Don Terrill’s Speed-Talk

I had a Scat 3.75 x 5.7 assembly that hit the cam with a .375 lobe. The skirts hit the crank too

Call up Eagle tech support. They'd have a better idea about any limitations to your idea.

With the low cost of a Scat 4340 I beam being only $260.00 it is not worth trying to upgrade a stock rod.

http://www.jegs.com/i/Scat/942/36000/10 ... tId=761555

I think it all depends on how you feel about buying new pistons.

firebuick wrote:thank you for reply i plan on using a eagle rod also and a eagle 3.75 crank internaly balance

my cam is a old comp cam 294s 248/248 at .050 525/525 lift whit 1.6 roller

my piston are flat top forge srp 40 over

head are edelbrock performer rpm 185 cc whit 70 cc chamber

this is mainly for the street whit a few 1/8 miles drag

yes i plan on balancing rotating

Internal balance with a 5.565 rod,,,,
Good luck with that

Mike,

Please elaborate more here about internally balancing a 400 short-rod engine.

Thanks,

pdq67

pdq67 wrote:Mike,

Please elaborate more here about internally balancing a 400 short-rod engine.

Thanks,

pdq67

Pretty simple really
How many stock 400's do your see that are internally balanced?
There is a reason GM hung all that weight on the damper & flywheel same as a 454,
Not enough room for a counterweight without the piston hitting it,,
Unless you want to spend a fortune on Tungsten of course,,

Thanks for the come back.

In other words, you don't have to cam-cut the counter-weights for piston shirt clearance.

Just the added expense of installing enough heavi-metal to internally balance it.

pdq67

Stay away from that eagle crap. Hard and costly to balance.
Go with the scat stuff and use the 6" rod combo because you can internal balance them easy with most pistons.

The 5.7 rod crank is more costly to balance with lighter pistons.
You can also get a " No Holes Balance" direct from scat with a complete rotating assembly at a very reasonable extra charge but the piston choice is what determines the balancing cost. Ligher pistons available today make some cranks harder to balance and there fore more costly as they were designed for a 1850ish Gram bob weight, When you get to 1700 or less most times metal has to be added which costs more money.
As for the power difference unless you dyno the engine back to back with the different rod lengths you would not see much seat of the pants difference but it will last longer and make more on top with the longer rod as long as you have decent heads to feed the engine,
JMO

ProPower engines wrote: Lighter pistons available today make some cranks harder to balance and there fore more costly as they were designed for a 1850ish Gram bob weight, When you get to 1700 or less most times metal has to be added which costs more money.
JMO

You have that backwards. A lighter bobweight will need the counterweights cut or drilled. A heavier bobweight might require heavy metal/tungsten.

And although I prefer Scat as well, the Eagle stuff has gotten much better. I've used a bunch of their Olds H-beams lately with no issues.

ProPower engines wrote:Stay away from that eagle crap. Hard and costly to balance.
Go with the scat stuff and use the 6" rod combo because you can internal balance them easy with most pistons.

Eagle cranks might be wacky in some ways but I've found that their stuff is usually very easy to balance, Scat is generally harder or at least more unpredictable.



http://www.the351cforum.com/viewtopic.php?f=9&t=203

6sally6 wrote:Is there a "Chevy-type"(non custom made) rod that's a little shorter than 6" but longer thanstd 350 rod?
6sally6

5.850 SBC rods are as common as dirt.

I did almost the same thing many years ago (1978). 377 (400 block, 350 crank and rods ) broke crank, changed to 400 crank and 5.565 chevy rods with good bolts. Shift point dropped from 7500 to 7000 but no clearance issues with standard base circle cam (Comp Cam.650 lift, 280 @ .050) or pistons (BRC). The car was much quicker with the increased torque. Had to change from 6.50 to 5.86 rear to use it. I never had any problems with rotating assembly even though it was externally balanced. I have ran several externally balanced engines over the years with no issues at all.

Is there a stock engine that uses 5.85 rods?

there are a lot more piston choices at reasonable prices for 5.7 or 6" rods
Think ahead