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Rebuilt 1275 refuses to turn over

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C

Cujo

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Hello,

I am new to this site but would appreciate any collective wisdom on the following. Just finished rebuilding a 1970 Midget for my mother. Went to turn over the engine and will not go (and this is my 12th engine rebuild over the years on many different cars). Thought maybe I had had a "duh" moment in assembly so took it back out and stripped it down. Ring gaps are fine, cylinders honed, valve guides all clear... Crank spins fine with pistons out (all bolts on the flywheel etc. are the right length)and so on. The only thing left are the new rod bearings which are new from Octagon Motors here in Canada. They are standard size but starting to wonder if they are mislabeled? Anyone else ever had this experience? Any other reason anyone can think of? This will be the engines third time out of the car.

Thank you
 
Plastigage.

NEVER trust bearings and journals to be "right".

Obtain some Plastigage, use it, tell us what the readings are.
 
Try over at the Spridget forum also. - welcome!
 
Are you talking about an electrical question here or is the engine so tight that the starter won't turn it over?
Did you put it in 4th and try to push the car to see if it really was seized?
BillM
 
Yes, my question would be, how did the engine turn over by hand after the pistons and rods were installed?

Are the rod offsets correct, I don't know if they would even go in otherwise, but I guess it could be possible.

Call me if you like at the shop tommorow, or pm me and call me at home today if you're in a jam on time , I do these motors for a living and will help you sort it out on the phone. There's a handful of things that could lock a assembly down.
 
It is locked tight - will not turn over in fourth. Have another set of bearings now so will try those one rod at a time and see what happens.

Thank you
 
Plastigage.

Don't just go throwing parts at it.

If they're too "loose", and it turns, and you fire it and damage the crank, then what?

Get some plastigage.
 
Could also be a rod or main cap turned around backward, remember it's always bearing retaining tab to bearing retaining tab on the same side. Here's what I would do, take it back out, put it back on the engine stand, take one piston and rod out at time, see it frees up after each removal, work your way toward the mains the same way, starting with the center main, the last thing you remove that freed it up, is your culprit. One time I had a bearing shell on a MGB it measured fine with the ball mic, palstiguaged fine, but the shell ended up being a bit long and it pinched at the parting line, ended being the center main bearing in the cap, and I did just what I described above to find the culprit. It could be journal size on the crank, but I looked first for wrongly install cap, rod or main, or bearing shell issue.
 
If its like the MGB engine then check the last 2 pistons and rods that you put in. You have to turn the engine over to get the last 2 pistons/rods in. If it turned over till then you can narrow your search. Any chance the starter jambed in the ring gear and thats your problem? Bob
 
Extruded soft plastic rod (thickness about double that of a hair), used to determine bearing-to-crank space. Two "standard" thicknesses, "red" or "green" depending on initial tolerances.
This Web page will give you some overview. I suspect it is available there, just not common in the "chain" type shops. Ask around a machine shop.
 
You lay a piece on the journal, install the cap, torque to spec, DO NOT TURN THE ENGINE, remove cap, lay the paper wrapper against the smashed plastigage and read what the REAL bearing clearance is.

In this case, I would do ALL mains and ALL rods, just to be safe.

If a used crank, someone may have had one bad journal turned and had a special bearing size for that, that you may have match for all 4.

Or, wrong (or mixed) main caps or rod caps.

Sure the caps are all on right?

I did an engine once, rusted, stuck, got it all done and some yay-who had LOST the main caps and put "other" caps on it.

Back to the machine shop for a line-bore.
 
Plastigauge Manufacturing Co.
Unit G Ash Grove Industrial Park Heath Place
W. Sussex
Bognor Regis

https://www.plastigauge.com


Plastigauge & Plastigauge Mfg. are trademarks of Elinvac, Ltd., West Sussex, United Kingdom

Looks like this stuff is MADE "over there".
 
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