New Bottom End

[peter 20]

Is there an engine building gude somware?

 

Ive just rebuilt the bottom end on my 2.0 turbo with new big ends,mains and a good crank.

 

I put the mains in all oiled up then the crank, everything turned over smoothly.

 

Then the new big end bearings went in, and torqued down, this consequently stops the engine from being turned over by hand!

 

what have i done wrong? could the conrods be warped somehow?

 

Realy need some help as you can imagen how sick i feel after replacing the said bits with the engine in the car!!

 

 

Thanks!!

[Miles 331 1 Cars]

Sounds like the wrong size bearings, did you check the big end size?

[Anthony 1,003]

It will be much stiffer to turn over even if you've got it right, as you're now pistons up and down the bore as well (especially at the top and bottom of the stroke). It should turn with a bit of effort by hand turning the flywheel, but will be much harder to turn than when it was just the crank spinning on the mains with no rods/pistons to move.

 

You did get the big end bearing caps round the right way, didn't you? The notches should both face each other. Obviously each cap is matched to each rod, so don't mix them up! Mistakes here will certainly make the engine very hard to turn over, and will knacker the shell and crank if you were to try running it.

[peter 20]

they are the correct size fortunatly, as when i torqued the first one down it still turned over fine but if any of the rest are, it becomes very stiff.

 

Could the conrods have become mis-shaped due to the heat from when the bottom end when it failed previosly?

 

Or could i have somehow put them in wrong?! as the shells that sit in the conrods didn't quite sit flush?

[peter 20]

OH!! the notches should face each other.....

 

ill go turn them round, hope the shells are ok

[peter 20]

Just turned the bearing caps round and what a difference that has made, turns over quite freely apart from one bearing is very slightly scored, remarkably the others look like thay haven't been touched.

 

however when this said cap is torqued it becomes noticably stiffer to turn over compared to the others.

 

will i need a new shell for that particular one?

[Miles 331 1 Cars]

'heat from when the bottom end when it failed previosly' I guess the engine had the death rattle then which if so then the rod could well be out of round and I would not use it without checking it first

[BusEngineer 7]

I had an Mi16 rebuilt that had a spun shell on number 3 rod, when the rods were checked number 3 rod was oval but more worryingly so was number 2, as the crank had bent slightly, two replacement rods and a crank later all was well . . . . . apart from my wallet!!

What was the reason for the rebuild??

Edited November 5, 2010 by BusEngineer

[peter 20]

well probably worse actually it sized, i managed to free it off then started it and immediatly switched it off as there was the big end knock. The odd thing is it never missed a beat until it siezed, there was no knocking sound at all.

 

So the crank came out and into the bin, Luckily no shells had spun at all so they were all replaced.

 

Even though i know the answer to this question, is there some possible way to remove the conrod without taking the head off? if only...

 

I could try a different bearing cap in the hope that is whats distrorted and the conrod itself is somehow ok.

 

I realy should have fully rebuilt this engine before putting it in the car, after ive just replaced head gasket water pump turbo, and now the bottom end! What else could go wrong?!

[Tom Fenton 1,548]

I could try a different bearing cap

 

No you can not do this as the cap is matched to the rod and line bored. Swap a cap and it will make it worse.

 

Plastigauge is what you need, google it.

[peter 20]

that will only show that there isnt any clearance as its niping the shell.

[peter 20]

Right, ive found the cause. The no.2 conrod has deformed so the shell wont sit flush. So head off and change the conrod!

 

Does anyone know the compatability of the older xm 2.0 turbo and the newer 406?

 

Iknow the pistons are different but will the xm conrod fit the 406 piston and crank??

 

As i can only get hold of xm conrods atm.

 

thanks

[peter 20]

Problem solved! new conrod and bearings and it turns over smoothly!! quite relived.

 

just for referance, the xm rods do work with the newer 406 pistons. (the length and pin size are the same)

 

ive swapped the 1.6 box for an mi16 one while i was on so hopefully the top speed should be more than 122 wich was the limiter in 5th.

 

Anyone know how much longer the mi16 one is, mph per 1000rpm?

 

thanks

[Anthony 1,003]

Mi16 'box is just shy of 20mph/1000rpm in 5th from memory.

[peter 20]

So its quite short then! That would be 125mph if the limiter was 6250 so the 1.9 box must be the longest as im sure that did 135.

 

I wunder if it would pul a turbo diesel box, If i think they are about 26.7 mph per 1000 as a 306 diesel does 80mph at 3000rpm giveing a theoretical top speed of 166mph

 

Realy could do with somthing in the middle!

[welshpug 1,666]

I think its 22 mph/1000 rpm, but worked out for the 195 55 tyres, so closer to the 20 that Anthony said.

 

 

Why are you bothered about its top speed though? unless you do a lot of motorway miles and 70 mph is right on boost.

[peter 20]

Well ive just taken it out for a very gentle run and all seems spot on so far!

 

As for why i want a longer gearbox, the 1.6 would cause it to be well into the limiter on most tracks. Which obviously isnt ideal for decent track times! Also its a road car where longer top gear is very usefull on motorways etc so you can cruise at a higher speed without it feeling like the engine is being strangled!

 

The mi16 ive just fitted doesnt feel much longer that the 1.6. so that will be coming off tomorrow for a 1.9 one

 

How about a diesel box with different final drive?