Hot Rods Stroker Crank Info

[CFM-Z440]

There has been a lot of talk about the two different hot rods stroker cranks and the pro's and cons of each. I decided to do the math to find out for sure and this is what I came up with.

Stock specs...

The stock crank has a 62.6mm stroke, a 107mm rod, and a rod ratio of 1.71

The +5 crank has a 67.6mm stroke, a 107mm rod, and a rod ratio of 1.58

The +4 crank has a 66.6mm stroke, a 105mm rod and a rod ratio of 1.58




The stock crank at 10,500rpm

Mean piston speed 4294.8 Ft./Min.

Piston acceleration 160,400 Ft./Sec/Sec






+5 crank at 10,500rpm

Mean piston speed 4638.1 Ft./Min.

Piston acceleration 176,358 Ft./Sec/Sec

(Does not raise advertized compression if used with a stroker piston)

(If not used with a stroker piston, it requires a spacer plate, cams degreed, and raises compression by one point)






+4 crank at 10,500rpm

Mean piston speed 4570.1 Ft./Min.

Piston acceleration 173,948 Ft./Sec/Sec

(Raises static compression ratio about 0.8 of a point over advertized)



So there's the truth, both stroker cranks should have roughly the same reliability, and will have about the same side load. However, be careful with the +4. They dont require the use of a stroker piston which means the extra stroke is going to raise your compression roughly by 0.8 So a 12:1 piston would be 12.8:1 which is not necessaraly "safe" on premium pump gas, depending on your cams and avaliable fuel. You can use the LTZ (3 layer) base gasket to help remedy this.

The +5 crank can also be used with a non stroker piston if a spacer plate is used. This affects the compression the same way by about a full point. So a 12:1 piston would be about 13:1 which is most likely not going to be usable on premium pump gas at all. When a spacer plate is used, the cams will also have to be re-degreed because raising the stack height of the cylinder will advance the cams.

The +5 crank can be used with stroker pistons. This adds to the cost of the build, but does not require any extra measures for cam timing, and the advertized compression will be correct.


Here's a good read on Piston speed and acceleration.
http://ftlracing.com/tech/engine/rsratio.html

Here's another pretty good read on rod ratio and some other things.
http://www.victorylibrary.com/mopar/rod-tech-c.htm


So there you have it

[kfxguy]

ehh...the rod ratio of the +4 is 1.57..... but im splitting hairs!

but i wouldnt hesitate to use either one as i stated earlier. the +4 is so awesome because you dont have to buy a special piston....so even if you needed to just change your crank because the stoker is wore out...why not do a plus 4? well worth it even if your not racing...makes the bike so much more fun. i wish i had a stock bike to throw a crank in...that would be an awesome all around Z!

[CFM-Z440]

If you want to split hairs the rod ratio of the +4 is 1.5765765765765765765765765765766 which rounds up to 1.58. I felt no need to clarify that.

[kfxguy]

QUOTE (CFM-Z440 @ Jun 14 2010, 10:24 PM)

If you want to split hairs the rod ratio of the +4 is 1.5765765765765765765765765765766 which rounds up to 1.58. I felt no need to clarify that.[/b]

i know....was picking with you

[cataway]

QUOTE (CFM-Z440 @ Jun 14 2010, 08:24 PM)

There has been a lot of talk about the two different hot rods stroker cranks and the pro's and cons of each. I decided to do the math to find out for sure and this is what I came up with.

Stock specs...

The stock crank has a 62.6mm stroke, a 107mm rod, and a rod ratio of 1.71

The +5 crank has a 67.6mm stroke, a 107mm rod, and a rod ratio of 1.58

The +4 crank has a 66.6mm stroke, a 105mm rod and a rod ratio of 1.58




The stock crank at 10,500rpm

Mean piston speed 4294.8 Ft./Min.

Piston acceleration 160,400 Ft./Sec/Sec






+5 crank at 10,500rpm

Mean piston speed 4638.1 Ft./Min.

Piston acceleration 176,358 Ft./Sec/Sec

(Does not raise advertized compression if used with a stroker piston)

(If not used with a stroker piston, it requires a spacer plate, cams degreed, and raises compression by one point)






+4 crank at 10,500rpm

Mean piston speed 4570.1 Ft./Min.

Piston acceleration 173,948 Ft./Sec/Sec

(Raises static compression ratio about 0.8 of a point over advertized)



So there's the truth, both stroker cranks should have roughly the same reliability, and will have about the same side load. However, be careful with the +4. They dont require the use of a stroker piston which means the extra stroke is going to raise your compression roughly by 0.8 So a 12:1 piston would be 12.8:1 which is not necessaraly "safe" on premium pump gas, depending on your cams and avaliable fuel. You can use the LTZ (3 layer) base gasket to help remedy this.

The +5 crank can also be used with a non stroker piston if a spacer plate is used. This affects the compression the same way by about a full point. So a 12:1 piston would be about 13:1 which is most likely not going to be usable on premium pump gas at all. When a spacer plate is used, the cams will also have to be re-degreed because raising the stack height of the cylinder will advance the cams.

The +5 crank can be used with stroker pistons. This adds to the cost of the build, but does not require any extra measures for cam timing, and the advertized compression will be correct.


Here's a good read on Piston speed and acceleration.
http://ftlracing.com/tech/engine/rsratio.html

Here's another pretty good read on rod ratio and some other things.
http://www.victorylibrary.com/mopar/rod-tech-c.htm


So there you have it [/b]

you did not coment on which or how much spacer plate to use with the +5

[CFM-Z440]

QUOTE (cataway @ Jun 15 2010, 04:39 AM)

you did not coment on which or how much spacer plate to use with the +5[/b]

Well if someone is going to try to build their own spacer plate I'm sure they can figure out that they will need to allow for an extra base gasket.

[kfxguy]

You need .100 thick spacer plate and you can get it from cometic.

[mana_z400]

now that's some good math! gotta save the numbers!!

that's a damn neat good work!!

[cataway]

QUOTE (CFM-Z440 @ Jun 15 2010, 10:16 AM)

Well if someone is going to try to build their own spacer plate I'm sure they can figure out that they will need to allow for an extra base gasket.[/b]

cometic offers more than one thickness of spacer plate.

my self i used the .100 and 2 drz base gaskets

[o2bfst]

awsome write up cfm..

[don'tletoff]

Here is a question stock z owners might want to know. If you put the +4 crank in a stock buggy, what octane gas will it need? I'm currently going to put a +4 in my quad and slowly upgrade the rest, but I would like to ride it until I have extra cash to buy another add on, so wondering if 93 will work with the stock piston? Not sure what stock compression ratio is or what it reccommends for fuel, but I have ran 87 pump since day one and it has never skipped a beat, so guessing with the +4 93 octane should work????? I have no clue to be honest, just asking.

btw, great thread!

[CFM-Z440]

QUOTE (don'tletoff @ Jun 15 2010, 07:19 PM)

Here is a question stock z owners might want to know. If you put the +4 crank in a stock buggy, what octane gas will it need? I'm currently going to put a +4 in my quad and slowly upgrade the rest, but I would like to ride it until I have extra cash to buy another add on, so wondering if 93 will work with the stock piston? Not sure what stock compression ratio is or what it reccommends for fuel, but I have ran 87 pump since day one and it has never skipped a beat, so guessing with the +4 93 octane should work????? I have no clue to be honest, just asking.

btw, great thread![/b]

Thank you,

It would be 424cc's and right about 12:1 if you use the stock style (3 layer) base gasket, which would be plenty safe on 93 or even 91 octane. You may even be able to push down to 89 octane but you had better be carefull if you try that.

If you used the DRZe base gasket (single layer) you would be closer to 13:1 which is most likely going to be too high for pump gas.


If I were you, however, I would do the other mods first, Exhaust, carb, cams, intake, ect as you will find better results sooner, for less dollars that way. The reason is because you wont gain much by installing this crank into an otherwise stock engine. If the breathing abillity is poor for 400cc's, it wont help much to try to run an even bigger engine with the same poor breathing.

[don'tletoff]

QUOTE (CFM-Z440 @ Jun 15 2010, 11:00 PM)

Thank you,

It would be 424cc's and right about 12:1 if you use the stock style (3 layer) base gasket, which would be plenty safe on 93 or even 91 octane. You may even be able to push down to 89 octane but you had better be carefull if you try that.

If you used the DRZe base gasket (single layer) you would be closer to 13:1 which is most likely going to be too high for pump gas.


If I were you, however, I would do the other mods first, Exhaust, carb, cams, intake, ect as you will find better results sooner, for less dollars that way. The reason is because you wont gain much by installing this crank into an otherwise stock engine. If the breathing abillity is poor for 400cc's, it wont help much to try to run an even bigger engine with the same poor breathing.[/b]

Thanks man, good info.

I guess i'm not complete stock (my engine is), I do have K&N, Jet kit, and yoshi full pipe. I just figured since I have to split the cases I might as well throw the +4 in there and then my next mods will be carb and cams, and eventually cw cylinder with 94mm cp piston.

[arrowblazer71]

Here we go, im reviving a dead thread. I found out my z had the stroker kit it has a p6001 hot rods piston. I called wiesco they dont make a stroker piston. Does anyone know of any other piston manufacturer that makes a stroker piston. The hot rods one is 256 bucks