# 4 Cylinder OHV Engine new cylinder head. A work in progress



## gbritnell (Sep 24, 2009)

At the time I built my 4 cylinder engine there weren't any commercial spark plugs available. The supply of plugs built in the 60's had just about dried up and they weren't the right length for my engine anyway. The solution, build your own, which I have been doing for years. With the new supply of spark plugs manufactured by Rim Fire I wanted to try them out in my engine but the problem is that when I made my engine I tapped the head for 1/4-28 threads and the new plugs are 1/4-32. My engine runs well enough with my Teflon plugs but with the high rpm it starts to erode the Teflon at the tip. There is no way to make the 32 thread plugs fit in my 28 thread holes so I decided to make a new head. My original head is cast iron, Durabar to be more exact. It is an extremely fine grained iron which cuts very nice and holds nice sharp corners. I like it for the fact that I don't need to make valve guide/seat inserts for the head, everything is just machined into the head. The first few pictures show the piece of iron and my steps in machining it. I always face the widest face first. This gives me a larger surface to locate my edge cuts to. After cutting this face I rotate the block 90 degrees in the vise and cut the narrow edges. You can see in the one picture I use a piece of heavy copper wire as a backup to put even pressure on the irregular surface. My final step is to use pinch down clamps to hold the piece tight against the parallels for the finishing cut.


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## gbritnell (Sep 24, 2009)

Next up came the center drilling and drilling for the various holes, head bolts, push rods, rocker posts etc. There was no specific order, I could have done the combustion chamber side first but chose the top. With the round column mill/drill I set up for the longest tool so that I don't have to move the head any more than I have to.


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## gbritnell (Sep 24, 2009)

I then flipped the block over to start on the port openings and combustion chambers. After touching off my block to get my centers I first center drilled the locations for the ports. The finished hole is .213 diameter so I went in with a .203 diameter drill to rough it out. The finished hole would be done after the combustion chambers were machined so that if I got any little chips on the corners I would have material to clean up. After drilling with the .213 drill I redrilled with a small center drill in the bottom of the pocket for my valve guide hole. The valve guide is .062 diameter so I drilled it undersize and then reamed the guide holes.


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## gbritnell (Sep 24, 2009)

The next operations were to rough out the combustion chambers. I calculated how far down I would have to go with a .625 end mill and plunged out each chamber. After this I got a .750 diameter end mill that had the corners worn down and ground a .062 radius on them. The bore is .750 diameter so this would give me a witness for my finishing steps. The combustion chamber is a pent roof shape with 25 degree slopes on the sides. I then layed out the combustion chamber in AutoCad to see what sized cutter I could get into the chamber to rough out the remaining stock. I used a .250 diameter cutter with a .062 radius on the corners. The depth was .143 at the center. I worked down to this depth then walked back and forth until I just came up to the .750 diameter witness.


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## gbritnell (Sep 24, 2009)

In the pictures you can see how nicely this iron cuts. At this point the port openings have a nice sharp edge but I still have a little stock to come off. No sense taking a chance after all this work. Now I calculated the ramp for my 25 degree roof angle and decided on .025 over and .012 up. All of the radii in the combustion chamber are .062 so to finish up I used a .125 ball mill. As I made my steps I watched the corners with a Mag Lite and worked my way out to the witness diameter. These little cusps will be hand ground and polished when all the machining is finished.


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## gbritnell (Sep 24, 2009)

Now it was time to finish up the port bores. I had the head set close to the job so that I would get a minimum of deflection while using the .125 ball mill so it had to be moved back up for the final drilling. I have made many hundreds of parts on this old mill and it has served me well, I just hate having to repickup my work all the time when changing tools. At least the digital readout helps. The final two pictures show the picking up of the part and the final drilling. Actually the closeup shot in the last posting was after the final drilling. I just used it to show the completed combustion chamber machining.


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## gbritnell (Sep 24, 2009)

This is a little addendum to this first part of the build. To show that we're all fallible I am including a couple of pictures of my oops. You can see how many steps were involved in machining out the combustion chambers. Everything went splendidly until I was done. I took my last cut and as I cranked the table away in Y I forgot to lift the cutter that last little bit, result, a little ding. I could probably live with it but what if someone takes my engine apart 50 years from now and says "what a shoemaker" I might roll over in my grave ;D
Anyway, I drilled the offending divot out and I will put a little iron pin in it. I'll show the results down the road. I'm off for a couple of days of dirt biking so I won't get back to machining till next week.
gbritnell


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## cobra428 (Sep 24, 2009)

George
Thank You,
I feel like I'm getting a leason on how to do my Whittle V8. No ream on the Valve guide holes.? Next installment? Or no? Not necessary?
Tony


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## gbritnell (Sep 24, 2009)

Hi Tony, you must have missed it. It's about halfway up in the set.
gbritnell


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## cobra428 (Sep 24, 2009)

Sorry G
I must have dozed off in class :hDe: Rof} scratch.gif
Tony


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## gbritnell (Sep 28, 2009)

Today we will start back on the build. The next step which I didn't document was turning up a piece of iron to fit in the pin hole. That being done I tapped it in place, about .0025 press fit. The next three pictures show the combustion chambers benched out. I used a combination of small mounted stones in my Dremel flex shaft holder and some round riffler files to clean up the fillets. The black that you see in the combustion chamber is marker ink. I blackened the whole chamber first and this shows you where the high spots are for grinding and finishing.


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## gbritnell (Sep 28, 2009)

Up next was a quick step to put the exhaust ports in. Just a matter of centering the part up with my edge finder and then moving to the proper spot and center drilling and drilling. (.213 dia.) I drilled down till the bit broke out into the port and then went a little farther until I could feel the drill touch the far side of the port.


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## vlmarshall (Sep 28, 2009)

Excellent thread... I forget how small this engine is, until I see photos like the one with the giant edge-finder in it. :bow:


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## gbritnell (Sep 28, 2009)

This next step leaves no room for error so after setting up the angle with an indicator and reestablishing my centers I started to put the spark plug ports in. The design of the head has the spark plug port tucked down along the inside edge of the combustion chamber so the angular and location dimensions need to be right on. The first step was to center drill for the hole. You can see that the starting point fell .012 off of the corner of the head so I pecked with the center drill making sure that it stayed true to the center. The next step was to plunge with a .187 ball mill and open up the hole for the 1/4-32 tap drill. I only went far enough to get a good true hole so that the drill wouldn't wander. I then spotfaced with a .312 diameter endmill down to the plug seat.
The final step in this set was to open up the clearance groove with an endmill. This is a preliminary step as more layout and machining will be necessary in this area.


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## gbritnell (Sep 28, 2009)

Here are several shots of the head after removal from the mill. The spark plug ports were tapped. You can see how accurate the setup has to be by the location of the port in the combustion chamber.


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## gbritnell (Sep 28, 2009)

I spoke earlier about using a dial indicator to set up my angles. The next couple of pictures explain what I did. I first set the part close with my protractor. In this case it was a little over 12 degrees. I just snug up the vise to that I can tap the part with my copper hammer to get a fine adjustment on the angle. I then pick a dimension in the X direction that will give me enough room to move the indicator, in this case it was .50. In that distance I find the length of the side opposite (tangent function). Once I have moved the .50 I quill down until my indicator reads -0- and check my digital readout number.


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## steamer (Sep 28, 2009)

George,

Awesome post!  Keep going I'm taking notes as fast as I can!
 ;D
Dave


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## gbritnell (Sep 28, 2009)

The next operation is to put the intake ports in. The ports are siamesed and are close enough that they require some extra steps to insure that they pass between the head bolt holes and wind up in the center of the previously drilled port. With the part on an angle I couldn't just pick up an edge so the part required a little bit of old fashioned layout. Here you can see me 'wiggling' the center lines. These ports are also .213 diameter so I used a .25 center drill taking care that I didn't go all the way down to the body of the drill. The first two ports went easily but the second two which overlap the first holes needed an extra step. I took one of my extra .25 dia. center drills and chucked it up in my lathe. I then ground the body down to about .209 diameter. The reason for .209 was my figuring that if it ran out a little bit I wouldn't be oversize with my starter hole. That done I reset the part to the required angle, center drilled, and drilled until it broke into the port. 













The final operation of this series was to center drill and drill for the 2-56 manifold mounting holes.


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## Krown Kustoms (Sep 28, 2009)

That looks great, I love the siamease ports.
I probably would have broken a drill or two.
-B-


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## gbritnell (Sep 28, 2009)

Tomorrow's operations will be to finish up the shape around the exhaust flanges, open up the spark plug pad area and radius most of the corners in that area. A little bit of added information. I have 14 hours up to this point. 
gbritnell


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## gbritnell (Sep 28, 2009)

Krown Kustoms, that is why I ground up the center drill for the port operation. Having the first port in I had to go deep enough to get a good starter hole for the second. It was also close enough to size that the drill picked it up and ran true. 
gbritnell


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## Krown Kustoms (Sep 28, 2009)

Nice job.

I will defiantly be keeping up.

-B-


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## gbritnell (Sep 29, 2009)

The exhaust port side of the head now needs finishing up. I first started by removing the excess stock from behind the flanges and cutting the head bolt pads to depth. I then removed the head from the mill and mounted my old header pipes to the face so that I could layout the flange shape on the head. With that accomplished it was back into the mill to step around the flange shapes and finish up my blend cuts. After this the head was set back up on the spark plug angle so that I could clean up the seat area and enlarge it a little. The original design was for my homemade spark plugs which have a longer shank on them and the .312 counterbore was adequate for clearance. This new head will be using the commercial plugs and they need more clearance for the hex.


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## gbritnell (Sep 29, 2009)

The rocker arm cavity is next up. The head was set up and indicated once again. I went back to my Cad drawing to get some end point dimensions for my .187 end mill. The ends of the rocker cavity are at 6.08 degrees so I needed a tangent point to stop at. I first made a .025 deep cut which is the top of the valve guide bosses and then went down to the full depth of .150 for the remainder of the cavity. I used a .094 dia. mill to run along the front edge. I had .124 space but didn't want to use a .125 endmill and have it cut too wide. I took out as much stock as possible for the next operation.


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## ozzie46 (Sep 29, 2009)

Wonderful work!!  :bow: :bow: :bow: I can only dream!

 Ron


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## gbritnell (Sep 29, 2009)

With the rocker cavity milled out it was time to cut the valve guide bosses. I made up a spotfacing tool that had the center drilled out to the O.D. of the bosses. The outside edge has a small radius to match the fillet around the inside edge of the cavity. I didn't want to tear down my vise so cutting the flutes required some hand filing. The tool is made from drill rod (silver steel) so the filing was a little harder. I filed the clearances on right up to the edge of my flutes. After hardening the tool I would use an abrasive disc to clean up the faces and thus sharpen the edges. I reset my spindle speed to around 640 rpm and slowly quilled down to the deck of the rocker cavity.


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## ChooChooMike (Sep 29, 2009)

GREAT step-by-step pictures (again). Keep it up !!! +1 Karma 

Mike


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## gbritnell (Sep 29, 2009)

I might add at this point that anyone who has purchased a set of drawings for this engine and they get to the point of building the head I will lend out the counterboring tool I made. It's not that complicated but unless you want to make your own I have one available.
With the bosses finished it was time to machine the end angles on the rocker chamber. I set my vise over on the required angle and used the same indicating procedure that I used previously. I started out with the .187 dia. endmill and got as close to the valve guide boss as possible and then went in with a .094 endmill to finish up the inside wall. Now it was just a matter of setting over the vise to the other angle and finishing it up.


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## gbritnell (Sep 29, 2009)

Only two machining steps to go. The outer head bolt holes needed a clearance counterbore down the side of the wall so that my socket wrench would fit and finish tapping the remaining holes. I still need to make up a valve seat tool but that won't take long. With the machining complete some hand work was in order. All the outer corners needed to be radiused. The lower corners got a quick hit on the sanding belt and then some hand filing. The corners on the rocker chamber had to be done by hand. The outer two weren't too bad as I could get my files on them without interference but the inner two (exhaust side) were a combination of using a small burr and filing. While filing I had to leave stock at the bottom to match the fillet along the outside wall. This was then cleaned up with a small round file. Some final sanding and polishing and we have one 4 cylinder head. Total time around 21 hours with only two miscues. The first being the little nick in the combustion chamber that needed to be pinned. If you look at the pictures you'll notice it came out quite well. The other was when I was using the .094 dia. endmill in the rocker chamber. I was cleaning up along the front wall (exhaust side) and when I got to the end I misread my readout and started to move backward (Y) and nicked the top of the end valve guide boss. Luckily I was only down .018 so once the valves are assembled it will be hidden. This one wouldn't be as easy to fix as the first. Anyway, I hope you enjoyed the show and possibly learned a thing or two. I have a show to attend in a couple of weeks so I'm not going to take it apart until after that. 
gbritnell


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## zeeprogrammer (Sep 29, 2009)

Fascinating thread. Great detail.


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## cobra428 (Sep 29, 2009)

Absolutly Beautiful Geroge :bow: :bow: :bow:
 Oh ment to let you know I picked up some Tap Magic. I used it tonight on the Whittle. Looks like the stuff works great thanks
Tony


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## Deanofid (Sep 30, 2009)

George, there is so much good info here for us builders! Thank you for taking the time to pass it on.
Much appreciated.

Dean


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## idahoan (Sep 30, 2009)

Beautiful Work George.

Thanks for taking the time to document and share your work with us.

Dave


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## PhillyVa (Sep 30, 2009)

George,

I agree...*Thank you* ffor sharing Thm:

Regards

Philly


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## gbritnell (Sep 30, 2009)

I didn't think I had anymore to post to this thread but this morning I made up the valve seat cutting tool and being that some members had trouble with their valves seating I thought I would post it. Normally I make my cutter up with a drilled and reamed hole in the center into which I can insert a piece of stock the diameter of the valve guide. The ports and guides on this engine are so small that I made the tool up in one piece. I turned the pilot to go into the valve guide hole (.062) and the next diameter is the port size (.213). I made an undercut where the 45 degree angle starts so that I would have a good sharp seat. I then put it in my dividing head and cut 4 flutes on it, making sure to go below the .213 diameter. I then filed a small amount of clearance behind the 45 degree cutting edge bringing it right up to the edge of the flutes (with a magnifier). The next step was to harden it, drill rod, carrot orange, dunk straight into water and then polish the diameters. Now using it by hand I insert the tool into the port and and valve guide hole and turn it ever so gently, watching my progress. What you see in the picture is about a .010 seat. When I disassemble the other head I will spot the valves just to make sure that they hit all around on the seats.


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## cobra428 (Sep 30, 2009)

George,
I was looking to make the very same thing. Then I thought of a reverse countersink

http://www.yardstore.com/browse.cfm/4,5318.html

The only problem is they only come in 100 and 82. Can cut pilot to suit. Thinking about using the 100 till your post. Still thinking the commercial tool will last forever

Tony


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## gbritnell (Sep 30, 2009)

Tony, it's just that with these small engines valve seating is quite critical and the more accurately you can put the seat in the less trouble you'll have with sealing. A countersink is unsupported so I'd have reservations about using it. The tool you see in the picture took about 20 minutes to make. When you cut your seats if they aren't concentric it will take much more time than that to go back and make the part over.
gbritnell


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## cobra428 (Sep 30, 2009)

Very true George, the biggest problem with my H/M was grinding valves to get a good seat. I was figuring that a commercial tool would be ground more accurate and using the pilot thru the valve guide would keep me nice and concentric. Is that all the seat you use?
Tony


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## gbritnell (Sep 30, 2009)

Tony, yes that's all the seat I use. I find that the bigger I make it the harder it is to seal. Going by automotive and motorcycle practice the seat area is about .05-.06. If you have a three angle valve job you have 30 degrees above and 60 degrees below the 45. With a smaller seat you have less chance of something (carbon) sitting on the seat and holding the valve open. These are just things that I have found over the years. Others may have different thoughts on the matter.
gbritnell


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## cobra428 (Sep 30, 2009)

Thanks George for the inside info. I will rememder that for my Whittle V8
Tony


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## putputman (Sep 30, 2009)

Geo, that photo of your valve seat cutting tool tells it all. With the undercuts at the pilot and angle assures that you will get a good sharp valve seat. The pilot, angle, & shank can all be cut in one set up that will result in a zero TIR.

I am building a small single cylinder engine with a 3/8 bore that will require two valves and a spark plug in a small area. Plan to use a couple of hardened Royal Punch Pins for the valves. They have a 60 deg (120 included) angle head. The pins are manufactured by swaging the heads, consequently leaving a parting line, or seam, or ridge, on the angled surface. If I can grind that surface true, I will use them. I would then make a valve seat tool, using your design to match the valve.

Thanks for the post.


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## ariz (Oct 1, 2009)

I'm thinking to do the same too, to restore (or remake) the valve seat on the power head of my scuderi engine

thanks gbritnell


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