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914World.com _ 914World Garage _ Engine Question

Posted by: V6914 Oct 20 2005, 11:32 AM

Anyone, knows of the top of there heads, the min side clearance of a 2.0 rod?

Thanks

Posted by: Dr. Roger Oct 20 2005, 11:43 AM

Very small.

Posted by: ArtechnikA Oct 20 2005, 11:48 AM

minimum clearance ? interesting; both the rod big end and the crankshaft wear to create larger clearances...

The Spec Book (FWIW) says this about connecting rods: axial play (mm) 0,10 - 0,40 nominal new; 0,70 wear limit.

Posted by: Jake Raby Oct 20 2005, 12:09 PM

My spec is a min of .015.. Max of .021

Your cam and lifters will love you for it...

Posted by: ArtechnikA Oct 20 2005, 12:16 PM

QUOTE (Jake Raby @ Oct 20 2005, 02:09 PM)
My spec is a min of .015.. Max of .021

that's inches, yes?

0.015" ~= 0,4 mm
0.021" ~= 0,5 mm

so that's not *too* far off the Spec Book numbers...

Posted by: V6914 Oct 20 2005, 01:11 PM

Thanks for the info guys.

The reason I ask, I just found a set of rods for my 82mm 2.0 jrl crank, there Toyota Supra Turbo rods, this is the 2nd set I've picked up, the first set were from 86 -92 Supra Turbo, the problem with these, there alot of trouble cause there way long, 5.980 and after resized there still 5.935.

This 2nd set is from 93-98 Supra Turbo, there 5.590 long, and after resizing 5.545, and what makes these rods so cool, not only is the rod length, well with in a trouble free install, but the width of the big end is (2.020") .010" wider than a stock 2.0 rod (2.010"), and should drop right in with out any further expense.

And the Bonus feature, an expense I would of had to pay on any other rod that I had decided to use, the the cap and rod already have alignment pins, not the alignment sleaves like Scat or Carrillo use.

I'll post pics tonight.

Posted by: Dr. Roger Oct 20 2005, 01:20 PM

As I understand it, excessive side clearances will allow too much oil to get by and decrease oil pressure to critical components.

Too little clearance and you won't be able to turn over your engine and if you can barely turn it over it will create excessive heat. Right on the money is where I try to get this clearance.

My engine rods and crank came from different sources also and required machining to get it just right.

Jake knows best.

Best of luck to you.
Roger

Posted by: Jake Raby Oct 20 2005, 02:39 PM

Too little of clearance also leads to excess oil temps and premature rod bearing wear, especially if your end play is a tad loose- the crank moves fore and aft as you push on the clutch and as the engine accelerates and decelerates and really works on things.

>018 is my sweet spot,

Posted by: type47 Oct 20 2005, 03:12 PM

hmmmm, education needed. jake, how could rod clearance affect camshaft and lifter performance? seems to me, they are not connected. respectfully asking for an explanation/description.

Posted by: Jake Raby Oct 20 2005, 05:34 PM

Easy.. Look at the position of the cam lobes in comparison to the crankshaft rod journals.... Each cam lobe has a rod journal directly over it and as centrifugal force sheds oil past the rod bearings a huge portion of it is tosssed right on top of the lobes/lifters.... I have tested this theory in my spin device I built just for cam/lifter trial and error testing.. It absolutely makes an impact. Here is my tool used for proving the fact.
user posted image

http://www.aircooledtechnology.com/lifters.htm
Its all in the combo!

Posted by: V6914 Oct 20 2005, 11:25 PM

Here's a pic of the 93 - 98 Turbo rod.

Attached image(s)

Posted by: V6914 Oct 21 2005, 01:04 AM

QUOTE (V6914 @ Oct 20 2005, 09:25 PM)
Here's a pic of the 93 - 98 Turbo rod.

Another

I'll, post pic's of the finished product , when finished

Attached image(s)

Posted by: DNHunt Oct 21 2005, 06:51 AM

You did mention an 82 mm crank, right? Are those rod bolts gonna clear? I know the rods for my 78 mm crank have metal removed there. I would sure like to be at your place when you mock it up. Don't get me wrong i hope it goes but I have concerns with them collideing with the cam and the webbing on the top of the case.

Dave

Posted by: ArtechnikA Oct 21 2005, 07:05 AM

QUOTE (DNHunt @ Oct 21 2005, 08:51 AM)
You did mention an 82 mm crank, right? Are those rod bolts gonna clear?

and by placing them on the bottom, you have an engine that must have the case split to replace rod bearings. for an engine that's designed to come apart frequently (race engine) that may be an okay tradeoff. i like the idea of being able to pull a rod with the case together to inspect or replace the rod bearings whenever the cylinders are off.

just another tradeoff an engine builder must face...