When to Rebuild Engine-warning signs...?

[Oracle]

Ok, for our engine guru's out there, can you guys run the list of things warning us to start thinking rebuild? Include general matters such as mileage, but add the other 'indicators' as you see fit. Thankx in advance cause I think a BUNCH of us are wondering at what point to go ahead and bite the bullet as opposed to waiting and incurring more expensive damage...thanx

[Andrew]

1. Low oil pressure at idle with a known good indication, or the idiot light comes on at idle

2. Excessive smoke/blow by

3. Frequent fouling of plugs with oil

4. Knocking

5. Low compression

6. Poor engine sealing (leakdown check)

[joe]

I'd say the obvious warning signs are low oil pressure, burning oil, internal noises. Doing a dry and wet compression test periodically is prolly the best indication of the actual condition of the motor.

[Jambo1]

What oil pressure should we be looking for at idle, say running about 800 rpm's?

[joe]

Originally posted by Jambo1:
What oil pressure should we be looking for at idle, say running about 800 rpm's?A generally accepted rule of thumb is 10 psi per 1000 rpm and you're fine. I think the motor "needs" about 7-8 psi/1000rpm to not do any damage(?) so 10/1000 is ok.
Tricky part here comes in when you try using the "for entertainment value only" stock Jeep oil gauge :D

[jaz459]

what i have happening is it will run @ 45+/- 5 psi until i make my first stop when warm then it drops to 8-9 psi while stopped then will move back up 35psi +/- the issue I have is after i stop the valves tap for a few seconds until pressure builds up again.

[andy d]

depends on the use the rig is going to see. i ran my 84 wag til it needed valves and cam. a run down to new befford. rig was straining to do 70. it had a 170k on it.it used a qt of oil in 300miles. leaked and burned it. the mains rapped 'til the oil got to them. 83 made it to 180k, a bad fuelpump gassed out the oil and it seized. it too had issues. i have about 35 k on a re-manned longblock. so far so good.40 lbs pressure idling along @30mph

[kreb]

on my recent rebuild the first signs of oil throught the air cleaner were it for me. i fixed all the vacuum lines and pcv work and nothing changed. bad rings on the the 1 and 3 pistons.
had low oil pressures as well
benjamin

[jaz459]

I did the vacuum lines last weekend and checked the pcv valve I have not done a compression check yet, but will in the near future. I don't like the valves tapping. I am not sure what kind of damage is being done everytime I sit at a stop light.

[desert_freak]

Jaz459 (update your sig with vehicle/specs) what engine are you running? The I6 in our rigs are notorious for having a loud valvetrain and guys here have run them for years with LOW oil pressure. When I first got my J10 the valve noises had me pretty concerned, that was 18 months ago and it is my daily driver. I use a lot of oil (not really any blue clouds though), labors up steep grades and clacks but it just keeps plugging along, will do 70 all day long with 4.10s and 32" tires. Next summer I will treat my baby to a new stroked I6 and a MUCH larger carb and maybe a offenhauser intake.

Sorry for the digression, I recommend you the wet/dry compression tests as well, it's the best place to start.

P.J.

[Bob Barry]

The bearings tend to go before the rings. A good sign of a need for a rebuild is if the valvetrain is tapping and motor-flush doesn't cure it. That is a sign that the cam-lobes are rounded, which is often coupled with worn cam bearings, which mean that the main bearings are not far behind.

This tends to happen at about 160,000 miles for a normally-maintained motor, -50,000 miles for a poorly-maintained motor, or +50,000 miles for an unusually-well-maintained motor.

[kreb]

oh yeah i had some bottom end tapping as well. the main bearings did go out. it was at 50000 on a real cheap reman'ed unit, build it right the first time

benjamin

[Oracle]

Why would only the connecting rod bearings on one or two cylinders go bad and nothing else in an engine? (at least nothing else obvious).

[Dan G]

There are some 'inherent' spots that don't get 'enough' oil in an AMC engine. If you do a search for oil bypass or something like that you'll find one or two issues, one is that one/some of the rear cam bearings don't get enough oil and someone has come up with a way to 'fix' the problem with a drill, a tap, and some flextube. The second issue runs more oil to the timing chain as that allegedly doesn't get enough oil as well.

I say allegedly because I have over 200K miles on my GW and she needs a rebuild (desperately) and I have researched some of these issues. Amazingly, the problem i don't have is oil pressure.

These modifications were made mostly for streetrod and track motors, but don't we all wish we could wring 360 HP (or more? NOX?) and 500 ftlb of torque from these motors?

[OBX-AUTOMOTIVE]

ONE GOOD INDCATION.....WOULD BEEEE.. ....ONE OF THE RODS....ON THE "OUTSIDE" OF THE OIL PAN!!!!! :eek: :rolleyes: smile.gif

[gsmikie]

and the number one sign that you want/need a new motor ................you cant stop thinking about caddy power tongue.gif

[Marvin Gates]

Right ON, gsmikie! can't do it right now but its at the top of the list. MG :D :D :D
Really like the idea of a super cruiser with a Caddy.