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TR6 Help! Need help from TR experts with this frustrating TR6 pushrod/rocker/valve issue

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sammyb

Luke Skywalker
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To catch everyone up on my situation: the '74 TR6 I bought was a non-runner due to a broken off spark plug. I took off the head, sent it to the machine shop. It checked out fine for flatness, so was not milled. (The valves also tested out good...so after removing and retapping the plug holes, I got it back.)

When I reassembled with a new head gasket, I wound up bending a pushrod and breaking the rocker arm closest to the firewall (#6 cyl) because the pushrod seemed too long. I just got new pushrods and a replacement rocker, and even adjusted totally out, it is still too long. The gap between the rocker shaft support and the head with no bolt on is maybe 2-2.5 cm.

Has anyone ever heard of such a thing? Remember, no mods were made to the head or block between remove and refitting except for a new head gasket, which appeared to be the same thickness. Only one pushrod is too long -- the last one. I checked in there with a light and magnet and it doesn't appear that anything is in there blocking the pushrod from seating.

I'm at a total loss for where to go next. Anyone have gone through a similar experience? I'm all ears, since I don't want to break any additional parts.
 
Sam - just a thought. How's the "long" pushrod measure against the old one that was in the same place?

Tom
 
Sam
did you check the push rod with another one to see if they were different,they do have two different sizes of pushrods for these engines
Philstr6
Phil
 
Along the same lines, does the pushrod go up & down if you turn the crank? Like Andy, I'm thinking the tappet is out of its bore, or jammed in place somehow.
 
You say the pedestal is a couple of cm's from sitting in it's place on the head ?
If you haven't, loosen ALL the rocker arm lash adjusters so that no valve stem or push rod is being pressed on by it's rocker arm and see if all the pedestals will sit down properly.
I suppose it's possible the rocker shaft has a bend, otherwise the pedestals should plop right down under the conditions I described.
 
To answer the questions:
1) The new pushrods are the same length as the old ones. The reason I have the new one is because the old one got bent due to this exact issue.

2) If the pushrod is not in that position, the rocker assembly fits just fine and the pedestals all sit flush. Basically it is just that one freaking valve screwing up the geometry.

3) I have turned the engine, and it does go up and down. Since it goes up and down, I'd guess that rules out the cam follower.

I'll go back tomorrow and spray some carb cleaner down there and really get everything perfectly clean to see if maybe there is something that is keeping the pushrod from seating in the cam follower that gets pushed away when I stick something down there (and isn't metallic, so isn't being picked up by a magnet) but falls back in every time.
 
George_H said:
Could it be a head from a GT6?? As I remember they are "shorter"
Click to expand...

The key here is that the pushrods were fine and the valves appeared to be properly aligned and adjusted (as one could tell by eyeballing them) when I took the rocker assembly off, the pushrods out and the head off three weeks ago. The only thing that has changed is the head gasket. My gut says "some piece of garbage stuck down there", but I've poked, swiped, wiped and haven't found anything. I'm going to try different cleaning methods tomorrow.
 
Hi Sam, is it possible that a previous owner milled the head? When turning the engine over are you having "spring bind". Have you compared valve stem height with the others? Have you tried one of the other pushrods that seem to fit, in that position? You are going to be buying at least one anyway so buying two wouldn't be a big deal if it bends? Is it possible a piece of the old head gasket fell onto the lifter? It could form to the lifter and if it is nonmagnetic could be difficult to detect.
 
Sam, my vote is something fell in the lifter and the push rod jammed it in tight, so a magnet would have a hard time braking it loose. Painful, but you will have to get a new head gasket and remove that lifter.

Wayne
 
Tom,
It is absolutely possible that the previous owner had the head milled. Valve stem height appears to be the same, and I've tried multiple pushrods in there.

Even though it was a metal head gasket that I took off, I'm beginning to think that you might be on the money. I'm going back up to my garage this afternoon and am going to use all the conventional tools (air blowing, suction, cleaners, etc...) to ensure that there is nothing on that face of the lifter.

Thanks guys...I'll report back later today.
 
As we thought...I'm just a COMPLETE KNUCKLEHEAD!!! Part of it is that my eyes aren't as good as they were a few years ago, and the other was the nature of the blockage: it was a freaking NUT, like one used to secure the rocker shaft. Since the nut was the same color as the block casting and sitting flat, it was almost impossible to see way down there and the pushrod had a small feeling of being in center (but obviously not like it was truly seating in the lifter).

Even after I finally identified it, it took a good 30 minutes to actually get it out. The magnet wasn't narrow enough to get far enough into the lifter area to attract. I triend all my tools, then decided to walk into the other side of my shop to get some scrap 12 gauge Romex from my electrical wiring project. I took one wire, stripped the end off and bent it into a narrow hook. It was touch and go, but it worked. It's amazing, because for a nut to fall into that area is a one-in-a-million shot. It only falls in one angle and direction, so getting it out of the last bit was a very tight fit.

But everything looks much better now. Maybe tonight I'll set valve clearances and see if she'll FINALLY run!
 
Glad you got it out! I've used a glob of grease on the end of a wooden dowel to retrieve small objects before. Now back to the reassembly.
 
Yeah, Elliot, grease globs are great tools. I have used grease numerous times to hold the ball bearings to the spring that go into the detente on my Ferrari 308 GT4 headlight and turn signal stalk mechanisms. Nasty little buggers. Unfortunately today I didn't have my grease up at my other garage. Even if I did, I can't say that I would have thought to use it, since I generally have it in my head as something to use for a specific reassembly technique.
 
Thanks Tom. My mechanic buddies always tell me that I'm too hard on myself, because everyone at some point gets too close to see the rational and starts grasping at the irrational...or as they say it, everyone does stupid crap. I suppose that if the stupid tax was only about $15 worth of parts, I got off easy!!!
 
Good thing that nut didn't fall somewhere else in the engine. Could have caused allot more frustration than a broken pushrod.
 
I hope I am as lucky... good for yoy Sam!
 
Some of you may know this trick. If not...

When you need a magnet to do a job like Sam had to do. Take a screw driver and some heavy gage insulated wire. Like the Romex Sam mentioned. Wrap the wire several times around the shaft of the scredriver so that you have a spiral of wire running from the handle to the tip. Strip the last little bit of each end of the wire. Then touch one end on the positive terminal of a car battery and the other end on the negative terminal. It will spark!
The screw driver will be magnized enough to retrieve small items like nuts and screws. It's also useful for getting a screw into a small area that your hand or fingers won't fit.
The magnitism lasts for quite a while. To demagnitize rap the shaft of the screw driver on something solid.

BobH
 
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