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Old 08-09-2005, 07:27   #1 (permalink)
351 XE on LPG
 
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I come to my Ford brothers for help . . .

The 351 in my XE came with a set of bolt-on YT non adjustable roller rockers. For some reason the previous owner had machined quite a bit of metal off each rocker foot, (between 1 and 2 mm), but I wasn’t aware of this when I performed my rebuild, and torqued each one down to the required 24 ft/lbs thinking that because I was using a hydraulic cam that no adjustment was necessary. Since then I’ve learnt from this forum about lifter preload and methods for measuring it.

Two years after the build I start hearing a knocking sound from the top-end so I perform my first lifter preload check. This is when I discover the shaved feet. BUGGER. Each lifter had WAY too much preload. I ordered a set of new feet from YT and they were a lot higher then the ones I had installed. I also ordered a set of CRANE shims of various thickness, so there was no excuse for me not getting a perfect preload. I also bought a set of new lifters.

I discovered a valve with a damaged tip. Instead of being flat it was concave, as if the roller had hammered a channel into it. I checked all the rollers and they were fine. I know that valves are supposed to rotate, but obviously this one wasn’t. I rotated it manually with a set of vise-grips, to try and loosen it up. I then covered the head with an old towel and made a little hole in it for the valve tip to stick out of, then used a miniature grinder and carefully removed the groove by grinding the tip flat. The towel caught the metal filings. Though a very rough approach - I figured it was worth a try, and I could always shim it to the correct preload.

Once assembled and back on the road it was quiet and ran stronger then it’s ever been since I built it. I was so happy. Having the correct preload really made a noticeable difference. As it turned out, I didn’t need to use the shims (except for the damaged tip), because with the new feet they all came within spec (between 20 and 60 thou).

But wait . . .

My happiness lasted less then a week, when suddenly while on the freeway the motor started making a loud knocking sound, and started missing (along with the occasional LPG carby backfire). BUGGER. No matter what I do I cannot fix this problem. I checked the roller rockers and preload over and over and couldn’t find the cause. I finally thought that maybe the damaged valve was getting stuck open and being tapped home by the piston, so I shoved the XE under a tarp for the last 9 months while I set about building my new garage.

Since then I’ve had the heads redone. The excess preload had taken it’s toll. Some valves needed replacing and all the inlet guides needed new K-lines. The Stellites on the exhaust needed a slight grind to make them flat again. One of the heads required a slight shave as well. Some of the valves were quite loose in their guides and all the stem seals had gone hard.

Then while reading Ford Forums I discovered that I’d stuffed up again and should have run the new lifters in in the same fashion when I ran the new cam and lifters in over 2 years ago when I built the motor. It never crossed my mind. BUGGER. Maybe I’ve damaged a lobe on the cam. How can I tell?

During assembly I noticed that a couple of the lifters didn’t have their pistons hard up against their circlips. A little tap set them right. I used the same new lifters and was going to try and bed them in once the motor started, but the damn same knocking noise came back. I’ll be buggered. The erratic missing and occasional carby backfire is all still there. Changing the timing had no effect.

Any ideas PLEASE?
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Old 08-09-2005, 17:30   #2 (permalink)
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Re: I come to my Ford brothers for help . . .

by a dial indicator. Set it up and measure the lift on each lifter and compare to camshaft spec. If it's not even close? Your up for a new camshaft.

I gather the plugs are right? The only time my clevo's sounded ordinary is when I've had a valvetrain issue. Sounded like a chaff cutter rofl. When the plugs weren't right I shot some big arse flames out the back. Looked good but sounded real bad.
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Old 08-10-2005, 21:34   #3 (permalink)
351 XE on LPG
 
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Re: I come to my Ford brothers for help . . .

Thanks Brenx

Plugs are new and I've rechecked them and swapped them around.
Sometimes it sounds like the lifters aren't pumping up. The oil pressure is 80psi at idle and 100psi at 2000 RPM.

What could cause the lifters to starve from oil?

At idle it is inconsistent, sometimes almost stalling, then the revs come up automatically, but always running rough like it's only running on 4 cylinders. It's a good thing the motor is chained down in 2 places.

The knocking sound comes and goes, but increases with revs. It appears to come from the same location deep in the block (not near the rockers). Touching the accelerator while on the road and placing a load on the engine usually results in a carby backfire.

I'll get a dial indicator and test the height of each lobe.

I've got an old TQ40 cam that I can use if necessary (with new lifters of course).
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Old 08-11-2005, 03:26   #4 (permalink)
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Re: I come to my Ford brothers for help . . .

could be sticky lifters
didn`t you say that some were stuck when you were putting them in.

that would explain it being eratic if the lifters are sticking sometimes and letting go sometimes.
if it was the cam worn it should be doing the same thing all the time you would think.

when i was running hydrolics i used to have trouble with lifters all the time.
only ones that i found would last were - Speed Pro 900-R
the R in the part number stands for race ( naturally ) and are a heavy duty item.

you can only hope .easier to change than the cam too.

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Old 08-11-2005, 23:28   #5 (permalink)
351 XE on LPG
 
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Re: I come to my Ford brothers for help . . .

I don't think its a case of sticky lifters since I was driving fine along the freeway then all of a sudden it's running like a noisy pig.

I can't work out what is causing the vicious carby backfires, because even if the cam is worn or the oil pressure is down, these conditions wont hold a valve open so that the flame front escapes into the intake and explodes the LPG mixture.

I pulled the spark plugs and removed the intake and turned the motor over freely with the starter. Oil slowly made its way out of the lifters, but all the cam lobes stayed dry.

Tonight I'm going to attach a drill to the oil pump drive shaft while turning the motor over at the same time to see if I can get more oil to the cam and lifters.

Has anybody done this before? If so, how much oil should be squirting around the place to gauge if the results of my experiment is normal?

I'm starting to think that maybe a piece of silicon from a gasket has broken away and blocked one of the oil galleries? I may be guilty of applying too much sealant, though I never have any leaks.

Any ideas for clearing a blockage in an oil gallery?
100 PSI pressure doesn't seem to work (if this is in fact the problem).
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Old 08-12-2005, 02:03   #6 (permalink)
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Re: I come to my Ford brothers for help . . .

I recon you have killed a few lifters with the excessive preload you gave them originally. When they were preloaded full on, they didnt have anymore collapse in them, so wer'nt noisy, and still opened the valves properly. Now that you have preloaded them correctly, they could be collapsing in the lifter after the motor has started and not opening the valves enough, plus having excessive valve lash. Just now and then, as you know old/worn hydraulic lifters can be very spuratic.(first ever use for the word spuratic for me.haha)

Also, if the original "excessive" preload was past too tight, there is a very good chance of wiped cam.
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Old 08-12-2005, 02:18   #7 (permalink)
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Re: I come to my Ford brothers for help . . .

i still think lifters.......

they are the only part that can vary their performance or travel during engine opperation. ( be spuratic )

the cam lobes etc will always remain the same during a drive , if it`s stuffed it will stay stuffed it can`t come good as you drive.

a lifter can be working fine then stick solid or colapse then come good again. as xdclevo said spuratic
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Old 08-12-2005, 05:21   #8 (permalink)
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Re: I come to my Ford brothers for help . . .

C'mon, stop using words above my payscale! It's sporadic by the way........<davis>

Agree too, due to the on/off nature of your problem it would lend itself to being something variable such as lifters. I'd still measure the lobes with the lifters out though - just to be sure.

Oil blockage? Draino? That would be a real tough one to clear a small inaccessable oil gallery blocked by some foreign material (gaskit goo etc) which would be resistant to most cleaners anyway. There are oil addatives you can run to clean systems from sludge and then flush it out with an oil change - but I doubt they'd have any effect if it was silicon?? You'd hope the pump screen and filter would catch most floaties.

ps: great to see the old beast has the tarp removed though.
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Old 08-12-2005, 06:52   #9 (permalink)
351 XE on LPG
 
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Re: I come to my Ford brothers for help . . .

Thanks guys for taking the time to read and respond.
I really appreciate each of your suggestions.

I'm sorry if my long thread has mislead anyone, but I did put in a set of new lifters when I replaced the RR feet and they worked perfectly for 4 days, then all of a sudden everything started running rough on the freeway.

It wasn't gradual, it was running perfect one second, then rough as guts and stalling the next. The audible knocking sound is also consistent, but comes and goes, (tends to run smoother and quieter at idle). If lifters were sporadically dropping in and out, then I'd expect the sound to be inconsistent and sporadic as well.

Also, I dont understand how faulty lifters could cause such drastic backfiring thru the carby? I can picture a lifter reducing or preventing the valve to come of it's seat, but I cannot picture a faulty lifter holding the valve open when it should be closed, thus allowing the ignited charge to travel back past the valve and into the intake manifold. It just doesn't seem logical.
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Old 08-12-2005, 07:19   #10 (permalink)
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Re: I come to my Ford brothers for help . . .

Have you taken the rockers off since it went bad again? Any loose parts, obvious breaks, 7/16 ring spanners?

Have you dropped your oil - looking for any metallic parts?
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