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Rb25Det Not Turning Over?


SYK-200
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hey guys iv'e been rebuilding a rb25 from the ground up, i put the bottom end back up, with CP forged pistons and rb26 conrods (which my brother got :unsure: ) i had it all spinning, THEN i put the head on, tightened it down (stupid thing to do) then spinning the crank, and it seems its locked in place??? doesnt turn clockwise/anti-clockwise??? its STUCK ?! i double checked that the valves wern't hitting pistons, they wern't. So i only have 2 other feasible options. either;

1. Iv'e tightened the con-rod bolts to tight, but this cant be because iv'e spun the engine before hand.

2. The head hasn't been machined to fit the new 87mm CP pistons, which is causing a sort of lip between the block and the head, so the piston cannot move.

Does anyone have any helpful ideas, i need a solution urgently, as this is for my year 12 automotive HSC and i need the engine complete ASAP! :(

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yes cams are in the motor, i made sure valves aren't touching by checking which pistons are at the top, and then checked where the lobes are on the cams to make sure none of the valves were pushed down, i have CYL 1 at BTDC and the cams at 15 degree mark where they are mean't to be, and their is no timing belt

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If there is no cam belt, then the cams won't turn with the crank, and you will end up with valves still protruding into piston space.

What does "CYL 1 at BTDC" mean? Do you mean TDC? (B = Before)

How does the RB26 rod compare in length to RB25 rods? Maybe the RB26 rods are too long, and are trying to push the piston crown into the combustion chamber.

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thanks for that info mad082, really appreciate, im thinking of taking the head off instead of the cams, as its alot easier, BTDC, it just before top dead centre, where i its mean't to sit, or its top dead centre. im still learning mechanics, so bear with me please! :) the engine has no movement Clockwise OR Anti-Clockwise, like the pistons are superglued to the cylinder wall lol...

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yes, but if you just take out the cams you can confirm it is pistons touching valves which is the most likely. Just undo the cam bolts slowly, start at the middle and undo a turn or 2 at a time on each bolt.

also, are the spark plugs in? if so when you try and turn the balancer it is producing compression which can make it harder than you expect to turn the motor. But either way I would not turn it far before putting the timing belt on.

You mentioned #1 is at TDC which is correct. The pin in the cams should point at the marking on the backing plate, or about 280o on lnlet and 70o on exhaust.

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But if it was the valves hitting, i would atleast be able to move it the other way, like clockwise would make piston go up a little more and hit valve, but if i go anti-clockwise, it would just go back down not going near the valves, and no their is no sparkplugs. thanks alot for the info :)

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But if it was the valves hitting, i would atleast be able to move it the other way, like clockwise would make piston go up a little more and hit valve, but if i go anti-clockwise, it would just go back down not going near the valves, and no their is no sparkplugs. thanks alot for the info :)

not really. you have pistons going up and pistons going down at the same time. so the valves may be hitting 2 pistons stopping you from turning it either way.

but regardless, you shouldn't be trying to spin the engine without the cams turning as well otherwise you run the risk of damaging both pistons and valves

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hey again, got some new updates; i took the head off today and it wasnt the problem, the engine is still locked in place, so me and the teacher tomorow are going to turn the engine over and have a look at the bottom end to see anything wrong,if their is nothing wrong their we are going to take off the oil pump, is it possible for the oil pump to cease up?

i would appreciate any information you would give,thanks

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problem solved!!! ---> the oil pump has seized up somehow when i put it on the crank. the engine now turns again! just recieved some new parts aswell, timing belt, gaskets, and new gauges ;)

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yeah i took apart the oil pump,the bolts were TIGHT AS :down: it fell apart in the 3 pieces but it's stuffed, it doesnt turn at all, so im going to buy a brand new oil pump or good 2nd hand one. It was the same one as i took off when i was rebuilding it...oh well, atleast we found the problem,and it was nothing serious like pistons hitting valves etc.

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