Engine Masters rod ratio test results
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Engine Masters rod ratio test results
for the ones that watched it what was your take on it? Were you surprised the shorter rods made more power?
Re: Engine Masters rod ratio test results
Is there a YouTube link to that or something? I'd love to watch that.
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Re: Engine Masters rod ratio test results
No ... not at all.
Some people have simply kept their mouth shut because all the "experts" out there know everything; without actually testing.
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Re: Engine Masters rod ratio test results
I have to ask if the intake and exhaust tracks as well as the cams matched to the individual rod ratios before I believe that a short rod ratio will make more power than a long rod ratio.
Only because of less piston/cylinder side-loading for the longer rod ratio is all.
pdq67
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Re: Engine Masters rod ratio test results
All of the 900+ hp sprint cars went from 6" to 5.9" rods as the intake tracts grew larger.... Like 2.900 or 3" butterflies.....pdq67 wrote: ↑Mon Mar 02, 2020 10:15 amI have to ask if the intake and exhaust tracks as well as the cams matched to the individual rod ratios before I believe that a short rod ratio will make more power than a long rod ratio.
Only because of less piston/cylinder side-loading for the longer rod ratio is all.
pdq67
But its probably as much about the piston and rings as it is about the r/s
Re: Engine Masters rod ratio test results
Exactly. If the camshaft wasn't optimized for each rod length, The test is meaningless.
Mike Jones
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Re: Engine Masters rod ratio test results
Those of us there back in the day remember the 302" SBF would never make any power "because the rods are too short for a 3.00" stroke" and today with good heads, those little suckers are running a 3.40" stroke with a worse rod/stroke ratio and making enough power to split the block.
A 302" has a 3.00" stroke with a 5.090"connecting rod. The 347" increases the stroke to 3.40" and a 5.40" rod. This drops the rod ratio from 1.696:1 for the 302" to 1.588:1 for the 347".
A 302" has a 3.00" stroke with a 5.090"connecting rod. The 347" increases the stroke to 3.40" and a 5.40" rod. This drops the rod ratio from 1.696:1 for the 302" to 1.588:1 for the 347".
Jack Vines
Studebaker-Packard V8 Limited
Obsolete Engineering
Studebaker-Packard V8 Limited
Obsolete Engineering
Re: Engine Masters rod ratio test results
In my experience the only time a shorter rod makes more power is when the intake port is too big for the cubic inches and they keep the same heads and intake, headers. Joe-71
Joe-71
Re: Engine Masters rod ratio test results
In 2003, I built a street driven SBF 331 using 289 rods that are 5.155". I used a KB322 383 Windsor piston. Rod Ratio works out to be slightly less than a 5.4 rod 347...1.586. I also used fully ported '70 351W heads with 1.94/1.6 valves and had some valve unshrouding done (160cc intake ports and 60cc exhaust ports). 9.8:1 compression. Single Plane intake, 750 HP, 282S Comp Cam, Dougs stepped Tri-Y headers. The engine makes 430 HP @ 6500 and is still making 400 HP @ 7000. More than just about anyone in the SBF community would have believed. Maybe i got lucky and choose components that all worked very well together.PackardV8 wrote: ↑Mon Mar 02, 2020 12:06 pm Those of us there back in the day remember the 302" SBF would never make any power "because the rods are too short for a 3.00" stroke" and today with good heads, those little suckers are running a 3.40" stroke with a worse rod/stroke ratio and making enough power to split the block.
A 302" has a 3.00" stroke with a 5.090"connecting rod. The 347" increases the stroke to 3.40" and a 5.40" rod. This drops the rod ratio from 1.696:1 for the 302" to 1.588:1 for the 347".
65 Mustang FB, 331 custom built with 289 H beam rods and 383W piston, 282S cam, Ported Maxx 180s, T5z, 9" 3.89 gears. ~460HP@6500
2013 Corvette 427 Convertible daily driver
2013 Corvette 427 Convertible daily driver
Re: Engine Masters rod ratio test results
Ok, thanks.
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Re: Engine Masters rod ratio test results
^^^^^^^^^^^^^^ I agree with this statement. One of the advantages of longer rods is the fact that there is more piston dwell at TDC, however the camshaft needs to be designed to take advantages of this feature, as well as other features of long rods. Camshaft design for a long rod engine will be different than the camshaft design necessary to take advantage of short rod features.
Bill
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Perfect Circle Doctor of Motors certification
SAE Member (30 years)
ASE Master Certified Engine Machinist (+ two otherASE Master Certifications)
AERA Certified Professional Engine Machinist
Re: Engine Masters rod ratio test results
On the show, they had basically 'too much cam and head'... The short rods made more top end, and the long rods made more low end power. But it wasn't huge either way. When they did a steady state run (engine locked to one speed) the numbers were pretty much identical.
478 inch Big block Chevy (big bore, short stroke... 4.5" bore, and less than 4" stroke) with 365cc heads and a big roller.
478 inch Big block Chevy (big bore, short stroke... 4.5" bore, and less than 4" stroke) with 365cc heads and a big roller.
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Re: Engine Masters rod ratio test results
Without each rod ratio engine completely optimized and tuned for that combination, I personally don't think it gives us anything except something to continue to discuss, which is fine. I do believe there is merit in using the best ratio for your particular application.
If memory serves me, I believe it was Pro Stock veteran Warren Johnson that said his rod ratio was whatever connected the piston to the crank, but he was also very cagey about what he was actually doing at times.
If memory serves me, I believe it was Pro Stock veteran Warren Johnson that said his rod ratio was whatever connected the piston to the crank, but he was also very cagey about what he was actually doing at times.
Re: Engine Masters rod ratio test results
It's all combination, they both will work just like different things. In a wide open no holds barred build rod length would be way down the list for me. In a limited class rule type deal it can move substantially up the list in my opinion. Just swapping out rods and not optimizing the build is a waste of time and effort, maybe it works and maybe it doesn't.