Rod knock problems

[john84]

Hi all, am looking for some advice about my 7m.

i recently started a project 7mgte, i bought a car with the head already remove as the owner was fixing the hg but didn't finish the job. the head had been skimmed already so i assembled it and put it back on with a metal hg and arp's.

once i got it going it turned out the was a very slight knock from the bottom end. i shrugged this off and decided i should pull the engine and sort the bottom end, with the engine out i removed the head and made a start on the block.

i had a good block from a supra which i had written off in the past, just to be safe i bought some new big end bearings standard size as i new the crank had never been ground. i realise now that was a mistake as there is more than one standard size.

anyway, i built the engine up and put it in the car and all was well.........until on one of the very first test runs the bottom hose clip broke and the hose came off blowing the hg due to overheating.

by this time i was getting pretty tired of taking it to bits, anyway, i sorted out the hg and changed the oil and filter etc.... and thats when i heard the dredded knock again. Now i'm not sure if it was water contamination or my error in buying "standard" bearings but either way i hold my hands up.

i pulled the engine and had the crank ground .25 and the bought the bearings to suit from the shop, re- fitted it all and thought all would be well.

with everything torqued up to spec the engine did feel a little tight to turn but it did turn.

i put the engine back in and all was well, i was so chuffed to finally have my car on the road again. i let the engine idle for quite a while before driving it at all and drove it very gently to run it in.

HOWEVER.....after about 250 miles i heard the knock again and my heart sank to my boots.

does anyone have any ideas before i throw myself off somthing tall?

Thanks, John.

 

[Mk3runner]

Get mains honed? Where's the bearing damage? Mains or rods. Was it to spec?

 

[lsaint07]

maybe this could be some motivation in a positive way.

http://www.supramania.com/forums/showthread.php?t=97477

I hope the link works

 

[CyFi6]

One thing you could do to avoid this again is start measuring your shit. If you dont have the tools to do it yourself have your machine shop blueprint everything and give YOU the numbers, then you figure out what you need to do. Just because you can turn the crank, or it feels right doesnt mean a damn thing. Chances are you have a rod out of round that keeps putting you back in the same position. Is it the same rod that keeps going?

 

[john84]

I've not looked to see where the latest damage has been. it's a good point that you make about maybe having a dodgy rod, but the setup on this block was fine until i swapped the shells with "standard" sized ones.

Ive had the mains done as well, i thought i might as well seeing it was going to the machine shop anyway, they took .25 off and supplyed all the bearings to suit.
i realise that being able to turn the motor doesnt mean the everything is right, but the point i was making was that it was a little harder to turn than i would have expected, mainly after putting tourque on the no:6 big end.

I will be curious to see if there is any damage to that one.

one thing i forgot to mention is that i fitted a new oil pump when i did the block the first time, i've had no oil pressure issues and ive not adjusted the boost.

Thanks, John.