Change jetting for milled head?

mike97760 said:
I have had several engines with heads that were milled .040 or .050 and didn't need to richen the jetting. Run it, read the spark plug then decide.
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Thank you. Not looking to take it down too far, just want to give my kid a little more go power to get used to
 
Depending on how far you have it milled - you get to a point where it'll actually want less fuel rather than more (until you up the cam/valve lift, etc.) If all you are doing is gaining a bit of compression over stock, no need to change the jetting.


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I was planning to put putty on the piston to measure valve clearance then mill about half that amount. Is that a good approach or should I just plan to remove a certain amount?
This is my first time modifying a clone and want to stay on the conservative side
 
Eric85629 said:
I was planning to put putty on the piston to measure valve clearance then mill about half that amount. Is that a good approach or should I just plan to remove a certain amount?
This is my first time modifying a clone and want to stay on the conservative side
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I am certainly no clone expert, so maybe some others will want to chime in.
I would think the very best thing you could do with these engines is to let them breathe. The carburetor is too small to begin with, so opening up the carb would be the first (best) option in my opinion. THEN, you can go with a bit bigger cam, some mild porting, tuned exhaust, etc.

Just be sure to use a billet flywheel if you are going to turn more than factory recommended rpm. Personally, I'd use a billet rod too, but then while you've got the rod and piston out, might as well replace the piston with an aftermarket one and a longer rod (same price.) You can see where this is going, right? Have fun with your build!
 
Eric85629 said:
I was planning to put putty on the piston to measure valve clearance then mill about half that amount. Is that a good approach or should I just plan to remove a certain amount?
This is my first time modifying a clone and want to stay on the conservative side
Click to expand...
None of the engines that I put milled heads on had valve to piston clearance problems and all of them had .308 lift cams in them. I doubt a clone will.
Just thought of something. Used to be you could buy a flat top clone piston. Might be easier for you.
 
CarlsonMotorsports said:
I am certainly no clone expert, so maybe some others will want to chime in.
I would think the very best thing you could do with these engines is to let them breathe. The carburetor is too small to begin with, so opening up the carb would be the first (best) option in my opinion. THEN, you can go with a bit bigger cam, some mild porting, tuned exhaust, etc.

Just be sure to use a billet flywheel if you are going to turn more than factory recommended rpm. Personally, I'd use a billet rod too, but then while you've got the rod and piston out, might as well replace the piston with an aftermarket one and a longer rod (same price.) You can see where this is going, right? Have fun with your build!
Click to expand...
She will be in jr1 AKRA rules so not much breathing is happening with that tiny restrictor plate...otherwise I agree 100%. Already have the cam that compliments the lower rpm curve, billet flywheel & good carb. That's why I'm guessing a little more compression and get rid of some internal friction points is the next thing a DIY guy can do.
 
mike97760 said:
None of the engines that I put milled heads on had valve to piston clearance problems and all of them had .308 lift cams in them. I doubt a clone will.
Just thought of something. Used to be you could buy a flat top clone piston. Might be easier for you.
Click to expand...
Lucky for me I have a stock car racer buddy who's a machinist. Milling the head ought to be easy enough. Then it's time to see how to properly set up the push rods
 
Eric85629 said:
She will be in jr1 AKRA rules so not much breathing is happening with that tiny restrictor plate...otherwise I agree 100%. Already have the cam that compliments the lower rpm curve, billet flywheel & good carb. That's why I'm guessing a little more compression and get rid of some internal friction points is the next thing a DIY guy can do.
Click to expand...
I'm sorry, I figured you were running unsanctioned "run-whatcha-brung" type deal.
Be aware that AKRA has rules that you must follow for how many CCs the combustion chamber must fill. You can't just go milling the head and putting a thin gasket in it to raise compression, you need to consider piston pop-up, the dish of the piston as well. CC it and mill per rules and it will definitely help. FWIW, small plates like excess fuel, so consider going up on jet to make power in the power band that you will be running.
 
CarlsonMotorsports said:
I'm sorry, I figured you were running unsanctioned "run-whatcha-brung" type deal.
Be aware that AKRA has rules that you must follow for how many CCs the combustion chamber must fill. You can't just go milling the head and putting a thin gasket in it to raise compression, you need to consider piston pop-up, the dish of the piston as well. CC it and mill per rules and it will definitely help. FWIW, small plates like excess fuel, so consider going up on jet to make power in the power band that you will be running.
Click to expand...
Thanks, I am aware that there are CC restrictions, just not very familiar with how much can be milled to stay within the rules. You are right, I need to learn how to measure the CC & make decisions from there
 
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