rodknock rebuild... rod advice?

[MmmBoost]

been driving with rodknock for a while now... and within 1 month im gonna pull the engine and rebuild the bottom end.

i cant find anywhere in the tsrm that says to check the connecting rod big end for roundness, but i remember seeing it somewhere. anyone?

what im planning on doing is buying an already cut crank with main and rod bearings and replacing that with all seals, and new oil pump. ive already had the motor out once to do this because of knock, but even though the bearings were shot, the crank still looked good and measured up within specs according to the tsrm. plastigauge was also good.

so, what should i do? should i look for a good set of used rods? i know that they are the same for na and turbo, so i should be able to come by at least 6 good ones. if i do have to do this, im gonna put in new pistons with rings and pins along with the new rods. but if i dont have to break the seal between my block and head id be happier. it just got a mhg 2000 miles ago, and im nervous about it re-sealing...

rodknock is the only thing left to this thing that i havent completely fixed yet, and i just want to do it once. thanks in advance for advice or experiences

your turn:

 

[suprarich]

You do realize that driving around with a rod knock is driving metal contaminated oil everywhere oil flows, including your top end and cams. Don't be surpized to find some nice score marks on the cams, and signs of metal impregnation or galling on the cam journals. You should take the head off and have it tanked or you could be sending some metal right back to your new crank, rods, and pistons.

 

[staticpat]

You do realize that driving around with a rod knock is driving metal contaminated oil everywhere oil flows, including your top end and cams.

Don't forget the turbo feed lines. Metal bits will eat up your bearings bad.

 

[MmmBoost]

at this point i have no other choice... the cams are already scored, and turbo will be getting replaced soon too.

 

[7Mboost]

Hm by a months time you will need new jdm 7m. I drove my Corolla I got for free for about 2 weeks like maybe 10 minutes a day and it got worse very fast...finally threw rod threw the block while trying to obtain 8500rpm:biglaugh:

 

[MmmBoost]

ive been driving it like this for almost 4 months now...
also my other car (buick 3.8L) drove for 3 years with a rod knock. we finally got rid of it cuz the tranny took a shit.

also, i dont know why i would need a JDM motor???

anybody got any ideas about connecting rod roundness??? i know ive seen it in writing before, i just cant find it!!!

 

[jdub]

You will need to take the rods to a machinist to get them re-sized. Get them matched to the crank so you can use a standard size or over size bearing.

 

[MmmBoost]

im probably just gonna buy new(ish) ones...

 

[jdub]

If you want to do it right...used rods should be re-sized

 

[johnathan1]

LOL...it says "MK3 Drifter" I wonder if that correlates at all to your rod knock? :biglaugh:

 

[MmmBoost]

no... actually, thats more of a recent thing... the rod knock started after a bhg....

jdub, so by having the rods resized, do they weld in extra material and then re cut the to standard size? or do the cut them oversize? i will already be using undersize bearings for the new crank, but will i need to find bearings that are under and oversized?

btw, thanks for the reply!

 

[starscream5000]

Hm by a months time you will need new jdm 7m. I drove my Corolla I got for free for about 2 weeks like maybe 10 minutes a day and it got worse very fast...finally threw rod threw the block while trying to obtain 8500rpm:biglaugh:

What's the deal with this whole "buy a JDM engine" thing? You don't know what you're getting, just because the compression is okay on a JDM engine doesn't mean it will run good. Save your money and just rebuild your old engine, or if too much material has been removed from the head and block already, find another 7M around to redo. Buying a JDM engine is a big waste of money that could be saved and spent on other things for the supra... :3d_frown:

 

[jdub]

The rod is taken apart and has a very small amount of material milled off where the cap mates with the rod. The cap is re-installed and it is then "bored" to OEM spec or to match your crank if it has been turned and micro polished....this allows the use of a stand size bearing vs. an oversize. ARP bolts (torqued to spec) are a very good idea for the rods...they will need to be used when the rods are re-sized. If you really want to do it right, balance (with the pistons) and shot preened as well.

 

[starscream5000]

Heh, you just covered this in another thread .

 

[MmmBoost]

thanks jdub!