35hp gx200, or 50hp gx390

How you got 36/31 in a gx200 head when 32/28 is pushing it already, with the seats overlapping...
 
If the $$ part is crucial, then using the JR. 249cc billet is the only rational choice.
I know of, and have never heard of, a billet JR block motor blowing up.
I doubt there has ever been a broken block.
It puzzles me that anyone with concern about their expenses, will mess w/a clone block.
It is little more than a tin can in comparison to the billet piece.
 
I currently have a 35.5mm/31.5mm combo in a cast head. The motor will be 16.1 static compression, and will seal up with the sleeve and groove in the head. I will take a picture next time I go to the shop.
 
You know "Young" I have gotten the last regular head I had tested to 117cfm @ .450" lift, it originally was 109cfm. I cut the valves head smaller from 32.5mm to 32mm, blended the guide, and flatten the area around the seats to unshroud better.
 
Minidragbike said:
I know you do, I seen them
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I wasn't aiming that at you.. LOL.. I have found out (as you stated before), most heads do not flow what people think they do..usually by a fair amount. I can understand now why people (even you) doubted my HP numbers ..based on what is commonly built. I sent a stocker engine to Sneaks to race.. it showed like 12.58 on his dyno, and showed like 12.71 on mine (both showed the peak at 5500) .. so..if my dyno is way off, his must be as well??
 
Minidragbike said:
You know "Young" I have gotten the last regular head I had tested to 117cfm @ .450" lift, it originally was 109cfm. I cut the valves head smaller from 32.5mm to 32mm, blended the guide, and flatten the area around the seats to unshroud better.
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I'm glad the flow info we got here helped you in the changes needed on your head.. now lets see some race results!! :)
 
youngengines said:
I wasn't aiming that at you.. LOL.. I have found out (as you stated before), most heads do not flow what people think they do..usually by a fair amount. I can understand now why people (even you) doubted my HP numbers ..based on what is commonly built. I sent a stocker engine to Sneaks to race.. it showed like 12.58 on his dyno, and showed like 12.71 on mine (both showed the peak at 5500) .. so..if my dyno is way off, his must be as well??
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Those are close numbers, you and he is both calibrated very similar. I believed you personally only because I seen the picture of the heads you tested. I can look at a head, even way across the country and know if it flows well or not.

Way back years ago, we talking about 7 years ago on this site, in this section I was the only guy out of like 20 guys to have a 100cfm head. Those 20 guys was all older and so called wiser than me. But the flow bench don't lie.
 
Flow plays a very specific part of hp building. Too much flow is generally worse than a little too little.
Thinking you can look at the pic of a ported head and know the flow is delusional.
Each engine wants a certain amount of flow. The capacity of the engine to use the flow, is the stream of flow you build to.
 
PD Power said:
Flow plays a very specific part of hp building. Too much flow is generally worse than a little too little.
Thinking you can look at the pic of a ported head and know the flow is delusional.
Each engine wants a certain amount of flow. The capacity of the engine to use the flow, is the stream of flow you build to.
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To much flow? Lol. You need to call all those blown fuel guys your always talking about and tell them to jerk those blowers off. It takes massive power to spin those baby's up. You would become an instant genius. And then again, maybe you are confusing too large of cross section and fuel suspension and crazy stuff like that. I wouldn't have any idea. And then again those turbo's. My car has one and its darn fast. I increased the boost and just wow. Do you think that more psi means more flow? It is a a 3.0 liter and will run a 12 second quarter mile. I suspect that is allot of air flowing through those heads.
 
motorhead said:
To much flow? Lol. You need to call all those blown fuel guys your always talking about and tell them to jerk those blowers off. It takes massive power to spin those baby's up. You would become an instant genius. And then again, maybe you are confusing too large of cross section and fuel suspension and crazy stuff like that. I wouldn't have any idea. And then again those turbo's. My car has one and its darn fast. I increased the boost and just wow. Do you think that more psi means more flow? It is a a 3.0 liter and will run a 12 second quarter mile. I suspect that is allot of air flowing through those heads.
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Psi is more a measure of restriction. you need something to push against. Turbos are different as if you drop the restriction then the waste gate will move more air up until it hits the same amount assuming the turbo can flow enough air.
Reduce the restriction in a mechanically drive supercharger and the pressure drops, I wouldn't say you can have to much flow but when it comes at expense of velocity in the ports you sure can.
 
Too big of cc runner, too big of valve, or too big of carb, sure. Too much flow? Maybe PD mis-spoke or we are all just taking him out of context.
Afterall, everything has to work together. Cam, cubic inch of motor, combustion chamber, etc etc etc.
I would say you most certainly can have mis-matched parts for the amount of flow available or vice versa. Good example is the high school kid who simply bolts up an 850 Holley on their basically stock grocery getter and wonders why it won't idle or drive smoothly any longer.
 
Thanks Mini and Young Gives me some real good tips for my heads and compression. I have real good opens but always looking to improve and my reliability is about as good as a blueprinted amimal
 
CarlsonMotorsports said:
Too big of cc runner, too big of valve, or too big of carb, sure. Too much flow? Maybe PD mis-spoke or we are all just taking him out of context.
Afterall, everything has to work together. Cam, cubic inch of motor, combustion chamber, etc etc etc.
I would say you most certainly can have mis-matched parts for the amount of flow available or vice versa. Good example is the high school kid who simply bolts up an 850 Holley on their basically stock grocery getter and wonders why it won't idle or drive smoothly any longer.
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I was just poking at PD. And I agree with your comments. I agree with PD when he says that we are designing the motor around the flow capability of the head. When I am building an all out modified I generally try to increase the cross section to maximize flow to the point that I have not created to narrow of power band. This is also what we are designing the motor to. I don't want to go for all out hp numbers and compromise acceleration off the corner.

I didn't mean to sound so crass PD. Sounded funny last night.
 
motorhead said:
I was just poking at PD. And I agree with your comments. I agree with PD when he says that we are designing the motor around the flow capability of the head. When I am building an all out modified I generally try to increase the cross section to maximize flow to the point that I have not created to narrow of power band. This is also what we are designing the motor to. I don't want to go for all out hp numbers and compromise acceleration off the corner.

I didn't mean to sound so crass PD. Sounded funny last night.
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Did you just mention cross section??? That's not a common conversation when it comes to these engines.. unfortunately.
 
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