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Engine bottom end assembly questions.


Guest Anonymous
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Guest Anonymous

Well I finally got my bottom end together. I used a dab of assembly lube and torqued everything to spec. It was very difficult to rotate the engine by hand before torquing the main caps, but now with them torques it's almost impossible. Is this right?

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Guest Anonymous

Should turn easily with no binding. Are you sure you have the right cap in the correct location and orientation for each bearing. They are not interchangable in location or rotation. Is the thrust bearing in the correct location? Did you check clearances with plastigage? Good luck

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Guest Anonymous

Is it possible that I put too much assembly lube in? I plastigauged it quite a bit to make sure I was withing tolerances.

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Guest Anonymous

Make sure the main caps and rod caps are in the right orientation otherwise they tend to cock to one side and bind up the crank.

Even though theoretically this should make no difference, when I was mocking up my friends engine it made a noticable difference when I mucked up the rod cap orientation.

Take it apart again and check each bearing for signs of rubbing. Then take everything apart and reassemble one part at a time...ie conn rod #1 then #2 to the crank etc to check fits. Do the same with the crank to block but only do one main cap at a time. Make sure everything moves easily when torqued up.

If you don't get it to spin freely it means somewhere there is interfereence which will undoubatably be bad for engine life, if you can even get it to turn over and start in the first place.

-Bernard

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Guest Anonymous

I've posted before about the often overlooked requirement to also reduce the width of the #3 main journal thrust surfaces when grinding a crank.

The main bearings sets for undersize journals all come with thicker thrust bearing area, if your shop did the crank journal diameters only, you will not have the required clearance on the thrust face, and the result is a binding condition due to insufficient endplay.

The thrust width specs for reqrinds are in the manual.

Yes, the crank should spin easily if the main bores are in alignment & everything is OK. Do not continue if there is any binding, it's not going to "wear in" without serious damage risk.

Always check crank endplay during assembly, specs are in the book.

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Guest Anonymous

Well I'm hoping when you took the main caps off that you marked which one was what and direction. If you didn't there are only no less than 15 possible combinations that they could be. remember to align the tangs correctly.. IMHO.. plastigauge sux... pull off your main caps and look for the shiney spot.. make sure there is zero dirt in the tang grooves or behind the bearings.. next time when you assemble... zip all the main caps down with a air gun to "light tight".. then torque each one... from center out.. and after each main cap try and spin the crank... then you'll know if the last one fucked up.. ;) Party On

Kris

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