2QUIK6

With several threads floating around about failures, was wondering what are the estimated limits of the LT1 and LT4 timing chains as far as lift and spring pressures go?

If you had an OEM fail, what was your lift and spring pressure specs?

SS RRR

Shawn97Z28M6 (moderator of TX forum) had a LT1 stocker fail when the car was bone stock. He had to slam on his breaks and ZING... the timing chain broke.
I think Fred (Injuneer) is running a LT4 XD with a solid roller setup.
If you have any doubts then just get a XD for your peace of mind. I've had one in a 847 cammed car (something like 170lbs on the seat and 370 on the nose) spinning to 6500rpm and all was well when I had that combo.

2QUIK6

I forgot to mention, most of the failures revolve around the wp gear or cam gear wp teeth. I have an XD now, and I plan to keep the gear driven wp as its a daily driver and needed reliability since its the wife's car.
I plan on doing a cam swap soon and was looking for alternatives in case I get it apart and see some extreme gear wear after 10k miles.

Never heard of a stockers wp gear teeth wearing, but the cam has .600 lift so it will continue to have some stout springs so a stoker may not be an alternative...thats what I was actually looking for answer on.

SnakeOiler

Am I missing something here? What does lift and spring pressures have to do with a timing chain?

2QUIK6

Has everything to do with it. Higher spring pressures and lift ramp rates means more stress on the timing chain.

1racerdude

Is this a built engine?
If it is make sure the 3 galley plugs have their required holes grilled in them about a .030-.040 hole.

96LT1TX

well I will say that if you go to a XD, watch out for the water pump gear. I ate my water pump gear up twice with the stock setup, once I put a cam in it started getting teeth ripped off. Once I finally figured out why it was over heating there where no teeth left on the water pump gear at all. I would go electric water pump personally, I dont understand why people think it is less reliable than the mechanical water pump. I went through 2 mechanical water pumps before I went to this electric one, best thing I ever did. Once your mechanical water pump fails (if your impeller shaft bends) you will leak your coolant onto your opti and blow it up too. Happened to me at about 5000rpms once, car just sounded like it seized, and well 600-700$ later, and about 2 years later, the teeth where gone on the gear and caused some more problems.

2QUIK6

Ok..this thread is going nowhere for my original question. As stated above, I already have an XD set and know of some of the inherent problems with that set and wp gears..be it from not installing the correct wp gear for that set which is common, or some other issue.

What I have never heard is the stock timing gear and wp gears failing...so I'm considering going back to stock LT4 gears or LT1 gears if I can positively identify what their recommended limits are for spring pressures and I won't be revving to the moon, 6000-6200 max.

2QUIK6

Its a stock original short block, which plugs are you referring to?
Is it the plugs right above and to the side of the cam in these pics? Looks like there is already a tiny hole in them (motor is not apart now..these were pics of previous cam gear issue)

1racerdude

If it has the holes no need to worry unless they are stopped up. That's oil for the chain and WP gear.

2QUIK6

Ahh...didn't know that back when I had them apart or I would have checked...looks like that could get clogged easily, probably another reason for some failures, but there are some larger holes right above that for oil from the lifter valley to pour down once pressure is up.
Those tiny holes in the plugs I guess have filtered oil and under pressure to push the oil out the holes...so they shouldn't normally get clogged if the oil is filtered passing thru it unless some trash got reverse flowed from the crank or cam bearings.
I'll sure check them out when its apart thanks

96LT1TX

my problem happened with stock water pump gear and stock timing set. I reinstalled these with my cam and somehow when I checked on it after that the gears where destroyed. Knocked out the wp gear and installed elec wp, no problems since (obviously).

2QUIK6

Did you happen to install a new Bosch wp when you did that cam swap?
There were a ton of the Bosch pumps made with defective bearings and the defective ones you could barely turn the wp shaft by hand when new...those were chewing up teeth as well.

I'm maining asking about how much spring pressure is too much for a stocker timing set?
With that said, I probably should not worry too much about the teeth before I get it apart as I ensured my replacement pump had a freely turning shaft. I'm betting a large portion of the torn up wp teeth can be contributed to failed or incorrect tolerences in the wp shaft bearing.