MoMo's example is an old standard given in "Feet per Minute" If you really think about it the piston is motionless for a few degrees of crankshaft rotation. FPM average takes into account the tremendous loads placed on the piston starting and stopping.

I only run forged parts in anything that I build. I call my red line 7000 rpm. I have 355 ci. Even with all my careful assembly I would not attempt to enter a race that would require my motor to run anywhere near 4000 fpm for any extended period of time.

 

A friend of mine did the 396 stroker on his LT1 camaro. If you want to check out what he did and runs check out the link to his site.
http://personal.atl.bellsouth.net/ms...est/camaro.htm

Mark B.

 

do you know what he runs for a redline?

 

I reved my 396 sbc to 7200 when it was a solid roller. Now that I am back on hydraulic roller, I have shift points at 6300-6500 and rev limiter at 6700.

I run the Callies crank, Oliver rods, and J&E pistons. I have zero worries spinning it up.

 

Ya know what? I have to apologize. I came home from work, and my daughter was on the computer scanning photos half the evening and then I forgot!

I did check the formula on a 396 SBC with 3.875" crank, and it wasn't as bad as I thought. It was close to 6000 rpm at 4000 fpm. Actually, slightly over. However, at 3500 fpm, which would be for non-forged parts, rpm dropped down...I wish I could remember. I want to say 5600 rpm.

That could be old school. A lot of engine builders rely on much improved metallurgy for breaking through old limits. I'd still be concerned about it, however.

What my book says is 4000 fpm can be run reliably and continuously on an engine with forged rotating assembly and 4-bolt main. And you can pop up into the 5000+ fpm range for brief moments, but risk the engine coming apart for extended periods of time.

The rod/stroke ratio of a 396 with 3.875" crank and 5.7" rods is 1.47, which is really really bad. If you can increase it to 6 inch rods, that improves to 1.55, about the same as a 454 big block. In comparison, a 396 big block is 1.63, so those rev well. With such long stroke, 1.47 means that very little time is spent in dwell. Therefore, the change in piston speed is much more abrupt.

Why not find a 400 block and build a long-rod 406? You'll get the cubes and a 1.60 rod/stroke ratio too. You'll have your cake and eat it too. Plus, you'll spend a lot less on the engine.
Just a suggestion.

 

well, going with a 396 on a 350block will limit you to 5.85 rods or was it 5.875 I can't remeber but it's then with a 1.5 ratio. I don't want to do a 400 block because the additional block is a pretty big expense and having everything fit the stock stuff without modification makes things easier. It also is nice to keep the whole numbers matching thing for later on. Not to mention no one knows what's inside that stock block when they tell you to pop the hood before you race :D

 

Never say you limited to 5.85 or what ever. 6 or 6.125 would work fine with 3.875 and 4.00 strokers. JE might even have pistons for 6.250 rods. You just have to buy small base circle cams, stroker rods, and grind the bottom of the block pan rails for clearance. Last year I built two motors with 6 inch massive H beam steel bushed rods one was my driver 383 and the other was my racing 393 with 12.8 pistons

 

what kind of pistons do you have on your 3.875" crank? Are they a custom job or did a vendor have them?

 

Here are those formulas I promised.

Piston speed in fpm = stroke in inches x rpm / 6

rpm = piston speed in fpm x 6 / stroke in inches.

3500 fpm is supposed to be the reliable limit without forged parts, and 4000 fpm is supposed to be the reliable limit with forged parts.

 

If I am not mistaken he use to run the car up to 6500. One day he got on the car going up a bridge and blew the valve stems out of his tires. I thought that was hilarious.

Mark B. :cheers:

 

Atleast he found the "weak link" in his drive train, and it wan't his tranny :lol:

 

I don't think this question was directed at me, but my J&E pistons came directly from J&E and they were an item straight out of their master catalog of products. 3.875" crank stroke, 5.85" rods.

Chris

 

The question was directed at the 6" rod post above. But I have looked at those pistons and called JE and they told me that they only take a 200 HP Nitro shot. That probably should be enough, but my current setup will allow me to go to a 250 HP shot. And someday I'm hoping to get my supercharger so I'm not sure how it'll hold up to that.