6.135 or 6.385 rod length?
#11
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Re: 6.135 or 6.385 rod length?
Originally Posted by cstraub
. . .and mock up the assembly. I can't remember how many customers have had guys bring in a "good" deal on a rotating kit, have them balance it and then take it home only to be surprised that the counterweights hit the pistons. Their complaint then falls on deaf ears from who they bought it from because, "sorry, you have had it machined therefore we can't take it back". Your know out around $600 for balance work x 2.
Nobody,
That 2" deal I agree. That's the number among the top engine builders.
Nobody,
That 2" deal I agree. That's the number among the top engine builders.
GPM the 850's are marine motors in pairs (2boats).
1 set I freshened at 200 hours, the other set are sill in the boat with roughly 80 hours. I think these guys turn them around 6000 RPM.
Short rod combo's do make more bottom end torque, but I've yet to see a HP difference between the two if we're not talking about extremes.
#12
Geronimo36
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Re: 6.135 or 6.385 rod length?
How about a 1.48 rod-stroke ratio in a 580 cu. in. blower motor? 6.700" rod with a 4.5" stroke and 4.53 bore.
Normally we would have went with a 6.535 rod but the previous engine builder put in the 6.700 rod so that's what I'm stuck with.
8.5 to 1 compression.
Normally we would have went with a 6.535 rod but the previous engine builder put in the 6.700 rod so that's what I'm stuck with.
8.5 to 1 compression.
#13
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Re: 6.135 or 6.385 rod length?
Somthing else to look at is the piston gets pulled out the bottom of the bore further with a short rod, causing the piston to rock.
Last edited by JimV; 03-08-2005 at 02:46 PM.
#15
Geronimo36
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Re: 6.135 or 6.385 rod length?
Originally Posted by cstraub
I think you are much better off with a full skirt piston in the marine enviroment.
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Re: 6.135 or 6.385 rod length?
The short rod long rod will never be settled there are to many benefits in both directions, that's why I've tried it both ways. As far as the 632 CI motors it's just to hard to get any longer rod with a 10.200 block. This block is the cheapest way, not the best to build it. You will find that engine builders never agree on a lot of things and it just goes to personal preference usually from good or bad experiences.
The best advise is to put out different views and come up with your own way to interpret it.
All my life I have learned from trial and error (usually error) and come up with my own way to view subjects like this, because even though someone has good advice I still want to know if there is a different way and why. Truly smart engine guys will never take something for granted, they will listen and then try to prove that theory wrong until they know that theory was right.
Smokey was the first person to say get the longest rod you can fit in the motor, but most great engine builders don't take this advice.
GPM these short rod 632's make brutal torque down low.
The best advise is to put out different views and come up with your own way to interpret it.
All my life I have learned from trial and error (usually error) and come up with my own way to view subjects like this, because even though someone has good advice I still want to know if there is a different way and why. Truly smart engine guys will never take something for granted, they will listen and then try to prove that theory wrong until they know that theory was right.
Smokey was the first person to say get the longest rod you can fit in the motor, but most great engine builders don't take this advice.
GPM these short rod 632's make brutal torque down low.
#18
Re: 6.135 or 6.385 rod length?
Nobody, I'm sure the 632's make the torque down low, I was just curious if it fell off or kept going. I like to experiment with different combos also.
Last edited by GPM; 03-09-2005 at 08:00 AM.
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Re: 6.135 or 6.385 rod length?
Originally Posted by GPM
Nobody, I'm sure the 632's make the torque down low, I was just curious if it fell off or kept going. I like to experiment with different combos also.
I'm sure it would depend more on the head and cam selection than anything.
I do know on some small chevy RR motors I've experimented with had unusually long rods and they don't seem to have the grunt the normal rod ratio motors had. Hard to see on the dyno, but at the track you sure could. I think any extreme either way is bad.
#20
Re: 6.135 or 6.385 rod length?
just another opinion here. its been my experience the numerically low rod ratios dont like to wind as high or as fast along with all the other stuff these guys have said, I read in one a smokey yunicks books that for a N/A engine 1.88 is optimal but on a BB chev its pretty unabtainable. You will give up a little low end torque though but its all stuff that needs to be thought out in conjuction with drive ratio and prop pitch.