geerookie

So some facts about the motor and then the problem.
This is a street car turned race car. It's a '99 LS1 and it had 88,000 mile when it became a race car only. Now it has almost 116,000 miles.
The motor had never been apart except for evrey winter I would replace the valve springs and about 2 years ago I put in new CompCams hardened push rods. They are 7.400 length.

This winter I tore the car apart and tore the motor down to the short block. I reinstalled 243 heads, '04 Z06 cam, new LS7 GM lifters, the old 7.4 push rods, new lifter buckets (drilled) and the high volume GM oil pump with the 42lb relief spring. I also added an EOC. I used the ECS block adapter, AN10 lines and a '09 Z06 oil cooler.

So. before the motor work I had typical lifter noise but one on the drivers side seemed extra noisey. After the motor work when I started it after a little warm up it was very quite and MUCH quieter than before and not a hint of lifter noise. The car has been started, run for 30 minutes or so a few times, pulled in and out of the shop 4 or 5 times and then today I went to the dyno.
First 7 pulls were fantastic. The 8th pull I thought I heard a loud ticking noise but after if idled for awhile I didn't hear anything to I dismissed it.
The pull was down a bit on horsepower and with the changes we make I would have expected it to stay the same or go up a bit. We were still at about 11.8 on fuel ratio and VERY conservative on timing.
The next code load was aimed at a much better air/fuel ratio (12.2) and adding a little more advance.

The pull went ok but I heard the loud ticking again and so this time I got out of the car right away but left it running and sure enough I could hear a lifter tick on the odd bank. Just like the old setup...hmmmmm.
Went to get a friend to listen to it (didn't turn off the car and when we got back the noise was gone.
Also, that pull was about 30hp down from the previous. Just to make sure we didn't mess something up we went back to the previous code rev and pulled again. Down 35hp and the loud ticking was back but after it idled for about 4 or 5 minutes it quiets down and with 6 or 7 it is silent again.

Revlimiter is 6500, oil temps are in the 180 range, oil pressure is 25 at idle and 60 from 3k - 6k.

What baffles me is the lifter is fine at idle and just moving the car around but on a WOT pull on the dyno it starts ticking.

Any help, suggestions, ideas or direction are welcome

mountainbiker2

I thought mine was a bad lifter, but it was a broken piston. This is what mine sounded like.
https://vimeo.com/37996732

Steve A.

trackboss

I'm guessing, but I think you may have incorrect pushrod length=wrong pre-load. Quite some time ago I read something about the ls7 lifters being different than your originals. It's been a while, but when I put lifters in my car I needed custom pushrods. You need to find out the stroke of the lifter piston and what the recommended pre-load (very important)is for your application. Bolt/torque down the rockers (factory type) properly, and set zero lash with adjustable pushrod. Then add the recommended pre-load of the lifter so that the piston is sitting somewhere in the middle. Too long of a pushrod (too much pre-load) can cause damage to the lifter as well as never allow the valves to close all the way resulting in less power. Too short and the actuation of the valves will lack control as well as rattle and possible cause damage as well.
FWIW, my stock lifters ('99) used 7.4" rods from the factory, but I ended up using 7.350" with the cam motion link bar lifters. The 7.4" bolted in, but were tight (couldn't spin the pushrods with my fingers). I never fired it up with them as I suspected they would be wrong. There is zero noise with my current combo.
It will be tought to get your fingers behind the rockers on ls heads to spin the pushrods because the valve cover rail is high and very close, but it is possible.

geerookie

This is all true except for the internet rumors about the ls7 lifter height being different. But even if the pushrods were to long it wouldn't explain the rattle of only on one or two lifters and only after a pull and only on the odd bank. And then it goes away after a few minutes of idle. Then doesn't come back for regular driving.
I'm going to Pocono tomorrow and I'm going to see how it behaves on the track. Hopefully that will give some more data points.

AU N EGL

116,000 miles ??? might be time for whole new engine.

geerookie

I have a spare in the shop but this thing just did 370/370 on the dyno with 12/1 a/f ratio and extremely conservative timing.

I don't think she's done yet.

sperkins

Bah!!

Mine just clicked off 146k miles this weekend.

RX-Ben

Did you check lifter pre-load?

geerookie

Figured out the problem and thought I would post the solution in case anyone else runs into a similar situation.

The problem was a defective o-ring on the pickup tube for the oil pump. The reason it only affects one cylinder is because the number 7 lifters are the first fed by the oil supply directly after the pump. By the time it gets past #7's lifters the air has dissipated enough that the rest of the lifters work fine.
The new part number is 12557752.
Below is the GM TSB for the issue.

Engine Knock or Lifter Noise (Replace O-Ring) TSB #02-06-01-038 - (12/02/2002)

Engine Knock or Lifter Noise (Replace O-Ring)
2001-2002 Chevrolet Camaro

2001-2003 Chevrolet Corvette

2001-2002 Pontiac Firebird

2002-2003 Cadillac Escalade, Escalade EXT

2000-2003 Chevrolet Suburban, Tahoe

2001-2003 Chevrolet Silverado

2002-2003 Chevrolet Avalanche

2000-2003 GMC Yukon, Yukon XL

2001-2003 GMC Sierra

with 4.8L, 5.3L, 5.7L or 6.0L V8 Engine (VINs V, T, Z, G, S, N, U -- RPOs LR4, LM7, L59, LS1, LS6, LQ9, LQ4)

Condition

Some customers may comment on an engine tick noise. The distinguishing characteristic of this condition is that it likely will have been present since new, and is typically noticed within the first 161-322 km (100-200 mi). The noise may often be diagnosed as a collapsed lifter. Additionally, the noise may be present at cold start and appear to diminish and then return as the engine warms to operating temperature. This noise is different from other noises that may begin to occur at 3219-4828 km (2000-3000 mi).

Cause

The O-ring seal between the oil pump screen and the oil pump may be cut, causing aeration of the oil.

Correction

Inspect the O-ring seal and replace as necessary. Use the applicable part number listed below. Refer to the Engine Mechanical sub-section of the appropriate Service Manual.

Parts Information

Part Number Description
12557752 Seal-O/Pmp (O-ring) (F and Y Cars)


12563963 Seal-O/Pmp (O-ring) (C/K Trucks)

RX-Ben

Everything survived in one piece, I hope!!!

geerookie

Yes. I ran on Pocono long course all day Sunday but still notice the lifter rattle at the turn in for devil's elbow. Then it would go away. Car held up and never had any issues.
I just took the front of the motor apart, pulled the oil pump and confirmed that the o-ring was the issue. Got one on order and will have it back together for July.

The main track is smooooooth! The infield is still the same
The bump is what it is. It may be a bit smoother.

Cobra4B

Greg... was the o-ring defective or did you install it wrong? On www.ls1howto.com they're very specific about putting the o-ring on the pick-up tube first and making sure it seats correctly w/o pinching.

geerookie

From the research I have done on this it seems that the original o-ring is a bit small and the replacement is supposed to be a bit fatter.

In my specific case the o-ring was missing It has been awhile since I put the motor together but I went back and looked through all my parts and looked in the old oil pump and I couldn't find the o-ring. My guess at this point is there wasn't an o-ring so I didn't install one when I put in the new pump. Now I know that it needs an o-ring

I learn from my mistakes and hopefully someone else will find this solution if this ever comes up again in the future.

Cobra4B

Sheesh... I'm surprised you had decent oil pressure to begin with. You read about people botching the o-ring install on cam swaps from time to time. The car will never build proper oil pressure from the get go.

geerookie

It was a near perfect press fit which is probably why I never thought twice about an o-ring.