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Discussion Starter #1
Alright Fellas, finally got the 400 all buttoned back up in my Bronco last night, but with issues.

About a month and a half ago, I regasketed/sealed, new coil, new double roller timing set, etc. to freshen it up. A couple weeks later, the Bronco acted like it jumped time again. After a mile jaunt home, sure enough it was 20+* off. So I tore back in to it doing a little here and there. Timing set is perfect, no debris or metal in the oil pan, and I threw a new remand Motorcraft distributor in last night (which now comparing the old dizzy to the new, I believe was the culprit all along).


So back to the problem, everything is buttoned up, I fire up the Bronco, and I hear a good bit of noise coming from the drivers side, top end I believe. So I shut it down after a few seconds of running. I check to make sure everything is lined up properly, and it was. So I give it a shot again, she fires up...still making the same noise, but I got a light on it real quick and it was holding at 15*...great. I give it a touch of throttle and it dies after running for about 15 seconds. I re-evaluate what's going on and figured the third time is a charm, she fires right up, but didn't wanna idle for shit...so I shut it down after about 5 seconds.


So my thought process is, the cause for me jumping time initially was a fubar'd distributor. Which in turn, because of a 20* timing error, caused me to drop a push rod or two...bend a valve or two or potentially collapse a lifter. Does this sound to be on the right track?
 

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Pull the valve cover. It would be the quickest way to check for any damage to the top end or collapsed lifter. Or at least pull the plugs and check for fowling, that would tend to point to top end problems. I hope there's a cheap fix for you.
 

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Thanks man...figured I'd pull the VC's tonight, but get as many suggestions as possible first.


And the cheapest fix I've found would just be swapping the engine...I've been offered a free 400, a $75 400 and a $250 460. Cheaper to swap engines than even buy a cam kit...haha.
 

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So my thought process is, the cause for me jumping time initially was a fubar'd distributor. Which in turn, because of a 20* timing error, caused me to drop a push rod or two...bend a valve or two or potentially collapse a lifter. Does this sound to be on the right track?
Doubtful. The ignition timing is controlled by the distributor, the cam timing from the cam. I have never heard of ignition timing directly causing a bent valve or pushrod.

there are only two possibilities that come to mind....

One is a sheared, missing, or broken cam dowel pin. This could allow the cam to move relative to the cam timing sprocket, affecting both cam timing and ignition timing. It could also cause for bent push rods or valves if the valves contact the pistons. I have never heard of this happening, but I am sure it is possible.

Second is a bound up oil pump. If you have oil pressure you can rule this one out. Oil pumps can pull a piece of debris in them that will catch in the rotors, effectively seizing the pump. This will cause oil pump drive shaft to twist until it breaks, leaving you with a running but noisy engine due to no oil pressure. Typically, when this happens the cam and distributor gears are damaged by the increased load of the seized pump. Repair for this is to replace the cam, lifters, distributor gear, oil pump, and oil pickup. This is not an uncommon failure....

Good luck, let us know what you find:popc1:
 

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I would suggest pulling the distributor out and look at the oil pump drive rod. If you swapped the distributor and then started having what sounds like valve noise then i would be questioning what is driving your oil pump. Maybe the new distributor is too short or too long and the rod isnt running the oil pump correctly.
 

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Discussion Starter #6
Doubtful. The ignition timing is controlled by the distributor, the cam timing from the cam. I have never heard of ignition timing directly causing a bent valve or pushrod.

there are only two possibilities that come to mind....

One is a sheared, missing, or broken cam dowel pin. This could allow the cam to move relative to the cam timing sprocket, affecting both cam timing and ignition timing. It could also cause for bent push rods or valves if the valves contact the pistons. I have never heard of this happening, but I am sure it is possible.

Second is a bound up oil pump. If you have oil pressure you can rule this one out. Oil pumps can pull a piece of debris in them that will catch in the rotors, effectively seizing the pump. This will cause oil pump drive shaft to twist until it breaks, leaving you with a running but noisy engine due to no oil pressure. Typically, when this happens the cam and distributor gears are damaged by the increased load of the seized pump. Repair for this is to replace the cam, lifters, distributor gear, oil pump, and oil pickup. This is not an uncommon failure....

Good luck, let us know what you find:popc1:


A couple questions, would I be able to test the cam dowel without tearing back in to it? IE, rotate the crank and and see if the rockers are moving? If it is the dowel, I should be able to replace that right? Should just be able to pop the thrust plate off and replace?

Next...I have good and easy spin from the oil pump when I was trying to get the distributor in...wouldn't signs of binding have shown up there?


Thanks for the help.
 

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Discussion Starter #7
Alright...just went out and started it. I had oil pressure...about 60psi. The top end noise didn't appear to be as bad, but daggon the engine was shakin all over the place (I used to be able to place a glass of water on the air cleaner and you could barely see a ripple) and the idle speed was through the roof.
 

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sounds like you have a gremlin on your hands......

Everything can be fixed with a little time and know how how. I'm thinking when I get serious about it it shouldn't take too long tracking down the problem. I haven't done anything to it the last couple of days, but I plan on hitting it hard over the weekend. Start with a compression test, then check push rods and lifters, then tear the snout off...again.
 

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Everything can be fixed with a little time and know how how. I'm thinking when I get serious about it it shouldn't take too long tracking down the problem. I haven't done anything to it the last couple of days, but I plan on hitting it hard over the weekend. Start with a compression test, then check push rods and lifters, then tear the snout off...again.
I did some more thinking on your problem.

Did all this start right after you changed your distributor? The 351W and 351M share the same distributor....except for the gear. The Wheezer gear is smalller. Is it possible you got a 351W gear on your new distributor?

The sheared cam dowel pin is a VERY unlikely culprit. I would think you could check for this by simply removing the distributor cap and rotating the crank forwards and back. Check that the distributor shaft moves as the crankshaft turns.
 

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Discussion Starter #11
I did some more thinking on your problem.

Did all this start right after you changed your distributor? The 351W and 351M share the same distributor....except for the gear. The Wheezer gear is smalller. Is it possible you got a 351W gear on your new distributor?

The sheared cam dowel pin is a VERY unlikely culprit. I would think you could check for this by simply removing the distributor cap and rotating the crank forwards and back. Check that the distributor shaft moves as the crankshaft turns.

The issue started before the dizzy swap, and I was about 29* out of time. Then I swapped the dizzy after I dug inside and didn't find any problems, and there is still an issue but doesn't appear to be the same issue, because now I'm in time but it runs like crap.


As for the dowl pin, I sheered the cam eccentric bolt, and drilled it out. So I don't think I sheered the dowl, but is it possible the dowl pulled out of the cam while I was drilling?
 

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The issue started before the dizzy swap, and I was about 29* out of time. Then I swapped the dizzy after I dug inside and didn't find any problems, and there is still an issue but doesn't appear to be the same issue, because now I'm in time but it runs like crap.


As for the dowl pin, I sheered the cam eccentric bolt, and drilled it out. So I don't think I sheered the dowl, but is it possible the dowl pulled out of the cam while I was drilling?
Did not know this....it might be worthwhile to pull the timing cover and have another look. Hopefully it was not an expensive cam. Good Luck!
 

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Discussion Starter #13
Did not know this....it might be worthwhile to pull the timing cover and have another look. Hopefully it was not an expensive cam. Good Luck!

Naw...it was just a stock 400 with a carb and intake. Dug in to it yesterday and it appears at least 3 lifters are garbage, and there is about 1/4" of play front to rear in the cam. I figure this is as good a time as any for a top end rebuild. I figure I'll probably go with a Comp DEH255 to make the swap as easy as possible, without having to get new rockers or get any head work done.
 

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Naw...it was just a stock 400 with a carb and intake. Dug in to it yesterday and it appears at least 3 lifters are garbage, and there is about 1/4" of play front to rear in the cam. I figure this is as good a time as any for a top end rebuild. I figure I'll probably go with a Comp DEH255 to make the swap as easy as possible, without having to get new rockers or get any head work done.
Good idea and good cam choice....get the comp lifters too, and use their break in oil.

The play in the cam concerns me, the front thrust plate should hold the cam in position between the cam and cam sprocket with almost no play (a few 0.001", not 0.250"!). It sounds like maybe your cam plate is either missing or sheared the bolts off the front of the block. Get a new thrust plate and bolts before you dive in, it is cheap insurance.
 
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