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Timing chain & gears question |
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401MATCOUPE
AMC Addicted Joined: May/20/2010 Location: Salisbury, MD Status: Offline Points: 5367 |
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I am going to bring this back up....the perfect storm.... I posted video of the latest 343 on my run stand. On assembly of the engine, like most of us, I checked everything. Engine ran on the stand great, no issues, as I was tearing down to paint, I noticed the distributor gear was pretty dry..looked at the cam drive gear is was not real wet either. I know of the newer cam gear issues and alignment. I checked the oil transfer hole on the block side of the cam gear...yes it was off, but when mated to a (not the) cam, I blew air pressure through the hole and it flowed fine. So as I tore back into the engine to see what happened, I pulled the gear retaining bolt and washer, dry inside....then pulled th efuel pump ecentric, all dry, cam timing gear......dry, up to the oil that came dripping out the camshaft oil transfer hole. Then I looked at the hole in the cam in relation to the oil transfer hole in the gear....NOT aligned. Dug out the cam I checked the airflow with and they were not at the same place, very close but off enough the block the oil. I machined the oil transfer hole in the cam gear wider to catch the mating cam hole.....I thought I went far enough in this check, but I guess a stack up of tolerances of the Comp Cams Roller Timing set (I think really a SA gear piece by P/N) and the installed camshaft were not playing nice together.
So lesson learned......when checking the cam transfer hole check with the actual pieces that you are using.... I think the oil I saw during priming may have just been drips form the assembly process and were spun off during cam break in run by centrifical force. You can see these distributor gear oil holes during priming through the fuel pump mounting boss on the drivers side of the engine. It may take two to do this...one to run the drill/pump, second to watch the oil actually coming out. There is a first for everything....just hoping this helps someone else. Since I caught at this point it only cost a front cover and pan gasket set and a couple of hours....at least not installed.
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Ross K. Peterson
68X,GoPac,343,AT,52A(1stCar) 68X,GoPac,390,4sp,52A 69X,GoPac,390,4sp,64A 70X,GoPac,390,4sp,87A,8 70X,GoPac,390,4sp,BBO,8 70 Jav SST,390,AT,BSO 74MatX,401,AT,Prototype 74MatX,401,AT |
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sweatlock
AMC Addicted Joined: Apr/28/2014 Location: Largo, FL Status: Offline Points: 3322 |
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This is good information and a great "lessons learned."
To be frank, I don't think I received a good response to the original question posed, which is regarding the selection of a timing chain and gears. The most obvious difference between a stock timing gear set and an aftermarket set is the multiple grooves (2 and up) on the face of the aftermarket cam gears as opposed to the single groove on the stock cam gear. Is there an aftermarket set (all that's available now except for NOS) that duplicates the factory setup and doesn't try to "improve" upon it? |
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RamblinMan
AMC Addicted Joined: Sep/26/2007 Location: Port Charlotte Status: Offline Points: 1237 |
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I have used Cloyes and SA in most of my motors (of multiple makes). Since I'm a tinkerer and will never have a motor together for 100k miles without changing cams, etc., I have never had a problem with a double roller chain set, even the budget ones have never presented a problem. The AMC oil slot is the only thing I would worry about and even that is an easy fix (though it's kinda sad that it's necessary). Most sets are now made by the finest oriental craftsmen unless you are prepared to pay pretty good coin for an American made one. If it was a common failure item, I wouldn't scrimp. I am willing to spend some serious dough whenever it's necessary, but IMO a high dollar timing chain is poor return on investment.
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The Right Reverend of Blessed Acceleration
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SC397
AMC Addicted Joined: Apr/30/2009 Location: Michigan Status: Offline Points: 5480 |
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Again. They ALL need work. Just pick the one you think is the best and fix it. It may have changed now but Edelbrock, Comp Cams, Engine Pro, and SA Gear all the same one. A Cloys will need some work too. Even a True Roller has some issues. Edited by SC397 - Feb/21/2015 at 2:51pm |
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401MATCOUPE
AMC Addicted Joined: May/20/2010 Location: Salisbury, MD Status: Offline Points: 5367 |
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Rick,
I have to agree, any modern replacement should be checked. I have made a video of a cut away timing cover and with a "reworked" oil slot in the rear of the cam timing gear...but same front 6 slots between the front of cam timing gear and the rear of the fuel pump eccentric. Man, that is a lot of flow.....I'll post later today in another thread. I think you are right in closing off all but two holes.
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Ross K. Peterson
68X,GoPac,343,AT,52A(1stCar) 68X,GoPac,390,4sp,52A 69X,GoPac,390,4sp,64A 70X,GoPac,390,4sp,87A,8 70X,GoPac,390,4sp,BBO,8 70 Jav SST,390,AT,BSO 74MatX,401,AT,Prototype 74MatX,401,AT |
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sweatlock
AMC Addicted Joined: Apr/28/2014 Location: Largo, FL Status: Offline Points: 3322 |
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I guess what I'm asking then if they all need work, is which set needs the least amount of rework or 'massaging' to be good, and which sets to simply avoid? Also, when closing off the grooves, what method is best? I've heard of brazing and (believe it or not) JB Weld being used.
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SC397
AMC Addicted Joined: Apr/30/2009 Location: Michigan Status: Offline Points: 5480 |
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Not to mention RTV silicone as well. - not recommended. The Cloys is better as far as the oil cavity location where the oil oil from the cam lines up..... depending on cam. That is just it, you have to correct that cavity and the 6 slots on the front. It does have a little better transfer slot but even that should be checked. |
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SC397
AMC Addicted Joined: Apr/30/2009 Location: Michigan Status: Offline Points: 5480 |
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sweatlock
AMC Addicted Joined: Apr/28/2014 Location: Largo, FL Status: Offline Points: 3322 |
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Perfect - that's what I was looking for.
Thanks! Best regards, Glynn |
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