cc'ing a U-20 head.

[dneuman]

Hello All,
I need to actively start to put my engine back toghether. I had the head re-done but I know its too thin. I want to cc my heads so I can figure out how thick of a head gasket I need to bring the compression down to about 8-1 and to restore the correct valve train geometry. Has anybody ever done this before and would you please give me some guidance.
I understand that you fill the combustion chamber up with a measured amount of light oil and that it helps to put a piece of flat glass over the head to know when you have really exactly filled the chamber.
So how do I do this exactly? I imagine I will have to fiugre out a way to mount the head to my workbench and to get/keep the head perfectly level. I am also going to need to turn the crankshaft to close all the valves. How do I do that when the head is off the engine and sitting on my workbench (without screwing everything up??).
Thanks,

[FergO2k]

Daniel,
http://www.hydrostream.org/ArticleArchives/CCHeads.htm

I saw other references where they used cooking oil.

Only need to turn camshaft so that valves in each cyl are closed, then do each cyl individually.

Fergus O

[dneuman]

Daniel,
http://www.hydrostream.org/ArticleArchives/CCHeads.htm

I saw other references where they used cooking oil.

Only need to turn camshaft so that valves in each cyl are closed, then do each cyl individually.

Fergus O

Hey Fergus,
That comes back as a bad link???

[FergO2k]

Hey Daniel, very strange.
I entered "cylinder head cc" into Google, and it was #4 on the listing.
http://www.hydrostream.org/ArticleArchives/CCHeads.htm

try this one:
http://www.valvoline.com/carcare/articl ... 4&scccid=5

[datsunrides]

As far as CC'ing the combustion chambers, you are on the right path. Make sure both valves are COMPLETELY closed, put a light coat of grease around the chamber, seat a thin, flat piece of lexan with a small hole drilled in it to put fluid into the chamber and fill it with a colored liquid (water with food coloring works good) with a graduated syringe untill full. You can buy these as a complete professional setup, but unless you plan to use it often, it probably is not worth the cost. Fly cutting the head will not affect valvetrain geometry as these engines are overhead cam, not pushrod. It DOES affect valve timing and chain tension. The best way to find out how much your head has been cut is to measure the thickness from the head gasket surface to the valve cover sealing surface. I'm sure someone here has a spec for that or try your local machine shop. The "new" dimension minus your dimension would equal the additional thickness required to bring everything back to spec.(plus the thickness of the original head gasket). You can make a down and dirty set of head blocks by simply making a X out of a couple of 2 x 4's screwed together in the middle. Rest your cylinder head in the X and shift around untill level.
Hope this helps!

Mark

[dbrick]

Don't forget to properly figure compression you also have to add in the area from the top of the block to the top of the piston at TDC. With dome pistons this may be a negative. To seal the top of the piston you can pack the area around the top of the piston to the top ring with a bead of grease.
The swept area can be calculated with stroke x{(.5 x bore dia) squared}

[FergO2k]

Um, don't mean to be a smart a$$, but shouldn't that formula be
pi*(0.5xdia)squared ?

[dbrick]

Shut your Pi hole

[dbrick]

Yes, stroke *{pi[(0.5xdia)squared]} So they were right, you do need to learn math!!

[SLOroadster]

How much was taken off the head? To fix the cam towers, get the correct shims. The Bob Sharp manual says stock should be 44ccs. It also tells you how to do it.

Will