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Timing issue
#1389844 Fri Dec 25 2020 09:46 PM
Joined: Dec 2020
Posts: 11
J
New Guy
Hello all!

I have a 51 3100 with a 216, which I believe is a 48 216. I have been dealing with the well known stumbling/hesitating under acceleration. I’ve done just about everything that is usually done with the exception of replacing the dizzy. The odd issue I am having is when setting the timing on the bb, my bb bounces around consistently when the engine is missing. Anyone experienced this before?

I have accomplished the following: ignition system replacement(points, condenser, plugs, wires, cap, rotor) carb has been replaced, valves have been adjusted, ran with valve cover off and all valves operating properly... and proba Lt more that I missed.

I pulled the dizzy out and I specked it and there seems to be a lot of up and down play on the gears. The vacuum advance works properly from what I can tell. The dizzy moves under acceleration.

I have dual straight pipes and a 12v conversion.

Re: Timing issue
Junior_51_chevy #1389881 Sat Dec 26 2020 11:01 AM
Joined: Feb 2004
Posts: 23,004
H
'Bolter
Have you removed the breaker plate and inspected the centrifugal advance system? It sounds like you've got some broken or missing springs on the advance weights. You should be able to turn the rotor a few degrees clockwise against spring pressure, and it should return to the same place every time you do that. The angle of the gears on the distributor and the camshaft keeps the gear pushed one direction while the engine is running (up, I believe) so vertical play isn't an issue unless it's really excessive.
Jerry


The murder victim was drowned in a bathtub full of Rice Krispies and milk.
The coroner blamed the crime on a cereal killer!

Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
Re: Timing issue
Junior_51_chevy #1389905 Sat Dec 26 2020 04:58 PM
Joined: Dec 2017
Posts: 973
D
'Bolter
Couple of things to tinker with here. The wear between the gear and the bottom of the distributor body shaft can only really be corrected by removing the gear, removing the guts, and shimming under the shaft itself. Installing shims between the gear and the distributor body shaft, common with the V8 distributors, actually moves the breaker plate pretty high, sometimes way too high, from the distributor lobes. So what you might try is loosening the clamp and pushing down on the distributor body which my help take up some of the slack.

What number is your distributor? The reason I ask is that the early distributors did not have the spring and Bakelite pad arrangement as part of the grease cup. As far as I know this was a later addition to help with shaft stability as it wore. If your shaft is really worn, and does not have the spring arrangement, a wobble might be what is causing the fluctuation. There are no bushings in these distributors.

You might also consider pulling the distributor out, take it apart as far as you can, and give it a through degreasing and inspection of the advance weights. Pay particular attention to the springs and whether the pins are tight, the springs are both in place, and the weights are free and working. Lube the weights with some light oil, grease the springs and pivot points with grease (I like the red or blue stuff myself), then put it back together and reinstall, making sure you press the body down tight before tightening the clamp. Recheck the point gap and install. Get the motor running and put a dwell meter on it and make sure the dwell is within specification. Then check the timing and see if it is still fluctuating.

Last edited by Dragsix; Sun Dec 27 2020 04:59 AM.

Mike
Re: Timing issue
Junior_51_chevy #1390067 Sun Dec 27 2020 09:52 PM
Joined: Feb 2004
Posts: 23,004
H
'Bolter
I've come up with a way to press a hardened sleeve over the distributor shaft that's fitted to a Torrington needle bearing in the housing just under the centrifugal advance that totally eliminates the wobble and dwell change caused by shaft and housing wear. It's a fairly simple modification that only requires a little bit of machining.
Jerry


The murder victim was drowned in a bathtub full of Rice Krispies and milk.
The coroner blamed the crime on a cereal killer!

Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
Re: Timing issue
Junior_51_chevy #1390092 Mon Dec 28 2020 02:42 AM
Joined: Dec 2017
Posts: 973
D
'Bolter
That is very clever! Would you be able to post photos? I would love to see how it’s done. The excess vertical movement can really play havoc with the timing


Mike
Re: Timing issue
Junior_51_chevy #1390093 Mon Dec 28 2020 02:58 AM
Joined: Feb 2004
Posts: 23,004
H
'Bolter
The bearing doesn't control vertical movement, although a thrust washer or a flat needle bearing could be added at the top during the machining process pretty easily. This one is a Torrington needle bearing pressed into a counterbore in the top of the housing that will control lateral movement of the shaft. I lube the upper bearing by inserting a grease fitting in place of the cup, spring and disc. In the process of "blueprinting" the distributor, I also use a dial indicator through the hole for the wiring connector to check the lift of each cam lobe once the lateral play of the shaft is removed, and use a diamond dust needle file to match up the lobes. It's pretty impressive how much error there is in cam lift from lobe to lobe.
Jerry


The murder victim was drowned in a bathtub full of Rice Krispies and milk.
The coroner blamed the crime on a cereal killer!

Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
Re: Timing issue
Junior_51_chevy #1390575 Thu Dec 31 2020 03:40 AM
Joined: Dec 2020
Posts: 11
J
New Guy
Sorry for the late reply fellas, I had some shoulder surgery today. So I was convinced to install langdons HEI kit, so I put one on order. I’ll pull my old one apart and rebuild it once I’m able to move again. I tried buying a dwell meter and they are extremely hard to find. I bought a multimeter type and it doesn’t work as advertised..

Re: Timing issue
Junior_51_chevy #1390586 Thu Dec 31 2020 05:24 AM
Joined: Dec 2017
Posts: 973
D
'Bolter
Ebay, plenty of them on eBay.


Mike
Re: Timing issue
Junior_51_chevy #1390603 Thu Dec 31 2020 01:38 PM
Joined: Apr 2005
Posts: 10,049
Grease Monkey, Moderator General Truck Talk & Greasy Spoon
Bought two dwell meters off eBay this year. Shipping was almost more than the units themselves.


Martin
'62 Chevy C-10 Stepside Shortbed (Restomod in progress)
'47 Chevy 3100 5 Window (long term project)
‘65 Chevy Biscayne 4dr 230 I-6 one owner (I’m #2) “Emily”
‘39 Dodge Businessmans Coupe “Clarence”



"I fought the law and the law won" now I are a retired one!
Support those brave men/women who stand the "Thin Blue Line"! Hug a cop!
USAF 1965-1969 Weather Observation Tech (I got paid to look at the clouds)

Re: Timing issue
Junior_51_chevy #1390604 Thu Dec 31 2020 01:41 PM
Joined: Jan 2010
Posts: 4,673
D
Shop Shark
This is why I miss sears

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