Eagler's Nest
Engines => 2 Cylinder => 1/2 vw => Topic started by: Bugsmasher on December 10, 2013, 05:33:42 PM
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Hey guys....I was fweebyschnepter on the yahoo site. Like this regular forum better ! I am continuing my head modifications and have made some good progress and wanted to see if any others were interested in the work as it goes. Be warned it is not for the faint at heart , but it will yield a much better flowing head which equals more power. Power gains where reliability is not affected is always a good thing. I will provide a detailed set of steps as I have went and post flow bench results as the finished heads are tested against the primary setup as delivered. Let me know and I will start posting things as a running guide of sorts as what I have done up to now.
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Knock yourself out man! I would be interested in seeing what you are doing.
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This pic shows the void in the intake runner. The flow bench and flying a string shows very turbulent flow here. This area will be corrected to flow a ton better than it does as delivered. A major power gain is right here....and it only costs a little time and a few parts. The exhaust will also be addressed. More to come later. Same bat channel....same bat time......
BTW flying a string is a way an old timer showed me how they used to check their progress on porting heads. Take a shop vac and seal it to the intake runner....hold a string while it is "flowing" and look for vibrations on the string as you move it around the port letting it show what is there. A steady string is smooth air....vibrations are poor flow eddies in that area. Are tends to go where it wants to....not where you think it should.
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I meant to state a major improvement in flow of my post above....now edited. I am working some crazy hours and trying to keep it together. So the idea was to make the sleeve and port the pocket to accept it. A prototype was made of aluminum foil. Then at the aviation area at Lowes... it just so happened they have a 1-1/2" tube with an elbow already mandrel bent. The only caveat is that a 320 grit DA sanding in required to remover the nickel / chrome from the underlying brass. Didn't want any of that in between my piston rings and nickies! Now a trim here and there before I cut the guide clearance and plot where to place a couple solid rivets. Pending I decide on a different mounting method. The last pic is chowing foil inserted into the pocket and covering the void. This will hopefully work out to be a super smooth flowing intake runner and make a huge improvement on the ability to get a smooth column of air into the cylinder. An effort is being made to get most of the flow towards the cylinder wall by biasing some of the smoother surfaces throughout the pocket work.
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This is what I am trying to get with my heads.......smooth flow. This should be what the intake runner profile looks like when done. It will not be the ideal port....but a magnitude above "stock" as delivered. But even those have worked great....so this should prove to yield more power. Time will tell...back to work for me. The exhaust ports and combustion chamber will be discussed next with mods/improvements made.
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looking good. You should see a decent increase in HP. for your efforts. The fine details in head work make more HP. Of course it shows that"you know that" :-)
Bill
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Too exotic for me. I like to keep it stock simple and low cost. For extra power from the VW I like to boost the bore and stroke. No matter how you get the power, displacement, supercharge, turbocharge, port/polish, we always end up limited by the air cooling as the power becomes greater than the original design. The 94mm bore and 82mm stroke with a Type I VW engine will make all the power I can expect to perform reliably.
Norm Heistand my .02
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Too exotic for me. I like to keep it stock simple and low cost. For extra power from the VW I like to boost the bore and stroke. No matter how you get the power, displacement, supercharge, turbocharge, port/polish, we always end up limited by the air cooling as the power becomes greater than the original design. The 94mm bore and 82mm stroke with a Type I VW engine will make all the power I can expect to perform reliably.
Norm Heistand my .02
Welcome to the forum here. Would be great to here more about your projects!
As a data point I have a Cassler 94mmx86mm powering a Fisher Classic. Max Cyl temp I have ever seen is 310F in a climb. Max oil temp I have seen is 185-190 F. I think my cooling system can handle more HP. Cassler rates it at 85 HP.
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That's the beauty of my working on this. It does not affect reliability... only improving what is already being used. More efficient flow characteristics have proven a goal from way before my time in building anything. I just seen and area that had room for lots of improvements. I don't expect "Putt Putt" performance across the envelope but do look for power improvements above stock without supercharger/turbo additions. You'd be surprised what can be coaxed from some careful head work. Think diesel... low rpm stump pulling power. That's my train of thought with these...relative low lift , low rpms.
Experiments with back-cutting the intake valve are going great. It seems the best flow on intake is a 30deg. angle about .020 wide gets really nice flow up to about .500" lift. I am going to rest there on that and chamber side exhaust lips are next on the valve....a wide, plain 45deg face is flowing best. These seats don't leave much room for forming a venturi...the 60/75 deg. will be almost non-existent unless I replace them with wider seats and shape them.
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If you use the Hummel prop extension there is a Wood Bar Dyno available configured to rate a 45 hp engine at 3600 rpm... Contact Joe Spencer (Rockiedog) on the list when ready for a full pull...
Steve
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OK that would be great ! I have finished the heads up today and are ready for valve seat cutting. I have to wait for my new guides to get here....hurry up and wait some more. All of my part are from Scott...with exception of carbs, mag. I have his prop hub. I will let you know when I am ready for putting fuel in the carbs.....a ways off from now though.
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I'm sure you're already aware, but for others out there reading this and considering it, a good trick for blending the valve seat into the chambers when porting is to take an old set of valves and grind them until the ground seat angle face meets the outer diameter of the valve face. Then you can install the valve in the head and blend the seat and chamber without worrying about damaging the valve seat.
I'll certainly be interested in seeing the finished product and the flow numbers.
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That little ledge , just outside the valve seat, where the chamber protrudes above the valve seat..... leave it there! It enhances flow below .460" lift. We had discovered this some years ago when building a Briggs and Stratton style super stock jr. drag engine. Even on most aftermarket heads we leave it if the cam is somewhat mild. Now with .630" and above lift....then it needs to be blended out into the chamber. Most of those cam profiles are....shall we say extremely violent compared to what we are going for . I wouldn't blend that away until you dye trail the head on the flow bench.....then you'll see how the flow gets up off of the chamber floor heading right for the cylinder wall. Try to bias the intake runner work to get the flow towards the cylinder wall making a swirl as the piston travels down. That's a torque increase and that little step is your friend..
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Hi Bugmasher,
I am getting a great eduction following this post. Thank you.
John
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Cool stuff, and I agree with the philosophy.
have you happened to have read Engine airflow by harold bettes? lots of info in it.
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Yes some time ago. Most of my head work is from hands on and flow bench numbers....that's where the big headaches can start. Trying to concentrate efforts now on getting the case assembled and done. The heads are almost finished...yet to make valve covers. I need a day stretcher...day job keeps cluttering my fun time.
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following... any updates?
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Yes ... I have abandoned the tube insert idea in fear of it creating a problem. So with good intentions I am making a plug of solid aluminum to be formed to fit into the void and be welded securely where the original intake port is blocked off on the outside of the head. This way I can keep weld heat away from the valve seat and get a much more secure modification. Trying to finish wings- engine case- dealing with health issues and bills. I did find a source for 1.375" ally tube with a radius that would work.....but that goes back to welding near a seat- not doing that. They are a press fit on the walls of the valve seat. Been teetering the idea of getting a new head and starting from scratch. But I have these in hand paid in full. I wish I had the time to learn sand casting .... guess I could cobble a CNC file for a head.....lots of time and probably wouldn't cool well as the V-dub's. I want to think I will fly it this year. I need a day stretcher......or stay up more hours.....
As for the flow data I will share. It is worth doing from that standpoint. What it will yield.....hopefully more power and torque.
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OK some progress has been made on the headwork. Turned off the plugs from T-6 and fitted them to the head. Now a little cleanup with a sanding roll then drill out to lighten . Preheat to 275 then weld port plug in place. Back to the flow bench when this is done and the numbers will be posted. I am going to flush mill the outside of the plug off , chamfer edges out before welding....it will be worth all the work. If you die grind a lot of material...take a lesson from me. Outside away from the house....blow shoes and clothes off before entering house. My wife hates a metal splinter stuck in her foot !