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4.3 roller lifter issues?

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Old 06-21-2012, 02:24 PM   #1
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Unhappy 4.3 roller lifter issues?

I have a 1991 S-10 pickup with the 4.3 engine. This has the adjustable lifters that need to be adjusted to zero lash and at least a 1/2 turn more of preload.

I bought the truck and the valve train was extremely noisy. I removed the intake and found the majority of the rockers were loose as were the push rods. I found the rocker studs were being pulled out of the heads, loosening the valves, and causing this issue. The rocker nuts were NOT backing off.

I bought 12 new Pioneer shoulderless screw in studs at $0.99 each. I pulled all the studs, tapped each hole to 7/16" course and screwed in the studs using Locktite stud and bearing mount to insure they stay in place.

I adjusted the valves making very sure I was on #1 TDC and set 1/2 the valves at zero lash + 1/2 turn of the nut. I rotated 360 degrees and set the remaining 1/2 of the valves. This is the way I have done this for years with no issues. It was done right.

Attempted to start the truck and little to no compression. Finally had to loosen all the nuts by 1/2 turn to get the engine to start. It then ran, and rather well, but the valve train was noisy. I attempted to adjust the valves, with it running, and when I would get to zero lash, I would start putting in the 1/2 turn of preload and the engine would kill. I don't care how slow one tied this, it would kill the engine.

My question is this. Is there an issue with roller lifters going bad and collapsing? I have never seen a flat tappet lifter act like this. The flat tappet lifters will sometimes adjust up slow, but they do. What is happening here? The whole issue is not with the studs as that has been fixed, the issue seems to be with the lifters themselves. I have oil at all the rockers and the amount is normal for a small block. My feelings are the lifters have collapsed and are not working properly and this is causing no adjustment. I am hitting the bottom of the stoke of the center piston and when I try and put in the 1/2 turn preload, this opens the valve and the engine dies.

Anyone else ran head on into this issue and what is the fix? New lifters?
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Old 06-21-2012, 03:25 PM   #2
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Re: 4.3 roller lifter issues?

I have two roller motors and adjusted the valves just as you described and no issues.
Old 07-08-2012, 09:46 AM   #3
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Re: 4.3 roller lifter issues?

This saga is coming to an end.

I removed all 12 lifters from this truck and found at least two that are totally collapsed. The plungers are seized in the down position. These are basically now solid lifters. I took one apart that had no internal pressure and found the check ball on the bottom of the plunger galled and would not seal.

It should start and run today. The lifters were replaced with used ones from a running 305. These were all taken apart, cleaned, inspected and appeared to be in great shape.

When rolling the engine over from #1 TDC to #4 TDC, I now have compression. Will let you know when it runs and the final results.
Old 07-08-2012, 09:30 PM   #4
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Re: 4.3 roller lifter issues?

keep us updated on this.

I have adjusted several engine (roller and flat tappet) like you tried by letting eng run. never had a issue.
Old 07-22-2012, 03:27 PM   #5
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Re: 4.3 roller lifter issues?

I have not worked on this due to the extreme heat here.

I did find 7 collapsed lifters. When the wire clip is removed, I cannot get the plunger to come up or get the plungers removed. The lifter is locked up solid in the down position. I put in the used set of good lifters and it will still not start. I am thinking the loose valves, due to the rocker studs coming out of the head, has pounded the lifters to a point of failure. I have never seen this before in any engine but I have also never seen an engine with this loose of valves.

The valves are working properly and I blame the no start on a set of Autolite plugs. I believe they have died a miserable death and most of the six will not fire. Have a set of new AC's for a replacement.

Hopefully it cools down a bit here and I can get this running. It is believed the bad lifters caused the flooded plugs and issues of no start now. Will let you know what I find.
Old 10-14-2012, 09:37 AM   #6
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Re: 4.3 roller lifter issues?

The autopsy is complete.
The engine came out and is in a pile.
I have not seen an engine this dirty EVER.
The last owner may have changed oil, once, in the life of the truck.
The oil pump intake screen was plugged with sludge, old gaskets and excess rtv.
The mains were OK but abused.
It had spun one rod bearing, either 5 or 6.
The real kicker was the rings.
Virtually every ring, on every piston, was stuck in the pistons.
No wonder one cylinder had 50 pounds compression.
It appears the plugged oil pump screen starved the engine for oil, which totally trashed the lifters, and spun the rod bearing.
This engine is the Poster Child for oil changes.
Do it, and at least every 3,000 miles, or more.
This engine was trashed for a lack of maintenance.
Now will have the machine shop see if the block is OK.
May just find another engine.
This is what one gets when you buy used and have to tow it home.
Only got $300 in a very nice extended cab 4X4 so I am all right, yet.
Old 10-14-2012, 10:24 AM   #7
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Re: 4.3 roller lifter issues?

I set the preload on my 4.3L V6 in the following manner.The preload on my lifters are precisely at .005" or 1/8 turn, total lifter travel .060". Comp Cams Short Travel lifters with 3/8"-24 poly-lock nuts, screw-in studs and roller rocker arms. The procedure is the same for OEM lifters as follows:

Stock 1987-1991 roller lifters, GM-5234890 (AC Delco HL-112), .120" total travel, .060" preload (1-1/2 turn) using 3/8"-24 rocker arm studs.

#1 cyl. @ TDC on compression stroke (firing)
Set exh. valve preload on 1,5,6
Set int. valve preload on 1,2,3
Turn crank 360 deg. CW

#4 cyl TDC, on compression stroke
Set exh. valve preload on 2,3,4
Set int. valve preload on 4,5,6

Rotate crank 360 deg. CW to #1 TDC. Install the distributor firing on #1.
Old 10-14-2012, 10:27 AM   #8
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Re: 4.3 roller lifter issues?

time for the V8 swap...
Old 10-14-2012, 09:41 PM   #9
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Re: 4.3 roller lifter issues?

I know you are way past the lifter issue, but I have had the same lifter issue with worn out flat tappet lifters too. New lifters always fixed the miss for me, except when the cam lobes were worn off.
Did you find a used engine ? Did you rebuild your old engine ?
Old 01-11-2013, 08:40 PM   #10
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Re: 4.3 roller lifter issues?

The machine shop ground the crank, bored it and a valve job.
$900 later, the engine is back together.
It got what it needed.
Not yet in the truck though.
It will run, and sweet, when done.
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