The project plan includes a few things that may require the added strength of either an aftermarket rod, or a forged 951 rod. This could be more than required, but its for a long term use issue:

The block will be sleeved to 106 (and a possible deck plate)

JE pistons will be fitted at 9:1 or a bit less on compression

85-86 cams are being purchased so that the rpm range will be a bit higher possibly.

Higher tension springs will be fitted to the heads so that I don't have to worry about hitting 7k once in a while on shifts (whether or not there will be power there remains to be seen)

Crank will remain stock, but will be drilled for oil path improvement

A DTA efi system will be tuned to get the most from the engine, and I can set the rev limiter to as low or as high as I can find power.

Eventually, A SC kit (ala Murph) will be fitted, thereby increasing the 5.6L engine output from somewhere around 370 to ~700crank HP. UP to 18psi may be used to find out quickly I can get from 30-130.

Sounds crazy? Yep. I got all the time in the world, and everything is apart, so I need to do this now. I think not updating the rods would be a mistake, though what sort of upgrade is needed is another issue. At that HP level, we are only at 350crank if you devide by half (ala951), and they don't break rods until there is an oiling issue. They routinily use the stock 86 forged rods past 400 REAR WHEEL hp with no issues (in a straight line)

 

I think Sterling Gee is using Ferarra? rods. They look very substantial.

 

Brendan,

With those plans and that kind of money outlay, it just seems a false economy not to call up a few rod manufacturers and get quotes on custom rods. Especially considering the forced induction. I've heard good things about Eagle Rods.

 

Its not as much money as you may think. You just have to find items at good prices for the value at certain times.

I may have found some forged 944 rods (both the 83NA and 86 turbos had forged), and I would think that those would be a good solution.

The pauter company is down south of here just 45min., and thiers are 1800 for a set for the 928 standard lenth, etc. I would assume that cunningham and carillo would be more. Well see. I may just bite the bullet.

Is there any way to test a used rod to see if its up to snuff?

 

Magnaflux might be okay to check for cracks/etc.

 

I was thinking of that word but couldn't come up with it.

 

Brendan,

You are quite correct about the strength of the forged 944 rods.

Rods are kinda like religion - what's "best" depends on who you talk to.

The are many "good" manufacturer's out there. Many folks in the business of building "serious" race motors will list Pauter, Carillo, and Arrow if forced to pick a short list of the "better" stuff.

This does not mean that other stuff won't work, just those companies all have darn good overall reps and have product that many in the game would recommend.

Some of the properties are application specific, some aren't. Then there's the H-Beam v. I-Beam debate - the destructive testing results seem to run counter to alot of the marketing hype out there.

Pauter makes a nice 951 rod at a decent price point, but keep doing your homework, find the solution that works for you.

Greg

 

Brendan,

I know you are considering 944 rods at the moment, but going back to a comment you made about Chevy rods, and it being possible to accecpt a shorter rod... While it may be true that you can accept the shorter rod by moving the pin on the piston, this is not a good idea.

Shortening the rod length will alter the rod angle when the crank throw is perpendicular the cylinder centerline. The flatter angle will increase cylinder side load, which will wear the cylinder wall and the piston in an oblong manner. Additionally, the piston is more likely to oscillate or shudder as passes the middle range of it's stroke.

Longer is better... but of course, you don't want the piston pin to end-up in the ring lands, lol.

Anyway, just thought I would throw that out there.

Regards,
Abdul

 

Abdul , Brendan is running a stock crank 78.9 mm stroke. The typical stroker 928 crank is a 95.25 or 16.35 mm more for 8.175 mm more side movement when the piston is half way down , in addition most strokers end up with about a 5.85 inch rod instead of the nearly six inch stock rod . The stroker engines I have seen have worked O K with that additional side loading .

 

Abdul
As Jim says,it does not seem to be a problem, there must be 1000's if not 10's of thousands of US domestic V8's hot rodded this way(longer stroke = lower rod ratio). The manufacturers do it them selves, 327 to 350 to 400, 427 to 454, if you work out the rod ratios the 928 comes out well at 1.89, ideal is 1.80 to 1.85. The small block Chevy 350 comes out at a lot worse at 1.64 in stock form & at 1.72 with longer racing rods

 

Jim

At 5.85" are the strokers using modified +150" SB Chevy rods ?

 

the stroker cranks have the big end rod journal made standard small block chevy size , drilled like a chevy and use chevy bearings . The chevy rod small end wrist pin is almost the same size as the Porsche pin and are easily modified . That allow you to use a fairly normal chevy rod .

 

Jim
The journal size was the only problem I could think as far as modifing a SB rod to fit, of course with a new (stroker) you can have it any size you want ! 2.10" or 2.20" ?

Some Chevy race engines use a Honda ? 2.00" journal, too small? Drag racing only ?

BTW, the Chevy LS-1 engine uses pins of 0.945", exactly the same as 928

 

One of many passing thoughts has been to offset grind a stock 928 crank using the small honda size 2 inch which moves the centerline by 1/2 of the difference in journal size ..........thus increasing the stroke but by the time $$ you spend doing that you might as well call Moldex and have a custom crank made .

 

So the LS-1 has the same pin dia. but what about rod width? I think changing this may be an issue, as the machining costs could go to close what it would cost for a set of forged aftermarket rods.