dist gear shim
Printed From: TheAMCForum.com
Category: The Garage
Forum Name: AMC V8 Engine Repair and Modifications
Forum Description: AMC-made V8 engine mechanical, ignition and fuel from basic repair to high-perf modifications
URL: https://theamcforum.com/forum/forum_posts.asp?TID=91785
Printed Date: Apr/20/2024 at 12:29am
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Topic: dist gear shim
Posted By: xspiriment
Subject: dist gear shim
Date Posted: Jan/11/2018 at 8:18am
| I'm going through early point dist, has too much shaft end play. Was wanting to finish it this weekend and drop it back in. Didn't really want order and wait for a shim kit to come in. Do you think a standard steel washer is ok or are dist shims some special material. Thanks Paul |
Replies:
Posted By: Lyle
Date Posted: Jan/11/2018 at 12:09pm
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I wouldn't put a steel washer in there. If you are in a pinch a fibre washer, just like they use in electric motors, is the way to go. Older hardware stores have them in a box with different sizes or an industrial fastener place will have them.
Those distributor shims are usually polished and hardened steel, fibre washers or brass if really old. Mild steel washers will just eat away your distributor housing and may score the shaft. |
Posted By: needafasterAMX
Date Posted: Jan/11/2018 at 7:49pm
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i would be careful, there is a reason for more end play then you would think that is needed when the dizzy is out of engine. ------------- 74 AMX, 401 Viper spec T56 6 speed trans Hydroboost brakes with rear disks from a Avenger 3:73 TG rear,now Trutrac with 3:15 A Turbo is in my future. |
Posted By: Steve_P
Date Posted: Jan/11/2018 at 8:34pm
| Is there an end play spec? And why would a conventional steel flat washer somehow wear the distributor when a hardened one wouldnt? |
Posted By: amxron
Date Posted: Jan/12/2018 at 1:54am
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These are always sloppy. Remember they were made by Delco! I put a couple of these washers from old distributors on mine years ago. It was a sbc speed secret! BTW a plain washer will wear dropping metal into your oil. Ron. ------------- AMXron Fleet/Jeep Mgr. Orbit AMC/Jeep 50-1787 |
Posted By: Lyle
Date Posted: Jan/12/2018 at 7:48am
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A conventional washer is neither polished or low friction. On the aluminum housing it will act like an abrasive and pick up aluminum as it rotates, then aluminum will be rotating on aluminum - one of the worst bearing combinations, and things will go bad quite quickly. There are aluminum on aluminum combinations that work like 2 cycle engines that have high silicon aluminum blocks and soft aluminum pistons - these do not "pick up". Aluminum based bearings on steel shafts - specific metallurgy.
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Posted By: Greyhounds_AMX
Date Posted: Jan/12/2018 at 1:08pm
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I found that when I shimmed the distributor gear to reduce the clearance to what appeared to be a reasonable amount, the engine would then eat the gear. ------------- 1968 AMX 390 w/T5 |
Posted By: 6PakBee
Date Posted: Jan/12/2018 at 1:41pm
That's interesting. Would it be reasonable to assume that when the engine is running the distributor shaft moves outward? ------------- Roger Gazur 1969 'B' Scheme SC/Rambler 1970 RWB 4-spd Machine 1970 Sonic Silver auto AMX All project cars. Forum Cockroach |
Greyhounds_AMX wrote:Posted By: Lyle
Date Posted: Jan/12/2018 at 3:17pm
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The distributor shaft moves up and down with acceleration and deceleration. It's a 90 degree gear and that's why it wears, tough angle to transmit motion on a spline gear no matter how little load. Shimming should be done to recenter the distributor gear with the camshaft gear. In most cases you will find shimming top and bottom is required. If you don't know were to shim then check against a known good distributor. I don't have one out of the car or I'd provide a measurement from the top or bottom of the gear to the housing flange. |
Posted By: needafasterAMX
Date Posted: Jan/12/2018 at 3:26pm
exactly , It can be shimmed to get what play is in the dizzy, But it is a process, not hard, but not as easy as shimming the dizzy by itself. ------------- 74 AMX, 401 Viper spec T56 6 speed trans Hydroboost brakes with rear disks from a Avenger 3:73 TG rear,now Trutrac with 3:15 A Turbo is in my future. |
Posted By: Hurst390
Date Posted: Jan/12/2018 at 4:33pm
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Loose end play always here ------------- SC/Hurst Rambler 11.62 120 100% Street Legal |
Posted By: billd
Date Posted: Jan/12/2018 at 5:18pm
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I remove some of the end-play and have never had an issue, however, there are other variables at play here - would they have been eaten anyway? It is possible it wasn't your shimming out some of the end play that did it? Less end play, as long as you don't take out so much thermal changes cause a bind, should cause no issues - unless of course you shift worn areas into unworn areas and so on...... perhaps the gears would have gone south anyway. Are you SURE it was the removal of some of the end play that did it? -------------  http://theamcpages.com" rel="nofollow - http://theamcpages.com http://antique-engines.com" rel="nofollow - http://antique-engines.com |
Posted By: Boris Badanov
Date Posted: Jan/12/2018 at 6:24pm
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How much play do you have? You need a bit to allow in oil. ------------- Gremlin Dreams |
Posted By: Bill F
Date Posted: Jan/12/2018 at 6:54pm
| Remember they are bevel gears designed to run at angles to each other. The forces when running should set the gear where it needs to be. I'd be careful changing the shims. |
Posted By: billd
Date Posted: Jan/12/2018 at 7:20pm
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But since all that is happening is removing some of the play, there's no reason it should "eat gears". If the range was up .010 and down .010 and all you do is narrow that, you aren't introducing any new part of the gear to the other gear. Now if you made the play LARGER it could move into unworn areas but removing play unless you made it tight as things heated up there's no reason. No angle is changing - it's moving up and down within a range as it is, you are simply narrowing that range. My bet - unless there was no play left when it got hot,, it wasn't the act of removing excess play - it was something that was going to happen anyway, but was being blamed on taking out some of the play. The gears were already touching in that range, the range just got a bit smaller. ------------- http://theamcpages.com" rel="nofollow - http://theamcpages.com http://antique-engines.com" rel="nofollow - http://antique-engines.com |
Posted By: jcisworthy
Date Posted: Jan/12/2018 at 7:37pm
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I shoot for .010 end play ------------- Specializing in dyno services, engine building, and cylinder head porting rbjracing.com Phone Number 518-915-3203 |
Posted By: billd
Date Posted: Jan/12/2018 at 7:50pm
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That's about where I go with 'em. Never a problem. I use regular machine shims. ------------- http://theamcpages.com" rel="nofollow - http://theamcpages.com http://antique-engines.com" rel="nofollow - http://antique-engines.com |
Posted By: Rebel327
Date Posted: Jan/12/2018 at 9:24pm
| TSM has spec. |
Posted By: Lyle
Date Posted: Jan/13/2018 at 7:31am
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The distributor gear will get "eaten up" if you shim the distributor shaft down so when hot there is no clearance with the oil pump shaft. The distributor gear is the weak link. There is suppose to be at least 0.010" between the top of the oil pump shaft and the distributor shaft were they will interfere, not the engagement, to allow for thermal expansion. If the distributor end play is too large the timing will "float" excessively. Picture the shaft riding up or down a slope and how the rotor will move - it has to rotate as it moves up or down.
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Posted By: xspiriment
Date Posted: Jan/14/2018 at 8:23am
| Thanks for all of your inputs. There is a end play spec of.010 minimum. i'm going to set it for about .015 that should be good. I had an excess of .030 with a very worn shim so that's why I shimming it a little tighter. Thanks again. |
Posted By: bobsterfl
Date Posted: Mar/13/2018 at 3:05pm
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Got this answer from RobbMc performance some time ago. He was formerly an engineer at Mallory (I believe) so has some experience with these things. "The minimum endplay is .010" to allow for expansion of the aluminum housing. Maximum endplay is debated but I like to keep it under .030". When you drill the hole, make sure the hole is lined up with the oil pump drive tang. Use the washer between the gear and the housing but make sure the OD of the washer is no larger then the root diameter of the gear teeth or the washer will rub on the cam gear. I've seen Mallory AMC distributors supplied with the Chevy washer which is too big. If I remember correctly, the AMC washer is 7/8" OD. Be sure you have the washer in place when you drill the shaft." Robb make some good products for AMC's. Check his website at http://www.robbmcperformance.com/ |