bent push rod question, or two

[spikey]

Ok where to start, I've actually had the jeep parked for a little over 9 months doing quite a bit if work to it. I took out the GM Turbo 400 and put in a T-18 , then added a Holley projecton among other things.

Now in the past I've had some issues with this thing jumping time, and I put in a new timing chain. I had no other issues up till I parked it. And that should bring me current.

I've been having a tough time tuning this Holley kit. Like my mpg was as low as 5mpg at one point, but I was back up to 8mpg and making adjustments between fillups. I've only had the jeep back on the road around 30 days now.

So Thursday morning when I started it up I heard a not so good clicking noise. Saturday I drive it about 20 miles to a friend's to help me tune it a little better.

Well, you could tell when we got it in tune cause that's when the click turned into a smack and bent the push rod. Or so I thought.

I know I'm long winded sorry. But if you look at the picture the rod on the left is what bent, and the lifter is ceased or collapsed. But what I can't figure out is the rocker arm that goes on the right one is loose. Even with the bolt tight. What causes that?

What would be my fix? I am an oddball and have a rebuildable AMC 304 in the garage so I have an extra set of heads I could drop off while I try to fix mine??

Sorry if I'm long winded just try to get everything out there.
Thanks for any info

 

[mtnwhlr]

Have checked the valve to make sure it's not seized?

 

[caveman]

Have checked the valve to make sure it's not seized?

Also chech if the rocker is binding.

 

[spikey]

I replaced the bent rod and put the rocker arms back on, then turned the crank by hand till I saw the rocker arms move. If that's what you mean? Although now that I'm thinking about it it started raining pretty good so I closed up and came in for the night. I didn't get to see the one on the right move. I'm guessing it should move fairly close in time to the other tho?

 

[caveman]

It should move about one revolution of the motor from the other pushrod of the same cylinder.

 

[spikey]

thank you for that. Just got home from work and turned it by hand. The one on the right only moves half as much as the one on the left. if even that much. I'm guessing it's time to pull the intake?

 

[johnbilt]

I think the rocker mounts on a pivot ball and it is designed to have some play in it. The hydraulic lifter will make up this difference once you start it and get some oil in there. However, you could have a collapsed lifter as part of the strain on the valvetrain which bent the pushrod. I would be suspect of the valve also since it apparently kissed the piston.

 

[Bent]

Did you use rebuilt heads? When you grind the valve seats, the valve sits deeper into the head, which causes the rocker arm to hold the push rod lower. If you use a rebuilt head you need shorter pushrods or rocker arm bridge shims.

 

[spikey]

I personally haven't touched the inside of the motor, aside from putting in a new timing chain. From what I got it if the po when I bought it, was that he had put in a comp cams cam and lifter lifter set. He threw in a 360 with the jeep cause he was going to build that. So as far as I know it was never rebuilt. There is a serial number on the push rod, so I could Google it and see what it says

 

[mtnwhlr]

I still think the problem is in the valve either its sticking or bent I would start there. IMO

 

[spikey]

I finally figured it out. It took a few for a couple reasons. ! honestly I was just bummed I just got it back on the road after putting so much money in it and it had to be trailered home. so I just let it sit for a couple weeks. 2. I work too much.

So I started looking at what happened. First off, it threw time, again. It was only a little over a year ago I had a thread on here that I had going that I ended up changing out an edelbrock double roller timing chain. Well when I started checking things with this, my timing mark was down at 6clock. so when I pulled out my lifter it led me to go ahead and go down to the cam. lol



So now I've had a buddy offering me a 360 with some head work done on it for about 2 years now. I may as well take him up on it. $200 for a 360 why not. Plus he found a guy that wants to upgrade his 4 banger and sold my AMC 304 as a core for $200 so I'm in a fairly good place with it




Sorry it took me so long to get back to the thread. but yea, it all related to a worn out cam.

Thanks for the help as usual guys

Spike

 

[Torxhead]

Thanks for the update.

 

[gutthans]

There isn't enough information to be definitive...but here's the basic scoop.

The non-adjustable valve train on the AMC motors is, by nature noisy and loose. There is about .020 difference between the shortest and longest pushrod in any given stock motor. A failed lifter, a loose rocker hold-down bolt, or a bad cam lobe can cause the pushrod to get cocked and bounce until it catches on the edge of the lifter or the rocker arm lip...then Pow! it bends!

So, since you put a new rod back in, do the following:

1. Loosen all spark plugs and remove/examine the affected plug NOW

If the plug looks undamaged

2. rotate crank by hand (wrench) SLOWLY
3. check for the rocker/valves to open/close

If everything seems to work...

4. replace/tighten the plugs
5. do a compression check on the bad cylinder and two others

If that checks pretty OK (+ or - 15 lbs.) (@ near to 130 lbs.), then the piston is good...

6. do a leak-down test(see how long that cylinder will hold compression compared to another cylinder).

If the cylinder will hold within 10 lbs. for 2-3seconds compared to another, then your valve is undamaged

7. Now you have to check the cam lobe and maybe the lifter. Get a dial indicator or rig up some way to accurately measure how far the valve stem moves when you hand rotate the crank...do this for the affected rod and any other similar valve (intake/intake, or exhaust/exhaust)...the reading should be within about .005 - .008 if your lobe is still good.

At this point you can find a slightly longer pushrod (like from an Olds V-8) which is what I use to compensate for wear over time, or tear down to the lifter if the motor won't idle properly. BUT, IF you need to go after the lifter...I would consider a valve job. That of course depends upon your motor mileage...you'll be out about $300 - 500 depending on your skill level, so a whole rebuild isn't out of the question.

Oh yea...must have not seen the latest...sorry to hear the lobes were toasted...PAY ATTENTION...USE MOBIL 1 TURBO TRUCK or HIGH MILEAGE OIL...Flat Tappet cams NEED ZINC PHOSPHATE (ZDDP)TO RUN WITHOUT WEARING. Look for a C4 or SL rating on your oil of choice..New cars do not need it due to changes in spring pressure and new oils don't have enough for older motors!!!

http://www.mobiloil.com/USA-English/MotorOil/Files/Mobil_1_Product_Guide.pdf Please go here to see what I mean.

 

[spikey]

Gutthans there's some great info there thank you. Just a touch too late. lol

The really sad thing here is since the first timing chain had to be replaced a year and a half ago I had a friend telling me I had my cam going flat. But he's one of those "know it all" types so I blew him off. I knew that I've only had this cj 3 years, and the cam was put in about 2-3 years before I bought it. lesson learned.