T head engine by Brian

[Gordon]

Try putting some lube on the valve stems to see if that works before making new parts. If the valves are sticking in the guides some penetrating oil should fix the problem for at least a short time.

 

[johnmcc69]

Great looking engine Brian! I really like the orange touches & the black fan, it seems to really "Pop" out.
What will you do for a finished base? (If any..)

John

 

[Brian Rupnow]

John---I never put a finished base on any of my engines. Once they run properly, they go up on the shelf "as is".

 

[Ghosty]

Brian, this is what is in the re-coil kits, I have several.
Cheers
Andrew

 

[Brian Rupnow]

Ghosty---After I thought about this long enough, I determined that I can Loctite 1/4" steel plugs with an internal #10-40 thread into the far side of the aluminum piece and avoid buying helicoils----I think.

 

[L98fiero]

Question--do you have to have a special tool to insert helicoils? I have a couple of 10-24 threaded holes in my aluminum cylinder head that are getting kinda funky. I can buy a bag of helicoils for $12, but I I buy a "helicoil kit" the price shoots up to $45

In your situation you'd need the helicoil tap, generically it's an STI tap, and you can use a 10-24 screw and file the end down by filing off the last thread along it's minor diameter so that it creates a 'hook' for the tang to catch on for a driver, for just a few helicoils it will work and then like gartof said, use a punch to knock the tang off.

 

[johwen]

Hi Brian,
Like I said before Up your valve spring pressure slightly to overcome the drag on the valve stem or slightly increase the stem clearance easy done.. Cheers Brian

 

[Brian Rupnow]

I dipped into the Rupnow fortune today and bought a 10-24 Helicoil kit which comes with all the necessary drills, taps, etcetera and about 40 inserts in different lengths for $116.00. While I was picking up the kit, I picked up some very heavy, bull-doggy looking compression springs to be used as valve springs. The valve springs I have on the engine now are 0.026" diameter wire size. The new ones I bought are 0.049" wire size. They are also larger in overall diameter, so tomorrow I will machine new valve cups that go on the valves to center the springs. This business of valves sealing one day good enough for the engine to run, and then not sealing the next day is ridiculous.

 

[Brian Rupnow]

The Helicoils worked great. I have never used them before and I must say, they work fine and don't require a lot of work to use them. I did machine new spring cups and install them and the heavy valve springs on the engine, but it didn't really help. I then took the cylinder head off the machine and ran a 0.200" diameter drill up from the bottom side of the valve cages, about 0.6" to cut down on the amount of friction between the valve stems and the valve guide portion of the valve cage. I took the heavy springs and cups off and put the originals back on. I reground the valves. Nothing really helped get my compression back. Something I have noticed over the years--When the seat portion of the valve cage gets too large, it is almost impossible to get a good valve seal. I'm stumped at the moment. I may machine new valve cages and reface the valves in the lathe, more or less starting over again with the valve sealing issue. I have rechecked the valve and ignition timing, but they are fine.

 

[SirJohn]

The Helicoils worked great. I have never used them before and I must say, they work fine and don't require a lot of work to use them. I did machine new spring cups and install them and the heavy valve springs on the engine, but it didn't really help. I then took the cylinder head off the machine and ran a 0.200" diameter drill up from the bottom side of the valve cages, about 0.6" to cut down on the amount of friction between the valve stems and the valve guide portion of the valve cage. I took the heavy springs and cups off and put the originals back on. I reground the valves. Nothing really helped get my compression back. Something I have noticed over the years--When the seat portion of the valve cage gets too large, it is almost impossible to get a good valve seal. I'm stumped at the moment. I may machine new valve cages and reface the valves in the lathe, more or less starting over again with the valve sealing issue. I have rechecked the valve and ignition timing, but they are fine.

Brian, do you make the valve angle and the seat angle the same? If I remember correctly, there should be a couple of degrees difference so that there is a minimum contact point.
John

 

[Brian Rupnow]

No John--I cut the valve seat at a true 90 degree included angle. the valves are machined to have a 92 degree included angle.

 

[Brian Rupnow]

I spent all of yesterday flogging a dead horse. Today I am going to make new valve cages and loctite them into the head. A close visual inspection of the existing valve cages shows that the seat area has become too large because of repetitive lapping to get a good seal on the valves. Also, due too the method I used when making them, the seat area is not perfectly centered on the guide area. I tried to take picture to post here, but my digital camera can't get a shot which shows it clearly.

 

[Brian Rupnow]

So, here is a family picture. The cylinder head with new valve cages pressed and loctited in place, the old valve cages which have been pressed out (You can see the excessively large valve seat area in the picture), along with valves, keepers, and springs. I haven't used my special tool for cutting new valve seats into the cages yet, I'll wait until the Loctite dries 24 hours. I am now using my wifes old digital camera, as it takes pictures much more clearly than mine. Design review came back to my customer today on the welding fixtures I designed, and it looks like I will have a full day tomorrow just making all the changes.

 

[animal12]

So , I'm trying to learn some of the lingo here , the parts that your calling the " valve cages " would those be the same as valve guides ? What are you folks using for valve seats on engines like this ?
thanks
animal

 

[propclock]

We usually refer to a valve cage as both the guide and seat and port.
Typically Loctite in place or press fit. This so the valve is not
seating directly on the soft aluminum.

 

[animal12]

OK , thanks . I'll be doing some digging around here for some time to get somewhat on the same page , or even just in the same book .
thanks
animal

 

[Brian Rupnow]

It's been a wild and crazy two weeks since I first had this engine running. I have been very busy changing my shop around to make room for a big DoAll Bandsaw and preparing to sell my smaller metal cutting bandsaw. Strangest thing---the engine ran fine before I painted the flywheels and gas tank, but after the paintjob I couldn't get this thing to run for love nor money. These engines are not terribly powerful, and I was having enough interferance between the large timing gears and the aluminum casings over them to keep the engine from running on it's own. The engine ran again on it's own for the second time about 3:00 this afternoon, and I've been chasing down interferences and tight spots until about 20 minutes ago. The small carburetors from Traxxas are just right for these engines I build, but the throttle is very loose so that it can be operated by a servo. I don't use servos to control my engines, and the default setting is for the carburetor to open the throttle wide open just from engine vibration if I don't have something connected to that throttle. Tomorrow I will post a better video out in my main garage where there is lots of natural light with the garage doors open, and I have a better hook up for the engine throttle.---And yes, that little 10 blade fan being ran from the flywheel by a rubber o-ring puts out an amazing amount of air over the cylinder.---Brian

 

[payner]

Brian . Are you interested in having a look at the servo and tester I was telling you about , I can't remember the exact cost but about $15.00 - $20.00 . A lot cheaper then $150.00 for a complete RC system.
Bill
PS . Engine looks and sounds great .

 

[Brian Rupnow]

Bill---I would be interested in looking at them.---Brian

 

[Brian Rupnow]

So this is it kiddies. The engine is completely finished, runs the way I like, and looks pretty too. I had a few problems with valves not sealing, but new valve cages were made and the problem was fixed. This has been an interesting engine to build, and it is similar in many respects to the flathead engine I built ten years ago. Complete plan sets are waiting to be sent out to anyone wishing to build this engine.($25 Canadian funds), contact me. Thanks to all who have followed and commented on the forums as this engine came together.---Brian Rupnow