Benefits from longer rods on mild BBC?

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Got Torque

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Oct 29, 2003
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Stockholm, Sweden
I'm collecting some parts to build a mild 467 BBC. It will most likely use hypereutectic pistons for cost reasons and have a mech flat tappet. The goal is 500hp SAE with pump, pulleys and alternator.

I'm fully aware that longer rods on BBC's work well and why. That is on more radical race engines as far as i know and i would like to know if i would see any gains on a engine that will never see rpm over 6000.

I don't know of any 450-550hp street 467's with 6.585 long rods for example. Does any of you guys have a milder bigblock with longer rods?
Did you gain anything from it power wise?
The final question is if you believe the weight of a longer common "cheapie" I beam rod is about equal to a set of stock 3/8 truck rods? I haven't gotten to the part where i weigh mine and thought someone might know..
 

Al

Pro Stocker
May 25, 2003
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I've never seen a big block with longer rods other than a stroker. A 6.385 rod is usually used with a 496ish motor and anything longer is for 540s and up.
 

Goob

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Jun 6, 2003
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Finding the correct compression height piston in a hyperutectic is probably the toughest part of that deal.
You might run across something if you do the math on your needed compression height to match a set of +.250" or +.400" rods.
Do some catalog searching.
You'll need to step up to a decent forged piston I'd bet.

Certain benefits of the longer rods are worth it regardless the usage, in my opinion.
I wouldn't be too concerned about the rod weight difference, if you can get into an I-Beam with 7/16" cap screws.
Everything out there will balance in without too much expense.
 

Got Torque

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Oct 29, 2003
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I guessed as much. I am fairly surpriced of all the wierd combinations on hypereutectic pistons Keith Black offers though. Maybe they have what i'm looking for.

I was thinking the same Goob, ther BB has extremely short rods for it's stroke and enough piston height that i should be able to find a piston for a .400" or more longer rod without ending up with a very "short" piston.
I'd like to get rid of as much cylinder wall pressure from the piston as possible to reduce negative torque and save the bores a little.
-Rebuilding stuff here is expensive enough as it is!

You are probably right, i might be forced to look JE and similar brands. I do know Mahle does have what i need...for 729bucks :cry:
 

ProJunk

Dragway Regular
Sep 12, 2006
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Glendale, AZ
I've taken a look at the possibilities on a similar deal, and, with a 6.535" rod, you can build a 3.76" stroke or 4.00" stroke engine using shelf-stock KB forgings. They have pin heights available, as well as numerous dome configurations, that will work with either combination. I haven't looked at the hypereutectic offerings, but if that's what you want, I'm sure they have those as well. You aren't going to need to go to a mega-dollar piston to accomplish your goals.
 

Got Torque

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Thank you, -i will look more into that. I see you have rods for sale to fit my app. ;)
 

ProJunk

Dragway Regular
Sep 12, 2006
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Got Torque? said:
Thank you, -i will look more into that. I see you have rods for sale to fit my app. ;)

Sent you a PM.
 

Excelerater

MalibuRacing Junkie
May 22, 2003
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I would keep your rod lenth stock,Chevy did a good job with the 6.135
sizing in 427/454 engines -
 

Got Torque

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Excelerater said:
I would keep your rod lenth stock,Chevy did a good job with the 6.135
sizing in 427/454 engines -

Could you elaborate that for me please?
I know GM techs many times did the right thing, but why such a short rod?

Optimal to me would be a tall deck to get some real length on the rods and keep a good skirt on the pistons so they don't rock in their bores.
 

Horsepwraddict

Pro Stocker
Mar 3, 2007
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Princeton MA
Got Torque? said:
Excelerater said:
I would keep your rod lenth stock,Chevy did a good job with the 6.135
sizing in 427/454 engines -

Could you elaborate that for me please?
I know GM techs many times did the right thing, but why such a short rod?

Optimal to me would be a tall deck to get some real length on the rods and keep a good skirt on the pistons so they don't rock in their bores.

i also would like to hear an elaboration. 454's have a low rod ratio.
 
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