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I'd go with the 6.250" rod, as shelf pistons are available, and cylinder wall loading will be slightly less. The rock won't be an issue, and the negligible difference in dwell doesn't add up to anything.

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10-4, I lost a cylinder wall on a 340 block earlier this year, so I would put the longest practical rod in it to minimize cylinder side loading, and get a better piston design at the same time. the longer compression height stuff can get top heavy.

I just put together a X block with the 3.790" crank, and used a 6.300" long rod.

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I appreciate the input! you have a pm

What was the rod ratio in that 340 you were running?



what do others think?

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I'd use a 6.25 or 6.3, length of the piston is really the sum of the skirt and the compresion height so it's not all about the CH. But a longer rod makes sense as that's very close to the same r/s ratio as a 6.36" 383 rod in a 451 which works really well. All else being equal a 3.79 will rev higher and make about the same power as a 408 with a little less mid-range torque. Better suited for a 4 speed or a light car than an auto, an auto I'd just build a 408-416.

Don't overthink it though, build a solid reliable combo and go have fun

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Hey Wize, as always I appreciate your input!

Wondering how the 3.79" stuff works better with a 4 speed though? Unless one has the gear for the torque multiplication with the stickshift I always thought and auto would be better...although nothing is cooler than a stick powershifting the gears screaming in the RPM band please enlighten me

This is a street car though, and it will be a 4.10 gear 28" tire combo, so I don't really want to rev it to the moon since i really can't lol...and as said, it will more than likely see some nitrous use in the future

I guess I may be theorizing too much, but I felt like learning something new about this...its winter so im always cooking up new ideas in my head with all the downtime

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10-4, I lost a cylinder wall on a 340 block earlier this year, so I would put the longest practical rod in it to minimize cylinder side loading, and get a better piston design at the same time. the longer compression height stuff can get top heavy.

I just put together a X block with the 3.790" crank, and used a 6.300" long rod.

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I appreciate the input! you have a pm

What was the rod ratio in that 340 you were running?

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Mshed,

I say generally because there's less of an RPM drop between gears in a 4 speed and less torque is absorbed with a manual giving you more net power to the wheels. A 4" arm helps offset that some but a long arm stroker can sometimes have trouble putting all that additional torque to the ground through the middle. By moving hterpm upstairs the shorter arm/somewhat higher revving motor can put it to better use upstairs.

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I never thought of it like that...thanks for breaking it down for me

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I run a 3.79 in the race car... its a 9" deck R3 block
with 6.1 chevy Eagle H-beams with CP pistons and with
that combo the oil ring is up in the wrist pin bore...
no big deal there, it has a bridge... I normally turn
it to 8200 but have been as high as 9600 but it didnt
make power past 8300... with the heads and cam I
need to spin it... its only 405ci

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Get the piston made to suit your intended purposes, get the stroke you are after and wherever the rod length falls run it. Dont get all caught up in the rod/stroke BS. Have the piston built to withstand the HP and cylinder pressures you inted and get a rod made to fit the stroke with that piston.

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id run a shorter rod with NOS youll end up with more meat on the piston top,ringlands in a better location,more piston stability too.if its gonna see alot of street miles that also makes a difference.most of these long rod combos are drag only so they dont have concerns regarding wear during street crusing.i have a short rod sb that was bulit for spray and runs pretty good on motor also.6"rod 4"stroke indy 230s... 9.7s @3400lbs on 275/60DRs no NOS passes yet and its a true street car.

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There will still be plenty of piston available for a thick crown using a 6.25 rod and 3.79 stroke.

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thanks for the info Brian!

The class I was thinking of running just became N/A only and max cubic inch of 385ci, so this 3.79" arm stuff just got that much more appealing

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id run a shorter rod with NOS youll end up with more meat on the piston top,ringlands in a better location,more piston stability too.if its gonna see alot of street miles that also makes a difference.most of these long rod combos are drag only so they dont have concerns regarding wear during street crusing.i have a short rod sb that was bulit for spray and runs pretty good on motor also.6"rod 4"stroke indy 230s... 9.7s @3400lbs on 275/60DRs no NOS passes yet and its a true street car.

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so you are saying long rod combos would increase or decrease wear on a street motor?

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id run a shorter rod with NOS youll end up with more meat on the piston top,ringlands in a better location,more piston stability too.if its gonna see alot of street miles that also makes a difference.most of these long rod combos are drag only so they dont have concerns regarding wear during street crusing.i have a short rod sb that was bulit for spray and runs pretty good on motor also.6"rod 4"stroke indy 230s... 9.7s @3400lbs on 275/60DRs no NOS passes yet and its a true street car.

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so you are saying long rod combos would increase or decrease wear on a street motor?

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long rod is great if your comp height is 1.5" or more.its the piston that the issue not the rod.the piston gets skimpy,likes to rock around when comp height is short, rings are in the pin area also.the crank you have most likely has a mopar rod journal size so i would run a stock lenght H-beam or 6"if their available.

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