Brian Builds the Kerzel Hit and Miss I.C.

[GailInNM]

Brian,
You may have said, but I can't find it if you did. What fuel are you using. If you are using naphtha, Coleman or equivalent, try switching to gasoline. On my engines gasoline gives more power per stroke. If there is a bit of excess friction some where in the system causing the engine to slow down it may be enough to overcome it and keep it running. If using gasoline already, is it fresh?
Gail in NM

 

[Brian Rupnow]

Gail---I've been using Naptha. I will try real gasoline and see what happens.----thanks----Brian

 

[Brian Rupnow]

Gail---No real joy with the gasoline except stinkier and foggier!!! I am holding out really high hopes for better results with a new intake valve. Its making me crazy---I flip the engine by hand and it spins freely. I wiggle the intake valve stem a little bit, flip the engine over, and it bounces back like it had ran into a wall!!!

 

[gbritnell]

Brian,
It sounds like your valve guide is too loose. The reason I say that is because if the guide was tight (relative term) and the valve wasn't sitting on it's seat properly no amount of jiggling would align the valve with the seat. On the other hand if the guide was loose and the valve wasn't seating properly in one spot so wiggling it caused it to seat then I would say that your guide, valve or seat could be the culprit.

In my thread about building the new 4 cylinder OHV engine head I show and explain how I do the valve seats for my engines. (page 3)
http://www.homemodelenginemachinist.com/index.php?topic=6205.30
As has been stated every component of a valve job is important, the valve head concentric with the valve stem, the valve guide concentric with the seat and the fit of the stem to the guide. The concentricity of the valve head to stem is the easiest to check out, just chuck the stem and indicate it until it runs dead true then put the indicator on the seat area and see if it is concentric. The stem to guide clearance should be no more than .0005 for say stems up to .125 diameter. The last thing in the equation is the concentricity of the seat to the valve guide hole. Even if the port hole and the guide hole are a little off if you make up a rigid tool like I show and just let it skim the seat surface it should take out any irregularity.

It's not that it's rocket science but it requires a little bit more accuracy on the part of the builder to overcome this part of IC engine building. I would say more builders have problems with this aspect of IC building than any other part.

George

 

[Brian Rupnow]

George---I'll ask you the same question I asked chuck --(I think he missed it or he would have answered)

-This may be my next step. There's nothing else left!!! I bought a foot of 3/8" drill rod when I bought the 1/4" drill rod to make the valves---Thinking of course that I might have to build a valve seat cutter like you did. I don't have much if any experience with drill rod. I do have carbide lathe tooling and some carbide boring bars, but no other carbide tooling. Can I end mill the four "facets" with conventional HSS tooling, sharpen it with a small grinder or file, then harden the drill rod by heating it cherry red and a waterquench?

 

[Metal Butcher]

George---I'll ask you the same question I asked chuck --(I think he missed it or he would have answered)

Can I end mill the four "facets" with conventional HSS tooling, sharpen it with a small grinder or file, then harden the drill rod by heating it cherry red and a waterquench?

Yes on the end mill. Sharpen with a slip stone after heat treating and drawing back (tempering).The piece will become non-magnetic when the critical temperature is reached (one way of telling). Water quench only if you have W-1 drill rod. W-1= water, O-1=oil, A-1= air hardening.

The link below should give you the basics you need to harden tool steels properly.

http://www.uddeholm.com/files/heattreatment-english.pdf

-MB

 

[Brian Rupnow]

MetalButcher---Thanks ----Can you explain the bit about "sharpening with a slipstone" please. I'm not sure what a slipstone is.

 

[gbritnell]

Hi Brian,
Here's what I do. You can mill the desired tool with a high speed end mill. Turn the pilot just long enough to allow the 45* cutter part to touch the seat area. The rest of the stock from the pilot to the 45* cutter can be just a little smaller than the port diameter. The pilot should be made size for size with your guide hole. After the tool is hardened if the pilot is a little too tight you can emery it down until it just fits in the guide hole. Cut your 45* seat diameter a little larger than what your valve opening is. Example: if your valve head is .25 dia. then make the O.D. of the cutter .312 diameter.
Cut your flutes (at least 4) and cut some relief on them leaving about .015 from the cutting edge to where the relief starts. (a small land) Now harden the tool. Get it cherry red or until a magnet won't stick and dunk it into the liquid of your choice, ATF for oil hardening or just plain water for water hardening. When you stick it in the liquid plunge it straight down and then rotate it around.
For small tools I don't anneal them and I've never had one break, especially a seat cutting tool.
Now using a magnifier, unless your eyes are much better than mine, stone the small land area (.015) back away from the cutting edge with a diamond hone or a small whetstone giving it a little angle for clearance.
You can also stone the face of the cutter to remove any small burrs .
Now put the cutter in a small drill chuck and oil the guide post and slip it into the valve guide hole. Just using the weight of the chuck, rotate it slowly until you see a nice uniform seat form around the port opening. At this point you should be good to go but as a secondary step you could just hit the seat/valve with a little grinding compound.
Put the valve into the guide and grab it from the back with a small drill chuck, (small drill chuck) and allow the valve enough up and down movement to get some lapping compound under it. Now rotate the valve all the while lifting it up and down to recharge the compound under it. By that I don't mean keep adding more compound I just mean this will allow the valve to pick up more compound from around the seat area. It shouldn't take but about 5 or 6 cycles of this to clean everything up nicely.
Now clean everything scrupulously. You don't want any compound left in the port hole or in the valve guide hole.
If the valve gods are on your side you should have a perfect seal.
George

 

[Brian Rupnow]

cut some relief on them leaving about .015 from the cutting edge to where the relief starts.

George---This is the only part I'm not sure how to do. Do I use a file?--Seems like an awfully small area to work in without damaging the cutting edge of the adjacent flute.----Brian

 

[Metal Butcher]

MetalButcher---Thanks ----Can you explain the bit about "sharpening with a slipstone" please. I'm not sure what a slipstone is.

Just another way to say sharpening stones. They come in a variety of shapes and grits and are used to sharpen irregular shaped cutting tools, where a flat all purpose 'sharpening stone' wont do.

Examples: http://www.sharpeningsupplies.com/India-Slip-Stone-Set-P78C30.aspx

http://www.thebestthings.com/newtools/norton_slips.htm

-MB

 

[gbritnell]

Brian,
You can use a small jeweler's file and the above mentioned magnifier. You only need enough clearance so that the cutting edge touches and not the flank.
George

 

[cfellows]

Hey Brian, guess I missed your earlier post... I'm a bit of a putz with hardening and filing and honing. I didn't harden my cutter since my valve seats were brass. Also, tried grinding some relief behind the cutting edge, but I didn't get very close to the cutting edge, so there is about a 1/16" land behind each tooth. As a result, I had to press kind of hard to get it to cut. And, at the end of the day, I'm not sure how successful it was. I still had to lap the valves.

Chuck

 

[Brian Rupnow]

The continuing education of Brian----Thanks guys. I had never heard of a "slipstone" before. Now I'm off to google "Jewellers file".---Lord, I feel pathetic sometimes.

 

[Brian Rupnow]

Hey Brian, guess I missed your earlier post... I'm a bit of a putz with hardening and filing and honing. I didn't harden my cutter since my valve seats were brass. Also, tried grinding some relief behind the cutting edge, but I didn't get very close to the cutting edge, so there is about a 1/16" land behind each tooth. As a result, I had to press kind of hard to get it to cut. And, at the end of the day, I'm not sure how successful it was. I still had to lap the valves.

Chuck

Thats the question, isn't it Chuck. Is it really worth making a tool to cut one valve seat!!! I'm torn here. I really don't want to take the head off this engine again after tomorrow. I will definitly make a new valve from drill rod , because the stem on the intake valve is undersize. I do have a container of Permatex valve lapping compound, and the seat (valve cage) is made of brass. I can do a heck of a lot of lapping in the time it would take me to make a valve seat cutting tool like George Britnells. I'm not sure I'm a total putz at filing and honing, but I'm light years away from Georges abilities. I think the plan will be #1---Make a new valve #2--Lap the valve. #3---Lap the valve some more. ---#4 Then lap it a bit more. #5--Put some permanet marker on it and do the concenticity test. #6---Pray----#7---Reassemble engine.

 

[RonGinger]

I would give up on lapping compound. For a small engine like this you want a very small seat- likely no more that 5-8 thou wide. Think about the scale factor- the seat width in a big engine is only a thin ring, maybe .050 wide.

Make a new head, keep the seat as sharp and square as possible, then make Georges tool and give it just the smallest hand turn for a tiny ring.

Is also make a simple plate to bolt the head to, like what you did to test the cylinder. Put aire pressure on it and test for leaks

 

[jpeter]

I'd suggest that after doing a slight amount of lapping remove the valve and inspect the seat to see if the compound is cutting completely around the seat. What'll happen if the seat's not concentric with the guide is the valve will be offset and won't completely seat. That trouble's not too oncommon cuz drills don't always start in the center where they're suppose to.

Lapping will only remove a few .0001 of an inch so lapping a valve into a non concentric seat probably won't work.

The seat cutter is not a bad idea. They're not complex to make. Fifteen minutes with a lathe and dremel grinder and you'll have one in your hand. They're just a 45 degree angle cone with a short straight turn for a guide. Grind a cutting edge on it after you harden it. Just turn it, heat it with a torch, and dip it in oil. I've had luck dremeling a slot for a cutting tooth on soft steel then raising a burr for a cutting edge. Harden it after that. To harden it I like to spin it in a hand drill while I heat it and dip it. It tends to heat it more evenly that way. Forget about tempering it. The seat wants to be cut really narrow, maybe .003 so hand cutting it only requires a few turns of the tool. (maybe 2 or 3 turns) Don't push too hard or you may gouge out an area.

 

[NickG]

I'd recommend the method Gail used on his tiny, drill & ream the guide, counter bore then cut a very narrow seat with counter sink. Minimal lapping is required, just enough so there is a clean polished ring all the way around. People really seem to go over the top with lapping.

Nick

 

[Metal Butcher]

I'll be facing the same issue of getting valves that seat and seal completely. The idea of making a 'valve cage' with the reamed stem bore, reamed clearance counter bore, and valve seat all cut in one set-up seems to be the only way to achieve the accuracy needed.

I fail to see how a machined, hand sharpened seat cutter twisted by a shaky hand would be more accurate than precision ground factory made cutter's, guided by the rigidity of a machine spindle. ???

In the event that the shop made seat cutter is the only way out (no cage), with out a detailed drawing and step by step instructions, a beginner couldn't even think... of making one. :shrug:

-MB

 

[Brian Rupnow]

I just pulled the intake valve and miked the stem. --Right on 0.093 at the top end away from the valve head, ---But 0.088 down closer to the head, in the guided area. It was held in the 3 jaw at the end where the head is.-appears that during machining the small end kept deflecting away from the cutter and not cutting, whilst the end closer to where it was held in the chuck didn't deflect, so consequently ended up smaller. Will watch cloer for that next time around (in about 15 minutes).

 

[jpeter]

The comment regarding how a guide could be more accurate than a machine: Its is because the drill used to drill the valve guide hole, unless special care is taken, often does not start in the center, thus making the guide hole off center. The seat cutter is constructed with a guide on the tip that extends into the valve guide hole so if the hole is somewhat off center the cutter guided by the guide on the tip will move the seat over to center.