mock up for clearance
 

Figured the best way to judge clearance was to bolt up one rod-piston-cylinder-crank to check for clearance. So I did start to mock up one piston today. I used one of my new rod bearings and old bolts/nuts. Problem number one...only partially torqued, the fresh rods with new bearings was almost locked to the crank...very hard to move. I had the rods surfaced and resized by CAM in Denver. I measured the id of the rod and it was 54mm exactly where it should be. The crank is STD and was magnafluxed and polished. Only thing I can think of is maybe the Glyco STD bearings were screwed up and were an oversize? I checked the box and it was labeled STD. Can't think of what else would cause the rod to marry the journal. Never had that problem before...it was extremely tight. Before you ask, yes I used assembly lube. Not going to be able to check the skirt- case clearance if the rod won't move on the crank :( I moved the rod to a couple other journals and had the same problem. Thoughts...guys?

Speedo

Was it resized with bolts installed and torqued? If not then it is not round anymore when it matters.

retorqued
 

Yes it was. Same shop that has done it on every other rebuild. :confused:
Don't get it. Only other guess is wrong size bearings?

Speedo

That seems to be the logical conclusion since they are not hardened steel and machined to such tight tolerances.

if it helps, I've got a set of new 2.4 bearings here that I could measure for you. also a crank and rods. any checks I can do for you?

case solved...no 2R-3R pun intended
 

I found the problem. The particular rod in question crank bore ID measured out at spec. I called the machine shop this morning to confirm numbers. We tried to get a measurement fron Glyco for the std bearing thickness, but didn't succeed. Thought about this all day...what could be the problem? Everything was fresh.
Got home this afternoon and went to the shop to check one thing, bingo. My bad...the rod end had been somehow swapped around so that the numbers on both sides were not matched. I flipped the bottom around to match the top...torqued to spec and whadayaknow. Nice tight smooth movement. Well, the reason I wanted to do this partial assembly, was to check the clearance between case webs, rod and piston skirt. Lubed the two bearings, laid the crank in with the one rod assembled, bolted up the other case halve, added one piston and secured the cylinder without rings. Moment of truth...no binding anywhere :D
http://forums.pelicanparts.com/uploa...1326163686.jpg
I rotated the crank very gently both directions looking through the sump...nothing touching
http://forums.pelicanparts.com/uploa...1326163769.jpg
http://forums.pelicanparts.com/uploa...1326163807.jpg
My concerns were three fold...1) piston skirt hitting the case webing 2) piston skirt hitting the 70.4 rod due to different throw, and 3) rod hitting the edge of the spigot. Really hard to see inside the case through all the webing, but looks like I have at least 1.5-2 mms everywhere. When I add a base gasket , I am adding at least another .25mm, and case sealant wont add much, but it won't subtract anything either.
http://forums.pelicanparts.com/uploa...1326164071.jpg
I decided to do one more rough measurement. I measure the height of the cylinder above the case surface, and the depth of the piston in the cylinder at BDC, and subtracted the two figures. This gives me the height of the piston above the case at BDC
http://forums.pelicanparts.com/uploa...1326164246.jpg
Now I can pull the cylinder off at BDC and measure the play above the webing at BDC and see how close it is. I think I am fine...but this goes contrary to an old school shop friend I spoke with today who suggested that anytime he strokes a 2.2...he has to machine each piston (not the cases webing, the piston) in four places on the skirt. He told me that because the 2.2 pistons were taller than the 2.4, this was always necessary...hmmm.
http://forums.pelicanparts.com/uploa...1326164583.jpg
http://forums.pelicanparts.com/uploa...1326164610.jpg
Seems like I am good. I know everthing expands under heat...but if I show no signs of friction at all now, you guys want to weigh in?

Speedo

Think we are ok...
 

I performed two more tests today. Given that the more experts I talked to, the more varied the responses...clearance the skirts, clearance the case webs. So I was advised to do the clay tests and see what the deformation looks like. No clay nearby...so I did a different test. Worst case example. I set a piston without a cylinder on it...directly on the webs and rotated the crank. This low in the case, the only thing that could hit the skirts is the CB weights on the crank.
http://forums.pelicanparts.com/uploa...1326248193.jpg
http://forums.pelicanparts.com/uploa...1326248226.jpg
I did notice some slight movement of the piston from the crank when I rotated it...but very slight. So the next test is actually a measurement between the left piston in the cylinder at BDC. I measured from the top mating surface on the cylinder to the edge of the piston, and from the top to the case. Then I measured from the top of the cylinder with a straight edge to the edge of the piston sitting on the web
http://forums.pelicanparts.com/uploa...1326248499.jpg
Doing the math...the difference in the left piston at BDC to the right piston sitting on the web is 3.5 mm. To double check...I used the same straight edge I measured down to the dome of the pistons and subtracted the difference...3.5mm
http://forums.pelicanparts.com/uploa...1326248667.jpg
http://forums.pelicanparts.com/uploa...1326248691.jpg
And again I get 3.4-5 mm. By my calculations, thats 1/8th of an inch plus. So, I should be safe. I may still do the clay thing...but I was going to use that to see how REALLY close things were...like 1mm clearance. With 3.5mm I feel pretty good. Again...if you see a flaw in my analysis, please let me know.

Speedo

Hi there,
some recommendation from old europe on zenith carb setting:
Since it looks like you stick to a general "T"- setup, you should increase the venturis to 31mm, intake ports to 34-35 mm , mains 135, air correction 180, idle 55 or 57 as a starting point. Make shure float level is OK. That's key.
T distributor advance curve should do it.
Probably a good idea touse biral barrels.
Zenith parts are difficult to source but i could help, PM if needed.
Greets,
Robert