Simple question, I think

[gblaue]

I asked the over in the Camaro6 ZL1 forum, who always have an answer for everything, but crickets this time. I from old school small block days. On my LT4, where are the timing marks that I can see , and verify 0 Degrees TDC? Or do I got to stick a wooden skewer in the spark plug hole and turn it over slowly, and watch the intake and exhaust valves, and guess?

[blindsquirrel]

No wooden sticks, you need a piston stop. Turn the crank clockwise until it hits the stop, mark the balancer (you have to add your own timing pointer first). Then turn CCW until it stops and mark balancer again. The midpoint between those two marks is the true TDC - without turning the crank, adjust your pointer to that mid-way mark.

[edcmat-l1]

Piston stop or a small piece of tig welding wire and good "feel" will get you plenty close enough. Then you'll need to make a pointer (again, think tig wire) bolted to a timing cover bolt, and mark your balancer.

But, unless you think there's a mechanical problem that's changed it from where it should be, there's really no need. I've yet to see any LT engine slip a crankshaft reluctor ring.

[gblaue]

Piston stop or a small piece of tig welding wire and good "feel" will get you plenty close enough. Then you'll need to make a pointer (again, think tig wire) bolted to a timing cover bolt, and mark your balancer.

But, unless you think there's a mechanical problem that's changed it from where it should be, there's really no need. I've yet to see any LT engine slip a crankshaft reluctor ring.

Thanks for the quick reply. I have the supercharger off to replace the injectors. I am going to walnut blast the intake ports while I have it apart. I also bought a set of BTR brass bearing rocker trunions. I just want to make sure I find TDC before I go squirting high pressure air and walnut powder into the intake ports. A little paranoid, when I can't see it on the crankshaft.

[edcmat-l1]

I'd just do it by hand. Pull all the plugs, turn the engine over by hand. Watch each intake valve open, then on the closing use a small piece of tig wire, coat hanger, etc. and feel for the top of the piston as it comes up.

As for the brass rocker trunnions, they're nice pieces but with the rest of the valve train being stock kind of overkill and really unnecessary.

Once you're done with the walnut blasting make sure to spin the motor over several times with the starter with all the plugs out of it. It'll blow any remaining crap out of it.

The shop across the street from me is a Subaru shop and they do this procedure daily.

[blindsquirrel]

Oh. For that you don't need to find true TDC, the piston can be anywhere as long as both valves are closed. You couldn't tell if both valves are closed solely by poking the piston, as it's at TDC at both the top of the compression stroke and top of the exhaust stroke. You need to be able to see the rocker arms while turning the crank.