any one ever heard of the distributor gear breaking theeth? little story. i have owned this truck (79 4wd 150)for obout 15 years and know it very well. the problem is the gear gets ground down till the theeth are thin and break. this is 2nd time this has happened on differant motors. the newst motor is 2yrs old with about 10,000 miles. motor has been running flawless since the install. change oil way more often than needed, just dont like it when sits. the first time was about 10yrs ago with the old motor. i was young and dumb and chalked it up to my heavy right foot. but now new motor, reman dist form napa and same thing! any ideas????

 

i guess im alone on this one

 

Bad timing chain (slack), dragging dizzy ( worn out thrust bearing) or oil pump comes to mind. It doesn't like the stress it's going through. Do you have a hi pressure/volume oil pump?

 

replaced the dist. with a reman from napa. when first fired got bad back fire thru the exhaust. adjusted timing to 12 degrees and and it idled great. changed the oil not knowing where the dist gear theeth,shavings or what ever might have gone. well let it run till temp came up and took it for a test ride for about 2 miles and it ran great. i was at work fixin truck and work was closing so i left it there and drove the mstang home. latter that night the wife took me to work to get the truck. truck started right up and ran great. on my may home about 10 miles i heard a ticking or taping coming from the motor but runing fine. i figured header gasket leak from the backfire before. as i kept driving the taping got worse and then it started to miss badly. runing on 7 cyls i limped it home the rest of the way. parked it and went to the bar to drown my sorrows. any way , every thing i think of would cause miss but not tap or tap but no miss. havent looked at much yet, dist is still tight, pulled number 1 plug to set top dead center when seting dist, so checked plug and still tight, didnt see any sign of exhaust leak or burnt wire. dont know oil pressure as i only have dumby light(did not come on). any ideas and, or do think the problems may be related. no high pressure pump. the old dist did not turn as easy or as smooth on new one

 

do a compression test on all cylinders.

 

compression good on all cyls. all within 135 to 150.

 

<TABLE width="100%" border=0 itxtvisited="1"><TBODY itxtvisited="1"><TR itxtvisited="1"><TD vAlign=top itxtvisited="1">got good compression on all cyls, all with in 135- 150. all plugs look good. took off valve covers and all rocker arms move and have oil coming out of them when cranking over. its making a taping noise from both rear cyls. i think i read valves are not adjustable? is this correct? sound just like a valve tap. when a idle taps are consistant but when reving to around 2grand taps seem to come and go. put cheap oil gauge on and pressure is great. any ideas? im lost
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anyone? im lost

 

Did you check lifter preload ? As far as it loosing dizzy teeth, I'd check the gear position on the shaft. You can use a dial caliper to measure from the top of the block where the dizzy housing sits in the block, down to the bottom. Then measure the the bottom of the dizzy housing, down to the bottom of the gear. I'm not sure of what the clearance should be off hand, but it's something to always check when putting in a different dizzy.

 

The dist. teeth are usually from a bad cam bearing, or a shaved manifold it lets you tighten down the dst. to tight in relation ship to the cam. Now the ticking sounds like your lifters are on there way out or already bad.1 final thing the cam could be warped it dont take much.

 

If a cam bearing was that worn out you wouldn't have any oil psi.Timing chain would have too much slack to run. Lifters wouldn't work either.

The 335's don't have the dizzy in the intake, they go in the block. Milling has nothing to do with it.

If a cam had that much runout you wouldn't be able to even get it in the block.

 

tore motor down and found 3 bad lifters. lifters were not flat on bottom, they are worn into a concave and almost like dented. i guess i need new cam and lifters. do you think cam bearings would be ok to reuse? also with everything apart i can move the cam back and foward 1/4 inch. i was told told this is normal. true? also was told oil theses days have removed some adative that lubes flat lifters due to all cars theses days being rollers or over head cams. was told to use only shell rotella oil as it still has the needed adative for flat lifters. ive heard this from 2 differant guys. anybody heard this?

 

I suspect most guys will tell you to replace the bearings at the same time.

Not sure about the 1/4" play but I suspect it's OK, there's a retainer that bolts onto the
front to keep it in place.

If you have a flat tappet cam (non-roller) cam, you want ZDDP in your oil; this was
removed from new oil per the EPA some time ago. I understand BG MOA additive has
the stuff but in unknown concentrations? Not sure about the concentration of it in Rotella
these days, I'm under the impression/understanding it's no longer included in it, at least
in the same concentrations.

What you want is stuff like this (cost me about $10/4 oz. bottle from my machinist):

ZDDPlus™ - ZDDP Additive for Classic Cars - Agricultural Equipment & More

-ct

 

My bad on the manifold and block mistake' but the same is true over tightin the dist. and you will wear teeth. The concave on the lifters is normal the lifters spin on the cam lobes as the motor runs.Now how much wear is on them? How do the gears on the cam look any sharp spots or jagged edges. The only way to be sure on the cam bearings is to inspect them.

 

I went through this on a 351m in a 79 bronco it kept shearing the rollpin in the dist. gear. It was this way for a better part of a year till the cam gear broke, after a cam change and the cam bearings being replaced it never happend again. I put another 30,000miles on the rig. I did not rebuild the rest of the motor because of finaces at the time but all else looked good, it was a gamble but it payed off in the end.