'77 CJ360T (Café SOS) - Calling it Done (for now...)

[crazypj]

Re: '77 CJ360T (Café SOS) - Head and Valve Work Complete

I've seen it done with a Dremel (or rather a die grinder) but it sure isn't any kind of precision.
You have a couple of old bent valves (well, new bent valves really )
If the stem is straight, you can cut teeth into face/head with Dremel and use that to open up valve pockets, the bend will give extra clearance on diameter.
Just fit in guide as normal, bolt head down and spin onto piston at TDC
Valve to valve you measure with the head off at overlap, fit really light springs and turn cam.
Just before and after TDC is the 'danger' area
I shorten cylinders to zero deck, have to build motor to find out how much you need to remove

 

[Sonreir]

Re: '77 CJ360T (Café SOS) - Head and Valve Work Complete

Well... I suppose I better measure twice before I cut once. Thanks for the info, guys.

 

[teazer]

Re: '77 CJ360T (Café SOS) - Head and Valve Work Complete

The correct answer is to use a Bridgeport mill. To get extra clearance around the outer edges, I'd just use a dremmel with small carbide bit and lots of tape around the piston for when it breaks loose and lots of WD40 to stop the teeth clogging.

I have used a Dremmel to deepen pockets, but it's a very imprecise process. How far back did they pull the valves into the head and what is the spring installed eight now and what was stock?

To check clearance piston to valve, assemble the head with single soft springs on the valves and turn the motor over. As it approaches TDC, lever down on the intake valve to see how far down it goes. Repeat every few degrees until past TDC and then repeat on the exhaust.

Building a Hi Po motor means multiple build-check-strip-modify cycles to get it perfect.

 

[crazypj]

Re: '77 CJ360T (Café SOS) - Head and Valve Work Complete

Building a Hi Po motor means multiple build-check-strip-modify cycles to get it perfect.

It's actually a PITA, but, when finished becomes all worthwhile

 

[ariel.714 o/c]

Re: '77 CJ360T (Café SOS) - Head and Valve Work Complete

Liking those velocity stacks.. where did you pick those up at?

 

[Sonreir]

Re: '77 CJ360T (Café SOS) - Head and Valve Work Complete

Steel Dragon Performance made 'em up for me. Their prices may have changed in the last year, but at the time I think they were only $65 or so.

http://www.steeldragonperformance.com/

 

[ariel.714 o/c]

Re: '77 CJ360T (Café SOS) - Head and Valve Work Complete

Steel Dragon Performance made 'em up for me. Their prices may have changed in the last year, but at the time I think they were only $65 or so.

http://www.steeldragonperformance.com/

Nice man those are sweet looking. Did u need to rejet

 

[Sonreir]

Re: '77 CJ360T (Café SOS) - Head and Valve Work Complete

Yes, but I'm not sure how much of that is due to the stacks and how much is due to my other modifications. A lot has changed over stock in this build.

 

[Sonreir]

Re: '77 CJ360T (Café SOS) - Head and Valve Work Complete

Valves are back from the machinist and I picked up a new set of racing plugs.

The valves have a slight 30° backcut which can be seen if you stare at it long enough.

For plugs, I went with a set B9EGs.

 

[crazypj]

Re: '77 CJ360T (Café SOS) - Head and Valve Work Complete

cool stuff 8)
I would fit 8's until you get jetting sorted though

 

[Sonreir]

Re: '77 CJ360T (Café SOS) - Assemble, Measure, Modify, Repeat

This last weekend my Dad and I got a chance to put the head back on and check all the clearances using some more exacting methods. First the head was put in place without the head gasket and it was determined even at that point we had zero clearance between valve and piston. So we repeated the process with the head gasket on and took the time to hook up the machinist dial to sit in line with the intake valve (the valve suspected to have the least clearance). Also, this was without the valve springs in place so that we'd be able to freely move the valve within the head.

At TDC, with the head gasket in place, the intake valve has .010" clearance before contacting the piston. Not good considering that valve should be open .048" (according to the timing card that came with my cam) at this spot in the rotation...

Next step was to disassemble everything again and lay down something that could be used to identify the contact points. We borrowed a bit of playdough from my son's "toolbox" and placed a bit into each valve pocket within the pistons. The results of the left side are pictured here:

Left Intake

Left Exhaust

It appears that the tolerances on the pistons was quite tight and the extra 1mm of diameter on the new valves is exceeding what the pistons can handle. Interestingly enough, the right side isn't as close and so we micced out the head thickness and found the left side to be .005" thinner than the right. So there's something that will need to be addressed.

Anyway... after some discussion we're decided to cut down the diameter of the valves by .040" rather than remove any more material from the piston. The main reasons are cost and time, but seeing as how the ports haven't been altered, the extra 1mm on the valves isn't doing us any good anyway. The margin, of course, will be a bit thicker now, but better too thick than too thin.

Want a built motor? Here's the steps to follow:
1.) Take everything apart
2.) Measure everything
3.) Put everything back together
4.) Measure everything again
5.) Correct anything that doesn't fit or doesn't work
6.) Repeat two dozen times

I guess if it were easy, everyone would do it, right?

On the plus side, we've also double-checked the squish area and found it to be right around .040" and so that's a lot better than I thought.

 

[crazypj]

Re: '77 CJ360T (Café SOS) - Assemble, Measure, Modify, Repeat

Are the valve faces hardened deep enough to take a mm off?
You may be better getting stock valves, pocketing head a bit further or machine pistons as I described (It works fine, I'll see if I have pics)

 

[teazer]

Re: '77 CJ360T (Café SOS) - Assemble, Measure, Modify, Repeat

That is normal with big valves. I'd pop the pistons out and dremmel that cut out on the outer edges. Then go back to your formula of build-check- etc .

Looking at the pictures again, it almost looks as if there's a slight "wipe" mark on the inner side of each pocket. If so, that's the valves rubbing up against the pistons. great for your cat, but not good for engine parts.If those are contact marks, the valves must be pocketed by 1.0-1.25mm to get more clearance.

This is what separates the men from the boys. Get this stuff right and your motor will be faster and more reliable than most. Take enough short cuts and it will be a time bomb. Easy choice, right? It really is painstaking attention to detail that makes the difference.

 

[ducatiboy]

Re: '77 CJ360T (Café SOS) - Assemble, Measure, Modify, Repeat

I have to agree with PJ and Teazer. The simplest solution to this is to make the valve cutaway on the piston slightly larger to accommodate the larger valves. Ideally by machining but no problem with a dremel...

 

[crazypj]

Re: '77 CJ360T (Café SOS) - Assemble, Measure, Modify, Repeat

This is what I used to modify valve pockets for 800cc XS'650'
Didn't have machine shop access at the time but I did have a new bench grinder and power drill
Just lock piston at TDC (use primary gears) fit drill stop to valve stem with teeth touching piston then move stop about 1mm and carve away.
I could have spent more time to make a real cutter or even make this 'nicer' but I was in a rush and just wnted it done. It's going to be a lot more accurate than a Dremel

 

[ducatiboy]

Re: '77 CJ360T (Café SOS) - Assemble, Measure, Modify, Repeat

OUTSTANDING TOOL PJ!! ;D ;D ;D ;D

 

[Sonreir]

Re: '77 CJ360T (Café SOS) - Assemble, Measure, Modify, Repeat

Engine building is so much fun! /end sarcasm

I guess in an seriousness, it it. But it can also be bloody frustrating sometimes.

I just got back from the machinist and was speaking to him about the clearance issue I have with my valves and pistons. I talked to him about cutting on the pistons a bit to fix the problem but he said he didn't have the proper tool and advised me to not go any deeper or I'd blow a hole in the piston. It was implied that a bit wider on the flycut would be OK though.

So I asked, instead, about cutting the valves back down to stock diameter. He doesn't have the tool for that, either. At this point I was about ready to ask him what tools he did actually have, but I kept my mouth shut.

His suggestion was to get new pistons or increase my head gasket to .080". I don't really want to do the former and the latter sounds pretty bad (goodbye compression and squish band)....

*sigh*

Time to do some thinking.

 

[ducatiboy]

Re: '77 CJ360T (Café SOS) - Assemble, Measure, Modify, Repeat

Is your machinist a regular motorcycle machinist? And probably more relevant does he regularly do performance work on bikes? Seems to me if he does, then he would have the tools to do what should be a fairly routine job. I would have thought cutting bigger valve cutouts in the top of a piston would be a bread and butter kind of job for someone regularly doing performance work. If he doesn't regularly do performance work maybe you'd be better off finding someone who does. And if THEY say you'll blow the top off your piston, then you've got your answer. Regardless, a second opinion never hurt. Good luck with it!

 

[Sonreir]

Re: '77 CJ360T (Café SOS) - Assemble, Measure, Modify, Repeat

I'm pretty sure he's a car guy. .080" gasket might not make much of a difference on a 400ci motor, but that's a lot of compression lost when your chambers are only 25cc.

 

[ducatiboy]

Re: '77 CJ360T (Café SOS) - Assemble, Measure, Modify, Repeat

Don't compromise when you're this close to your goal!!!

And I'd be trusting the DTT gurus who have worked on and built these motors over and over again before some car guy with no tools ;D ;D ;D