Top Dead Center on a 4.0?

RamboPants · 12-11-2007, 01:11 PM

I need to replace a rocker arm and possibly a rod in my 4.0. Would i need to unbolt all the bolts and rockers just to replace 1? Would i need to find top dead center before unbolting anything?

AZ Jeff · 12-11-2007, 03:02 PM

This is like the third thread you have put up in the past 24 hours related to the valve train on your engine. I asked this before in one of the other threads: what makes you think your valve train has issues?

Do you have lifter noise (valve train clatter) with the engine running? If so, have you isolated it to this particular valve?

Furthermore, just because the rocker arm is loose, it's not necessarily the arm that is the faulty component. You may have a bad pushrod, or a collapsed lifter instead. (Having either one of those would probably result in lots of valve clatter, so that's why I asked what your symptoms were.)

The only way to know for sure is to measure valve lift on one or more cylinders and compare it against the one you suspect is defective/loose. Just pulling and replacing parts may be a waste of time and money.

RamboPants · 12-11-2007, 04:08 PM

No its the 2nd and you didn't reply to the other one. I getting tapping from time to time that i know isn't normal. I get tapping going up hills. I was changing my valve cover and decided to check to see if anything was loose, I noticed one of the rockers were loose. So i pulled it out and replaced it along with the rocker beside it and both pivots. Now when i tighten it, it dosn't move then when i check it a minute later its loose again along with the one beside it.

Mikeand · 12-11-2007, 04:14 PM

Uh yeah because the valve isnt being compressed, so no pressure on the rocker arms. Lol if they were totally tight all the time, how would they rock..hence rockers lol...You might be hearing pinging coming from inside the cylinders, since you say you hear it while going up hill or while the engine is under stress..or who knows could be a rod bearing, crank bearing...

RamboPants · 12-11-2007, 04:22 PM

crap, so those loose rockers i just replaced are fine? Oh yeah so why are all the other rockers tight?

AZ Jeff · 12-11-2007, 05:38 PM

Quote:

Originally Posted by RamboPants

crap, so those loose rockers i just replaced are fine? Oh yeah so why are all the other rockers tight?

Because those valves are partially or fully OPEN. Gotta remember, every valve is open for SOME portion of the rotation of the camshaft.

Valve train parts won't clatter just going up hills. It will clatter ALL the time when you have valve train issues.

Noises "going up hills" sounds like spark knock/preignition. That's REAL common on slight loads (such as steady mild grades) and with low engine speeds.

It's caused by carbon buildup on the piston tops and/or combustion chamber in the head, and is pretty common in older engines with high mileage.

Have you run higher grade gas? 89 octane or even better, 91 octane, will inhibit this spark knock. If you run a couple of tanks of this higher grade of gas, and it goes away, then you have POSITIVELY identified your source of the issue.

Do that, and tell us what happens. Personally, I think you are barking up the wrong tree with looking at your valve train, because the noise you describe does not sound valve train in nature.

RamboPants · 12-12-2007, 12:58 PM

Got the new rockers and all in place, Guess what...no more clicking.