I need help with my misfire/stumble...

[TechWeasel]

As some of you may know, I recently got my Sy running again after almost 2 years off the road. The problem I'm having now is that the engine idles and revs like it's not firing on all six cylinders. It shakes like a wet dog at 2500 rpm, as a matter of fact. It's also got a surge when cruising at low throttle openings.

To date, I've gone through the entire ignition - it's got six brand new CR42TS plugs gapped at .035, new plug wires that are properly routed so they're not rubbing, against anything hot, or crossed, a new cap and rotor, and a new stock coil. I think the problem isn't in the ignition, because all six plugs looked the same when I pulled them out to check them. They all have just a touch of tan forming arount the top of the insulator, and none of them look or smell wet or oil-fouled.

I have six new RC injectors, and all of them sound the same when I listen to them with my mechanic's stethescope. I did a power balance test today by unplugging the IAC connector, then pulling the spark plug wires from the cap one by one. Each time, the engine dropped revs. I'm not sure just what that means, since the misfire feels regular, but none of the cylinders seemed to make it worse than the others.

The one clue I have left is that the engine is making a sort of hollow knocking sound, similar to the sound made when you "cluck" your tongue against the roof of your mouth. Using the stethescope, I found that the sound is loudest on top of the driver's side valve cover, just forward of the breather hole. I can hear the sound all along the valve cover, but it's louder on the surface of the cover than when I listen to any of the three hold-down bolts.

Tomorrow, I think I'm going to pull the valve cover and see if maybe I have a loose rocker arm. Would having one lashed out of spec make that noise, and cause the symptoms I'm experiencing due to low lift? Also, what's the proper procedure for checking and setting lash, and what's the spec for our trucks? Finally, if I don't find anything wrong with the valvetrain, is it possible I've got a lifter that's collapsed?

Thanks in advance for your help...

 

[TurboTony]

That does sound like it may be a tight/loose valve. Another thing that I'd check for is a vacuum leak.

HTH

Tony

 

[TechWeasel]

That does sound like it may be a tight/loose valve. Another thing that I'd check for is a vacuum leak.

HTH

Tony

When I was putting the engine back in, I redid all the vac lines with silicone and replaced all the tees and check valves. It's possible that I may still have a problem, and it sure as hell is easier to inspect the vacuum harness than it is to pull a valve cover... So I'll check that possibility first.

I know our trucks are hypersensitive to little changes, but would a vac leak in the hoses really cause a miss noticeable from idle all the way on up? Or are you saying it might be a leak in the intake manifold gasket(s)?

 

[TurboTony]

I'm thinkin a leak on one of the intake runners...

Also make sure that it isn't an internal vacuum leak. Pull the pcv outta the valve cover, and block both valve cover grommets with your thumbs. If you have an internal leak you will feel it. Kinda a long shot, but i have seen it before.


Tony

 

[sytyguy]

What lifters are you using?

I have had nothing but trouble out of the Comp High Energy lifters. Waller and myself bought them and we both had lifters explode not long after build. We did buy them fairly close together, so it's possible we got a bad batch, but others have had problems as well. Not a good design (internal snap ring) IMHO.

My lifter exploded moments after initial fire up and didn't notice since I was setting timing, getting everything running right, etc...(you know the drill). Plus, it was my first big cam motor and wasn't sure how it would idle (not supposed to be THAT choppy ). After a while of driving and swapping some ignition parts, I snatched a valve cover and found a rocker getting a free ride. Replaced lifters with Comp 875 lifters (crush metal sleeve design) and all is well.

The characteristics were amazingly similar to those you describe. Misfire under load, bad vibration at odd rpms, loud valvetrain noise, etc... However, my evidence was in the black smoke and ugly plug, but your not getting those results, so it may just be out of adjustment as you said.

Hopefully this isn't your problem, but definitely worth a look.

Michael Hood
Syclone #1596
GAST

 

[TechWeasel]

OK, here's the latest...

I had enough time this evening before the sun went down to pull the driver's side valve cover. I didn't check to see where the crank was positioned, but I'm assuming that there's nowhere on the cam profile that I should be able to spin the pushrods with my fingers if the lash is set properly even with the engine cold, and I can twirl both of them on #3. Tomorrow I'll be pulling the #$%^@&*! passenger side cover too, and setting the lash on all 12.

According to the shop manual, the lash can be set on the exhaust side for 1, 5, and 6 and the intake for 1, 2, and 3 with the crank at TDC for the compression/power stroke on #1, and one more rev to put it at TDC for the exhaust/intake stroke on #1 puts the exhaust for 2, 3, and 4 and the intake for 4, 5, and 6 on the base circle. It also says the spec is to tighten the rocker nut until the pushrod can't be turned, then one more complete turn on the nut. Somebody want to double check me on this, please?

Also, I've got stock stamped rocker arms but guide plates on the pushrods (the heads are McCoy L-35's)... Is this gonna cause problems over time?

Thanks again!

 

[Hu Ryde]

An easy way to set the lash is to start the truck with the valve covers off and do it that way. Start at anyvalve and loosen the nut until you hear it clatter, tighen until it stops and go a 1/2 turn tight. Some go tighter and some go looser, it's up to you. And that's it go to the next. Make a oil splatter shield with cardboard and plastic bag. HTH

 

[TurboTony]

I've always found that one full turn is too tight. Tends to hold the valves open at RPM. Go just over 1/2 turn after you find zero lash.

About the guideplates, are your rocker arms self alighning? If so this is a bad thing you cannot run self aligning rockers and guide plates.


Tony

 

[TechWeasel]

I've always found that one full turn is too tight. Tends to hold the valves open at RPM. Go just over 1/2 turn after you find zero lash.

About the guideplates, are your rocker arms self alighning? If so this is a bad thing you cannot run self aligning rockers and guide plates.


Tony

Ok, 9/16 of a turn it is...

The rockers appear to be regular old stamped steel stockers, with the divot in the pushrod end.

Lookie...

[/img]

 

[TrboSy2051]

The plug wires should be routed and crossed the way they are in the book. I've had acouple of mustangs that would crossfire if the wires were routed wrong/crisscrossed here and there, and w/ our trucks it seems it may be worse. Check the schematics, and run them the same way. Just some info............
You have a good set up.............
Good luck, I know you have been building this thing for 2 years and want it to run.
Buddy

 

[Hu Ryde]

If the rockers are self aligning like the stock rockers with the 2 nipples on each side of where the valve tip goes you shouldn't have the guide plates there. This can cause trouble.

 

[TechWeasel]

Thanks, Jesse... I'll take a look at them today and see.

 

[E-Rue]

hard to tell from the pic cause the place we need to look, has a puddle of oil in it. soak that oil up and see if those are self aligning. that looks like a mccoy motor. they are prolly fine. mine were non-self aligning and looked just like those. but you should double check just to be sure.

e

 

[TechWeasel]

hard to tell from the pic cause the place we need to look, has a puddle of oil in it. soak that oil up and see if those are self aligning. that looks like a mccoy motor. they are prolly fine. mine were non-self aligning and looked just like those. but you should double check just to be sure.

e

Yah, it's a McCoy. Good eye...

Having the lash set so obviously loose doesn't fill me with a warm, fuzzy feeling about the rest of the assembly...

 

[E-Rue]

well i had a few bugs to work out of mine also. overall, im happy with my mccoy motor, just would have done a few things differently on the install. since you are doing your own install, hopefully you wont have the misfortune i have had. i think ive got about 10,000 miles on mine now. seems happy so far.
i used to check your site all the time, for updates on your engine install. you had a bunch of good photos and stuff.... step by step. is there any reason you took it down?

e

 

[TechWeasel]

well i had a few bugs to work out of mine also. overall, im happy with my mccoy motor, just would have done a few things differently on the install. since you are doing your own install, hopefully you wont have the misfortune i have had. i think ive got about 10,000 miles on mine now. seems happy so far.
i used to check your site all the time, for updates on your engine install. you had a bunch of good photos and stuff.... step by step. is there any reason you took it down?

e

The site's still up. www.techweasel.com - click on one of the many Syclone Rebuild links on the front page. I haven't done an update since the end of July because I've been spending my spare time wrenching instead of working on the site, but as soon as I get the truck sorted out I'll bring it all up to date.

Now, back to our story...

Today, I went back out and took a good, close look at the rockers. The valve end seems to be flat, with no dimples on the top, so they're not self-aligning and the guide plates are not gonna be a problem. With that little mystery solved, I pulled off the intercooler and all the other junk over the passenger side valve cover and yanked it off too. I indexed the crank to TDC on #1 cylinder and started adjusting the rockers. All of the ones on the base circle had loose pushrods... A fraction of a turn snugged up the pushrods, and then I added another half-turn and moved on. Once I finished the last of the six for this crank position, I went back and checked the first one I did, only to discover it was loose again. So, I readjusted it, went on to the next one, and so forth, a total of at least 6 times before the lash setting "took"...

With the lash finally holding (and the rocker nuts screwed way, way in), I turned the crank over a full revolution and set the other six rockers. Same story here... Adjust all 6, repeat... When I finally got them to settle in, I rolled the engine back over to TDC on #1 and checked those 6 again, finding that this time the lash setting seemed to be OK.

That's where I left off. I haven't buttoned up the motor yet, because I wanted to consult with everyone and see if this is normal, or if I've set the lash way too tight. Did I do this right, or should I start over, back them all off, and just set them once and not worry about the fact that when I come back to the one I started with, I can merrilly twirl the pushrod again...

 

[BillC]

I'm only guessing here, but it sound like you may have set them too tight. The lifters will settle down as you tighten the rocker nut. Depending on how much force you use to "twirl" the pushrods, they may seem to have loosened up.

When I set my rockers, I moved the rods up and down (rather than twirling) while tightening the nut until there was no more movement. Then I tightened the nut 3/4 turn more and locked it down (I used polylocks). I could still spin the rods after locking the nuts, but it took a little force. May not be the most common method for adjusting, but it seems to have worked.

If, however, the pushrods have some up-and-down movement when you come back after setting the rockers, you may have bad lifters.

 

[sytyguy]

Use the method Bill described. That is the proper way to adjust valves. Some people range from 1/4 to 3/4 turn to lock it down, but what you have sounds like far too tight.

When you turn the engine over by hand some of the pushrods will get loose. This is because the lifters are pumped down (unless you specified aftermarket anti-pump-down lifters be used....doubtful, and even they'll pump down over time) and give extra slack. You hafta take into consideration that they'll be pumped up when in operation. You could take up all the slack on old mech. lifters, but hydraulics require a different procedure (as Bill stated).

Please don't fire it off like you have it. WCS (worst case scenario), you could bend some valves, ruin a head(s), damage some pistons, etc...utter chaos ......I'd back them back off and redo it as Bill stated........just get 'em where they'll spin (no up/down movement) and lock 'em down to your liking (1/4 to 3/4 turn). Worked for me.

HTHs

Michael Hood
Syclone #1596
GAST

 

[E-Rue]

yeah, you shouldnt have retightened them.

if its easy, check the bottom of the rockers for the dimples. that is where they would be. i seriously doubt they are self aligning.

e

 

[TechWeasel]

After lookin at the FAQ on www.cranecams.com, I came to the conclusion that they're bottomed out the way they are now... :-? I'll go back and run the nuts all the way back up, and give the lifters some time to return to the "rest" position, then re-lash them.

What messed me up yesterday was the fact that when I went back to the first one, the pushrod spun just as easily as it did before I adjusted it. Oh well... by the time I'm done with this, I'll be able to write a FAQ for my site, so the experience isn't totally wasted.