Pistons hitting something - won't turn at all

[madramire]

Hi just wondering if there is a particular sequence to be used or position when installing each connecting rod in a Johnson V4 140hp (1984) to the crank?

The crank won't turn freely with the heads on (and smoothly), despite having turned freely without them on - complete novice here, project engine, not in a panic as I will just dismantle and reassemble again if need be, but the manual didn't state that any guidance for TDC or sequence/position for the connecting rods before putting the heads on. Pistons are not hitting the heads, I have checked that on port and starboard the upper and lower pistons are in opposite positions - they are - shining a torch in you can see the piston is not hitting the head wall... not sure if it just needs powering up and to be cranked that way.

Taking the heads off, the cranks turns freely, although, the pistons come out a bit more than I had expected - the top of the dome actually comes all the way out - is there something wrong here? Looking at pictures from before the rebuild, the pistons do come a good bit alright. I'm just not sure and don't want to hook it back up to gear again, connect the linkage, power her up and bang, something breaks

All advice much appreciated.

thanks in advance.

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06/27 - 2105:

Disregard post - checked my photos from pre-dismantling and discovered I was installing the heads upside down.

Thank god for digital cameras!

 

[Daviet]

Re: Pistons hitting head - won't turn at all

Re: Pistons hitting head - won't turn at all

If the pistons are hitting the cylinder heads, you have a problem.
Did you replace the crank, rods or pistons?

 

[mikesea]

Re: Pistons hitting head - won't turn at all

Re: Pistons hitting head - won't turn at all

If the rods are original,the replacement pistons ar correct.Im thinking you have pistons backwards?just an immediate thought.the topof the piston,the dome,whatever you want to call it ,I always looked at it like an arrow,the point of the arrow should point outward of the eng.are you sure your puttin the heads on the correct side?those 3 things are about the only things that would cause piston to hit head,unless you had the head/or block illed too much ,which is possible if eng was rebuilt a few times and no info stamped on

 

[madramire]

Re: Pistons hitting head - won't turn at all

Re: Pistons hitting head - won't turn at all

breather allowed now - I discovered from browsing through my digital photos from prior to disassembly - discovered I was installing heads upside down and on wrong side.

Now turning smoothly, and nicely... feels like good suction in there too, so hopefully compression is fixed now.

thanks for the advice though.