After market head on pro rmk 800

[chrishew]

i know this is kinda a dumb question but what does 13.1:1 head mean?? what do the numbers mean what is the stock head at??

A compression rating is the cylinder volume when the piston is at the bottom of its stroke vs the volume when it is at the top of its stroke. I believe the stock compression is 12:1, meaning there is twelve times the amount of space above the piston when the piston is at the bottom of its stroke compared to the space above the piston when it is at the top of its stroke. A high compression head lowers the distance between the piston and the head, or reduces the clearance. So the 13.1:1 P.A head has less clearance therefore the volume above the piston when at the bottom of the its stroke is 13.1 times the volume when the piston is at the top of its stroke. This results is a higher compression because the piston is squishing nearly the same amount of volume as the the engine with the OEM head into a tighter area when the piston reaches the top. So the highest compression ratio P.A. head is a 13.6:1 and the slightly above stock head is 12.5:1. All P.A. heads also use a much more efficent shape to the heads dome which also aids to the throttle response.

If any of you change to a P.A. head you should take some pics comparing the stock and P.A. dome designs.

 

[snowho]

I ordered the P.A head with a SLP pipe kit from parkland Chris called back and recommended the SLP head instead. He said SLP makes the head to work with the pipe/can combo at the RPM that the 800 RMK is meant to run at which is 8250 ish. Is any one running this set up?

 

[E-Zmoke]

I ordered the P.A head with a SLP pipe kit from parkland Chris called back and recommended the SLP head instead. He said SLP makes the head to work with the pipe/can combo at the RPM that the 800 RMK is meant to run at which is 8250 ish. Is any one running this set up?

Interesting...True SLP does make and test this stuff to work for their product but i find this very interesting. Perhaps Chris can chime in here to fill us in on this? I have never tried out in comparison the SLP head but I don't think it even compares to the PAR in the midrange.

I am curious to know what compression ratio SLP head part #12-394 and #12-395 are? Does anyone have this info?

SLP claims an "additional 3HP peak With a much more responsive midrange"
PAR claims a "4-5HP peak with 10+HP midrange"

I honestly think the PAR head is a better combo with the SLP pipe then the SLP head is but I don't have a dyno to prove this. Just based on the numbers I can find. Let's not forgot with the power commander you can tweak your map to compensate for running a different head other then the SLP head and lean it out where it needs to be leaned, add fuel if need be...the combo of the HUGE midrange gains from the PAR head and the top end from the pipe are insane. Just my thoughts...here is some numbers to support my opinion.

http://www.startinglineproducts.com/img/dyno/2011_Polaris_800_Stage-3-Final.gif
http://www.startinglineproducts.com/img/dyno/2011-Polaris-800-with-SLP-Single-Pipe.gif
PAR dyno'd claimed numbers: (no graph)
4500 +12 hp
5000 +14 hp
6000 +9 hp
7000+4 hp
7950 + 5.5 hp

 

[snowho]

I have looked at the numbers to. Chris did convince me it is a better way to go so thats what I ordered but I am taking into consideration that he knows his stuff so I trust him. On SLP's web site they have the stage 3 kit which includes V-force 3 reeds,and a primary/secondary clutch kit with claimed gains of 15 plus HP and 9 plus Ft lb. of torque .Never ordered these goodies yet but I did get the SLP primary springs.

 

[polaris011]

I have looked at the numbers to. Chris did convince me it is a better way to go so thats what I ordered but I am taking into consideration that he knows his stuff so I trust him. On SLP's web site they have the stage 3 kit which includes V-force 3 reeds,and a primary/secondary clutch kit with claimed gains of 15 plus HP and 9 plus Ft lb. of torque .Never ordered these goodies yet but I did get the SLP primary springs.

what spring did you order??

 

[snowho]

SLP blue/pink

 

[E-Zmoke]

I have looked at the numbers to. Chris did convince me it is a better way to go so thats what I ordered but I am taking into consideration that he knows his stuff so I trust him. On SLP's web site they have the stage 3 kit which includes V-force 3 reeds,and a primary/secondary clutch kit with claimed gains of 15 plus HP and 9 plus Ft lb. of torque .Never ordered these goodies yet but I did get the SLP primary springs.

Out of anybody Chris would know I'm sure he has seat time on both setups...

 

[Chrisco]

The SLP stage 3 kit makes its power at 8250 8300 from looking at the dyno sheet and talking with slp. Brads 13.1 head seems to make the best power at 8100 from what he says, so in this case I would like to stick with the slp head for this customer. He also likes to ride at home so this setup would be the way to go for him. I dont know the diff in head disign but if slp wants 8300 rpm to make power thats were its going to be.