Setback !!!

[tufcj]

I fired the AMX 390 yesterday for the first time. Primed the carb, had the ignition right on, and it started with just a couple of cranks. Quickly checked initial timing, no lifter noise, so I ran it up to 2000 to break in the cam. Oil pressure was about 60-65 PSI hot, coolant about 180-190. Everything looked good. Thermal check on header tubes ran about 900-930. Not running lean. Ran smooth at 2000 for 20 minutes. slowed her down to a normal 750-800 RPM idle, still looking good. While checking timing again, suddenly the idle dropped to barely running, timing jumped all over the scale, a couple of pops out the carb, and dead!!!

We cranked it a couple of times, and it's popping out the carb and exhaust. The pertronix maybe? We spin her to TDC and pull the cap, and the rotor is nowhere near #1 or #6. OH SHIT, it's the dizzy gear. Pull the dist and the gear looks fine. Look down the hole, and the cam gear looks like someone ran a round file down the middle of it. The teeth are completely GONE. These are brand new gears.

I know it's not oil starvation, I checked and double checked all the oiling passages. It doesn't look like cam walk, since all the damage to the teeth is in the middle of the gear. All I can think is I used one of MC's new pump covers without a bypass valve, and I have a set of hand lapped aluminum pump gears. Standard pressure spring. 10W40 oil used at startup, the engine was all pre-primed with oil before cranking.

This is about the 10th AMC V-8 I've built, and the first time I've eaten a gear. Gonna pull it apart this afternoon, and see what damage was done to the oil pump and cover, as well as how much metal got into the engine. DAMMIT DAMMIT DAMMIT

[Lifted79CJ7]

Dang it, all this gear chewing going on around here, I am starting to get scared to finish my engine!!

Jack

[jeepsr4ever]

and I have a set of hand lapped aluminum pump gears.

Aluminum oil gears! This has been the topic of distributor gear destruction before. Aluminum isnt a good oil pump gear material period and I would tell that to anyone who sells them. Bob you may want to get your money back on those gears and be comped a new distributor and cam gear.....



Terrible

[tufcj]

Well, I didn't get it apart today, just not motivated. I got the aluminum gears (machined billet and lapped) because I was told the expansion properties between the case/gears would be more equal than the sintered gears, and they would hold a more steady pressure thru the temp ranges. They are very nice, and all specs were good when I assembled it.

I've also been reading that the Crown gears use a different pitch than the OE factory gears, or the Mopar Performance gears. I just don't know. Too many variables. Just kind of bummed that it happened on THIS motor. I was being so careful to do everything right.

If the damage is severe, I may be ordering a new nickel cover.

Bob.
tufcj

[jeepsr4ever]

I was told the expansion properties between the case/gears would be more equal than the sintered gears, and they would hold a more steady pressure thru the temp ranges

These guys selling these arent hip on metallurgy. If it isnt cast aluminum with the same amount of silicone then it doesnt share the same properties or co-efficient of thermal expansion as the timing cover. Also billet aluminum expands more than twice as fast as cast......Binding!!!

Mopar gears are crown gear and all gears including factory gears are only able to manage a certain amount of pressure on the from the oil pump. Using high flow gears only leads to distributor and cam gear destruction.


These guys selling a high flow oil pump gear set have no clue what is actually going on in the pump itself. If you took the the pressure bypass away you would blow off 100% of your oil filters...bloated and blown or blown out the rubber seal or strip the threads on the oil filters. The AMC oil pump isnt where the oiling issues are 100% of the time. You arnet the first person to have these issues. I was told that even the person promoting these kits is having massive distributor gear wear...this is caused by overpowered pump issues usually in the form of binding or when using high flow oil pump gears. We have done this tech years ago and because we couldnt offer a set of distributor gear and cam gear with the high flow oil pump we didnt offer it to the public. If you look through the oiling section here you will find the issues with the aluminum oil pump and high flow oil pump gear seats....they arent engineered to work with their driving components

[Dusty]

Damn Bob that sucks, i hope it didnt swallow any of the boogers and damage anything else. Best of luck man thats always frustrating.

[rollen dean montoya]

i wouldn't trust anyone selling "hi performance oil pumps". i use stock parts unless they are not available. in that case i have them made to
the correct specs. just my thought.
good luck, later,rollen

[tufcj]

I finally got time to get it apart tonight. I really can't find any single cause of the gear failure. There was NO cam walk, the wear is straight down the middle of the cam gear. There was plenty of oil. There is no sign of any dragging or scraping of the oil pump gears or housing. There is very minor marking from metal fragments (expected). I saw the oil pressure gauge running at 60-65 PSI at 2000 RPM hot. My buddy says he saw it read 90 PSI at startup. All I can think is that the pump and/or pressure relief just put too much load on the gears. Doesn't look like there's anything big anywhere but in the pan. I'm going to flush the pan and pickup, change oil, and put her back together, hopefully I'll be running again sometime next week.

Got one of the new nickel coated covers coming (Thanks MC). Gears and such are on order locally. Don't know what I'll do with those aluminum pump gears. Anybody?

[jeepsr4ever]

those distributor and cam gears arent rated for a high volume pump. Pu them here or in your nearest recepticle

[tufcj]

Here's a couple of pics of the carnage. This gear ran less than 1/2 hour.





Hope to have all the parts and put her back together WITHOUT the HP oil pump this week.

Bob
tufcj