Connecting Rod and Piston questions

[KC Kirk]

8,000 miles and many years after an engine rebuild, my 87 Supra Turbo began to spew a large cloud of oil smoke out of the exhaust pipe and oil is found in pools throughout the intake system. The short-block (block, crank, pistons, rings, bearings) was done by a machine shop that was recommended to me by a local Toyota dealership. This machine shop is no longer in business.


I pulled the motor, stripped it down and noticed that the connecting rods were installed backwards (mark pointed to the rear), pistons were correctly oriented (mark points to the front).


Questions:
1) Would backward (stock) connecting rods cause the piston rings to improperly seat and produce blow-by?
2) Would a light-weight flywheel cause the same blow-by problem? (Fidanza, 11 pounds)
3) Both?



I also noticed a hole drilled into each connecting rod at the 11:30 position (345 degrees) when viewed from the front, proper orientation, which allows oil to spray upwards when this hole aligns with the crankshaft's oil holes. These holes seem to duplicate the function of the oil nozzles pointed to spray up the cylinder walls.


Questions:
1) Anyone else have these same oiling holes in their connecting rods or was this unique to my '87 Turbo ?
2) Do upgraded/racing connecting rods have these same holes?




In this rebuild, I am targeting 400 rwhp, or about 500 hp at the crankshaft (assuming about 80 hp loss from the crank to the rear wheels).


Questions:
1) Stock Pistons? If not, what do you recommend?
2) Stock Connecting Rods? If not, what do you recommend?



Thank you for your learned advice.

 

[quake]

flywheel has nothig to do with it you would have been better off to perform a leak down test and compression test before tear down. As for the rods i would install arp studs and have them checked and resized. I would get forged pistons with the smallest over bore you can get away with

 

[Motofool]

stock pistons and stock rods will withstand your power goals,

i would recommend arp rod bolts at the very least. and have your rod end's decked and recentered with new wrist pin bushings and have the main bores line bored and honed, also a polish on the crank if needed

if money is not a problem eagles and some forged pistons are never a bad idea, these should withstand upwards to 800horse though.


having a machine shop check end gap on rings would help alot with blowby.

having new hardware in the head would also prevent this issue in the future, maybe some stainless valves with new seals and a nice high quality valve grind.

 

[IJ.]

Squirters spray under the piston domes

Rod holes spray the thrust surface of the bore (and provide a fail point)

 

[Motofool]

oil in the intake systems sounds like you should inspect your turbo see how its doing

oil can get into your intake from the turbo seals or the pcv system other then that i cant think of any good areas that would produce enough to pool in your intake system.

 

[KC Kirk]

All:
Thank you for your responces. Any opinions on backwards connecting rods?

IJ., Grumpy Old Man:
Since the rods were in backwards, the rod-holes were spraying oil on the opposite side of the cylinder walls than was designed. Potential problem? Opinion?

Motofool:
The turbo was also rebuilt and still feels solid, no obvious leaks. I think the oil is from the pcv system being overloaded by excessive blow-by. I like your advice on pistons, rods and new hardware for the Head, thank you.