Since I use my car for track days on road courses and with a new engine that will be in the neighborhood of 500hp+ at the crank, I'm going back to the factory waterpump to insure sufficient cooling at sustained high rpm. This of course limits (severely) my timing chain choices. I basically have two options...

1) Stock LT4 roller timing chain & gears
2) LT4 Extreme Duty timing chain and gears

Many people on this forum and others have reported failures with the LT4 ED setup. This might have been because they reused the old waterpump drive gear vs installing the new gear that comes with the LT4 ED "kit". If not for the failures, this would be my choice.

The stock LT4 chain was deemed good enough by GM for 6400rpm (stock fuel cutoff). Road racing does not shock the driveline like the 1/4 mile does.

Which setup to use? Remember, I can't go the electric waterpump route (not enough flow at sustained high rpms) and I don't drag race.

Opinions welcomed

 

I have about 8000 track miles on a stock LT4, never a problem.

 

Can these LT4 roller chains and gears be used on the L98 and LT1 engines? If not what manufacturer makes a solid roller setup for the L98 and LT1 engines?

 

My last ED set did wear out the waterpump drive. I used all the gears from the kit. I also used a new bearing on the shaft. This was the main reason I went with the electric pump. The rest of the ED set was perfict so I reused it.

If I had to use the stock waterpump setup, I think I would use a stock LT4 setup with all new parts.

 

My belief is the reason most people have problems with the Extreme Duty Timing Set is because they don't put a proper damper on to take care of torsional vibration at higher rpm and higher torque levels.
With the water pump drive in place, it is even more important to eliminate torsional vibration.
The average home engine builder knows about balance problems and have the engine balanced, but most don't understand torsional vibration and how to eliminate it.
Torsional vibration and balance are not the same thing.

I have had the Extreme Duty Timing Set on my '92 with the water pump drive in place for about 45K miles with no problems, and I have had it apart to check the timing set -- it is like new.

If you are experiencing any of these problems, start thinking about torsional vibration problems and the need for an after-market damper (notice I didn't call it a balancer):
1) Broken cam bolts
2) Broken timing chains
3) Sheared water pump drive gears
4) Opti-Spark rotor destruction

You will almost always feel an out-of-balance problem, but you will probably never feel a torsional vibration problem -- even if the torsional vibration is enough to destroy the parts listed above.

With the added load of the water pump drive on the LT1/LT4 and the resonance problem it adds to the timing set, the LT1/LT4 is even more critical when it comes to torsional vibration.

Tom Piper

 

Thanks for the feedback.

Tom...
Did you replace the water pump drive gear with the gear that came with the LT4 ED kit or did you leave the stock gear in place? As a side note, I have an 6.75" ATI Super Damper for the new engine.

pmihaltian...
The LT4 timing sets (both stock and ED) can be used on an LT1. Not sure about an L98. The sets are made by Cloyes. I'm sure they have something for an L98 in their catalog.

Seems very odd to hear about the LT4 ED failures like Rich had, yet lots of folks run the stock LT4 setup without issue. Maybe I should quit over-thinking the issue?

 

A few years back when I did my engine work I talked to the Cloye's Tech Rep and he was openly critical of GM's descision to use the chain...

I went the electric water pump route, but I thought a double roller could be used with an OEM style water pump....???...I must be wrong if you are not considering the double roller..

 

I'm making 442rwhp and using the LT4 ED timing chain with an electric water pump. I don't have any issues. I've driven the car with ~300F oil temps on the autobahn, track days etc.. and never once had an issue with water temp.

I would have gone with the double but I wanted to keep the car ODBII..... Crank position sensor (misfire sensor).

 

I used the entire ED kit including the water pump drive gear.

Since you are going to use an after-market damper, my guess is you will be OK.


Tom Piper

 

Unfortunately no double rollers are available that work with the factory water pump.

The stock LT4 setup looks damn wimpy compared to the LT4 ED setup....but at least it doesn't shear teeth off! I'd rather stretch a chain than grenade an engine due to metal fragments.

 

Are there any aftermarket water pumps (other then electric)?
I'm about to change out my Opti and figured I would change the water pump while I'm there. Is there an upgrade to the oem pump or should I just order the stock deal.
I'll be changing plug wires as well - any suggestions?

EDIT: I just started my own thread for the WP so as to avoid a hijack of this one. Thanks - Dave

 

RichS did not have bleed holes in the front lifter galley socket head
plugs. A question was asked about this in post #10 of the second
thread below. RichS responded to say 'negatory' in post #12.

Prior to that failure, the drilled OEM press-in plugs had been replaced
with undrilled threaded socket head plugs.

In the third thread, Timz06 was asked whether his plugs had bleed
holes, but there was no response to the question.
As a counter-point, sothpaw2 mentions in the third thread that his
OEM LT1 plugs and those of Michael (MSR) boths had bleed holes.
sothpaw2 was of the opinion that there were issues with the
RC hardness values in his case,

.

 

Slalom, thanks for the research.

I have an LT4 ED crank and cam gear that I've run for years....with an electric waterpump as some will notice in my replies contained in the referenced thread. Having said that, I did run the ED set for ~1,000 miles this past summer with the mechanical water pump and the stock LT4 water pump drive gear (which had ~70k miles on it prior to the switch to the electric pump).

After reading thru the links provided, I have some comments....

- The stock LT4 water pump drive gear looks identical to the LT4 ED supplied gear
- I bought my ED gear set in 2003. Unfortunately the water pump drive gear was discarded during my move across the country in 2006 (never in a million years thought I'd need it!)
- After 1,000 miles, while I can detect a wear pattern on the cam sprocket teeth from the water pump drive gear, it doesn't look abnormal nor can I detect any edges/grooves/etc that would suggest excessive wear
- My oil gallery plugs have the .030 holes in them
- Cloyes sells a replacement chain...or at least they list one in their 2007 catalog

I'm thinking I may have the gears hardness tested (if I can find a place) and if they "pass", just put a new chain on there.

I know some people are violently opposed to replacing the chain only. However, I've never had an issue doing this in the past and frankly I wouldn't expect the manufacturers to sell just a chain if it was an issue.

I gotta say a timing chain should NOT be this damn hard to choose

 

LT4 ED here. No issues this far (but I haven't looked at my water pump gear lately).

I think stock WP/LT4 or LT4 ED is preferable to double roller/electric WP.

 

I have a ED LT4 timing chain assembly with about 8000 miles on it for $50 shipped. If anybody is interested.

 

I say there is no problem with the ED timing set.

The way I see it is the problem happens because the ED timing set is "stiffer" and transmits torsional vibration from the crankshaft to the other components in the timing set more readily.

Also, people that use the ED timing set are generally making much more HP and torque than stock -- this causes torsional vibration that is not there with a stock engine spinning to 5K rpm or less with the stock damper.
People making more HP and torque than stock need a damper designed to restrain that extra torsional vibration -- an after-market damper.
Even with the LT4, GM decided it needed a dual-mass damper for the extended HP and rpm -- so, logic dictates an engine making more than the LT4 needs a damper that can restrain more than an LT4 damper.

Do not confuse engine balance and torsional vibration -- a perfectly balanced engine can self destruct due to unrestrained torsional vibration.
You will most likely always feel an engine out of balance.
You will probably never feel an engine with torsional vibration so severe that it snaps cam bolts and timing chains.

All you need is the ED timing set with a damper that is up to the job for your modifications (extended torque and rpm).

As I stated in the post above, my '92 LT1 with AFR heads and Crane cam that is rev limited at 5K with an LT4 damper has shown NO signs of wear in 45K miles.
The reason: the LT4 damper is sufficient to restrain torsional vibration for my engine making about 400 hp and not reving over 5K -- and this is with the water pump drive gears.
But, the LT4 damper would probably not be enough to restrain torsional vibration on an engine making 450 hp and spinning to 6K.

Any time the destruction is on the front of the engine (timinig set, water pump gears, Opti-Spark rotor, broken cam bolts), you should seriously look into torsional vibration as the cause.
The problem with that is the normal "home" engine builder has no way to detect torsional vibration -- YOU CAN'T FEEL IT.

Tom Piper

 

Any recommendations as to which aftermarket damper to use?

 

LT4Bud would be a good one to ask.

I acquired his LT4 damper for my LT1 when he went to an after-market unit.
My LT1 is close to the HP and torque of what an LT4 is stock, so the LT4 damper is sufficient for mine.

Tom Piper

 

I'm using the ATI Super Damper. Aluminum with a steel hub.

 

Any interest in a contribution from a member of the non-LTx
section of the peanut gallery?

.