aggie88

Okay, LT1 wrench monkeys! What exactly does the TDC mark on a 95 LT1 (6 spd) look like and where on the crank pully is it? Plus ..... what is an appropriate number of turns for valve lash on a LT1 (all stock guts).

STL94LT1

TDC, the timing mark on the balancer is at 12 oclock.

Valve lash, 1/4 to 1 full turn.

emoshn

Now, wait a minute. My 92 LT1 has a non-keyed hub and balancer and no timing mark, nor is there a pointer on my timing chain cover...plus I have been told that you just have to pop the valve cover off, make sure you're on compression stroke of no.1 and use either a dial indicator to find TDC or the ol screwdriver in the hole technique.

Seeing as how the pulley balancer is not keyed to the crank, a mark on it would be pure folly.

As far a valve lash...I've heard 3/4 to 1 turn past 0 lash.

ConeKLR

Huh?
:confused:
What timing mark? :lol:

STL94LT1

To find TDC compression stroke of #1 cylinder. I remove #1 spark plug, pushed my finger over the hole, rotated the crank until my finger was blown away and then located a yellow marker on the balancer which was at 12 0clock. This was TDC compression stroke for the #1 cylinder.

For any doubters, I then removed the rockers and valve springs, replaced valve springs, replaced and adjusted rockers. Then rotated the crank 90* and repeated procedure on #8 cylinder. continued the 90* rotation following the firing order until completed. Put the car back together, fired the engine and never had to readjust the rockers.

SPD DMN

I either use the finger in the spark plug hole technique. Or I rotate the assembly until the exhaust valve begins to move and proceed to adjust the intake side rocker. Do the same to the exhaust rocker when the intake begins to move. That basically is a sure fire way to make sure the lifter is on the base circle before adjustment. Never had a problem doing it this way either.

AquaMetallic94LT1

There is a large arrow on the balancer face. Its very tough to see when the motor is in the car. I suggest you find #1 using the methods suggested and then put a paint mark on the balancer. Its true that the hub is not keyed so it is possible for the balancer TDC indicator to be misaligned.

You can set the valves using the two TDC positions or start with #1 and turn the crankshaft clockwise 90 degress at a time and set the next cylinder in the firing order. Use the alt pulley bolt to turn the motor. Its much easier. Double check your work by seeing how many threads are exposed in the polylock or above the bolt after valves have been set. The amount should be the same unless you made a mistake or the valves were worked on.

aggie88

Yeah - since its not keyed, I think its best to look at the valves and not depend on any balancer marks. I could not for the life of me see the arrow (Chilton's says its a "cast arrow") with all the stuff in the way.

As for the valve lash - Chilton calls for 1 turn - but I have the TPIS LT1 hints book and they call for 1.5 to 3 to squeeze top end HP! I don't think it works.

R Cook 92

There is an arrow on your damper, which should be at 12 o'clock when it is TDC. but if it was ever removed and improperly installed for some reason, it could be wrong... if your adjusting valve lash I'd highly recommend doing it one at a time... adjust the intake when the exhaust PUSHROD starts to rise. And adjust the exhaust when the intake VALVE is approx 2/3 closed... you'll get the hang of it. good luck... ohhh yea, I've done approx 3/4 turn past 0 lash.

SPD DMN

I do 1/2 turn past Zero lash. I would never go more than one full turn.

ConeKLR

okay, makes sense now. An arrow on the face of the damper is different than saying it has a timing mark on the damper. Timing mark would be like on the older motors, L98 and down which is used for manually setting the timing. :crazy: :lol: Guess if you have never worked on anything older than an LT1, there would be no confusion.
thanks
:lol:


[Modified by ConeKLR, 12:16 PM 7/24/2002]

James94LT1

As for the valve lash - Chilton calls for 1 turn - but I have the TPIS LT1 hints book and they call for 1.5 to 3 to squeeze top end HP! I don't think it works.


I've heard of guys trying this and thier motors barely ran! That too much
I don't understand why they say that?!?

aggie88

Thanks everyone for the tips. Unofrtunately, I am having problems. I tried setting lash by the TDC method, with 2 turns past 0, car ran but like a severe misfire. I redid it with the cylinder by cylinder method, this time with only 3/4 turns. Now it barely starts and is runnning so rough it won't idle. I've set lash, changed cams, etc on other V-8 hydraulic motors before. This is really confounding.

STL94LT1

Double check the spark plug wires, maybe they were switched when you put everything back together.

aggie88

Already checked. Unless they got damaged in the process, they should be fine. Can't find anything else out of order either.

STL94LT1

How did you determine TDC ?

The Green Rocket

Why exactly did you decide to relash a "stock guts" LT1? Normally with a hydraulic lifter cam you set the lash once at initial assembly and then never again. If the engine was running fine prior to your wrenching then your efforts were misguided. If the engine was already running poorly then this has to be one of the more unlikely areas to look at on a stock engine. Which is it?

The cast in "arrow" is in an impossible to see spot on the hub, not on the balancer that is bolted onto the hub. It should only be relied upon on a careful initial assembly, as noted, it can and does move from its original installed position.

On LT1/4 engines I like to watch valvetrain movement to help determine tdc. One of the tools I like is an air pressure "squeaker" that screws in place of a spark plug and it squeaks when piston is tdc.

If it wasn't running poorly before, then you did not really have tdc correct while doing adjustment.

Thomas

aggie88

How did you determine TDC?

You know- this may have been the problem when I set it the first time. But unsure since I set the lash at 2 turns that way. But setting it by the cylinder to cylinder method - TDC shouldn't matter - right?

STL94LT1

Using the TDC method you must determine TDC on each cylinder.

BBA

With stock valve springs, this much preload will force the valves off the seats when they should be closed, hence the motor will barely run.

BUT: It DOES work if you have replaced the stock valve springs with double springs with about 125 Lbs seat pressure and about 360-380 Lbs open pressure. In this configuration, the spring pressure will not allow the lifter to pump up and high rpm bleed down of the lifter is minimized.

I had a set of TRW retro-fit hydraulic lifters in my '79 383, adjusted with 1.5 turns preload, and the thing loved RPM's ( had a to put a rev limiter in at 7200 RPM because it would turn way past that if you floored it in first gear and didn't shift quick enough to second ).