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AKRA Cam upgrade

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cgray

Member
Have an older motor looking to upgrade the cam in has a cl-2 in it and It runs good but I am lacking top end. Faster karts start pulling away about 3/4 down strait away. Have tried what was supposed to be a cl3 in this motor and it was a turd, couldn’t get over 65-6600 out of it. It will crank up to 67-6800 all night with the cl2. Have another motor with a bsp4 and that motor pulls like a freight train. How does the ev6, trj a-4 or Dr. Fast cam compare to say the bsp4 in terms of pulling and top end? Will be run on a super heavy kart on 1/8 mile track 691ft around the groove. Gearing around 13/61 to 14/65 depending on conditions. Dropping around 11-1200 rpm.
 
Are you identifying the correct centerline on the cl3? If you don’t have that correct you will experience what you are. The ev6 , cl3, and the dr fast cams are really close to each other. If your head is done correctly and you have the cam set right and a good carb you should not have issues
 
Intake centerline with this new crank is 113.75 with the cl-3. I checked with the old crank before I tore it down it was right on 114. The guy I got the motor from said it wouldn’t crank up high either. I thought it was a timing issue because it only had 28 degrees when I got it. Put it back together @ 36 still pretty much the same with that cam.
 
I use both the bsp4 and EV6 cams I like the bsp4 for the smaller tracks it’s comes on quicker... the EV6 is not suffering down low but it shines up top.
 
I defiantly like the bsp4 that motor will out pull both of my brothers new Welch motors. I had been running that motor with a 880 pipe and a 13 driver. I may try a 930 pipe and a 14 driver on it and that may give the extra speed for the end of the strait.
 
Honestly al I haven’t even looked at the actual ratios I just gear by tach and feel. I can tell u the 13 pulls harder off the corner good for when the tracks real wet & slow, but if the track dries out the 14 is defiantly faster.
 
cgray said:
Honestly al I haven’t even looked at the actual ratios I just gear by tach and feel. I can tell u the 13 pulls harder off the corner good for when the tracks real wet & slow, but if the track dries out the 14 is defiantly faster.
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I can totally understand a higher ratio being faster on a better track, but the same, or nearly the same, ratio? I think if it was me I would leave the driver at 13 and take 2 teeth off the axle. Maybe even 3!
 
Ovaltech, track is around 1/8 mile 691ft in the groove according to mychron5. If the track is good I can flatfoot all the way around come feature time. If I can’t flatfoot I just burp it going in just enough to give it some air no more than a second if that.

Dyno Don, don’t know much about the head. There r no builders markings on it. It’s a it-111 has been ported, although very lightly mainly rough edges smoothed and short turn has been worked, has been milled,just about to the fin, you can still see the edge around the sealing surface but it’s pretty thin.
 
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So it's not a stock class engine ? Your rule package allows milling , I would be going a whole different direction with the cam .
 
Track runs AKRA rules is milling not allowed in AKRA? We just got back into karting pretty heavy this year after about a 15 year break. I was actually thinking about calling up Todd Miller and seeing if he sells a head/cam combo separate like JRPW or Dover. Most of the winners are running miller motors. At least that’s what’s on the side over anyway. I have always enjoyed building my own stuff and being able to run with the big name builders. On a Saturday night level anyway. My brother has been trying to get me to upgrade my chassis, he thinks I’m loosing speed with my old 04 blaze octane. I drove his 18 rival one night though and I hated how that thing handled.
 
I like the .880 pipe and 13 driver combo 1/8 mile on a heavy kart. I feel that 36 degrees of timing is a bit too much in my eyes. 33-34 degrees would be suffice.
 
on this motor 36 does seem to be a little high it wants to run quite a bit hotter that the bsp4 motor. Could be the different flywheels bsp4 has a PVL the other a raceseng.
 
Do yourself a favor and do a leakdown after it is hot and cooling down to touchable condition. You learn a bunch with that test. Porting is allowed in AKRA
 
Have you cc'd the engine ? Are you using a thicker head gasket ? Stock rod , crank , ect ? Not many Saturday night tracks will do many checks in tech , but if you decide to go to a bigger event , you may get tossed . I have taken a Cl3 above 7000 rpms and had no issues . I like the Cl2 on small tracks . I run in the Super Heavy class or Sumo at times and my drops are usually no more than 500 to 600 even on the tight bullring 1/10 mile I call my home track . I would say its more a kart issue rather than engine . JMO
 
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