TheSamba.com :: View topic - 1200cc 40 hp connecting rod installation problem??

Wed Apr 16, 2014 7:07 pm

Hi,

Still with question about 1200cc 40hp engine,apreciate your advices.

Now with rods problem.......These old rods use bolts and aparently the offset not well between both sides of the rod (cap), to install new bearings do not soft move like a 1300-1600cc rods, which is the way to center them and achieve soft move?

Regards.

Wed Apr 16, 2014 7:30 pm

You tap on them with a small hammer as you torque the bolts.

And if you have forge marks on the rods, they are offset - always install those with the forge mark facing upwards.

-Andy

Wed Apr 16, 2014 7:40 pm

glutamodo wrote: You tap on them with a small hammer as you torque the bolts.

And if you have forge marks on the rods, they are offset - always install those with the forge mark facing upwards.

-Andy

ok, but "You tap on them with a small hammer": to the side rod cap (numbers) or bolts head or down the caps?

Thank you

Wed Apr 16, 2014 7:45 pm

I'd say, all of the above if you have binding. You might want to torque in a couple of steps and check for binding, and tap-tap, as you go.

Wed Apr 16, 2014 7:49 pm

glutamodo wrote: I'd say, all of the above if you have binding. You might want to torque in a couple of steps and check for binding, and tap-tap, as you go.

Perfect, apreciate your help, thank you glutamodo.

Thu Apr 17, 2014 6:25 pm

Did you measure?

Thu Apr 17, 2014 6:37 pm

drscope wrote: Did you measure?

After many hammer/torque attempts and work keep the same problem, crank and bearing measures are fine, but aparently my rods not round, check O.D. each and have different measures: 57,75mm and 57,85mm, aparently re sized work is necessary...not think it is so difficult to align to work well, surely there is a problem!!

Fri Apr 18, 2014 11:30 pm

Here's a god simple way to check the clearances. Plastigage. Commonly found at auto parts stores up here. http://www.plastigaugeusa.com/how.html

Sat Apr 19, 2014 6:43 am

mrbigmax wrote: Here's a god simple way to check the clearances. Plastigage. Commonly found at auto parts stores up here. http://www.plastigaugeusa.com/how.html

Thanks, but "not round" is a real problem, all rods tight after many different alignment trials, maybe they run "not alignment" in the past....the ideal O.D. round measure is 2.2755" (57,80mm).
Regards

Wed Apr 23, 2014 4:27 am

Finally, before resized work, machinist could rods alignment work well, and they were all good round to 2.2767"(+/-0.0001), only was necessary to slightly soften new bearings, the process was done with polishing paste (valve seats) in a tool crankshaft type (of the corresponding measure) turning the each rod with bearings installed softly (full bolts torque) being spent only small points that pressed the movement. Now all rods down softly by gravity, clearance aprox 0.003" between OD rods (with bearings) and crankshaft.

Regards.

Wed Apr 23, 2014 6:59 am

I'm not sure we're understanding each other. You can't put valve grinding compound on bearings - it will imbed in the bearing and grind down the crank journal.

Wed Apr 23, 2014 9:52 am

Dr OnHolliday wrote: I'm not sure we're understanding each other. You can't put valve grinding compound on bearings - it will imbed in the bearing and grind down the crank journal.

ok, an old journal crankshaft was used, very slightly fine compound grinding was use, after a few rod turning to loosen, polished and wash new bearings.

Wed Apr 23, 2014 6:25 pm

(using my best Chris Rock voice) "Nah - I wouldn't do that shit, man!"

Really, insert bearings are soft / abrasive powders are hard. Hard abrasive particles get stuck / imbeded into soft bearings. Result is trashed crank and engine.

I have never heard / read about such an approach in 49 years of reading hot rod or other car and motorcycle enthusiast magazines and books, or in auto shop class.

You are on the wrong path here, amigo.

Thu Apr 24, 2014 5:07 am

Dr OnHolliday wrote: (using my best Chris Rock voice) "Nah - I wouldn't do that shit, man!"

Really, insert bearings are soft / abrasive powders are hard. Hard abrasive particles get stuck / imbeded into soft bearings. Result is trashed crank and engine.

I have never heard / read about such an approach in 49 years of reading hot rod or other car and motorcycle enthusiast magazines and books, or in auto shop class.

You are on the wrong path here, amigo.

Apreciate your observation...... maybe the machinist use a special compound, after your post re-checked again the bearings and they are "really soft", like a new bearings, compound work only in small sectors....