The Stovebolt Site Forums The Shop Area Engine Shop 261 engine only turns half a round UPDATE 11-30

Most of you know I have a 1956 261 truck engine that was stuck tight in a car I purchased. I've pulled the head and cylinders are nice and shiny. The lifters were stuck but all are now free. Since I still can't pull, push stuff (heart surgery) my nephew has been helping a little till I can do stuff my self. (He is also a lifelong mechanic)
Problem: today he put the starter on just to spin the motor a little but it just would not budge. Got under the car with a flywheel wrench and a pry bar. The engine will turn about 1/2 round and stop....then turn back the same distance.
Anyone got any idea what is going on. The cylinders are clean/shiny and we lubed them good, the lifters are out, the driveline is not hooked up but it does have the clutch and stuff in it.
This is a new rebuilt engine, never started and when I pulled the head off it has all new stuff...blah blah blah...


I guess its time to pull the bottom pan.....or can anyone think of something else. The timing cover is on but I can't see it being a problem. The engine is still sitting down in the car but it'll be easy to pull. What say the 261 experts......oh, does the 261 rod bearings have a notch in them? Just curious right now.
Opinions please.

You got me with this one. last engine I had the would only turn about a half turn had a very bad bent push rod. As soon as the cover came off it was clear to see. Only a few things can hang up the bottom end like what you have, one of them is a rod hitting the cam shaft. Wrong year cam could do that. Another thing would be a bolt catching the bell housing. That is tough to catch until you actually see it happen. That is about it. If the dizzy is still in place you could have an issue with the oil pump, but what ever it is you will find it on the stand for sure. Let us know what it is. Curious minds would like to know.

Pull the spark plugs and see if you can borrow a borescope to look inside the cylinders. I bought one from Harbor freight awhile back, but the scope is too big to go through a plug hole. It still lets me look through bigger holes, but all I can do with a cylinder is get a long-distance view. Snap-On makes one with a 1/4" diameter scope that's very handy.

235/261 rod bearings are the same- - - - -anti-rotate tabs on the rod and cap.
Jerry

Could be that when they rebuilt the engine they set the cam in wrong and didn't have the marks lined up.


Pete

I also wonder if the oil pump bolt was not screwed in all the was so the counter balancer may be hitting it.
I assume the head is still off?

OOPS! I missed the fact that the head is off! The problem has to be in the crankcase, then. A rod hitting the cam, a mis-timed cam, or the oil pump setscrew are all good possibilities. Gotta drop the pan to find out, though! Good luck!
Jerry

Remove the starter, then try it.

Some clarifications:
When I purchased this vehicle the engine was in and bolted down.
Never started...distributor wasnt' in, starter not in, no radiator, no carbs although the intake and headers were bolted on.
After soaking for weeks I decided to pull the head and side covers to be on the safe side and that's when I found 3 stuck lifters. Up until then I had not exerted much force not wanting to bend push rods..... But I could get it to turn maybe 1/3 round back and forth.

Its basically just a short block sitting in the engine bay now. Oh, I also know the starter is good. Its rebuilt by a fellow friend that's been in the business for years, Rebuilt and tested.

Perhaps the oil pump bolt....or maybe the cam as mentioned. I think its time to either pull the timing cover, or just pull it and put it on the engine stand where we can check it out. After its sat for about 10-15 years I think I need to do it anyway. I want to make sure the bearings, cam and such have plenty of assembly lube! Its just to much good nice new stuff to not do it.

I will say, as I took off the pans/covers, the intake/exhause and some other little things, it appears the guy knew what he was doing and wasn't a novice..... well, something is wrong!!

As mentioned I still can't do very much so I'm at my nephews mercy here. He will gladly help but time is limited. Maybe if I paid him

Thank you guys for your input. I will keep you posted.

This is a very interesting problem. Now if the crankshaft is easy to turn then can you tell if they are hard stops? Engines stuck with rust will exhibit a softer stop as in they sort of jamb and it takes an effort to back off. Are the two points roughly 180 deg apart?

truckernix, before surgery and I could rotate it a little it felt like hard stops, and to my nephew as well. The cylinder walls, as well as the rest of the engine is slick and nice. When we turned it the little we could a couple pistons moved a good bit and the cylinder walls looked great. We also lubed the heck out of the cylinders.
I don't think its a full 180 off. Since the distributor was never put back in the engine I wouldn't think it'd be 180 off but I don't know if the timing marks are right yet.

Does the pan have to come off the 261 to get the timing gear cover off like the earlier engines? I still may be able pull it enough to see if the timing marks are correct.
Right now I feel so helpless and useless..... but I'll figure it out. Nothing left to pulling the motor! Thank you for your comment.

My opinion would be to pull the engine since most of the parts are now off the block,and put it on the engine stand,rotate it and take off the pan,and take a look,nothing in there, go and take off the rod caps and go from there. Pat

Wonder if some mice made a nest in the bellhousing and pressure plate area ? My 1954 261 had a mouse nest in it's clutch area,it was tight as could be.

Tim, before surgery I had "looked up in there" with a light but I also have not ruled out anything....including that area. I know the engine should be tight but in all my years I've only seen one, maybe two engines that "tight".
Keep the idea's coming guys. I'm hoping its like we usually find, something simple and we can smack our foreheads!

Cam timing can be ruffly checked by looking at the two cam lobes for one cylinder. When they are both at the top of there lifter lift(nose on top), that same piston should also be at the top of its stroke.
I.e., the two valves for that cylinder will be changing from exhaust to intake as the piston reaches TDC.
It would be easier to watch the lifter for any given cylinder for this test if you want to put them back in.

Alvin,
I know how you feel with the surgery ban on doing anything interesting! My ban was shorter but very frustrating. I think your motor is going to have to come out and then it will be obvious on the stand.

Alvin, I hope you heal quickly. I think you have a too long of a bolt in the flywheel/pressure plate that is causing the lock up on a half turn. Just my 2 cents.

Pre-Dave, thanks for the info on the lifter lobes. I did not know that....learn something new everyday. It'll be late Thursday or maybe Friday before I get back down to my nephews shop. Hang tight and I'll let you know what we find.....
and Mike, I'm gonna take another look up inside the bellhousing for sure.

Sorry I said the first part backwards, the lobes will be at the bottom of the cam.
Same deal though, you will see the exhaust lifter drop all the way down and the intake lifter just start to lift as the piston hits TDC.

I was going to suggest the long flywheel bolts as well. It may have turned perfectly when on engine stand and bolted in the truck and when they installed too long a flywheel bolt, all bets were off.

Alvin
?????????????????
Soooooo Whats up with this mill,
Or are You just dreaming of turnips,dressing,dark meat and gravy!
Need an update!
regards,
steve sr.

A friend of mine bought a 235 engine and trany as a unit, the thing wouldn't turn around but part way and back like you are describing. After a week of swearing among other things he discovered the previous owner had bolted the flywheel on wrong which forced an allignment pin from the flywheel/crank flange through and against the back of the block. once that was sorted out it turned out to be a good motor.
Best of luck
Jim

UPDATE: well guys, we can quite guessing...and remember, this is a newly rebuilt engine, never fired!

While I was traveling the last few days my nephew, a full time mechanic, pulled what was left of the engine out of the car. Problem is #2 rod bearing spun.

...its a shame but the PO HAD to have spun the engine and did the damage as it was stuck before I got it.

...plan is to pull the other rods and mains and take the crank to Spartan Crank who use to do work for my brother. I'll let him tell me what he can do to save it. I'll go from there. I'm hoping that besides him doing a little work that all I'll need is one rod bearing that is .020 over.

I'll let you know how we do but it'll be a few days. I just got home and I'm tired. Whew.

Hy Achipmunk, thanks for the update, now go and rest, but please keep us in the loop, belated Happy Thanksgiving.

See Alvin, I told you should have just given it to me....

John