jeepsr4ever
Here is a list of things that can cause distributor and cam gear wear.
1. Oiling holes throught the large timing gear, the groove for the oiling hole must be at 2:00 from the keyway, also all passages must be clear.
2. Cam bearing at the front of the block must have a groove in it, this sends oil through the cam at all orientation and rotation of the camshaft.
3. The cam must have a 90 degree oiling hole setup to feed the timing gear and must be free from casting obstruction.
4. Cam gear must be matched to the distributor gear. Their are 2 types of cam gears out there and at least 3 types of distributor gears, they CANNOT be mismatched, replacing just the cam gear will cause big problems.
5. The timing cover: The oil pump drive gear's shaft that connects to the distributor goes through a hole in the timing cover, this is a precision hole and if tapered can cause distributor gear wear through chatter.
6. Oil pump gears: Using longer than stock or poorly made after market gears can cause chatter, binding or premature wear of the oil pump drive gear's shaft hole. When you install a aftermarket kit that comes with new gears the idler gear pin MUST be longer. The cam and distributor gears are only rated at a certain torqueload. Some of the new gears available as of 4-22-05 are now hardened (both gears) and can withstand greater pressures
7. Oil filter.......Yes oil filters can cause premature dizzy and cam gear wear. If you run the wrong oil (too heavy) or a filter that gets clogged early or a filter that isnt a high flow you open up your oil filter bypass and not only send dirty oil through your motor, you also exerpt a high amount of pressure on the oil pump and that alone can cause gear wear, this happens mostly on start up. In late 87 chrysler got rid of the oil filter bypass on the oil filter adaptor, after market oil filter adaptors also have this cast in. Beware that if you use a high pressure oil pump spring without a oil filter bypass you run the risk of ballooning your filter.
8. Cam walk: Cam walk can be attributed to a cocked or poorly place cam plug (large freeze plug that hold the cam from leaving the rear of the block. Also cam walk can be caused by bad lifters, worn cam bearings, cam bearings installed improperly, or a poorly ground cam and in some cases a new cam that gets flattened on startup
9. Cam walk can also be attributed to lack of relief holes in the back of the cam, you see pressure can increase between the end of cam and cam plug, most of these cam must be checked, we have 3 in here with no relief holes...............dang summit
10. The retainer washer for the front of the cam that holds the distributor gear must also provide a positive seal for proper oiling. Off the shelf washers can sometimes have nicks or be convex or concave which to factory torque specs can lead to a loss of oil in front of the camshaft.
11. The installation of the timing cover without locator pins or worn location holes will cause a mis-orientation of the thrust on the distributor gear and eventually may result in a broken or heavily worn set.
12. Early Crown timing covers that were not checked for proper dimensional tolerance can attribute to up to 100% of the fast gear wear. Even today vendors should check for proper alingment.
I have seen a AMC V8 go 210,000mls without any cam walk and very little gear wear. I have also seen a AMC V8 go 2 miles and eat the gears. The factory engineers knew all this and they put these motors together accordingly. Building a AMC V8 can be a expensive build and its a dirty dirty shame to have something like a cam or distributor gear go out, this can cause Major scoring on the oil pump cavity and also can cause the oil filter bypass to open and voila, roached bearings. Hope these hints help anyone out who is building a AMCV8.
-MC
fuzz401
there must be a slight indentation on the back of the timeing cam gear
Elliott
Nice write-up, very nice. From what else I've read, incorrectly ground cams have at least two issues: 1) wrong journal dimensions and 2) lack of lobe taper that keeps the cam back in the block. I wouldn't rule out the possiblity that some will go flat due to incorrect sintering process or simply loss of tempering during a faulty grind.
fuzz401
cast timming cam gear
[img]http://img2.photobucket.com/albums/v11/fuzz401/104_0420.jpg[/img]
old style roll master cam gear
[img]http://img2.photobucket.com/albums/v11/fuzz401/104_0421.jpg[/img]
[img]http://img2.photobucket.com/albums/v11/fuzz401/104_0418.jpg[/img]
new style roll master with bearing cam gear
[img]http://img2.photobucket.com/albums/v11/fuzz401/104_0422.jpg[/img]
rollen dean montoya
does this apply to the I-6 258?
jeepsr4ever
nope the rules change dramatically for the sixes
Diagram1
I recently got a "Proform" HEI type distributor for my 73 CJ5 w/304 and have heard you shouldnt match a new drive gear with a old cam gear and vis versa. I was thinking of removing the old drive gear and putting it on the new distibutor rather than rebuilding the block. Is this and option I have? If so, is there anything I should be particularly weary about?
jeepsr4ever
Welcome aboard! :t:
Its true their are 2 different profiles on the dizzy gears these days. One is from the oem gear the other is from the import dizzy gear (the superior one) believe it or not. you may or may not be able to get away with doing that. You cant even take your old one and install it on your new dizzy as their are 13 teeth on each gear and MUST be matched. But lots of guys have just nstalled a new dizzy gear with success...I have had moderate success.
fuzz401
found this on the amc forum
More cam/distributor gear issues
From: Randy Guynn <amx69@swbell.net>
Date: Wednesday, February 18, 2004 08:23
This old bugaboo is rearing it's ugly head yet again. The latest
casualty comes from mis-matched parts. The cam did not have a groove in
the front journal, and the front cam bearing was not a grooved type.
This shuts off all oil to the front of the engine which in turn burns
the gears up.
Anyone & everyone in the AMC hobby needs to be fully aware of how the
gears recieve oil. They also need to understasnd the entire system of
parts , what is correct, what is not, in order the be sure they are not
going to have troubles in this area.
When the engines starts and oil pressure develops, the very first part
of the engine to recieve oil is the front cam journal. The oil splits
the path at that point and part goes thru the timing gears, the
remainder goes to the rest of the engine. The oil continues thru each
cam journal where it splits and oils the upper end and the lower end.
Back to the very first spot that sees the oil, the front cam journal.
#1, the cam, & or Bearing MUST have a 360 degree groove. No groove, then
the only time oil will get to the gears is once every 360 degrees, when
the oil holes line up, the gear will get a small squirt of oil and that
is it.
#2,The cam has a hole in the side of the front journal and it also has a
hole in the face of the journal. These two holes MUST intersect. If
these two holes do not join, then NO OIL ever gets to the timing gears.
#3,The upper timing gear has a pocket machined or cast into the rear of
the sprocket. This pocket MUST line up with the hole in the face of the
cam journal. If the pocket does not line up, no oil will go to the gears.
#4. The upper timing gear needs a heavy chamfer completely around the
I.D. of the hole where is slides on the camshaft. This chamfer is not
there to aid in fitting the cam easier, it is there to supply a route
for the oil to go. No chamfer, no oil gets to the gears.
#5, The upper timing gear also has two slots. One slot is for the keyway
that holds it to the cam, the other slot is for oil transfer. The oil
transfer slot MUST be free and open, no casting flash to block oil.
#6 Next the fuel pump eccentric comes into play. It will also have two
slots. One for the keyway, one fore the oil transfer slot.
#7, finally we come to the cam gear which drives the distributor. This
gear too has two slots. Again one for the keyway, the other for oil
transfer. The transfer slot must be open and lined up with all the other
oil transfers so there is an open groove which will supply the oil to
the gears.
#8, the Cam gear MUST have 4 small holes around the outside diameter of
the gears. 3 of these small holes are on the smae plane, lined up with
each other. The one hole will be offset. If this one hole is not offset,
then the keyway will block the oil going to it.
There are other issues at play here such as mis-machined parts, cam
walk, bad gears, etc. However, no matter how good of quality parts used,
if the oil cannot get to the gears then the gears will be burned/eaten up.
Maybe you are just freshing up your engine and think everything is just
fine, and it might be. But, just change ONE part in the ''oil circuit''
and that part could block oil from getting to the gears. This oiling
issue is VERY, VERY important. Everytime you assemble am AMC V8 you
should look EVERY piece over that makes up the oil delivery to the
gears. If you slack off here you are just asking for trouble when it
comes to AMC V8 engines.
fuzz401
[img]http://img2.photobucket.com/albums/v11/fuzz401/104_0458.jpg[/img]
[img]http://img2.photobucket.com/albums/v11/fuzz401/104_0457.jpg[/img]
jeepsr4ever
Great pic fuzz! I talk to Randy from time to time. He is a good guy and very knowledgable :t:
I have heard myths of fuel pump eccentrics being put in backwards....... :?: :?: This is not true as they share the same chamfer on both sides and a oil groove 180 degrees from the keyway. I agree with Randy's statement on addressing thew gear wear. Although I have successfully ran a camshaft without a oil slot tunning around it I do believe that the higher the flow the easier it will be on the gears. Oil type also falls into place. If you run a 5w30 the shear of the oil may actually cause the wear as well.
jeepsr4ever
little tip if your having this happen. Look at the end of the cam on the back side of the cam (nearest to the firwall) does the camshaft have relief holes for pressure? Should have holes to relieve the pressure between the end of cam and cam plug (freeze plug) new summit cams must be checked for these holes.
Hey AL you reading this?
Pics to come soon
FSJnovice
thanks for the info everyone.
73hornut
I was building my 401 short block, and when I was installing the cloyes timing cam gear, I noticed the the notch in the back that lines up with the hole in the cam, didn't line up. It was off about 1/8 in. Took my die grinder and widend the notch. Just something everyone should check.
Al Johnson
Whelp, I "think" I fixed my eating distributor gears problem. I finally broke down and bought a nickel plated timing cover from MC. Nice part for sure. I had to hone the tips of my oil pump gears to eliminate a slight scraping on the walls of the gear cavity in the pump. I have about 18lb pressure hot idle, and 60lb at around 1500 RPM and up.
I used 1" long spring pins for alignment pins. The factory ones are about 5/8" long, and I just didn't feel these were doing the job. Also, I had been cheaping out and reusing an old worn out pair, NOT a good idea. My timing cover, the old one, had worn alignment pin holes as well.
So with a fresh timing cover, and most importantly new long alignment pins, it's been going good for about 3 weeks now. I am afraid that I spent a lot of money on parts I didn't need before getting the combo right.
Hope this info helps someone else with their distributor gears!
Al
Elliott
Good deal Al, that certainly was a very long haul to sort that one out. Thanks for tip on the longer pins too!
Gremlin4ever
A misconception that I have experienced even at the parts house is the difference between "cam" & "timing" gears alone. I needed a new cam gear, but all the parts counter kept bringing out was the timing gear.
TIP: Cam gears drive the distributor gear while timing gears are run by the timing chain.
Please be careful when your on this topic were ever it may be, parts house or over dinner, or everyone will not be on the same page. And that will lead to an enrollment in your local Anger Management Program.
Just my 2¢
BRAD ARTHUR
i newly rebuilt a 304 amc. 500 miles after rebuild i had a cam gear get chewed up. and another 250 miles another cam gear wasted. which is where i am now???
at the time of the rebuild i used a summit 8600 cam, cloyes timing set, a bulltear nickel timing cover and oil filt. adapter, and Z&M JEEPS amc hei. ran great, liked the hei distributor. 500 miles later ate the cam gear that drives the distributor. tore it down and found 1- summit cam had 1 oil relief hole in end of cam, 2-cloyes timing set had flashing blocking the oil gulley to the dist. gear, and 3- the machinist that assymbled my motor used the old cam gear and i used the hei with a new gear on it. after talking with MC @bulltear i found everything could be wrong- the 1 hole, the flashing and mismatched gears.
so i ordered an edelbrock cam, removed the flashing , a new matched gear set from bulltear. the edelbrock cam had 1 hole also? installed it anyway, after talking with MC. got it running again!
after 100 miles i reset the timing pulled distributor and checked the gear. noticed the hei had a bit more end play than i remeberd. ran excellent for the next 150 miles.
then dead again, pulled dist. to find cam gear wasted again. took timing cover off again, checked the end play on the dist. and it has .125 (1/8in.) movement up &down. i know this was more than i started with. MC says it should be around .016 play.
my question is what could have caused this play in the dist., and what can be done to fix it. when i first installed it there was a gap between the dist. housing and the timing cover, and as per the instructions-use a gasket or a shim. wasn't a big gap and the gasket seemed to take care of it. could it have been tighted up to much and pushed the shaft up causing the excessive end play?
now with the timing cover off and oil pump installed , put the distributor in and seems to need a shim between the housing so it won't bottom out on the oil pump shaft. the shaft on the hei is 2 mm longer, from mounting surface of housing to end of shaft, than my old distributor. if the distributor had .016 end play looks like the gear and the shaft would be aligned properly.
any suggestions or thoughts, could the end play come from the first gear trashing, when the distributor skipped a tooth and died? then not checking the end play on distributor and running it cause a 2nd cam gear to go out??????
73hornut
Brad, If you look a few posts up, you will see what I wrote about the cloyes timing set. The notch in the back of the cam sproket is very narrow and dosen't line up with the oil hole in the front of the cam.
Jim
BRAD ARTHUR
hay thanks for the info , hopefully i fixed trhe oilingprob the first time but i will double check that one ths time. i beleive that after the first time the dist. jumped a tooth when the cam gear went, it pushed the dist shaft/gear up causing excessive endplay on the dist. not catching it i ran it 250 miles and another gear got chewed. the dist. gear rode up on the edge of the cam gear causing premature wear. the cam gear is wore right in the middle of the teeth, as if the teeth were split in two. and there apears to be no cam walk because it is wore in the center of cam gear. front of cam gear is high & rear of cam gear is high wore in middle.
