Hi all,

Looking for a couple of quick answers if anyone can help out.

Does anybody know if the pistons out of a TPI car are the same as those that were in an L69 car? I've got TPI pistons in my LG4 and I'm bending pushrods. I'm trying to figure out if I've got a valve to piston clearance issue (don't worry, I'll be checking for sure, I just want to know if it should even be an issue).

I've got to check and make sure I got the timing chain on (I'm allmost positive I got it installed right) and then check for piston to valve clearance.

Don't even ask about why I've got this setup...long story that I've learned my lesson by. No more cheap stuff, I'm doing things right from now on...

 

What cam have you got?

If it has less than about .650" of lift, then piston-to-valve clearance probably isn't a problem.

AFAIK TPI, L69, and later LG4s all had flat-tops; earlier LG4s were dished.

 

Thanks RB.

AFAIK it's the stock LG4 bumpstick. I can't imagine that would have any more lift than a L69 or TPI, but who knows. I'll have to prove it out with the gauges I guess. The pistons I pulled out were dished. The ones I put in were flat...

if I can provide any other info...let me know

thanks
Clem

 

The stock LG4 has less than .400" of lift... :sillylol: What a moronic idea! So you have nothing to worry about there.

Do you have the narrow slots in the heads for the push rods, and self-aligning rockers? That is about guaranteed to cause valve train distress, including bent push rods.

 

I don't have anything but stock '83 LG4 equipment besides the pistons and rods. So no self aligning rockers. I think I have found my problem though.

Keep in mind, the engine never even started...bent rods just cranking

Much as I figured, I'm sure it's going to come down to my own ignorance. I didn't even realize I was ignorant (just my own little joke there).

I tightened down the rocker nuts without realizing how to adjust them properly. I just cranked down on the nuts until they snugged up (bottomed out on the threaded portion of the stud)

Please tell me this is what's causing my problems. This should, I think, cause the valves raised off their seat even on the base circle of the cam. Therefore, when the lobe comes around, the effective lift is greatly exaggerated and crashes the valve off the piston.

make sense? (It makes sense to me how much of a moron I am)

Thanks
Clem

 

Ummmm, yeah, that could do it. Oh well, you needed new push rods anyway, didn't you?

 

That would definently cause the problem...buy new pushrods and then use the correct sequence for tightening them. That is to find the location of the engines rotation where both valve for a cylinder are meant to be closed and then snug lifters to where it puts minor tension on the pushrod and then on additional quarter turn. Hope this helps (and that I remember right!)