Go Back   DIY Go Kart Forum > Building Plans And Advice > Engines & Clutches

Notices

 
 
Thread Tools Display Modes
Prev Previous Post   Next Post Next
  #1  
Old 01-28-2017, 12:22 AM
bob58o's Avatar
bob58o bob58o is offline
Sick, Tired, and in Debt
 
Join Date: Jan 2016
Location: Under the Rothschild Whip
Posts: 7,475
Thanks: 3,214
Thanked 2,195 Times in 1,713 Posts
Default Hemi Predator Build #2

CAMSHAFT

NR 285-0211
http://www.nrracing.com/product-p/200cam-285.htm

0.285" Lift
250 degree duration (at 0.050")
102 Intake Center Line
111 LSA
7000 RPM

Camshaft, 285-0211: Small track cam for serious torque
Requires 11:1 or more compression ratio
Requires 26lb or more valve springs.

This cams likes big carbs and big ports. Will easily make 20 hp when used with correct combination. Best with 24 mm Mikuni, big valves, and high compression. Honda blocks must be clearanced to install.

---------- Post added at 01:01 AM ---------- Previous post was at 12:58 AM ----------

This is the best post I found about Honda / Clone / Predator Camshaft specs.... I shared before, but here it is again.
It originally came from Russel at NR

https://karting.4cycle.com/showthrea...cam-logic-more

"
There are four important numbers on a cam. ICL (intake center line), LS (lobe separation), duration, and lift.

Don’t worry too much about lift. The Honda head (i.e. port design) does not respond much once the lift at the valve exceeds about .350. A .275 lift cam with 1.3 rockers will achieve this. We have spent a lot of time on the flow bench, and unless the head is radically changed you will not see much gain past .350 lift.

Duration is another story. This is how long the valve is kept open. Hondas love lots of duration. We have run as much as 300 at .050, but 260 seems to be a good compromise better power and tractability. As duration goes up, so does the rpm at which max power is made. At the same time idle quality goes down along with low-end torque. An engine with a lot of duration will scream and make lots of power but can be a dog off the corners and/or trying to get started, not to mention idles at 3000 rpm.

Typically 210 to 220 makes for high torque motors that start and stop a lot, use low rpm stall/clutches, and see a wide range in operating rpm. These motors will peak somewhere between 4500 and 5500, and will pull to 6500.

250 to 260 are for the 7000+ motors that don’t see RPM much below 5000.

Needless to say, 230 to 240 cams fall in the middle.

One interesting thing about duration, the smaller the carb, the more duration can help a motor. With small carbs, usually the cam/ports will flow more than the carb can deliver. The only way to improve power is the hold the valve open longer. In other words, where going from a 240 to a 260 cam on a motor running a 28 mm Mikuni will only show a 10% improvement in peak HP, doing the same on a motor with a stock carb can show a 20% improvement.

Almost as critical as duration, is the ICL. This is the intake opening and will range from 98 to 116 degrees. It is also referred to retard or advance in the cam. This determines the where the peak torque will occur. Most cams fall in the 102 to 110 range. FYI: Honda 160s are around 105 and GX200s around 110 from the factory (retarded for emissions).
A cam with a 102 will have power range/peak around 1000 to 2000 rpm lower than a cam with 110 ICL. It will also have considerable more low-end torque and will pull a lot harder off the corners. For very, very small tracks this can translate into significantly lower lap times despite having lower HP. For Boats, winch boarding, rock climbing ATVs, these cams can make huge differences. Depending on the application, it is possible to stall a motor that has a high ICL, whereas advancing the cam produces great results.

At the other extreme, a cam with 114 ICL might peak in the 9000-rpm range. On a large track (1/2 mile) where the rpms never get below 7500, it would be unbeatable. However, you would need a clutch that engages at 5000+ just to get moving. Not always fun for a street toy.
The other important number is the LS (lob separation), which determines the amount of overlap. These will range from 100 to 115, but most cams will be in the 106 to 110 range. As a general rule the lower the number, the more HP, but the with a smaller power band. However, the wider (less overlap) the LS, the more dynamic compression a motor can build. For high compression engines, overlap is needed to bleed off compression at lower RPMs preventing detonation. Anything over 11 to 1 should be using a 106 to 107 LS. For lower compressions, it depends on how wide a power band is desired. If you want a power band of only a few 1000 rpm (typical for oval tracks), then go with a narrow LS, however if your rpm ranges from 2000 to 7000 (road courses), then you may want a wide LS.

The duration, ICL, and LS all work together and changing any or all of these numbers can have a significant impact on how a motor performs.

One final note, what works on the dyno does not always work on the track and vice versa. What works great in a Mini Bike may not be the best for a Kart, a dirt track cam is not going to be the same as a paved cam, etc, etc.

www.nr-racing.com

The part number of our cams tells the ICL and LS. The first number is the lift, the second set is the CL, and the last set is the LS. For example

280 0207 .280 lift 102 ICL 107 LS
252 0607 .252 lift 106 ICL 107 LS
252 0207 .252 lift 102 ICL 107 LS
252 0211 .252 lift 102 ICL 111 LS
274 0607 .274 lift 106 ICL 107 LS"


---------- Post added at 01:15 AM ---------- Previous post was at 01:01 AM ----------

CYLINDER HEAD

NR Racing Hemi Head
http://www.nrracing.com/product-p/headhemi.htm

Lightweight Stainless Steel Valves
28mm Intake (vs 27 stock)
25mm Exhuast (stock size)
Fully Ported and Bead Blasted
Milled 0.040" (should be around 17.5cc - 17.75cc)
Aluminum retainers and Split Keeper
3 angle valve job
26 lb springs (37 lb Valve Springs if I rev to 7500 RPM)
Lash Caps

Stock Rocker Arms (Don't think I can fit 1.2 Rockers and keep the compression I want with the Hemi Head without cutting valve reliefs in the piston EDIT: or welding the chamber.)

---------- Post added at 01:22 AM ---------- Previous post was at 01:15 AM ----------

PUSHRODS

http://www.nrracing.com/product-p/cmpr-55.htm
x(2)

CrMo
3/16"
5.44" Long (vs 5.54" stock) I think either will work


"Heavy Duty Chrome Moly Push rods. Considerably stiffer than stock. Use with all HD springs. Capable of 10,000 RPM +

ALL PUSH RODS ARE SOLD INDIVIDUALLY. YOU MUST ORDER 2 PER MOTOR


Select Length based on the following.

GX200, 160, and 6.5 Chinese OHVs
5.260 Stock Length; Use with stamped Rocker Arms
5.160 (-.100); Use with Billet & Roller Rocker Arms
5.110 (-.150); Use with Billet/Roller Rockers along with extensive milling (>.065")
5.440 (+.180); Allows use of 160 Lifters in 200 blocks to reduce valve train weight. Reduces combined lifter/Pushrod weight by approx 7%. Use with stamped Rocker Arms
5.340 (+.080); Allows use of 160 Lifters in 200 blocks with Billet or Roller Rockers.
212 Predators (Old Style)
5.200; Stock length
5.110 Use with Billet & Roller Rockers
212 Predators (Hemi Head)
5.544 Stock Length, most applications
5.440 (-.100) use with extensive milling
5.260 use with NR Racing Hemi Rollers
5.160 use with NR Racing Hemi Rollers and heads milled .065 or more, also with large base circle cams.

Also available in unfinished. Must be cut to length. Includes tube and two ends

All push rods are sold individually.

Note: Due to differences in cam base circles, deck heights, head milling, gasket thickness, etc. actual push rod length can vary. Pushrods are sold for the experienced engine builder.
We recommend you assemble the motor first and then determine correct pushrod length. One of the best ways is to grind a stock pushrod until you get correct geometry, measure, and order one closest to that size."
__________________
History doesn't repeat but it rhymes Name a successful fiat currency in the last 5k years
 

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off



All times are GMT -6. The time now is 03:51 PM.