I remember your issue with valve float, did not recall it was with a small BC cam though. I can see that at higher rpms, but this is at 1500-2000 its the loudest, shouldn't be any valve float in that rpm range.

 

Well, as a point of reference, I'm running a XFI cam on a small base circle with Scorpion 1.7s and don't have the valve train noise you're complaining of. Stock LT1 lifters and 1/2 turn preload. I'm using Crane's duals set at 140# on the seat (I forgot the kit number but I can look it up if it becomes important).

I don't have the noise problem you're complaining of, so unless my setup is an anomoly, there has to be something else going on here. There has to be parts hitting together to cause this.

What preload are you running? Crane issued a bulletin a few years back saying additional preload can cure noise complaints. An additional quarter turn may solve the noise issue.

What procedure did you use to set the preload?

Did you use an adjustable pushrod to verify the correct pushrod length? Several things can effect the correct pushrod length.

Can you determine which lifters are causing the noise? All of them? Just one? Just a few?

How many miles on the lifters?

There's got to be an answer here. We'll keep at it until it's found.

Jake

West Point ROCKS?

 

I went from stock lifters to LS7 lifters and back to new stock lifters.
Yep, measured for correct PR length, I've verified every valve with the sharpie method for for the centerline wear pattern.
For preload, I use the spinning the pr method until you feel the tension in spinning it. Have tried 1/4, 3/8,1/2, 3/4 and full turn preload, no difference. I've been thru everythign more times than I care to remember now.
There's not any one particular valve clacking, its all of them together, never have heard a valve train so loud.

 

Let me try to brain-storm this:

I believe most of us know that RRs aren't as quiet as the stock rockers are. From all I've read that's one of the main reasons GM modified the Knock module for the LT4, which came with 1.6 RRs. The LT1 module was sensing false knock (hearing the rocker arms); so the LT4 module was programmed to be less sensitive.

Any sign of rocker contact with the underside of the valve cover(s)? The witness mark(s) may be very faint. Because of my advanced years (LOL) I use a magnifying glass and a strong light. Faint enough to be barely seen but just enough to make noise.

How about the paper clip test between the underside of the rocker arm and the retainer with the valve at closed position? At the valve closed position, the clearance will be at the minimum.

What about the covers themselves; cast aluminum covers help dampen sound. Those don't actually reduce the sound, merely makes the sound less, ah, hear-able.

What about oil viscosity? Have you tried using different oil viscosities? Perhaps a one step up in viscosity may make a difference.

Is the noise absent when the oil is cold, like when the engine is first started after sitting, say, over-night and only returns once the oil has warmed?

Flat side up on the rocker trunnions? Don't laugh, one guy just went through a long thread on his valve train problem only to finally find he'd installed one rocker with the rounded side UP.

There's some disagreement as to how the correct pushrod length is to be determined. For example, CompCams says that with the lifter on the base circle of the lobe, the roller of the rocker arm should be slightly INBOARD of the center-line of the valve stem.

Then, as the valve beings to open, the roller tip should move OUTBOARD and become centered over the valve at mid-lift of the valve.

At full lift, the roller should be OUTBOARD of the center-line of the valve stem. As the valve begins to close the roller moves, again, to the center-line of the valve and finally returns to the INBOARD postion when the valve comes to rest/closed.

My personal opinion is the above method is designed to minimize guide wear. However, I can't automatically discount any effect on noise it will have.

Also, I've seen plenty of posts where guys have had problems using the "spin" method of establishing ZERO lash. Many guys, including me, recommend moving the pushrod in the "up and down" method to find true ZERO lash.

I can't say if, or how much difference using the different methods may make, but I suggest it's just something worth thinking about.

I recall someone posted that a possible cause could be insufficient valve spring SEAT pressure. Not enough to keep the valve from bouncing off its seat.

Considering all you've done and tried already, right now I can't think of anything else you could try. If I come up with anything else worth checking, I'll post it.

Jake

West Point ROCKS!

 

I really appreciate the detailed post Jake!


Yes, just comparing the noise to my LT4 powered truck, which has the same cam, but on a standard base circle, guide plates, and Comp Pro Mags. It's the '95 TA that I'm having the issues with.

Can't say that I looked real hard at them, nothing obvious, but I did have this problem once with the truck when I went to ARP polylocks as the allen screw stuck up too far because the rocker studs are about 1/4" longer than those on the TA.
However, with that said, I've used 2 different polylocks on the TA, the comp ones have a tall thicker head on them, and the Crane polylocks which have a thin short head, barely enough to even get the wrech on to tighten, so that effectively would make them about 1/8" shorter than the comps (I used them both with the Crane Gold rockers and thought that I had found the issue when I swapped them).. so I'm thinking this is not the issue since the noise remained after switching to the shorter polylocks, and BTW the allen screw sits several threads below the top of the nut so they do not stick up at all.

I used a little dental type mirror and verified the clearance on each and can see plenty of gap, probably a 1/16", between them. THis wasn't really an issue at all with the skinny topped bee-hive springs, they are alot closer with the dual springs.

They are the composite LT4 covers just like on my truck.

Already using 20w-50, havn't tried using a lighter oil though. I use that in both as they are both high mileage motors, 150k and 100k.

Doesn't seem to matter, its there but not quite as loud.

I always double check this, never ran one that way, but did put one on accidently that way once but noticed it right away because the allen set screw would sit at a different level than the rest.

I pretty much just try to get the trace pattern as centered best possible on the valve and not more than 1/8" wide, the length that is in there is 7.15"..which seemed odd with a small BC it would seem I would have needed slightly longer pr. I also have the thin VictorReiz head gaskets and the heads have been milled once, but I think that is only .010". Going longer made the trace pattern not be centered. This was done the first time using the solid lifter approach, then rechecked when the heads were swapped using the light spring from Home Depot approach... and since swapping the rockers I could see the trace pattern on all of them after just driving it around the block as all the valves had been colored with the sharpie.
I may reinvestigate the length, I have a set of 7.35" pr that I used with lash caps once upon a time.

My technique is kind of a combination of both, I usually move the pr up and down until all slack is out, then back it off just a bit and then spin it and tighten it back just to make sure, if there is a difference its not much more than about 20-30 degrees, and since I've tried all different amounts for turns past from 1/8 to a full turn and it didn't make much difference I've exhausted the preload being it I think.

This was the reason I tried the dual springs, however then install height came out to 1.83" for the dual springs, they should be installed at 1.80. The beehives were at an install height of 1.75". Since my cam is only .562 lift I could add some shims to reduce it some I suppose as both of these springs are capable of .600 lift at thier installed heights of 1.8 and 1.75. Not sure what .020" or so may make in spring pressure, especially at the low rpms I've having the issue at.

Thanks again, any suggestions are much appreciated.

 

I have installed hundreds of sets of Pro mags. No complaints here!
If anyone wishes to discuss there options, feel free to give me a call at my shop. I will beat anyone's advertised price on almost any performance part!
Jacob Cook 765-352-3626
Cook Performance Engines
www.cpengines.com

 

Generally, my thinking is that once I decide to change parts on these engines, some of the stock specs go out the window.

Take head bolt torque for example. Moving to, say, ARP head bolts, call for different torque settings on the head bolts than the FSM calls for. In fact, even the lube used when installing the ARP head bolts effects the recommended torque setting. So the reason some experience head gasket problems could well be because they used ARP head bolts BUT stock, FSM torque settings.

I agree, your pushrod length of 7.150 does seem odd, especially when you factor in your surfaced heads, the thinner head gasket and the small base circle cam. All of those would contribute to the need for a pushrod length longer than stock. Just as a frame of reference, to be running a shorter than stock pushrod seems to be unusual. Seems the length should be at LEAST .050 longer than stock and probably even more.

As an "old racer's" rule of thumb,"It's always better to run a pushrod that's a little too long than one that's a little too short".

When I set up my 388, using an adjustable pushrod length checking tool and running a small base circle XFI cam and re-worked AFR 190 heads, I came up with 7.500".

At first I said "WOW! THAT CAN'T BE RIGHT", so I checked and re-checked, checking different valves each time. Yep, that's what the position of the rocker tip showed I needed.

So I puzzled my puzzler for the longest trying to find the error in my ways (LOL) and the best I could come up with was, coupled with the small base circle, the the valves in my heads must be longer than stock.

I finally concluded that it wouldn't make much sense for me to go through the trouble of checking for the correct PR length and NOT believe the results I came up with. Why do it and then discount it? See what I mean?

I first decided on which procedure I'd use to check for the correct length PR and followed it. Like so many other things in working on these engines, there are differing views on how it should be done. So I don't want to start a war here. I chose to go with Comp's recommended method.

Also, I took extra effort to make sure the lifter was on the base circle of the cam lobe when checking for the correct inboard position of the rocker roller tip.

There are at least half a dozen different variables that effect pushrod length and changing any one can effect the correct pushrod length. As examples, the position of the cup in the lifter; the deck height of the block, etc. Depending on which lifters you're running, the cup height can be slightly deeper or shallower. Sometimes these variables can cancel each other out, sometimes not.

I bought the heads from a Forum member who had Bret Bauer re-work and port them, so I didn't know their complete history but, ultimately, I believed the numbers the checking pushrod told me.

So I bought a set of TFS 7.500s.

So, now my thinking is that since you've checked and verified just about everything you could think of and STILL the problem hasn't been solved, the cause must be something else. So trying different length pushrods is worth a try.

But as I said before, I believe selecting the correct length pushrod primarily deals with guide wear, so as not to side load the valve stems as they travel up and down the guide. I don't know if your noise is also effected.

Jake

West Point ROCKS!

 

Jake, I'd think that surfacing the heads and the thinner gasket would be cause for a shorter pushrod since the length from rocker pr cup to lift cup would be reduced when utilizing those 2 items??
But you did mention longer valves.....yes, the ferra valves that Lloyd uses are a tad longer than the factory valves, thats required usually to have a better selection of springs/hardware to get the required spring height for the higher lift cams....
That said...the taller valve would also be cause for a longer pr I'd think so the rocker geometry would remain the same.
So if the rocker angle/geometry is to stay the same and the BC of the cam is reduced and the valve is longer...a longer PR would be needed...
I'm going to go back and try using a longer length on the checker... I don't think I went any higher than 7.35" as that was pushing the wear pattern further to the outside....
Maybe try to do this sometime tomorrow evening....

 

Yep, you're right about the surfaced heads and thinner head gaskets. Seems my thinking got crossed up, sorry for that.

So, in rough estimate figures (since I don't know what numbers you began with), if the heads were surfaced .020 and the gasket is thinner by .014 (.040 vs .026) we'd be looking at .034

Of course if the orignal head gaskets were thicker than .040, then the difference would be greater. Let's say the original head gaskets were .050 and the new ones are .026 we'd be looking at a difference of .024 Add that to the surfacing of .020 we'd be at .044

I've always addws the lifter preload amount too. I did some more research on this today using GOOGLE, trying to find any other possible cause of your noise problem. I checked Circle Track magazine's site and a tech article says to add the preload amount in calculating pushrod length. I've always done that, but I wanted to refresh my memory just to be sure.

Circle Track also says to use the INBOARD, CENTER, OUTBOARD, CENTER, INBOARD, etc. method.

I do recall reading that sometimes when minimum preload settings are used, like 1/8th/1/4 turn, the lifter retainer/plunger can cause noise when the plunger comes in contact the retainer. This has caused lifters to fail too. Do you think that's why GM lists one full turn from Zero lash?

Unless a pushrod that's too short is causing the rocker arms to come in contact with the valve spring retainer, I can see where excessive guide wear can occur, but I'm still not convinced they would cause the noise you're experiencing.

Jake

West Point ROCKS!

 

On the heads I took off, there was some valve guide wear but not as much as I was expecting. The ones that went on were just redone and had no slack in the valves at all open or closed, so I don't see that as an issue given the heads have less than 1k miles on them at this time and none of the rocker tips were way off or anything from the center of the valve.
I'll pop off the driver side cover tomorrow and fiddle with the pr length some and see what I find.

 

Right. I don't think guide wear is at the root of your problem either. I believe that guide wear and its negative effects would only surface after thousands of miles of engine operation.

I've been chewing on this and came up with another thought: since you have one engine that is acceptably quiet and another one that's noisey, can you identify what, if any, difference(s) there are between the two engine setups?

If there are difference(s), one of them may be the cause of the way they operate differently.

If you will, please list the differences between then two engines; just those that could possibly effect the valve train and the noise.

More eyes on the issue may help and maybe I, or others, will see something that rings a bell.

Jake

West Point ROCKS!

 

Well at one point, both enines were setup identically except the noisey one had a small base circle cam, but was the same cam specs, the LPE211.
The noisey one also had LE2 heads on it, the LT4 had stock LT4 untouched heads.
But now through many changes trying to figure out what the noise could be it has been very different.
The quite LT4 currently has LPE211 regular BC cam, PAC beehive spings with +.050 locks, NSA Comp PRo mags, GM guideplates. Can't remember the pr length thats in there, but I think it must be 7.15 also because I have 2 sets of 7.35" prs because that was what it had before the PAC beehive spring change as it used lash caps (this setup was done by the shop that did the LT4 swap/install for me)

For the noisey LT1, its had various combinations of stock lifter, LS7 lifters, PAC bee hive springs, dual springs, NSA Comp Pro Mags, SA Pro MAgs, SA CRane Golds, all with the 7.15" PRs. Also, old LE2 heads, and now new LE1.5 heads.

I did get out today and popped off the drive side cover and put in the 7.35" PRs since I did have them on hand.

Here's pics of what the wear pattern is with the 7.15" PRs. Looks like it travels away from the center as the valve opens.



And here's the wear pattern with the 7.35" PRs installed: When the valve is closed, the tip is on the outter most side of thw wear pattern and as the valve closes it travels toward the center. Since these longer ones are still centered, and better centered than the shorter PRs I'll probably go back and install them befroe I do anything else, they did give alot more clearence on the rockers to the retainer tops. I did not try these longer PRs when I swapped heads, just popped in the 7.15"s that were already in there and verified they were still centered and didn't give it another thought.

 

I downloaded the pics then magnified them to get a better view. I used as my points of reference the areas of the valve stem that are UNMARKED by roller contact. Checking to see which UNMARKED area is the largest.

Referencing the 7.15s, if you look at the UNMARKED area of the valve stem tip you'll see more UNMARKED area OUTBOARD than inboard. That shows the roller is riding more INBOARD.

The 7.35s show the opposite, with more INBOARD UNMARKED area , but not by quite as much. That tells me the roller is riding more OUTBOARD using the 7.35s.

Although these differences are noticable, it doesn't seem that they could cause the noise issue. That is unless the pushrod or rocker arm is making contact with the block, head or retainer.

Based on what I see, I'd definitely go with the 7.35s.

Did you set the lifter preload adjustments identically when using both length pushrods?

I see you're running self-aligning rockers, right? Are both engines equipped the same?

Could the guides on the self-aligning rocker arms be contacting the retainers or valve stems?

Remember, when using the normally recommended preload setting of 1/2 turn, which translates into approximately .030", the pushrod becomes effectively .030" shorter because that much will be recessed into then lifter.

This is a real head scratcher.

Jake

West Point ROCKS!

 

Yes, After trying all different preloads to no avail, I now just do a half turn, the tighten the allen set screw to about 28ft/lbs holding the nut with wrench.

Yes, SA rockers on the noisey LT1, the LT4 truck has NSA w/guide plates. But, yes, they were identically equiped at one point but has morphed to the current setup trying to solve the noise issue.

Since the current spring tops are so much wider than the beehives, tey are very close to the rocker arm bottom, they don't appear to touch and there's not any wear, but there are some at the back that look closer and I can't get around them to view clearly. With the longer PR, there is added room under the rocker so I'm going to put in the longer PRs, at least on one side and see what happens to the noise on that side.

No, I've verified that none of the SA guides are touching the retainer or locks, they were on the other set of heads because a couple of the valve stem lock ridges were different lengths from the top so very slightly, and I noticed this is fairly common looking at several sets of LT1 heads at a friends shop. This current set of heads, all the valve stem tops from the lock ridge are the same, but I verified the clearence on each at all levels of lift.

 

Rob, I've been doing some research trying to find a post I read sometime back to verify what I recall before I posted here. I haven't been able to find it yet though.

But here's what I remember: From what I recall, it was posted that when the lifter is on the base circle of the cam lobe, the inboard (pushrod) end of the rocker arm should sit HIGHER than the valve end of the rocker.

If my memory is right about that post, that would give more clearance between the underside of the rocker arm and the retainer.

A longer pushrod would do the same thing. I'm trying to visualize this, but a longer pushrod would kick-up the pushrod end of the rocker, increase rocker to retainer clearance and, also, move the roller contact point on the valve stem INBOARD.

Any chance you can borrow a set of 7.500s to test with? Remember, that's what I ended up having to use with my small base circle XFI cam.

Are we getting close?

Jake

West Point ROCKS!