Box Stock

How would you build with these rules?

T

Tacmedic83

New member
Based on these rules how would you build this engine?
Start with an HF Predator and get creative, remember, it's green plate and will use an EVause carb and weenie pipe. What cam would you use and what other go fast goodies or tricks to get most power within these rules. I do not want to cheat as, well, I can't stand a cheater but also tech is very tight!


JR1: 6-10 years old
260LB WEIGHT RULE
Semi-Skilled kid class (Cage kart only)

*
Single cylinder OHV engines only (i.e. Clone).

Stock engine with a maximum displacement of 212cc.

Stock engine with a minimum combustion chamber of 24.58cc (To be checked through the spark plug hole with syringe).

Stock un-ported cylinder head is required (All head gaskets are legal).

Stock crankshaft unaltered (Aftermarket flywheel required i.e. ARC #6625).

Any*length connecting rod is legal.* Billet aluminum is legal.

Stock unaltered piston only (2.756” maximum).* *Head and piston must be of the same make and model (i.e. Hemi head to flat top Hemi piston).

CAMSHAFT REQUIREMENTS:* STOCK CAMSHAFT CORES ONLY, EZ-SPIN ASSEMBLY MUST REMAIN AS STOCK.* CAM LOBE BASE CIRCLE DIAMETER .865" -.005"/+.010"*MAX INTAKE LIFT ON CAM.225" - MIN.215" LIFT TAKEN AT THE PUSH ROD.* MAX INTAKE LIFT AT THE VALVE .261" TAKEN ON THE VALVE SPRING RETAINER WITH ZERO LASH.* MAX EXHAUST LIFT ON THE .232" - MIN.222" LIFT TAKEN AT THE PUSHROD.* MAX EXHAUST LIFT A THE VALVE .266" TAKEN ON VALVE SPRING RETAINER WITH ZERO LASH. (TO ACHIEVE ZERO VALVE LASH FOR CHECKING RUNNING LIFT, PRELOAD DIAL INDICATOR BY .001”)).

Stock rocker arms unaltered (1:1 ratio max). Hemi stock rockers are 1:11

Stock lifters unaltered.

Any push rod is legal.

Any valves stock size for that engine make and model are legal.

Valve Spring Installed Height Minimum .815 Maximum Spring Tension of 10.8 At a Height of .850 (Max Wire Diameter of .071”)

*
Any retainer and keeper is legal.



Stock valve cover unaltered (You may install fuel pump port).



Stock side cover unaltered.



Any ignition coil is legal (wire and boot non-tech item).



ARC single hole GREEN carburetor restrictor plate required unaltered.



Exhaust:* RappFab "Winnie pipe" turned up (EFR-RF-BS-CP-N) or ARC “Winnie pipe” (DJ-1138B) with RLV Mini 91 Muffler REQUIRED, no alterations.



Shoe Clutch only (Any make).



Stock appearing clone carburetor measuring a maximum .615 at the butterfly and .751” at the exit (Measured with ‘NO-GO’ gauge), any gasoline is legal including racing gas.* No alcohol over 10%.* Choke may be removed.



Any air filter and/or adapter is legal.



Aftermarket Carburetor spacers and insulators are illegal.



Fuel tank must be relocated and a pulse fuel pump installed.*

Vacuum may be accessed from anywhere on the valve cover or crankcase.



Stock pull start only unaltered.



Removal of governor and/or governor components is legal (Plugging holes legal).



Removal of oil sensor and/or oil sensor components is legal (Plugging holes legal).



No wedge bodies.*

3 piece champ kart bodies only
 
Assuming these are MARS rules, mod2 cam would be the way to go. You going to build it yourself or have a professional builder do it ?
 
I'm going to have it done. Just wanted to know others opinions. I was thinking mod2 or bsp3 after a little research. Just don't want to leave anything potentially on the table so to speak when I send parts to my builder.
 
What's the budget? Have you ever heard the old saying; "speed costs, how fast do you want to go"? Smarts is very helpful, but so is money.

My plan; buy as many engines as you can afford and measure them. A bore that is 90° to the crankshafta would definitely help.

A lot of good drivers out there, with good engines, and they're mostly smart. The challenge is to be a little smarter. Think of things others haven't thought of, or if they have thought of them, maybe they haven't tried them.

I believe, because this is such a competitive sport, attention to detail is crucial. I know if I was racing with them, there are some things I would have.

First off; a good exhaust gas temperature gauge. (EGT) An air density gauge. A lot of carburetor jets, both low-speed and high-speed. A 1% change in air density is said to need a change in air/fuel ratio of 1%. If you have a .038" high-speed jet, and you want to change the air/fuel ratio by 1%, because the air density has changed by 1%, it takes a .0002" change in jet size. You won't find any jets that size at the local kart shop. Fuel is about 700 times denser than air, be very careful when you open up jets. The slightest imperfection in the hole can disrupt the fuel flow, a lot.
 
That is a weird set of rules.. Vage on somethings.. I wonder how they are going to check install spring height on a Hemi??
Also can you run a RT head on a Hemi block? Its all Predator right..

The wording on the carb checks isn't correct.. Butterfly / throttle valve area is .751.. The venturi is the max .615 check is.. Then they say no chole is ok.. With that said I wonder if the carb is ONLY measurements and no visual beyond that? Theres no mention to e tube and jet requirements.. This leads me to believe a legal stock class AKRA carb won't be enough even with the green plate..

Billet rod will make it way more durable,, but it will not offer any HP advantages..

Its mentioned that the stock rockers are 1.1.. In reality they hardly ever true 1.1.. If your cam lift checks out why be concerned? They give checks on both ends anyway but most only check the lift on the actual valve..

As for headers you need the BIGGEST id pipe available with a 1/2' flange CNC port matched
 
Dover Power said:
That is a weird set of rules.. Vage on somethings.. I wonder how they are going to check install spring height on a Hemi??
Also can you run a RT head on a Hemi block? Its all Predator right..

The wording on the carb checks isn't correct.. Butterfly / throttle valve area is .751.. The venturi is the max .615 check is.. Then they say no chole is ok.. With that said I wonder if the carb is ONLY measurements and no visual beyond that? Theres no mention to e tube and jet requirements.. This leads me to believe a legal stock class AKRA carb won't be enough even with the green plate..

Billet rod will make it way more durable,, but it will not offer any HP advantages..

Its mentioned that the stock rockers are 1.1.. In reality they hardly ever true 1.1.. If your cam lift checks out why be concerned? They give checks on both ends anyway but most only check the lift on the actual valve..

As for headers you need the BIGGEST id pipe available with a 1/2' flange CNC port matched
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Mr Dover on the head I am not sure, that rule is in place to keep the non hemi head from setting atop the hemi flat top piston is only thing I am aware that they have checked. CC check is literally done with a syringe.

As far as the carb it only has to be stock appearing and when we have been though tech the only checks I have seen were that they pulled the choke out and checked diameter with go/no go guage. Any etube or jet or mods are fine as long as no epoxy is used.

The rockers were mentioned that hemi's tend to be 1.1. You are correct that as long as when lift is checked and you are within limits and rockers appear as stock that you will be fine.

As far as the header goes MOST are running the new thick flange weenie pipe you guys have and claim they get a few more rpm with it compared to the old weenie pipe.

I intend to give you a call on this build when I had together more in my mind ideas of what I needed but being new I wanted to put it out there and see what others may have for ideas too. Thanks for the reply.
 
FYI - I just dynoed a box stock 69730 RCT 9 at 9.58hp @ 4100rpms with just a jet change . Compared to the hundreds of stockers I've tested this is one of the best right out of the box .
 
sneaks12303 said:
FYI - I just dynoed a box stock 69730 RCT 9 at 9.58hp @ 4100rpms with just a jet change . Compared to the hundreds of stockers I've tested this is one of the best right out of the box .
Click to expand...

You can see the numbers, all I can see is the chart, and it doesn't look to me like peak horsepower is at 4100 RPM. I know, I know, I'm a pain.

Additional "I'm a pain". If the torque is corrected why do they have to say the hp is corrected?

To what do you attribute that little blip at the very top? I've never seen that before!

I wonder about your use of a clutch on your dyno tests? Not questioning your thinking, just wondering?
 
Sneaks, running a box stock class with weinie pipe and air box. Based on your graph would one be best off shooting for max rpm of only 4600 as long as you keep rpms above 3600 thru turns.
 
alvin l nunley said:
You can see the numbers, all I can see is the chart, and it doesn't look to me like peak horsepower is at 4100 RPM. I know, I know, I'm a pain.

Additional "I'm a pain". If the torque is corrected why do they have to say the hp is corrected?
Good pickup Al . Actual Pk was 9.54hp @ 3800 but that might B some clutch slippage . I do run a clutch for many reasons . Safety being one . The dyno sheet is always up to "interpretation. I consider Max Peak on this little gem between 3600-4400r's . At 4450 she's still pulling 8.94hp . The A/F tells me she was running rich . Playing with the jets could yield another 1/3 hp or more . She's a Keeper in my "Book of Box Stockers" And the split keeper retaining system on those 5mm valves is a Big plus .
As for the Corr TQ an HP , I have a choice . That simply tells me what I choose .
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I really think the 730 predators are under loved... they get 1/2 the goods we wanted from the old clone and o.g. predator
 
subbietjw said:
I really think the 730 predators are under loved... they get 1/2 the goods we wanted from the old clone and o.g. predator
Click to expand...
She's a Stroked an Bored Hot Rod clone . She breaks all the rules . The "rule makers" R afraid of her . LOL . She's the new girl in town .
 
cking said:
Sneaks, running a box stock class with weinie pipe and air box. Based on your graph would one be best off shooting for max rpm of only 4600 as long as you keep rpms above 3600 thru turns.
Click to expand...
This is open .990"exhaust w/open air flow,no filter .The weinie pipe an air box will take away HP . All bets R off .
 
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