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What kind of HP increase and torque increase can I expect from using a 6 inch eagle h-beam rod instead of the usuall 5.7 for my 350 chevy...
 

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Discussion Starter #3
6 inch rod

I was thinking that with the longer rod it gives a better angle of pushing on the crank. more straight up and down. I jsut heard they are a lot better so that is what I went with
 

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Street engine you are better off with the 5.7". Quicker to rev off of idle.

Chris
 

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Discussion Starter #5
6 inch rods

The motor is a strong built high perfromance street motor. It has victor jr heads 215cc. 11.5:1 compression. solid roller cam. Rev kit. Wiseco pistons. the eagle h-beam 6 inch rods, small journal steel crank, 4 bolt 350 block, msd pro billet distributor, msd 6A box, msd 4 stage retard, crank scrapper,lifter valley vents, barry grant might demon 850 carb, victor jr intake and up to 250 shot of nitrous. I have never had this motor out but plan to have it out in an s-10 within 2-3 weeks. Only thing that may be overkill is the carburetor.
 

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Absolutely zippo.
 

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"May the Schwartz be with you"
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The tangential angle on the crank throw is better with the 6" rod. It will therefore give some increase in torque.
 

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WV hillbilly
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Re: 6 inch rods

mychevystang said:
The motor is a strong built high perfromance street motor. It has victor jr heads 215cc. 11.5:1 compression. solid roller cam. Rev kit. Wiseco pistons. the eagle h-beam 6 inch rods, small journal steel crank, 4 bolt 350 block, msd pro billet distributor, msd 6A box, msd 4 stage retard, crank scrapper,lifter valley vents, barry grant might demon 850 carb, victor jr intake and up to 250 shot of nitrous. I have never had this motor out but plan to have it out in an s-10 within 2-3 weeks. Only thing that may be overkill is the carburetor.


make sure you try a 2" spacer on that combo, (juist about every motor I have witness such as your picks up quite a bit with a 2" spacer with the Victor JR.)


2wld4u
 

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Re: 6 inch rods

mychevystang said:
any idea of the gains from the spacer

mostly torque, on average about 20ft lbs, but I cant say for sure on your combo, its definatly worth trying... either that or a turtle (and or both..)
 

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lol, a turtle drops in your plenum and maximizes flow rates in a given RPM range, low-mid, etc... mid to high, I get mine from Brodix ;)


yeah, I know it sounds silly, but WOW what a differance it can make.........



2wld4u
 

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sitis nam accelero
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You most likely won't feel much of a difference. The longer rod will decrease load thrusted into the cylinder wall due to a decrease in rod angularity, which will reduce frictional losses and bore wear. So basically you're engine can flow to higher RPM's and will be more durable while doing it. The Rod length to Stroke Ratio (R/L) determines the angularity of the con. rod and having a 1.72:1 R/L ratio (assuming your crank's stroke is 3.48") is excellent. Increasing the con. rod length optimizes maximum power from the reduction of friction. What are you're intentions for the engine as far as street or strip, (low-mid peak torque or high end power). Lower R/L ratios don't really decrease power for engines running most of their life under 3000 RPM. Which is why the torque monster small-blocks 383, 406, 420 and even 468 made for great low end tire smokers. With their longer strokes and larger bores they had a major increase in low end power but were endanger of failure at high-rpms, from the lack of con rod length due to the 9.025 deck height of the small-block, so their R/L's were crazy low. Depending on the compression height of you're pistons you might have clearance problems with the 6" rods given the 9.025" deck height. To establish a proper zero deck compression height for you're pistons add half of the stroke and the length of the rod and subtract from 9.025. You might also run into con. rod bolt clearance problems with the oil pan rail and camshaft. The crankshaft, con. rods, and pistons normally run hand in hand, modifying one necessitates modifying the other. And as far as the 850 cfm carb goes, that large of a carb will affect your idle and throttle response if your engine is running under 500 hp. The other day I was reading an article in CHP (Chevy High Performance), and they were comparing different cfm rated carbs on an engine that put out roughly 450 hp at peak. The comparison showed that 850 cfm carbs werent necessary and/or efficient in an engine less than 500 peak hp. While the 650 made for excellent throttle response and power right off of idle it had limited mid-high power, the 750 cfm gave the most optimal performance for the engine. But I don't think they used a turtle :-/. The 2" spacer can help depending on what RPM range you are looking at. An open plenum spacer will improve high RPM performance but will decrease low end power and 4-hole spacers will improve throttle response for street driven cars. You might want to experiment with a combo of both. The turtle takes the spacer a step further designed specifically for an individual intake manifold to direct air and fuel for improved mixture distribution.
 

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rods

4 Jaw Chuck said:
Absolutely zippo.
I agree with 4 jaw on this one.

Before you start making any decissions go to thses 2 sites and read there take on this subject.

http://www.rehermorrison.com/ go to tech tip #10

http://www.iskycams.com/techtips.php#2005

These are 2 of the more respected names in the performance business.

I have asked before and i'll ask again.. All the people that have real proof ( no david vissard books or super chevy articles)of the increased hp, torque, piston life ect... from a longer rod please show it to me...... I'll even take a et slip where the only thing you changed in the engine was a longer rod......



Drewnashty, I am going to have to ask how a 19 year old has done all this research on this subject???? Or did you copy this info from someplace else?????


Keith
 

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Race it, Don't rice it!
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*** does age have anything to do with anything? Why do you assume a young person doesn't know anything?

He's right by the way.

All of our 388's use a 6.135 rod. Why?

Because it works. Our 406 uses a 6.3 rod because it works.

Gains in street motors are probably negligible. But if you have the money, I can't see what it would hurt.
 

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age

I never said that a young person can't know things. I just asked for his research..

As i am going to ask for yours????

Did you ever build one of those 388's with a 5.7" rod and compair it to the 6.135"????? Back to back with no other changes???? If so what was the hp number you got from your research????

Keith
 

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This is a small CID engine with a large induction system. The engine is more drag then street friendly. Long rods are better suited to engines that need a power band in the high mid range to high rpm range.. . not for engines that need start and stop power.

K-star,
No proof on more power. Rod stroke ratio is part of what dictates the VE's of any engine. So using the same cam on an engine and changing rod lengths is unfair due to the fact the cam is going to work better with one or the other.

Long rods have always been favored over the years. The increased dwell time help cylinder heads make power. That is changing. With modern head technology today, some engine builders are using shorter rods and reducing the mass of the assembly. This results in quicker reving engines that are able to get off the corner faster or obtain the rpm range needed for a shift quicker.

Do long rods work, sure I am not saying that. But as I always preach from my soap box, a well thought out combination will always be a better choice then a box of the best parts.


Chris
 

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rods

Thanks for your valuable insite chris.

Since i have started looking into the facts of the long rod issue i have found so many different opinions on the subject my head hurts. One thing i have found time and time again is the lack of hard proof for each side of the issue. A few conclusions that i have come to are.

There is a deffinate difference between drag racing engines and circle track engines on what rod works better. With the drag engines liking a shorter rod and a circle engine liking a longer rod.

Even in the best case of the proper length rod matching the proper cylinder head, cam combo.... over the non ideal rod
length same cam heads. It looke like a small hp/ troque increase... like maybe 1 percent, or less if your lucky... Agree????

I totally agree that a engine with the proper combo will always work better then one with the "best" parts. I think thats a very good way to state it....

I was in the process of collecting a 5.7" rod 6.0" 358 to run on the dyno with all the other factors being the same. I was going to run the 5.7" rod and then change to the 6.0" rod using the same heads, cam intake etc... Just the rod piston combo, maintainig the same static compression...but...... i plain ran out of money.. Then i got to thinking about spending that money on some more shop equipment and that sounded even better... If i hit the lotto i am going to do it and everyone will be invited to see the results... L.O.L.

Keith
 
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