Anyone out there running this combo with pistons in the 9.5 to 10.0 range? Can be forged or Hyper's. I have not been able to find a wide choice of pistons for a 4.28 bore, 3.76 stroke, and 6.385 rods. It would be for 781 open chamber oval ports for my nephew. I talked him into selling his Rect. heads, and I told him I will give to him a good set of bare 781 heads I had in the garage for about the last 10 years. Since his heads are bare also he would still have to have them gone over anyway. He understands now that for a mild 427 street motor and heavy car that this would be a better choice. I have really been only able to find 12 and 13 to 1 pistons. Thanks for any info. graemlins/beers.gif

Why not just use stock length rods. Hear longer is beter, but for his purpsoe he might not notice the difference. Piston selection for 6.135" isn't great.

you might check with REHER/MORRISON in the past they had a real wide selection of pistons for BBC,and either length connecting rod is a good choice. if you think in terms of rod ratio(length of rod divided by stroke) your only up to 1.7 with the +250, 1.6 with the 6.135.in trying to put that in perspective the 302 sbc had a rod ratio of 1.9, and that was a pretty respectable performing engine :cool:

Like Gene said, you are probably better off to stick with the 6.135" rods. Long rods are only beneficial in high RPM applications, with single plane manifold, adjustable headers and correct cam design. For this reason, you will have trouble finding shelf-stock pistons in the 10:1 compression range. If it were my engine, I would use stock length rods.

I have the same setup, stock length rods are the way to go. I have the rec port heads closed chambers. piston choice is limited. I use speed pro L 2300 which are about 9.8-1 for closed chamber heads casting 840's
car runs great on pump gas but lacks low end grunt imho. I only ran it once with an et of 13:30 at 103. poor 60 ft times though

Use a 6.635 rod and a more common 496(1.270ch) piston. This would give access to a more common compression height piston and increase the rod/stroke ratio to 1.765. If you ever decide to go 496 you have pistons, just need to switch the rods.
Caleb

Don't use a .400 long rod 3.76 stroke on the street you will not be happy. The motor looses most of its low and midrange torque but will flat fly above 7500rpm.

Originally posted by Mike Feudo:
Don't use a .400 long rod 3.76 stroke on the street you will not be happy. The motor looses most of its low and midrange torque but will flat fly above 7500rpm. Mike, my 3.600" stroke lil rat uses a 6.500" long rod...which does quite well in the torque department...it's a package of the right head intake runner volume, compression ratio, cam selection & timing events as well as torque converter/gear ratio that makes a package work (or not).

I'm certainly not saying I'd so such a long rod again, but your generalization was a bit off the mark.

I personally haven't seen any hard & fast data that shows longer or shorter rod lengths make any difference in power levels or power range (high or low). On Reher-Morrison's site there's an article on the subject where I believe they state that the rod's only job is to connect the crank to the piston and they feel length changes are of no real benefit.

I honestly wonder if rod lengths are a marketing ploy?...I can see piston side loading issues with short rods and parasitic losses from that, but the losses are likely minimal and bore wear is more than likely the primary issue with shorter rods.

I'm very undecided on this issue...not sure which length rod I'll use on a future 454 shortblock buildup. Leaning towards a 6.385" (+.250) rod as the Callies Dragonslayer 4" stroke crank has it's counterweights configures for that rod length.

i just want to say everyone should really pay attention to 10secbu, i think he offers up well thought out comments and common sense. graemlins/thumbsup.gif graemlins/beers.gif graemlins/thumbsup.gif

i just want to say everyone should really pay attention to 10secbu, i think he offers up well thought out comments and common sense. graemlins/thumbsup.gif graemlins/beers.gif graemlins/thumbsup.gif

I wasn't saying that a 6.635 (.5 longer) rod for a 427 would be my first choice, but the question was about piston selection for a longer rod 427. This piston rod combo would work and would definitely rpm well. Makes me want one with some 4.56 gears and a 4 speed. I actually thought of doing this before I decided to go 496 instead. :D
Caleb

From an engineering standpoint, long rods are the only way to go in a short stroke, high RPM drag race engine. This is due to the fact that the piston dwells longer at and near TDC. With proper cam timing and header design, the additional dwell time will help with cylinder filling by effectively scavenging the intake tract. A secondary benefit of long rods is the fact that they will slightly reduce piston side loading.
None of this, however is much of an issue in a street or street/strip engine. An engine that is properly designed to benefit from long rods will be severly lacking in low and mid range torque, as pointed out in previous posts.