Cam differences for jr1

Eric85629

Member
I'm learning about how to build engines 1 component at a time and my latest question is about cam choice. I'm allowed a cl2 (from dyno cams) but I see different styles- retard timing, minus lift, & normal.

I would assume minus lift would just mean the lobes aren't as tall but the timing would be the same as the normal. Would this be for a higher rpm engine? What's the purpose of minus lift?

For the 2 degree retarded timing cam, when would that be used? I understand advancing timing with a flywheel will create a spark at a different time so the combustion can be harnessed better. Would retarding the cam timing basically be the same as advancing the spark timing or am I thinking about this wrong?

Thanks for the help, I will be building my 7 year old her first clone engine during winter break and just want to understand why certain parts are choosen
 

Eric85629

Member
Changing cam timing moves the power band up or down the rpm range. Retarded would be higher rpm.
I would use standard cl2 .
I was planning on the cl2 but I figured it's good to understand the differences. Is the low lift cam meant for higher rpm to help with valve float?
 

flattop1

Dawg 89
No not for valve float, component weight and spring setup control that .
I believe it two fold.
Easier to stay legal on the lift check .
Also i believe that the low lift was said too produce more power at high rpm .
Honestly a call too Dyno for there recommendation would be worth the time spent .
 

XXX#40

2A supporter
I was planning on the cl2 but I figured it's good to understand the differences. Is the low lift cam meant for higher rpm to help with valve float?
I think I'd look for one of Vauses plate engine cam/head/carb combos and use the information he gave for setting it up.
Pretty sure dyno made those cams, dover has a plate package as well and would be a good option
 
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Eric85629

Member
No not for valve float, component weight and spring setup control that .
I believe it two fold.
Easier to stay legal on the lift check .
Also i believe that the low lift was said too produce more power at high rpm .
Honestly a call too Dyno for there recommendation would be worth the time spent .
Thanks for the insight
 

Eric85629

Member
I think I'd look for one of Vauses plate engine cam/head/carb combos and use the information he gave for setting it up.
Pretty sure dyno made those cams, dover has a plate package as well and would be a good option
I can look into different builders. I'm sure a build sheet would give a nice list of parts. I'm looking forward to building my own though and am trying to find knowledge as to why certain parts are used vs other similar parts for a desired result.
 

flattop1

Dawg 89
They aren't going too be forthcoming with that info .
If eric had a carb cam head combo . It would be a good investment .
 

Eric85629

Member
Bookie Power builds some top notch engines. He can also tell you all you ever want to know about which DynoCam is best for your class.
If someone would be kind enough to share info that can lead to be informed decisions, that would be great. I'm not even asking for the top secret stuff. Thanks, I'll look into that place
 

Colt sr

Member
If someone would be kind enough to share info that can lead to be informed decisions, that would be great. I'm not even asking for the top secret stuff. Thanks, I'll look into that place
I have an old clone built by rj Saylor that needs freshening up I would sell you. That's about as close as you could get to finding a builders secrets as to how they build their engines with out buying a race ready built engine
 

DD83

Member
What's your lift rule? what size track are you building the engine for? what rpm range are you shooting for? Is there a gear rule, or tire rule? all of these will need to be answered to give you any kind of advise....also do you already own all of the tech tools to make sure your engine will be within spec once built.
 

Eric85629

Member
I have an old clone built by rj Saylor that needs freshening up I would sell you. That's about as close as you could get to finding a builders secrets as to how they build their engines with out buying a race ready built engine
I thought about that- looking into a builders engine, but honestly I wouldn't know the difference between various parts. Even if I could identify the cam, rockers and other parts they use, it still wouldn't help me understand the WHY question.
What all would an engine need to get freshened up- bearings and rings?
 

Eric85629

Member
What's your lift rule? what size track are you building the engine for? what rpm range are you shooting for? Is there a gear rule, or tire rule? all of these will need to be answered to give you any kind of advise....also do you already own all of the tech tools to make sure your engine will be within spec once built.
Those are the questions I hadn't considered and I assume would dictate what parts would be required to achieve those goals. I've only been around karts for 2 years now and that was for a very limited stock predator class my kids are in.

Not sure about the specifics in the rules but it will be nkra jr1 rules. Dusty 1/5 mile track. No gear or tire rule but there is a drum clutch requirement. I don't have the tech tools but luckily can have access to them when I'm ready.

How do I decide the desired rpm? Is it based on the track size & grip?
 

Skidude

Member
You don’t really decide on RPM. Engines that are built to a certain spec will have their power band in a certain range. An unrestricted clone may turn in the 7,000 range, but a blue plate may be 6,700 or so. The smaller the plate the lower the RPM. The first thing you need to know is what rule set you are building to. NKA, AKRA, WKA, or some other tech. AKRA rule books are available at DynoCams.com and other places. NKA is available online for free, WKA can be purchased online too. That will tell you what you can’t do to your engine and have all the cam specs, (allowable limits).
 

Colt sr

Member
I thought about that- looking into a builders engine, but honestly I wouldn't know the difference between various parts. Even if I could identify the cam, rockers and other parts they use, it still wouldn't help me understand the WHY question.
What all would an engine need to get freshened up- bearings and rings?
What rj Saylor told me about the engine would be Bearings, rings, hone the cylinder, lap the valves, rockers and springs, and of course new gaskets. I am sure he does more than that to a rebuild. But I am pretty sure he puts a cl3 cam in each engine
 

Eric85629

Member
You don’t really decide on RPM. Engines that are built to a certain spec will have their power band in a certain range. An unrestricted clone may turn in the 7,000 range, but a blue plate may be 6,700 or so. The smaller the plate the lower the RPM. The first thing you need to know is what rule set you are building to. NKA, AKRA, WKA, or some other tech. AKRA rule books are available at DynoCams.com and other places. NKA is available online for free, WKA can be purchased online too. That will tell you what you can’t do to your engine and have all the cam specs, (allowable limits).
Yep, I have a lot to learn. Every time I place a dyno cam order they are sold out
What rj Saylor told me about the engine would be Bearings, rings, hone the cylinder, lap the valves, rockers and springs, and of course new gaskets. I am sure he does more than that to a rebuild. But I am pretty sure he puts a cl3 cam in each engine
I may be an idiot for passing this up but I really am looking forward to getting experienced with building my own. Thank you though
 
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