Missing again

[Texasdoc]

Well.... @#$%

First the broken springs Clicky - High Speed Miss Thread

Then the worn valves Clicky - Head Rebuild Thread

I finally got the motor back together. To set the preload on the valves I followed this procedure. All the polylocks had been undone - not torqued - since the rebuild, so all the lifters should be bled out.
1. twisted, lifted, pushed the pushrod while tightening the polylock.
2. Immediately when resistance is felt - zero lash.
3. Add 1/4 turn preload
4. Tighten polylock and set screw.

For most of the lifters, there was a noticeable resistance while turning that quarter turn. For a few of them, there was no resistance at all. I still turned it the quarter turn and set it. Initially there was quite the sewing machine sound on the passenger side while idling cold. It would decrease when warm but still rattled.

Went out for a drive and the miss above 3000 rpm is back. I'm not even at WOT. When I just creep up to 3000, it starts to miss.

Thoughts: Something wrong with setting those lifters' preload. I'm planning on doing a CLOSE inspection on the valve train tomorrow and doing a hot set of the preload with the engine running tomorrow to make sure the lifters are pumped up correctly.

I have the Howard's brand link-bar lifters. Hydraulic roller retrofit on normal cam in a non-roller block. Nowhere can I find the recommended preload for these. I think they are made by Morel for Howard's.

Blykins, what do you set your roller lifter preload to?

[wolf k]

Just a quick question, what method are you using to ensure that lifter is on the base circle of the cam prior to lifter preload adjustment?

[DanEC]

The method you use may be at issue although I'm a bit skeptical it's the cause of your miss. See post 14 of this thread for a concise explanation of the best way.

Valve Lash Setting

If the exhaust is opening- adjust inlet valve lash; inlet closing - adjust exhaust valve lash. This requires you to do each cylinder individually but it goes surprisingly fast.

Is your engine cutting out (elect) or is it stumbling (fuel)? Could be a bad plug wire (or more) or arcing between wires. What type of distributor are you using?

[blykins]

Set the intake when the exhaust is opening....set the exhaust when the intake is closing.

Get to zero lash, add 1/4 turn of preload.

[Texasdoc]

Exhaust open, intake close. That's the way I did it. But there were those few that didn't provide any resistance when I did that extra 1/4 turn.

Feels like it did when I had the previous miss. Ended up being two broken springs. Going to go all thru the electrical tonight. Will check springs and valve lash tomorrow. Confirmed timing. Both heads have a separate ground wire. Engine block grounded too. New MSD 6AL2 digital with clean power capacitor.

WBO2 reading about 15:1 at cruise at 3000rpm when it starts cutting out. MSD distributor, phased rotor, vacuum advance set to ported. Initial timing 20° with 34 total when vacuum disconnected.

[DanEC]

Hydraulic lifters leak down variably without the engine running - mine feel different from cylinder to cylinder too.

[blykins]

Originally Posted by Texasdoc

Exhaust open, intake close. That's the way I did it. But there were those few that didn't provide any resistance when I did that extra 1/4 turn.

Feels like it did when I had the previous miss. Ended up being two broken springs. Going to go all thru the electrical tonight. Will check springs and valve lash tomorrow. Confirmed timing. Both heads have a separate ground wire. Engine block grounded too. New MSD 6AL2 digital with clean power capacitor.

WBO2 reading about 15:1 at cruise at 3000rpm when it starts cutting out. MSD distributor, phased distributor, vacuum advance set to ported. Initial timing 20° with 34 total when vacuum disconnected.

That's normal for the lifters to act like that. Some bleed off, while some stay pumped up, depending on where they are in the bore, and if there has been any load on them.

Did you check coil bind clearance while you had the heads off/apart?

[Texasdoc]

Originally Posted by blykins

That's normal for the lifters to act like that. Some bleed off, while some stay pumped up, depending on where they are in the bore, and if there has been any load on them.

Did you check coil bind clearance while you had the heads off/apart?

I did when the springs broke. I will go thru the exercise again.

If some bleed off and others don't, how do you know if your setting preload correctly? If they are still pumped up, some are collapsed, some are stuck, how do you know if it is being done right and all are uniform?

Is the lifter is supposed to be in the middle of its travel when set cold? Is it supposed to be bled off, pumped up, etc? Seems like you would need to set it while running to get them all uniform. If set while running do you increase the preload twist to compensate for the lifters being pumped up with oil pressure?

[blykins]

It's all by feel.

The most common mistake guys make is trying to "twist the pushrod" while trying to get to zero lash.

The best approach is to back the adjuster way out, then move the pushrod axially up and down while sneaking up on the adjuster until you don't feel any free-play anymore. You will feel when the pushrod touches the lifter plunger. Once you get to that point, you dial in your preload and lock it down.

A lifter can be pumped up or bled down and the pushrod seat in the lifter will be in the same spot. There is a spring under the plunger and it makes sure that the pushrod seat is always in the same spot, whether or not the lifter is "pumped up" and full of oil.

Preload is usually around .030-.050" of plunger depression. That's generally around a 1/4 to 1/2 turn of preload.

[rodneym]

For ****s and giggles, as soon as there's no play, lock 'em down with no preload.

[Texasdoc]

Originally Posted by blykins

Did you check coil bind clearance while you had the heads off/apart?

Installed height is 1.8 - verified with micrometer.
Lift is .602 - verified with dial.

Coil bind for these springs is 1.080.
Installed height - lift at valve - 1/4 turn preload =
1.8 - 0.602 - 0.012 = 1.186.
1.186 - 1.080 = 0.094
So I have .094 coil gap. Right?

[Three Peaks]

May be a stupid question, but what rockers are you using? I had a set of lifters (Scorpions, I think) that would bind on the springs before they came to full movement because of the way they were radiused on the spring side. Put Comp Pro Magnums on and plenty of clearance and the issue was gone. Approximately same symptoms. My springs were also .650 rated lift and my cam was around .595 total lift.

Bob

[blykins]

Lifter preload doesn't take camshaft lift away.

TP has a very good tip. Check the rocker arms for binding, both on the pushrod side and the valve spring side. I've had several combinations where the pushrod would rub the rocker on mock-up. If the rocker doesn't hit the spring at closed valve position, it won't rub on open valve position.

[Texasdoc]

I have the Comp Pro Magnums as well. Plenty of clearance.

[Three Peaks]

Sounds like you are eliminating each item as you go. One thing I sometimes do is run the engine with the valve covers off to see if there is any obvious indication of problems with the valvetrain. It is messy and a hit or miss solution, but I have found several issues this way over the years that were relatively easy fixes (and a couple that weren't).

One other thing to try- not sure how well this will work but you could put a dial indicator on the head and see if all of your rockers/pushrods are moving the same amount. If they vary by more than a few thousandths, you probably need to adjust again.

Have you checked to see if your push rods are the right length? Just throwing things out here to see if each item has been eliminated. Eventually, if you eliminate all the other items, it works down to one thing. My money would be on rocker adjustment.

Bob

[Texasdoc]

Originally Posted by Three Peaks

Sounds like you are eliminating each item as you go. One thing I sometimes do is run the engine with the valve covers off to see if there is any obvious indication of problems with the valvetrain. It is messy and a hit or miss solution, but I have found several issues this way over the years that were relatively easy fixes (and a couple that weren't).

One other thing to try- not sure how well this will work but you could put a dial indicator on the head and see if all of your rockers/pushrods are moving the same amount. If they vary by more than a few thousandths, you probably need to adjust again.

Have you checked to see if your push rods are the right length? Just throwing things out here to see if each item has been eliminated. Eventually, if you eliminate all the other items, it works down to one thing. My money would be on rocker adjustment.

Bob

Thanks for the ideas. I spent over an hour, using a couple different techniques, and each came up with the same push-rod length. I was thinking about running with the valve covers off to see if I notice anything.

I reset all the lifter's preload. Each of them resisted that preload, as I would expect. I don't know why there wasn't the resistance that first time.

[wolf k]

Does the engine start to miss at 3000 rpm when reved in neutral?

[Texasdoc]

To me it sounds like it may be missing at idle but it is much more pronounced at 3k.

I will check the ground and 12V+ lead to the 6al box again. The signal leads are run separately from the coil leads. New-ish coil, new plugs, new wires, phased rotor, new cap with air holes drilled. I've tried a new distributor (previously) thinking it was the pickup. I'm banging my head here.

[spdbrake]

(You've probably already looked this.)
You mentioned a Phased rotor and drilled cap. Are you set so the rotor is to the left of the cap post at idle and then when its advanced to the center of the the post at full advance?
The small dia MSD are more prone to spark scatter if they get too far off the posts.

[Texasdoc]

When I check the phase, the rotor lines up perfectly on the post. When I rev it up, it moves toward the leading edge. Since I only have about 12 crank degrees of advance, I only have about 6 degrees of distributor advance. Vacuum advance activation doesn't change the relationship of the rotor to cap.

I think I may have found something. While tracing the wires to the 6AL, I found a place where I soldered the wire, then added shrink wrap. It just happened that when I zip-tied everything up under the dash, that solder joint got bent. It may have been a bad joint, failing intermittently causing the miss. It was the small red wire that turns on the 6AL. By the time I got it fixed, it was too late to start it. I will see tomorrow.