View Full Version : Engine build questions
So having finally got all the parts toghether to re-build my engine I have come accross my first issue:crap:
The crank went in fine, nice and free moving, the first piston and rod also went in well with a few mm of side to side movement once the cap was tourqed up, then the issues start:disagree:
the other three pistons and rods no matter what I do seem to be pinching the crank journals, I can't get any side to side movement once the caps are tightened:confused: they have all be back out at least three times and checked and are SUPER clean no grit/dirt, the caps are the coprrect way round with the bearings notch to notch and facing the back of the block. Been banging my head against a brick wall for the last 4 hours!:crap:
Plenty of oil/lube has been used also.
Any ideas?
New poster! (less than 10 posts)
...the caps are the correct way round with the bearings notch to notch...
But are the caps on the correct rods??
Yes, I made sure of that also:agree:
rs250nut
06-03-2011, 19:36
Did you number the rods so they go back on the right journal?
The crank jounals have been re-ground and i'm using new bearings, the pistons and rods have been put back in the same place.
Adam 005
06-03-2011, 19:42
The crank jounals have been re-ground and i'm using new bearings, the pistons and rods have been put back in the same place.
are all the bearings the same size
If your 100% sure on the rod and caps then you may have the wrong size bearings or the crank journals are out of shape. Has the crank been ground at all and was the engine a runner before it was stripped?
Also, are the pistons ok and moving freely at the small end?
All the bearings looked to be the same all stamped 0.25, the crank has been to an engineers shop where the mains had to be re-ground but the big ends were, fine he said, they also supplied the bearings.
:edit: the engine was running before it was stripped down, just a blown HG.
The small end of the rod seems to be moving freely on the pistions.
Personally I'd want to eliminate a suspect grind or moody bearings 1st. Take the crank out the block, attach each rod and see if they rotate freely on the journals.
If all is good there then next thing to look at is pistons, liners and rings. Are these all new too?
...the crank has been to an engineers shop where the mains had to be re-ground but the big ends were, fine he said...
I'd push them for a gratis set of bearings + grind on the big end journals if it does turn out they are the problem..
The only parts i am re-using are the pistons rods and caps, everything else has been replaced. Two of the rod/pistons i'm using were not from this engine but they had been clearly marked to match rod to cap.
To confirm my insanity i have just put cap number two onto rod number three and i know have a few mm of side to side movment once the cap was tightened??? Maybe the rods/caps were mixed up by the person i bought them off?
youngscottie
06-03-2011, 20:34
out of intrest are the pistons new on the rods
first time i got pistons put on rods the guy bent a conrod ever so slightly
when i torqued up the cap it locked the engine solid
done them myself since
just a thought
The only parts i am re-using are the pistons rods and caps, everything else has been replaced. Two of the rod/pistons i'm using were not from this engine but they had been clearly marked to match rod to cap.
To confirm my insanity i have just put cap number two onto rod number three and i know have a few mm of side to side movment once the cap was tightened??? Maybe the rods/caps were mixed up by the person i bought them off?
Possible. Do the machineing marks on the caps match the rods? Are you sure of the condition of the 2nd hand parts and if they came from a running engine?
Why the change of rods in the 1st place?
On further investigation, it now appears that both the rods/pistons from the engine before it was stripped are now not nipping the crank and turning freely:), however, the rods pistons that I bought second hand will not turn freely unless I swap the caps over, and on further inspection the the marks on the caps are actually on differnant sides.
They have been marked with a punch rod/cap number two have been marked opposite the notches and rod/cap three have been marked on the same side as the notches. Seems that they must have been mixed up before they were marked by the person who removed them from the engine they were in last.
I have also put one of my old pistons into the place where the above two rods have been and they tighten up and do not appear to pinch the crank.:crap:
it's the two rods and pistons I have changed, long story, to cut short one of my pistons had a few chunks missing from it near the piston ring area and the other was a flat topped one instead of the dished ones that were in place. and was ever so slightly higher compression.
The pistons and rods I bought came out of and engine that had spun a shell:crap: probably because the caps had been mixed up;)
youngscottie
06-03-2011, 21:27
dont know what your plans are but id get some plastigauge
for peice of mind
Sounds like you have nice miss-mash of parts there mate!
I was actually trying to save a few quid, as with most things looks like it was a false economy. Going to have to bite the bullet and get a new set of pistons and have them put onto my rods that have matching caps ect
I'm pretty sure the crank is good as the old rod's pistons tighen up without pinching the crank so that pretty much rules that out.
I just want to get the thing built and running! Seems to be taking an age:cry:
Adam 005
07-03-2011, 19:54
There is no need to waste money when building an engine. But there is a need to spend good money on new internal components which is must when building a new engine.:)
Well, i bit the bullet in the end and purchased a piston and liner kit and had them put on to the original rods that came out of the engine, (well apart from the one the engineers shop bent). Just in the process of building it all up.
I have come across something that i think is not quite right and i'm sure the engine builders amongst you will be able to tell me if i'm worried about something or nothing.
Baisically to cut a long story short, i have fitted the my new cam and it rotates nice and smooth untill i thighten up the retaining bolts on the end of the camshaft. It will rotate after this but it feels a lot tighter, (more effort to turn the camshaft) is this normal?
Ahhh BOLLOCKS! I have just snapped one of the bolts in the block! Wasn't even giving it the beans................royally miffed now! Hopefully i will be able to drill and tap it, can't be arsed with it tonignt now. :(
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