Jake, I'm leaning toward knock retard. Even though the tuner has desensitized the knock sensors he says it wouldn't be a bad idea to have the LT4 module in there. Especially with a cam of 111 lsa. Pete is going to help me do a little more checking on the valve train. When I was taking all of this apart I found a broken valve lock on the #1 intake spring. Also, the exhaust valve stem was chipped up around the edge at the top. So there is something going on that isn't right.

There is one positive thing. I ran a tap trough the crank snout to clean up the threads. They seem to be good enough to hold the bolt now. We'll see.........

 

Here's what I noticed: First indications of a problem begin at about 4250, then make a sharp dip at about 4600 then is ragged the rest of the way up.

Chime in if I mis-understood something?

AFR looks to remain relatively constant 12.5/13.0; I don't see any sudden or dramatic changes in AFR that could account for the power loss though. Yet, constant, steady fuel pressure should be verified if, for no other reason than to eliminate fuel as a factor. Gauge taped to the windhshield and a WOT blast will tell the tale.

I re-read how you adjusted the lifter preload and it's puzzling. The 'T' handle allen head tool is only used to hold the setting in place, once it's be established by the box/open end wrench.

Did you really do as you wrote, that you tightened down on the ALLEN set screw BEFORE setting the preload? Didn't you, instead, loosen the poly-lock until you heard CLACKING, then tighten the POLY-LOCK until the CLACKING quieted, then added the additional preload, THEN tighten the ALLEN HEAD set screw? Did I correctly understand what you wrote? Did I miss read what you did??

My thoughts:

4250 is a like a mid-range RPM and your jaggedness shouldn't have started THAT early in the band. If it began up top, closer to redline, sure, I can see that, but at 4250 and continuing on to the RPM you stopped the pull tells me something is out of whack.

So what was happening in the engine from 4250 and onward to cause that kind of action? My thoughts are pure speculation since I don't have any way of knowing with any high degree of certainty. Basically, I'm trying to brain-storm this, considering the POSSIBILITIES and then recommending they be examined one at a time. Sort of like a Process of Elimination.

Someone with the proper equipment and knowledge could probably zero-in on the cause, but best I can come up with is to point out the areas that jump out at me. So:

Ignition and valve train immediately comes to mind.

Ignition problems at THAT low a RPM - 4250 - could be a number of different things. I'm thinking weak coil, corrosion (one guy just found that on his plug wire connections), plug wires, Opti, ICM - I'm sure you know all the stuff involved here.

Would a weak coil cut in and out resulting in the jaggedness? If it could, would that set a mis-fire code?

Valve train problems could be noise causing timing to be retarded, but as I understand it, our systems pull OUT timing much more quickly (once it detects knock - either real or false) than it returns the timing once no knock is detected. Seems that the ragged up and down in the graph is just too abrupt for it to indicate timing being pulled and then put back in. Seems the OUT and IN couldn't happen that quickly. What do you think on that?

Lifters not able to follow the cam lobe profile are a real possibility. If the lifters are dancing on and off the lobes, you might see what the graph shows.

Let's talk valve springs. Valve spring dynamics/vibrations could be at work here, but again, at THAT low a RPM - 4250 - I wonder. . Which ones are you running, how were they set up; pressures, retainer type, etc. Were they set to a specific seat pressure or merely a specific installed height? Are you running spring cups?

Tell us about the rocker arms; whose are they, specs, SA or NSA, etc. Any indications of wear (the under-side) on them or the pushrods? Whose and what length pushrods. Same with the lifters; new/re-used, checked to verify they're "good"?

I'm going to continue to chew on this

Jake

West Point ROCJKS! Nation's TOP COLLEGE per Forbes Magazine!! Graduation Day Parade 20 May 2010!!!

 

AH, YES!!!!! Now we're getting somewhere! Valve Train!

The broken lock and chipped stem tells a story. I believe we're looking at geometry.

Was any rocker riding on a retainer? Many times the underside of the rocker arm will contact the retainer. That not only causes noise (causing knock retard) but can unload the locks and even result in a dropped valve.

The clearance may be too small and, at speed, shi* happens. Try the paper-clip trick to see what clearance you have. Longer pushrods will kick up the pushrod end of the rocker most times giving more clearance. I can't speak in absolutes since engine combos vary.

Shiny areas on the underside of the arm will indicate tell-tale clues of interference. SA rocker arms are GREAT for those kinds of interference problems, too. I also suspect that the side to side movement of a SA rocker, when the tabs continue to make contact with the valve stem tip, are also sources of noise and retard.

A LT4 module is a good move but the real cause of the unwanted noise has to be found and eliminated.

Was the hub bolt able to hold the torque? Was the hub a GOOD AND TIGHT PRESS FIT when going back on? If not, a broached hub for a Woodruff key is an option that'll keep that sucka in place.

Keep me up-dated; I'm still chewing.

Jake

West Point ROCKS! Nation's TOP COLLEGE per Forbes Magazine!! Graduation Day Parade 20 May 2010!!!

 

I'll try to address these best I can Jake.

On the lifter preload,
Did I say I tightened the locks down to start with then adusted them? Here is what I did one more time:

With the engine running I used the T handle allen wrench to feel the vibration of the rocker. As I tightened down the nut the vibration gradually got less. When it stopped I continued to tighten the nut 1/2 turn more then I tightened the allen nut with the T wrench. The boys at RPM motor sports checked the adjustment on the passengers side because it was easy to get to. They said they were all very close with a couple that were out more than the rest. I don't rememeber now which way they were out, to lose or to tight. Since that side was so close in adjustment I can only assume the drivers side was close also.

The spark coil,
Actually I did try two different coils. One the first dyno run there was new coil in because when I was first trying to start the engine I was having a issue that I couldn't pin down. I replaced the MSD coil I had on there with one from Advance. It was their cheapest one because they were out of the more expensive ones. Well, after the first run I decided to put the MSD back on just to see if that was the problem. When I went to RPM I had the MSD on so two different coils were ran on two separate dynos with no change. I also put a new ICM on with no change.

Since the crank sensor is tuned out I don't get any misfires showing up.

Someone else will have to chime in on the timing being pulled. As I stated the LT4 module may help this if it is happening. I have been talking with another tuner about this tune and said it's possible for it to be pulling timing. Of coarse he wants to sel sell me a tune so we all know how that goes. LOL

All of the valve spring, rocker arms etc, etc info is in this thread somewhere but here it is in brief. Patriot Extreme springs, CC full 1.6 roller rockers. 7.2 pushrods, guide plates, 7/16 studs.

I'm am trying to eliminate one thing at the time. That is why I have torn all of this back down to start with the cam. I basically only changed three things in this swap. The cam, the springs, the opti. and of coarse the water pump but we won't count it. LOL As I mentioned Pete K is going to help me with some more valve train checking. The opti..........well, I won't know if it's the issue until I get I get it running again. I going to put my old one back in which was doing fine before this swap. That will eliminate the opti being a issue or not.

 

Guess you figured out that the RR's are not self aligning. I looked for any clearance problems but nothing has jumped out at me. The rollers looks really close to center on the stem. Maybe slightly closer to the intake side of the stem but it isn't by much. Surely not enough to bounce off the stem. Now, I did run 7.1 push rods for a while after I first got it running. (As suggested by LE) That length was way closer to the intake side of the stem then they are now. Perhaps that is when some of the chipping was done.

I didn't touch on lifters in my last post, sorry. They are new GMPP lifters. I'm wondering if I should be running a thicker oil. The lifters seem to loosen up as the engine is run. Not fast but over a pretty good amount time. Seems like they just aren't holding the pressure these springs.

 

Your lifters are fine, LPE uses them for LT1/4's up to 6500 rpm with stiff springs, according to LPE.
With the timing cover off, this would be the best time to adjust rockers.

 

Thanks Steve. Although I never have done it like that before I think this time I will try it.

 

Probably should have done this already. I'm going to order a adjustable push rod and check these rods. One more thing will be eliminated for sure then.

 

When you say the roller tip of tHe rocker arm was more toward the intake side, where was the lifter? Was it on the base circle (which it should have been) or on the ramp, etc? Closer to the intake side when the lifter is on the base circle of the cam lobe is correct. However, if the lifter is on the nose or ramp, that's not.

So you use vibration, rather that sound to find zero lash, right? I know you said you've done it that way before, but that's the first time I've heard of the vibration method (thought I'd heard 'em all, too, LOL). Of course, you probably know I'm a die-hard advocate of the IC/EO method.

On both my son's 96 and my 96 I use 3/4 turn of preload. One FULL TURN may be even better; experimentation will let you know. If the 4250 issue lessens or goes away you'll know you're on the right track. I'm not reluctant to try different settings in fine tuning a combination.

The issue you have that you couldn't pin down when you first tried starting the engine, what did that turn out to be? Could it still be there, hiding or was it solved?

Usually, idle, loosen til clacking, tighten til clacking stops, slowly add preload (engine will stumble), tighten set screw. I don't really know what results the vibration method will give though.

If anything, I fall on the side of MORE preload rather than less; I've been writing about that on a couple of other Forums (CF's slow server tends to keep me on other Forums more and more lately).

I see no problem with using a heavier oil, as long as it's not over the top and you let it come up to temp before you lay into the engine. Factor in ambient temp, too, but I'm sure you know that. I run 10W 40 Mobil 1.

NSA rockers, GOOD!

You need to be able to insert a paper clip between the underside of the rocker body and the retainer. At speed stuff dances around a lot and that clearance is needed. Right where the roller tip attaches to the rocker arm is another tight clearance area. The roller should stand free and the rocker's body shouldn't come even close to touching. Some valve stem tips sit lower than others; something to get down really close to and check.
Since I'm as old as dirt (LOL) I break out the magnafing glass and a really bright light.

Sometimes a retainer change is needed to get the needed clearance. Guy on another Forum posted photos of how his CC RRs interfered with his retainers. There are LOTS of valve train issues on other Forums, like Ls1LT1, CamaroZ28, LS1Tech, etc. All sorts of carnage. One guy just found he was about to drop a valve seat on his LT1. It's AMAZING all the things going on with out valve trains. Good informational reading too.

Try the Magic Marker method to see where the roller tip of the rocker hits. Put the lifter on the base circle of the lobe, mark the stem tip, install the rocker with the amount of preload you're running and WIGGLE, WIGGLE, WIGGLE the arm. Remove and have a look-see. Should be slightly inboard.

What are the spring pressures like? I know Golds are highly recommended by LE, it's just the pressures I'm interested in. Some guys just throw 'em on and drive off into the sunset fat, dumb and happy. They outta be checked; eliminates yet another variable. My thinking is, like degreeing, how will you know if you don't check, see what I mean?

Really hope some of this helps. I wish I could just write one paragraph, tell you exactly what needs to be done and solve your problem, but alas . . . Hell, if it was easy everyone could do it. LOL

Jake

West Point ROCKS! Nation's TOP COLLEGE per Forbes Magazine!! GraduationDay Parade 20 May 2010!!!

 

BTW, if you aren't already, once you finish re-setting the preload and have tightened the set screw, use your box end wrench and give the poly-lock another tightening turn. That'll make sure the set screws are locked tightly and may prevent the loosening you were referring to. Just don't go "gorilla" on me or you'll crack the poly lock.

Remember, too, DON'T ASSUME ANYTHING. Don't assume that's something's OKAY, (such and such is new so I know it's okay), at this point EVERYTHING has to be checked and verified to actually be OKAY. If you don't, you'll remain at square one. Yea, I know, but that's how stuff gets found.

Jake

West Point ROCKS! Nation's TOP COLLEGE per Forbes Magazine!! Graduation Day Parade 20 May 2010!!!

 

Preload is vital with high spring pressure. Do the adjustment according to the manufacturer of the lifter. For Example , Comp Cams were a nightmare, and had to be done with engine off.
GMPP I do 1/4 turn after zero. This is always a hot topic, flames abound.

 

The chipped valve and broken keeper (in my opinion) suggests the rocker is colliding with the spring retainer, and/or pushrod length is way wrong.
Don't give up yet.

 

I give you credit for sticking with it, and solving it your self.

 

I ordered a push rod length checker rod. It'll be here Wed. Today I'm going to remove all the rockers and inspect the valve stems, take a close look at everything. I might do some reassembly of the front part of the engine.

 

Weav, even though I'm sure this proccess has been torture to you. This thread has been very imformative!! I'm also glad that Pete has vounteered to help. Often another set of trained eyes can help with overlooked issues.

Have you checked to see if the opti's rotor is loose?

 

For now, you dont need the pushrod checker.
On the valve with the checker spring,
Make sure the cam is on the base circle.
Install the pushrod
Clean the tip of the valve with alcohol and let dry
Color the valve tip with a black sharpie
Install the rocker arm
Adjust to zero lash plus 1/2 turn
Roll motor over 3 complete revolutions (with a ratchet)
Remove rocker
Snap a pic of the valve tip, and post it up.
The wear mark should be dead center, and approx .050-.060 wide
If this is good, your pushrod length is fine.

 

Thanks Mike

Still in the 30's here so I'm draggin my butt about getting back to it.

This has turned into a very long thread but I hope it comes in handy to anyone thinking about doing a cam and it will encourage them to do it the correct way to start with. I have found out that this applies to many aspects of this car. It doesn't seem to like half ***.

I can use all the eyes I can get!!!!!!!!!

I did check the opti by spinning the shaft. It was was very smooth. There is a very slight amount of side to side play. So I compared it to my old one and they both seemed to be the same.

Yep, I'm about to worry Pete to death. Hang in there Pete!!!

 

Will do.

 

Okay, this isn't the best picture but I believe you can see where the roller hits. Looks pretty close to center to me.

 

Yup. I doesn't get better than that.
In my mind, you have eliminated alot, and only 3 things remain.
1) Possibility of valve lash being incorrect when you first assembled it.
2) Rocker to retainer collision.
3) Spring pressures excessive.