LONG ROD STROKER 6.35 or 5.96 or 5.97???

[quadzila]

What are the advantages or disadvantages of a long rod. I have seen 3 different sizes and i am going to have a stroker built soon

 

[buickfever]

Good Question. I'm interested in hearing some opinions on the "long rod" stroker kit for mostly street use... Subscribed.

 

[bison]

A longer rod will slow the piston down as it gets near and passes TDC. This can be of slight advantage when selecting cam lobes and timing to use on turbo engines where a lot of backpressure is present. A 6.5" or longer rod with more than a 3.5" stroke is a compromise to the piston becuase of the short deck height. Around 6.35" is what id use. Some run the 6.5" with no problems though.

 

[buickfever]

Cool, thanks.

 

[charlief1]

A longer rod will slow the piston down as it gets near and passes TDC. This can be of slight advantage when selecting cam lobes and timing to use on turbo engines where a lot of backpressure is present. A 6.5" or longer rod with more than a 3.5" stroke is a compromise to the piston becuase of the short deck height. Around 6.35" is what id use. Some run the 6.5" with no problems though.

That's a pretty basic explaination but it is a little more complicated. By using a longer rod and a shorter piston the dwell time for the piston on the top and the bottom is longer which allows for a better charging of the cylinders. This also keeps the piston at TDC and BDC longer. By increasing the time the piston is at TDC during combustion it redues the knock oportunity slightly and on exhaust stroke it removes more of the exhaust. On the intake side the piston being at BDC longer means that you get a better filling of the cylinder.

The biggest advantage is the increase of torque from the long rods. The assembly will rev faster and since the rods are basically a lever, the longer they are the more fprce is applied to spin the crank.

Clear as mud now?:biggrin:

 

[buickfever]

That's a pretty basic explaination but it is a little more complicated. By using a longer rod and a shorter piston the dwell time for the piston on the top and the bottom is longer which allows for a better charging of the cylinders. This also keeps the piston at TDC and BDC longer. By increasing the time the piston is at TDC during combustion it redues the knock oportunity slightly and on exhaust stroke it removes more of the exhaust. On the intake side the piston being at BDC longer means that you get a better filling of the cylinder.

The biggest advantage is the increase of torque from the long rods. The assembly will rev faster and since the rods are basically a lever, the longer they are the more fprce is applied to spin the crank.

Clear as mud now?:biggrin:

Crystal clear. Thanks.

 

[turbofabricator]

That's a pretty basic explaination but it is a little more complicated. By using a longer rod and a shorter piston the dwell time for the piston on the top and the bottom is longer which allows for a better charging of the cylinders. This also keeps the piston at TDC and BDC longer. By increasing the time the piston is at TDC during combustion it redues the knock oportunity slightly and on exhaust stroke it removes more of the exhaust. On the intake side the piston being at BDC longer means that you get a better filling of the cylinder.

The biggest advantage is the increase of torque from the long rods. The assembly will rev faster and since the rods are basically a lever, the longer they are the more fprce is applied to spin the crank.

Clear as mud now?:biggrin:

All true. But.............There is really nothing to be found on the dyno (or track) to prove (or disprove) all of this. Case in point, 880 CID big blocks should in theory, wipe the crap out of the pistons (another benifit of long rods) but they just don't have that issue. Lots of math can prove or disprove all of this. Just when I think I understand the innner workings of an engine, someone easily proves me wrong.:redface:
Basically, use the longest rod that the piston will accomodate. (and is readily available). For racing, a real long rod with a oil ring support, will work great, but for the street, keep the ring pack where it belongs, outta the oil ring land. You will never see any difference between a stock rod, or a .5" longer rod. It has been debated and debated for years, where theory (and math) just doesn't make hay. If it is down on power by 4.5 horsepower, turn the boost up.
NOW........it's REALLY clear as mud.:biggrin:

 

[coach]

Another reason to use longer rods is it cuts down on cylinder sidewall push out pressure. When the piston drops to the bottom of the cylinder, it wants to push out before it pushes back up. Certain engines had bigger issues with this, I do not know about our V6's. The longer rod and relocated wrist pin keeps the rod further up in the cylinder and therefore cuts down on the outward push before it starts back up. May not apply to our motors, but just some added education.

:biggrin:

 

[cruzn57]

additionally

with a long rod, normally the piston is lighter, as pin is higher ,thus shorter overall piston.

 

[quadzila]

longer rods

has anybody used 6.35 rod on a stroker did you like the set up? wouls you do it again?

 

[thrlskr]

DLS stroker rods are 6.0.

 

[750H.P.V6]

There are a lot of theorys about rod length. It's generally accepted that a rod to stroke ratio of 1.7 to 1 or greater is better. Engine builders have been saying for years that longer rods make more H.P. Maybe and maybe not.

Bottom line is that if the rod to short you'll run into piston scuffing issues due to side load issues. If the rod is too long you'll run into stack up issues wherby the piston will be very short and the ring pack will be too high on the piston.

Short pistons are lighter but noiser due to a short skirt length with the same clearances. This doesn't mean much in a race motor but is really annoying in a street / strip motor. The best all round rod length for a 3.590- 3.625" stroke crank is between 6.200"- 6.300" in my opinion.

Good Luck

Neal

 

[Sydwyndr]

has anybody used 6.35 rod on a stroker did you like the set up? wouls you do it again?

Im running a 3.625 crank and a 6.300 rod, It makes lots of power. I would recommend it to anyone. took it to the track and at 13.5 psi of boost, pumpgas, with a 66 turbo and gn1's it ran 7.16 @ 96mph.

 

[Sam Colalillo]

My DLS stroker kit is a 3.625 crank with 6.35 rods.

When you do the math you can realize how slightly differnet the combinations are. The longer rod gives you optimized dwell time, less force on the cylinder walls, and a lighter piston. The disadvantage is the piston skirt hieght. In my opinion the shorter skirts are not a big enough disadvantage to consider the shorter rods, even if the car is a daily driver. A properly designed piston with a 6.35 rod is my choice for any stroker.

 

[quadzila]

thank you for the information, i am starting to get an idea of the direction to go for my build.

 

[750H.P.V6]

I agree with Sam that a 6.350" rod works fine too. Where you really run into stack up problems and piston noise issues is when running 6.500" rods. There are a lot more options available now then there were only a couple of years ago. The 6.350" K1 rods are hard to beat for the money.

Neal

 

[quadzila]

It seems that the long rod 6.35 is a popular choice for the stroker. Has anybody had piston noise issues is when running the 6.35 rod?

 

[turbobitt]

That's a pretty basic explaination but it is a little more complicated. By using a longer rod and a shorter piston the dwell time for the piston on the top and the bottom is longer which allows for a better charging of the cylinders. This also keeps the piston at TDC and BDC longer. By increasing the time the piston is at TDC during combustion it redues the knock oportunity slightly and on exhaust stroke it removes more of the exhaust. On the intake side the piston being at BDC longer means that you get a better filling of the cylinder.

The biggest advantage is the increase of torque from the long rods. The assembly will rev faster and since the rods are basically a lever, the longer they are the more fprce is applied to spin the crank.

Clear as mud now?:biggrin:

The longer rod will yield more desirable rod angles when the piston is at mid stroke, halfway between TDC and BTC, crank is 90 degrees to the cylinder wall. This is when the sidewall/skirt of the piston takes a beating. The longer the rod, the better the angle and less force is transmitted to the cylinder wall. A longer rod will make the piston more stable as long as the skirt isn't comprimised to much.
With that being said, I've been running 6.5" rods with a 3.59 stroke crank for years. I'm only running this rod because it was available cheap to me when I originally put the engine together. I have not seen any wear, noise, or any other ill effects of using this combination but If I had to start over, I would definetly start with a 6.35 rod since it would give you more options with the ring pack and keep the wrist pin away from the oil ring.
Allan G.