head porting

bsimon79

New member
Hi,newbie here. im new to karting and to small engine building. I like to build my own motors and do my own things to them. i have a little bit of experience with porting heads but there was one thing that I find different opinions on. I see the high flow heads that some sell and the valve guides are cut down to the port floor and there is no guide sticking up. Do they actually grind the valve guides still in the head or do they just install shorter guides? I want to do this to my gx160 but not sure about it. I want to know if It will cause more stress on the head and if it will gain or loose power. I notice that people with high hp motors have these heads because they need the flow. i want to do this to my head on my mild motor with maybe 8hp. Just a guess so please dont hate on me for that.I want to know if it will be too big of a port and loose power and flow like crap or if it will improve a lot and make a good motor. I plan on using stock sized valves and the head ports will still be the same size so i can use stock gaskets.

please help me out and let me know what you have to say

Thanks
 
The guide and bowl will make negligible difference on your engine, concentrate on the floor and short side radius.
 
I agree with KART43 but if you want you can gently hammer the valve guide into the head towards the valve springs, this way you will have the same length guide but its not in the way impeding flow (be very careful not to damage the guide or you will jam the valves), I use a small socket with the valve sitting in place and it works, just use a light hammer 6-7 oz and take your time. a 3 angle valve job will do wonders by reducing the turbulent air travelling through there (30/45/60 degrees) you can purchase a neway valve cutter online used for around $100. another good thing to do is to purchase an empty head that already has work done to it off of someone on BOBS 4 CYCLE, I have found some on here for 30-50$ but you will need to put your heads guts into the new head.
 
Backing out the guide or shortening it is done very routinely. In reality it offers very little gain in this application and the shorter guide offers less stability to the valve which could result in other problems. As far as head porting goes, its as much artistry as anything. The best porters in the world can just look and feel whats needed and can predict flows well before its put on the bench. Smoothing and blending is about all i do typically. If I truly need a top flowing efficient head I get it done. Barry Young is not too far a drive for me luckily. I have a head there now as a matter of fact. Many times what I think should improve flow just causes dead spots or sluggish velocity. Dont just make it big. Smooth may or may not be whats needed. I know i have not helped but what im trying to say is, effective head porting is not as easy as some will have you believe. Get one done by a true proffessional and then copy it. Reverse engineering and doing what others do is and has been a cornerstone of "racing" for many years before me and I am sure after Im gone. Search on here and facebook and find some pictures of some ports. Sneaks, Brad Hill, Youngengines all have posted them before. It may give you an idea as to what to do. Good luck.

See, Brad posted this as I was typing. Thanks Brad
 
Good advise^^^

Just remember air doesn't like to change direction or encounter obstacles. When you get a flow bench I think one of the first things you learn is air is pretty counterintuitive. It doesn't always do what you think it will.
 
Yes agreed!!!
One of my first 14cc head I did myself I took the grinder cut the guide down, and removed some material around the guide, and smooth sharp edges...
A 18cc head I open up the ports nice and big blended everything nice and smooth.

The result was the 14cc head flowed 85cfm, the 18cc head flowed 73cfm...
Lesson learned...
A ZOL 22cc head I ported the same as the 14cc head, it had the same peak flow as the 14cc head but flowed a ton more at low to mid lift...
 
I would suggest just buying a head from Barry or Brad. Buying all the tools and learning when you will only have just a couple motors ever. There is no need in going through all that.
Plus the head you will buy, will be 125% better than your experimental head would be. Which means more power. It will take you a minimum of 20 heads to even get close to what these guys do easily.

Unless you are about to start a business and will be doing heads weekly. Just buy them and be done.
 
Im not looking into buying alot of tools and i get your point. yes, if i were to go buy a head it would flow a million times better that my head but i want to do this for more of a learning thing. I like to do this kind of stuff myself even if it doesnt flow worth a crap. then if it doesnt work i can look for improvement. The only thing i was wondering about was grinding down valve guides and looking for more tips on porting these heads. I know without all of the tools and equipment the head wont work at its best. and i cannot afford a good flowing head. Im the poor guy looking to do whatever i can to add power and it only costs my time.
 
Yakattack im wanting to do what you did with the 14cc head. i was just wondering if cutting down the valve guide was good or if it will be bad for flow and performance. i dont want to have big ports and valves and all that i just a simple decent flowing head like your 14cc
 
How much do you think a good head cost?
It's cheaper than the tooling, plus the many hours and heads you will have to practice on along the way.

With or without guided it will flow good. It's the rest of the port you have to worry about.
 
Like MDB said tools, parts experience..
Lots of tools, lots of parts, learning everyday...
Ask questions and look at pictures....
I ported a lot of car heads... When it came to Hondas some of car stuff carried over and some good detailed pics of how and what MDB did came in very handy...

Now a days there is so much info and pics available look search all you can and
Learn...
 
Can someone please explain what it means when you're ordering a stealth head and there are options for .005 or .010 in the hole?
 
Can someone please explain what it means when you're ordering a stealth head and there are options for .005 or .010 in the hole?

That may be piston in the hole so they can get cc as close as possible. If not that how far the valve seats are sunk.
 
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