What is the biggest stroker?

[Jammies]

I've searched around for this answer, but haven't found it. What is the biggest aftermarket stroker that can be put in a Blaster? The biggest I've found/heard of is +4.

 

[blasterdemon7]

+4 is the biggest stroke crank for a Blaster. I beleave O'Conner racing does a motor with the + 4 crank and a Banshee piston rod. I'm not sure what the total stroke is with the crank and rod combo.

 

[Jammies]

"Piston rod" is the same as a connecting rod, right?

 

[Larry's Shee]

Yes on rod name, con rod is more common. Length of rod has nothing to do with stroke, stroke is 2x offset of center line of rod pin to c/l of crank. +4, +3 are what's commonly available. +3 is drop-in, +4 requires case machining.

 

[Prime]

There are a few +6 cranks out there, but that's because of manufacturing problems. The geniuses at Vito's didn't understand that they only had to offset the pin 1.5mm to make a +3, instead they offset it 3mm, creating the +6.

But to answer your question, +4 is the biggest you can go, however it will need the cases to be trenched. You can have the 115mm connecting rod on any crankshaft, and it does not affect the length of the stroke, just moves that stroke 5mm further from the center of the crankshaft.

 

[Jammies]

Uhhh... I have a pretty good understanding of these motors, but these stroker cranks confuse me.

"...they only had to offset the pin 1.5mm to make a +3" <--- That's confusing me. What pin is being "Offset?"

 

[Prime]

They offset the pin from the stock position 1.5mm further out from the center of the crankshaft. This makes the stroke 1.5mm higher, and also 1.5mm lower. Creating the +3.

Remember, the more stroke there is, the more torque per revolution there is.

 

[Jammies]

Ahh, that makes sense Prime. Thanks for that, of all the research I've done you're the ONLY person across many websites to say that.

 

[Prime]

That's very hard to believe. But, you understand now, right?

 

[Jammies]

It makes a lot more sense now. So in the end, is the conrod length increased?

 

[Prime]

I don't quite understand what you're asking. The conrod doesn't change length, and also does not affect the length of the stroke. If you have a 110mm rod (standard) the motor will rev faster but also put more wear on the skirt of the cylinder sleeve, where if you have a 115mm rod, the motor won't rev quite as fast, but will not be so harsh on the sleeve's skirt.

 

[Jammies]

Yeah now I'm confused... "Stroke" is how far up and down the piston travels, right? So wouldn't the connecting rod length directly affect that? Ugh... Told you this stuff confuses me :/

 

[Prime]

Yes the stroke is the length that the piston travels. But the conrod doesn't affect that length. It only affects where that stroke is in relation to the center of the crankshaft. If the conrod affected the length of the stroke, it would have to be stretchable. LOL

 

[Jammies]

Ok... I'm trying to grasp all this info.
So where does "+4" come from? Is that how far offset the pin is from stock position?