006, 09:24:47 AM »

I didn't take a picture that really shows the entire cover, but I did find some eBay items that looks just like it.

180005294976
http://cgi.ebay.com/ebaymotors/1974-Pontiac-400-Timing-Cover_W0QQcmdZViewItemQQcategoryZ33625QQihZ008QQitemZ180005294976QQrdZ1

290006846893
http://cgi.ebay.com/ebaymotors/Pontiac-326-350-389-400-421-428-455-Front-Timing-Cover_W0QQcmdZViewItemQQcategoryZ33625QQihZ019QQitemZ290006846893QQrdZ1

Most of the covers on eBay have the timing marker cast into them, which is something I now know to look for if and when I need another.

Wayne.

ta78w72 · « **Reply #19 on:** July 14, 2006, 10:19:21 AM »

Hey Wayne,
I was thinking about that dampener. I was totally incorrect on the whole degree thing. As long as the dampener has the groove in the right place, it doesn't matter what the size of the dampener is because what's really being adjusted is the relationship of the crank to the timing marks.

One for Wayne....zero for me!

1onehotTA...let us know if adjusting the timing those two degrees stops that knocking.

whwright · « **Reply #20 on:** July 14, 2006, 02:05:00 PM »

1onehotTA: If you're already knocking (from detonation) and advance the timing from 16 to 18 degrees BTDC your detonation will get WORSE. Don't just adjust the timing without verifying that the mark on your balancer/dampener is in the correct location.

Hopefully you're not hearing a bearing knock. If it has a very distinct and consistent tempo that changes with engine rpm, OUCH. Usually if you have a knocking bearing the oil pressure will be very, very low at idle.

Piston slap can also sound a lot like detonation, but usually an engine is burning lots of oil and blows blue smoke long before the pistons are loose enough to make noise. On the only car I've owned with pistons that "slapped," they would rattle on mild to moderate acceleration, and quiet down considerably when you put the pedal to the floor.

ta78w72: Are we keeping score? Is a magnetic timing probe some sort of fancy diagnostic tool?

Wayne.

ta78w72 · « **Reply #21 on:** July 14, 2006, 06:29:51 PM »

Wayne, I think the magnetic probe was some sort of tool the dealers used to set the timing.....but I'm not really sure. It doesn show it in the service manual but I've never read about using the probe.

By the way, I hope his detonation is timing related. This engine will ping like crazy when the vacuum advance isn't working correctly. Or he could have some other vacuum problem that's affecting the vacuum advance. I hope you're wrong about it being a bearing or piston slap.

whwright · « **Reply #22 on:** July 14, 2006, 08:42:03 PM »

You're right -- hopefully it's just "pinging."

I suppose the vacuum advance could get stuck in the "advanced" position and cause it to detonate.

Or it's possible the vacuum advance is connected to manifold vacuum when it should be connected to ported vacuum.

ta78w72 · « **Reply #23 on:** July 14, 2006, 09:27:20 PM »

To check the vacuum advance you set the correct timing, then with the timing light still hooked up, rev the engine to see if the timing changes. I believe he's got not only a timing issue....16 versus 18 but also some sort of vacuum line problem.

Wayne, wouldn't advancing the timing from 16 to 18 decrease detonation? The plugs would be firing sooner wouldn't they?

Of course the other nasty little thing is carbon build up.

1onehotTA · « **Reply #24 on:** July 15, 2006, 12:57:56 AM »

Well guys, thanks for all the help, I have solved my timing issue just about 95%. My distributor actually is already setup with an adjustable vacuum advance, I adjusted it out CCW about 3-4 turns and as I was turning it i would drive it in between turns, and slowly my knocking ceased with each increase in turns, still seems to knock some (not much at all) with the AC on going up a steeper hill, but I think I can fine tune and get that out, I may have to decrease my springs on my internal mechanical advance weights now though, as this adjustment on the vacuum is much much more of what my car needed. I had no idea that that allen wrench adjustment was even on my distributor, I thought that I would have to buy that part as an add on.

Eagle 1 · « **Reply #25 on:** July 15, 2006, 01:26:24 AM »

Good deal. Just keep working at it and you will finally get it worked out.
Do you have an aftermarket distributor?

Wayne I have seen the vacuum advance get stuck in the "advanced" position before.

1onehotTA · « **Reply #26 on:** July 15, 2006, 08:03:50 AM »

I have an aftermarket ProComp distributor that I bought thru a local distributor, my old one had alot of crusty wiring.

ta78w72 · « **Reply #27 on:** July 15, 2006, 08:28:27 AM »

Great thread guys!

whwright · « **Reply #28 on:** July 15, 2006, 09:50:28 AM »

Quote

Wayne, wouldn't advancing the timing from 16 to 18 decrease detonation? The plugs would be firing sooner wouldn't they?

Advancing the timing does indeed make the plugs fire sooner, and that makes "pinging" more likely. If combustion begins too early -- or moves too fast -- the flame/pressure front will peak too soon causing the violent vibrations we hear as "ping." Advanced timing isn't the only thing that can cause this problem; it can also be caused by poor fuel (i.e. low octane) or a hot spot within the cylinder. There are probably other more esoteric causes for this too.

Quote

Wayne I have seen the vacuum advance get stuck in the "advanced" position before.

I guess I've been lucky. The few I've had fail were the result of ruptured diaphragms.

Quote

I have solved my timing issue just about 95%.

I'm very, VERY glad to hear that you are getting this problem solved. Prolonged detonation can wreak havoc on bearings, pistons, and wrist pins.

We have found that the Pontiac engines we work on like to have 37 degrees of "total advance" without the vacuum advance connected. If you bought a ProComp distributor I would speculate that the mechanical advance curve is about right as it comes out of the box. (I never thought to ask -- you are disconnecting the vacuum advance when you set the timing at 16 degrees, right?) In the literature that came with the distributor should be a description of the mechanical advance curve. Use that information to determine the initial timing necessary to add up to 37 degrees and try that.

For example, my son's Pontiac has an Accell Billetproof (sp?) distributor, and according to the literature it has a total of 25 degrees mechanical advance. 37 minus 25 is 12 degrees. So we put his timing at 12 degrees initial. Just for grins he tried pushing it to 16 degrees and it rattled. At 12 degrees it runs just like he wants it to. We put a timing light on it, revved it to 3000 rpm, and confirmed that it really peaks at 37 degrees.

After that exercise we connected the vacuum advance and fiddled with it (like you're doing) until he got the idle smooth and the part throttle response where he wanted it. Of course, every time you mess with the distributor you have to mess with the carb as well, because the idle speed changes and the idle mixture is affected.

Keep us posted, and GOOD LUCK!

Wayne.

1onehotTA · « **Reply #29 on:** July 16, 2006, 03:25:19 PM »

Hey guys, I really really really should not of messed with my knocking problem at all, this car is now like "The devil wears Firestone" LOL, It is so fast I cannot believe it is the same car. I have owned it and worked on it religious for about 7 mos. now and it now pretty much looks like a new car inside and out, but it was a dog, now it is like officer friendly's worst nightmare, it is so HOT, in every bit of the engines powerband it is incredible, all with the minor tweak of the timing INCREDIBLE, if I knew how I would post a picture of my TA. Thanks for all of your help, I think my understanding of ignition timing is now complete. I think im gonna put some new plugs in though now also since my others were probably subject to some abuse of my untuned timing.