Stroker rod clearance

[SinCity]

Hi. Im sure this has been discussed, covered before so please bear with me......

Im planning on building a 427 sbc stroker Using a dart SHP block and a 4340 callies, compstar , H beam rod rotating assembly (CNC Motorsport) or similar.

My questions are, how much machineing etc is needed for the rod/block clearance.
Are these style of rods the best for this combo?
SHP block suitable for this
any other traps to beware of?

Any advice appreciated,Thanks, Brady.

[kevin@dart]

Most of what you need to know has been covered in this thread.


http://www.dartheads.com/dartboard/showthread.php?t=1167

[Awesome Bill]

no traps, to be wearing of, just common sense and making sure everything clears. We have been putting 4" crank and rods in these for a while with no problems @ all.

[SinCity]

Thanks Kevin, Bill.

[Awesome Bill]

Autually they fit better in the shp block!

[Nulafooto]

With a dished piston you should be fine. You should always check your piston/valve clearance when assembling anyways.

The 6" rod isnt an issue. It just means the piston pin is higher up on the piston than a 5.7 rod and it actually helps relieve some stresses on the rotating assembly.

[Awesome Bill]

Longer rods put more stress on the rotator and less on the cylinder, does increase dwell time and adds a little but always hurts the crank more because of the straighter line to push. On a greater angle, the cylinder wall takes the hit. Means very little between the 2 but just thought I through this in, maybe someone will talk about it!

[Awesome Bill]

Did you get my quote on the parts you need? Till December, Dart is knocking off $200.00 on those blocks!

[kevin@dart]

Longer rods put more stress on the rotator and less on the cylinder, does increase dwell time and adds a little but always hurts the crank more because of the straighter line to push. On a greater angle, the cylinder wall takes the hit. Means very little between the 2 but just thought I through this in, maybe someone will talk about it!

Rod length is a subject of much debate but I'll add my train of thought.

Yes, it is true a longer rod will reduce side load on the piston, rings, and bore. Shorter rods take a little bearing load off of the crank end.

In reality, and using using good parts, if a bias needs to be made it shoud be towards cylinder wall longevity opposed to the crank, considering the all too important ring seal.

I mean... The crank converts the linear motion of of the piston after combustion to rotational force. It's really just along for the ride in essence converting force and taking a beating from the piston. We all know that ring seal, and condition of the parts within are the keys to making good power. It's all about finding a good balance which I am sure we are all aware off.

Quite a few builders say a good balance is a ratio of 1.65 - 1.70 but getting there on a SBC is a bit of a problem considering a 4" crank with a 6.00 inch rod comes out at 1.50.

Anything larger in compression height starts to creep towards the ring pack, if it's forced induction you want the ring pack down.... blah, blah, blah.... This is common knowledge. With a 6.125" rod you're creeping towards sub 1.00 compression heights using a 9.025 deck with no clearance.

To me rod length has a greater effect on rpm range verse horspower than overall length. anything 1.50 and above will live quite sometime as long as the tune up is good and it's built well.

Shorter rods tend to fill the cylinder quicker and lower in the rpm range, as well as producing more torque in the lower range due to the increase in piston speed at a given rpm, and less dwell time at the top of the cylinder.

Longer rods tend suffer at the lower rpms filling the cylinders quickly as well as slowing down piston speed at a given rpm.

I have seen these shifts in powerband on the dyno with all parts the same besides rods and required pistons... It was almost as if we were retarding or advancing camshaft timing.