I was installing a 555 top end today. There seems to be a clearance problem with the pistons and the valves. I have not checked the actual clearance but I believe it is 0.00" It has MegaCycle cams (384-20) with 0.417" lift. They recommend 0.060" clearance.

Several options:
1. put the stock cams in
2. cut the pistons more to allow for the high lift (if there is enough material)
3. install a thicker head gasket (are there any problems with this?)

There was a board member (in CA I believe) who mentioned that he could machine the pistons for more valve clearance. I can not remember who but please post up. I may try searching for a past post later.

Looks like it am going to put the 500 top end back on until I can get this resolved. Getting good at rebuilding the top end. Can have it swapped out in about 2 hours. But not tonight.

Edited to remove the 'amp;' from after the ampersand (&).

What thickness gaskets are you using now ?

if you go with thicker gasket you will lower compression ratio, best bet is to trim the valve reliefs alittle,   if you go with stock cams i wouldnt think it would breath well enough to be useful to the added Cubes,  if you have an old headgasket, there is a trick with modeling clay on the piston to get a impression from the valve as it gets near the piston.  then you messure the from top of pistion valve relief to indent and should give you ballpark idea of clearance.   Bob B. step up if im wrong plz.

Using stock thickness gaskets. I have a thicker copper gasket that I have not tried yet. Measures approximately 0.028" thick.
I believe the pistons are Wiseco. There is an imbossed W with a circle around it on the inside bottom of the pistons.
Yeah, I was concerned running the stock cams with the larger bore and not having enough flow.
I will try to measure the clearances tomorrow. Someone had mentioned using a piece of solder to measure the clearance since clay can get distorted when removed and being measured. May try both methods.

Almost forgot...I have another head that has been milled and ported. I want to run it, so looks like increasing the valve reliefs in the pistons is the way to go.

Take the modeling clay and put some on the piston so it covers the valve relief areas. Make sure the piston surface is clean so the clay sticks. Put some lube on the valve face so it doesn't pull the clay up. Then do a rotation of the crank by hand (slowly).  After the head is off. Cut the clay across the middle of the valve relief. Then you can pull off some clay and measure the thickness of the clay on the piston.
The cams I run have .438" lift. Never had any clearence problems.
I'm running JE pistons with huge domes for high compression.
.060 clearence is probably a pretty safe # in case you miss a shift.
I would think .050 is fine (minimum). The valve springs will be floating before the valves hit the piston.
Any machine shop should be able to take a few thousands off the pistons if needed. Also the valve seats could be cut more to fit the valves a bit further into the head. The stems will need to be ground a bit to get them within specs depending on your shim thickness.
I run a shim under bucket setup. It uses Kawasaki 13mm shims. They come in .002 increments. After I do a vlave job, I sometimes have to grind the stems to get the exact clearence with the shim available.

I just did a race engine (Ford V8) and I hand cut the valve reliefs in the pistons to accomodate the larger chevy valve train.  I used the clay method and a die grinder and a lot of beer.

For cars, the valve manufacturers sell a deal that goes in place of the valve but has a cutting edge on it.  You install the valve cutter, put the head on, spin it a few times and you're good to go.  You can rent the tool from the valve manufacturer.

I would contact your valve manufacturer and see if they have something like this.

I would NOT do the hand cutting again.  I would wait the two weeks shipping to order the tool.

Shane
306 N2O Pinto

That reminded me of some friends that raced Porsches. They made their own cutter by brazing a piece of hardened tool steel on an old valve.
Same method you talk about. Just homemade :mrgreen:

Just checked the clearance with clay (plumbers putty actually). No problem with clearance. The minimum was about 4mm. With that much I am going to put on the milled head!
Now I am really confused. When running, it had the same buzzing sound as when the valves float. I did the cam to shim clearance twice, so I know that is correct.
What else would make the buzzing/vibrating sound? If the head gasket was bad, would it vibrate and make a similar buzzing sound?

The head gasket can't make any noises. It's compressed between the head and cylinder. There's no part of it that hangs out to vibrate.
Valve float only happens at very high RPMs. If your valve springs are too weak it could happen at a little lower RPM.
I tried a set of APE springs once (I use Kibblewhite normally). They were Kawasaki KZ1000 springs for race cams just like the Kibblewhites.
But I had alot of problems with them. The noise (like valves floating) happened at much lower RPMs. I tried less shimming to change the installed height trying to lower the spring tension. I ended up breaking the tip off a valve where the collets fit. I don't have a spring tension measuring tool, so I can't compare the springs to see what was going on.
A buzzing sound could just be something else on the bike making noise.
Maybe a good set of earplugs will make the bike run better  :lol:  :lol:

I am running heavier springs that are recommended for these cams. I had this same head & cams on the 75mm cylinder without any problems or weird noises. It sounded like it was coming from the engine. Never really rev'd it above 4k but the buzzing/ticking sound was at idle as well. Oh well, it is all apart again, swapping heads. The intake valves had some odd wear on the seats. The seat was worn concave in a small area, very easily seen. So I ended putting another set in but had to neck them down first. Took a lot longer than planned.
Maybe it will go away......will find out tomorrow.

QuoteI don't have a spring tension measuring tool, so I can't compare the springs to see what was going on.

Basic home made Valve spring tester.   Wooden or steel frame about 6" taller then a stadard cheapy bottle jack but wide enough for a cheap bathroom scale, place scale centered in frame, place jack in middle of scale and re zero the scale. using a section of pipe alittle bit larger diameter then most springs i test, i attach it to the top of frame work , i Cut/grind a slit up the length of the pipe.  now place the springs on the top of the jack and pump watching through the slit in the pipe for spring bind or compression limits(glueing an old messuring tape to pipe is helpful) then read the scale for height of spring compressed. this may not be the most accurate, but good way to compare springs of same type.

Finally!....I figured out what the real clearance issue is. Guess how I figured this out, the hard way. I put on the milled head with the .028 thick copper gasket and every thing turned fine...by hand. Once the plugs where in this is where the fun begins. I tried to start it and heard a tapping sound, guessing it was just one of valve-shim gaps that was a little big. It would pop and blow really black smoke out the exhaust. Now why would it be running that rich? So I decided to pull the plugs and make sure they were sparking, in case I damaged a wire when pulling the head. When I removed the right side plug, it had a shiney spot on it. Thought I just rubbed it when I removed it. When I removed the left side, the electrodes where bent almost together. The pistons were hitting the spark plugs! Luckily no damage. There are not bent much but enough to close the gap and not let it run. At least GS plugs are cheap!

Now for the questions.....
Can I install thicker spark plug washers to raise the plugs?
Are there different length plugs?

I hate to install a thicker head gasket and loose compression. The only other option I can come up with would be to put the stock head back on. Advise?

EDIT: I guess I could pull out the portable milling machine (aka Dremel) and create a relief in the pistons for the spark plugs. Just not sure how much meat is there without pulling the pistons out.

You can put an extra spark plug washer on the plugs. The pistons I have came with a spot milled for plug clearence.
It sounds like the right side is just barely touching if it only has a shiny spot on the plug. The left side didn't completely mash the plug end either. So it won't take much to get some clearence.

Do I leave the existing washer and have 2 washers? Or should I just have 1 thicker washer?

I would use 1 washer that fits in the cutouts in the top of the cylinder.
It would need to fit in the cutout and allow oil to pass around the stud.

I think it would be easier to use regular o-rings. You could get some that are thick enough to make up the extra space. The head gasket will contain the o-rings in their position. They won't be able to blow out under oil pressure.
And the heat shouldn't be an issue. I have o-rings on my gsxr500 motor that have worked without problems.

 

Oops I thought you were talking about something else.

On the spark plugs I would use 2 washers. But they should be spark plug washers, not regular flat washers.
That and a little dremeling on the pistons will solve the problem.

I got copper flat washers to use on the plugs. Is there a problem with using a flat copper washer with the regular spark plug washer? I am hoping that this will create enough clearance so I do not have to pull the head again and cut the piston.

Copper should work.

The washers fixed the piston-plug clearance issue by a little less than 1mm. There still is a tapping sound but sounds more like the valve-shim clearance.

It did not want to run. It will idle (sort of) but give it gas and it dies. The plugs are very black, so it is too rich. Before installing the 555, I dropped down a size in the main from a 147.5 to a 145 and lowered the needle by removing 1 of the 2 washers.

I am a little confused as to the required jetting. Would a larger displacement with a greater compression motor need to be run leaner?

I would think you need bigger jets. It may be too rich at idle. But when you
try to open the throttle there is not enough fuel for the air going in.

I have a air/fuel ratio meter. I installed an oxygen sensor in the exhaust.
The meter has different colored leds that show when it is rich or lean.
The problem I have is the race fuel destroys the sensor fairly quickly.
With unleaded fuel it wouldn't matter how long you played with the jetting.
But it is a great tool for tuning.