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Stroking the predator

D

D majors

New member
Was wanting to get more hp by putting a Stroker crank and a bigger piston. How far does the piston need to be in the hole. Does that determan how much of a stroke or do you compensate with the rod and head gasket
 
If you are putting the ARC stroker crank in... You are going to be using the Wiseco piston. You can mill the piston to get your desired height... It is not just a plug and play build... You have to measure everything first...then decide what you want to do!!!

Example I milled the piston .085 to get .015 pop up, then used a .045 gasket...

Or I let the piston pop up .085 circle milled the head .065 to allow for pop up and adjusted clearance with head gasket to get my desired clearance...
 
I appreciate your time and input.i know I'm gonna have to do some machine work on clearances with crank and maybe the cam.i know little about clearances,like how much the piston can stick out or about how much room I need in the head so it won't blow it off.i have a buddy that's a machinist so he can help me there.i run in an open class and need a little more hp.to run with the animals
 
Those Animals are mean!!!
I run against stroked Animals with my stroked Predator...
If I miss on tires or set up they eat me alive... I can just barely stay with them when I get to everything right...

Normally you want at least .030 piston to head clearance...
I run a .330 lift cam with 1.2 rockers, and only had to clearance the block at the top and bottom for the rod... Cam was fine... This is with a 14cc head with 32/27mm valves
 
NR Racing also has a predator stroker kit, you might check into that one also. Either way you go its not a plug and play job
 
I have just one more question before ordering my parts. Std size piston vs .020. The way I look at it, if I'm gonna spend time tearing it down it would be best for me to do all at once. Any problems with boring it that size. Does the head need to be cut also .020
 
Check the NR site. There are piston sizes where you have to re-sleeve the block. The Predator is a 196 block that's been bored already.

Sundog
 
not all predator blocks are the same as a 196, only the hemi predator will work if you want to use some of the same parts
 
I'm running the old style predator with 27mm and 24 mm valves I think. I'm not really sure. I'm thinking I'm just gonna buy a new block and keep that motor like it is and start from scratch. Do you think the hemi heads are better to work with or give better flow. Thanks
 
The hemi heads are better when you get into highly modified builds, but they require alot of port work to make them flow better than the old style predator head that you have now. If you have the head with 27/25mm valves then its likely an RTC-6 or RTC-8 head, which are my favorite heads when it comes to these engines. When you compare the head like you have now against the hemi head or even Honda heads, the RTC heads like yours flows a good bit more than the others in stock form, according to flowbench results that I have seen done by another builder. Add a little port work to the RTC head and you have a very nice head that will also accept aftermarket rocker assemblies that are already available, like the Champion rockers and several types of roller rockers out there now. The hemi head just recently had a set of aftermarket rockers available, which are the ones that NR Racing makes, and I believe there is one other company that makes them also but can't remember the name. What you have now is just as good as anything else to work with and build from, I would stick with it if it were me.
 
I think I will work with what I got. Thanks so much for your input. I've only been racing a couple of years and I don't know much about head work and so on. It started out as fun with friends but it has got competitive now. Anyone know about rockers and which ones work better. The advantages of roller rockers verses others. Thanks
 
The champion rocker's are a very good choice when you just want something that is stronger and more reliable than the stock stamped steel ones, they have been tested alot and can handle as much rpm as you can throw at them. Roller rockers are nice to have but to me the gains arent worth the cost of them, but that is just my personal opinion on them. Roller rockers offer less resistance at the tip of the valve than shaft mounted rockers like Champion or the stock rockers. Stout Racing has some modified champion rockers that are 1.3 ratio instead of 1.1 ratio, if you are wanting ratio rockers to give you more lift. Good thing about the head you have is that any rockers on the market that will fit the Honda Gx200 or clone engines will also bolt right up in your head too, so that leaves you a ton of rocker choices out there. Burris Racing makes a nice set of shaft mounted rockers, so does Dover Power.

Any of these rockers listed below will be a direct bolt in for your engine. Some might require you to remove the push rod guide plate that sits under the rocker studs, and you may or may not need to adjust pushrod length to get your valvetrain geometry correct after installing.

Here is a set of really nice ones made by Gage Motorsports, they are one of the best rockers on the market and used by many people...
http://www.nrracing.com/product-p/200-rollrcks-12-lite.htm

Burris shaft mounted rockers:
http://www.nrracing.com/product-p/burrock.htm

Here are the Champion rockers that Stout Racing sells, they have 2 different styles to choose from, i like the half moon style myself:
http://stoutracingengines.com/m-clone-parts.html

Mike Clements Racing also offers a very nice set of roller rockers that are available in just about all ratio's you could want:
http://www.mikeclementsracing.com/GX200page.html

Here is Dover Power's rockers they make and sell:
http://www.doverpoweronlinestore.com/catalog/item/8251221/10183966.htm
 
Thanks. That's a lot of good info. Now I just gotta process that and think about how it all works. The 1.3 ratio rockers holds the valves open longer to let more in and more out? I've never modified any motors,done a lot of work on them. Thanks
 
The ratio rockers basically multiply the lift of the cam, but at the same time they put more stress on the pushrods and valvetrain I believe. They will open the valve further. So if you have say a black mamba cam with .275 lift and you want to use 1.3 rockers you would multiply .275 X 1.3 and that will give you the amount of lift you will then have at the valve. Anytime your adding more lift its going to open the valve further and let more air and fuel in and out, which would not only increase power but it will move the rpm range of where the engine makes peak power, to a higher rpm, meaning you would need to turn more rpm than before. So think of It as moving your power band to a higher rpm range. I hope I worded that right, if not I'm sure one of these guys will chime in and correct me on it.
 
Ratio rockers change the amount of lift, they also change the rate of speed of the valve components travel to max lift. The load imposed on the components on the cam side of the fulcrum is also multiplied by the ratio factor. As an example if the spring resisted the cam with 26 lbs at 1:1 it would now resist at almost 34lbs.
 
I apreciate people who are willing to share their knowledge. I took my engine apart and did some measuring on what I had. My piston was in the hole .063. From valves to bottom of head was .161. Not sure what head gasket I had. I'm running the nr racing cam,270 series. 4500-7500 rpm. 11 to 1 or higher compression needed 274 lift 260 duration. Tilly carb,Stroker kit. When it's all said and done how much room do I need between the valves and the piston. I know I've also got to factor in the head gasket size to get the number I need. I just don't know how to get that number to get that 11 to 1 compression.
Would apreciate any help. Thanks
 
You have to start at the .063" in the hole, deck the block to zero use the Honda Gx200 metal .010 gasket, flat top piston. Assemble and measure chamber volume, measure valve to piston clearance, then mill head to get to your desired CR.
 
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