displacment?

[Ducman]

This ended up being a long ass post but its rainy outside, still storming here in CA and I'm bored. Hopefully it will shed some light on your situation and help others understand 4mm stroker/longrod and standard stroke/long rod setups. Disclaimer: I don't claim to be 100% technically accurate 100% of the time.

 

Here is a good (link click here) that has a brief explanation of the difference between a long rod and a long rod stroker crank, as well as CC#'s for displacement of a standard stoke, 4mm stroker, and big bore sleeved stock and 4mm stroker.

 

At .030 you'd be 382cc on a 4mm stroker. Your HP potential and what you will actually make really depends a lot on how aggressive your porting is fom mild to wild and even more on your supporting mods, carbs, pipes, reeds, timing, intake, domes. With mild porting on a 4mm stroker and mostly stock other than say pipes you could be anywhere from 45 to 65 hp. On a 4mm stroker with agresive porting and all the supporting mods that complement each other with perfect tuning you could be between 70 to 80.

 

In your case r6rider04, you do need porting specific to the 4mm long rod stroker crank for optimum performance. It may run on stock crank porting but not like it should. If your builder/porter knows what crank and set-up you are running then they should know how to port specifically for that set-up. A longer stroke and/or longer rod affects port timing differently than a stock stroke/stock rod.

 

4mm stroker 5mm long rod setups:

First most popular setup: If you have a spacer plate under the cylinders (approx 2 mm), this is to raise the cylinders up so your pistons don't go above the top of the cylinders due to 2mm added stroke length (2mm at top of stroke and 2mm at bottom). That takes care of the added stroke. Next you need wiseco 795 series pistons to run with the 5mm longer rods. The 795 series pistons have the wrist pin moved 5mm closer to the top of the piston so the distance from the top of the piston to the bottom of the rod stays the same as stock. Allows for use of standard cool head domes or stock head.

 

Second option (which I have): You can go without a spacer plate under the cylinders and get custom stroker domes so the piston actually goes above the top of the cylinder into the domes, (which also requires porting specific to this setup). If you want to change domes you have to get custom stoker domes made which are somewhat specific to each motor as far as getting proper squish clearance. 795 series pistons are used to maintain stock rod to top of piston length.

 

Third setup that I can think of, (someone correct me if I'm wrong) I think if you have an approximatly 7mm thick spacer plate you can run stock type pistons, but this will give you a really long total bottom of rod to top of piston length. (also requires specific porting for this set up). Also it adds a lot of transfer port volume. Maintains use of standard cool head domes or stock head.

 

Here is a (link click here) to a thread I started a while back when I was tying to figure out what was the effect of long rods on stock crank. Also affects 4mm stroker crank. The long rod by itself DOES change how the motor runs by how it is effected by the port timing. The long rod changes the angle of the rod to the wrist pin (decrases angle) when it is midway through the pistons travel. This puts less stress on the pistons skirts (increases reliability/longevity) to hold the piston true to the cylinder. The different crank/rod angles also slows the pistons down in the top and bottom of the stroke (increases dwell time) and speeds them up in the middle of the stroke. The faster piston speed in mid stroke requires increased port timing to get the same air/exhaust in/out. If you threw in a long rod crank into a stock rod/crank motor with the same port timing to compare the two set-ups it would gain torque/midrange but rev slower and loose top end with the long rod. Hope this helps.

[r6rider04]

thanks ducman very informative, i'll give the builder a call and look into this porting for the stroker crank, also would like to know what pipes are rcommended for the setup i have ie. stroker, porting etc, i have a set of T-5s right now

[FIRST BANSHEE]

when i lost the connecting rod bearing,  the guy said it could probably  be rebuilt, but rcommended the hot rod crank for reliabilty purposes and said if wanted to spend a lttle more i could go wth the +4mm crank with the +5mm long rods which would also be more reliable than the stock crank and give me some more performance... he's done alot of banshees so he knows what he's doing. but didn't mention any thing as far as porting for the stroker... just said i should also get the spacer plate to correct the port timing?? again  over my head

300897[/snapback]

just make sure your engine builder has all the info you gave us and he should make it right. good luck

[Ducman]

thanks ducman very informative, i'll give the builder a call and look into this porting for the stroker crank, also would like to know what pipes are rcommended for the setup i have ie. stroker, porting etc, i have a set of T-5s right now

300981[/snapback]

 

I'd run the T-5's they'll respond well to the mods. You'll want to spend any extra $ on other stuff soon anyways.

[r6rider04]

what do you think would be the next step up in mods after i get this all done, carbs, v-force reeds? just curious for now

[Ducman]

What all mods do you got now?

[r6rider04]

well when i get it back together it will have +4mm stroke, bored 30 over, toomey T5's, mild trail port and shaved head, reed spacers, jetted, pro-flo/k&n filter i think thats about it for anyway....