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AMC 360 Cam and Distributor issues

AMC 360 Cam and Distributor issues
G

GrantWiseman

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Location
Bella Vista, Arkansas
Vehicle(s)
1979 CJ-7, 360 V8, 3-Speed Manual
Hey Guys,
So over the last summer I dropped an AMC 360 into my 79' CJ7 , and recently the distributor drive gear stripped out, which is apparently a common problem. So I replaced it, and then I had a lifter give out, and it ground the lobe of the camshaft pretty bad. I did notice that it looked like the cam had walked out a little bit, because it looked like the chain had cut the corner of the timing chain cover, where the tab is over the harmonic balancer/Driveshaft. And when I took it all apart the distributor drive gear was worn through halfway already again, even though there was only a couple hundred miles on it!

I had a cheap no-name HEI distributor, which I've been told can cause problems. I'll be getting a better one if that is the case. Also I Know a new camshaft and lifters, timing chain (I may have damaged it trying to get it off and think its better safe than sorry) and valve springs to match. Is there anything else I should need to get?

And how is the camshaft kept from walking forward? The lobes on the cam are supposed to be ground at an angle to keep the cam towards the back of the engine, but will that be sufficient?

And lastly, whats the best cam and company to buy from?

Thanks for any help!
 
I installed a Crane 260H in my 401 last year when I rebuilt it. I am using a duraspark distributor to drive a MSD 6A. I also had read about cam gear issues so I purchased a matched set of cam/distributor gears, I think they were MSD if I remember correctly. I have put about 5k miles on mine since rebuild, and the gears are still in perfect shape when I looked at them a month ago.

One thing to keep an eye out for: I installed a fairly expensive double roller timing set when I did my rebuild, and during assembly, I noticed the the oil passage holes and channels on the cam gear were made incorrectly and I had to weld them up and remachine them to spec. I think this may be a problem with several brands of aftermarket timing sets. Cloyes was the brand I used.

Also, make sure the oil you are using has adequate levels of ZDDP in it to protect your flat tappet cam and lifters. All modern motor oils have had their ZDDP levels reduced to very low levels to prevent contamination of catalytic convertors. I use Valvoline VR1 racing oil because it contains levels of ZDDP appropriate for flat tappet use, and I can buy it locally. Joe Gibbs, Lucas, Brad Penn and others make oils such as this. It is more important at break in, or in an engine that has high valve spring pressure, but I run these types of oils even after break in and have not had any trouble with lobes going flat. It used to be that diesel truck oils like Rotella, etc. had the high levels of ZDDP in them, but that is no longer the case. YMMV.

Dave
 
OK, so do you think I could get away with just getting matching distributor gears, or is there an issue with tolerances with the distributor itself?

Unfortunately I don't have the equipment or know-how to machine oil channels in the cam and gears, so is there perhaps a good place to get an OEM cam?

Thanks for the oil recommendation! I'll get some of that for sure.

There didn't seem to be any mechanism to keep the camshaft from walking, is it just the way that the lobes are ground that keep it to the back of the engine?

Thanks!
 
As long as the distributor itself is not grossly out of spec somehow, then yes, if you fit it with a gear that is metallurgically compatible with the cam gear you should be ok. The easiest way that I found to do this was to buy a gear set from the the same manufacturer. I chose MSD #8005 distributor gear and #8007 cam gear. I don't know if these are the best option, but they worked for me. There are others out there that are cheaper, but I have had pretty good luck with MSD stuff, so that's what I chose.

I had never read about problems with aftermarket timing sets being made incorrectly, but when I placed the new cam chain drive sprocket next to the factory original sprocket that came out of the engine, I could immediately see the oil channels were different. If I remember right, the oil transfer channel machined into the face of the sprocket extended much further than the original, and if run this way would have resulted in a loss of oil pressure and no oil flow to the cam's distributor drive gear. I welded up about 3/8" of the channel and then threw it in the mill and machined the weld bead back flush with the sprocket surface. I don't know how to tell if any particular manufacturers product is made to spec or not before purchase. My sprocket may have been a one time error on their part for all I know.
The Cloyes timing set was the part that was made incorrectly. The Crane cam that I purchased seemed to be well made, but it was on a smaller base circle than the original cam which required me to use a non-standard length custom pushrod also. The push rods were not real expensive, but it was something I had to deal with. Pushrod length should always be checked before assembly any time you install a new cam or lifters because all manufacturers use different specs for base circle diameter.

As far as I know, it is the cam grind which controls cam thrust by virtue of the offset angle between the lobes and the lifters.
 
Update-- I got the cam, lifters, timing set, and a new distributor and drive gear all installed. Its all reassembled at this point. It seems to solve the play issue, the Cam is solid as a rock with no forward play at all.

So the issue I have now is that I can't quite get it to start for the break-in; I'm trying to tweak the distributor to get the timing right (I don't have a timing light to vacuum gauge but thats never caused me trouble in setting timing before), but it seems that one cylinder is backfiring up through the intake and retarding the whole engines operation. It'll turn over, and i've gotten really close to having it started, but it won't run yet. Any idea on what could be up? Maybe the valve got messed up when the lifter went bad?

Thanks, and Thanks for putting up with a newbie by the by!
 
Something sounds off timing wise back firing through the carb. Double check #1 TDC on distributor, firing order on plug wires (right rotation maybe?)
 
No clockwise and at top dead center the rotor should be pointing at the left headlight. I put a little mark on the dissy where the #one plug fits and then line it up with the rotor and it should be close enough to start.
 
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