Hey guys...

I've got 76cc heads... given they havent been milled. I'd like to learn how to CC them. My understanding is that I need a piece plexi-glass, and burette (measuring doo-hickey... never seen one, nor do I know where to get one!)

I've heard that guys use alcohol, heard about using transmission fluid... anything with color. What I dont know, is how do you measure the amount of fluid going into the head? Do you do it with a spark plug installed?

I've heard (dang it... I want to actually do something, instead of just hearing about it!) that you can use grease of some sort around the head, press the plexi glass against the grease, forming a seal.... what kind of grease?

Next, how do I know how much material I can take off? Probably a dumb question, but can I use a milling machine to take the material off? Or do you need some golly whopper fly cutter? I've got access to one, which is why I ask. Do you have to have a special fixture to mill a head?

I guess I come from the school of though... that I'll try anything once, I just dont know quite enough to try this one yet!

 

I haven't done it. I have a few thoughts to share, someone who has experience in this area can correct me if I'm wrong or add to what I post. I think the burrett is a glass beaker with measurements embossed in it like a measuring cup. It is different from a measuring cup in that it has to sit on a stand above the object you are going to cc and has a tube with an inline valve coming out of the bottom. You need to have the head "dead level" when you measure it. Spark plugs and valves have to be in and sealing, because you are going to fill the combustion chamber and measure how much liquid it took to fill it. If any liquid spills or runs out, you have to start over. I would use sticky wheel bearing grease, but use it sparingly. You need enough grease to seal around the plexy, but any grease that squeeses into the chamber will displace your liquid medium and throw off your calculations accordingly. The plexi should also sit tightly on the head. Also set up the burrette stand so that it can be moved while the head stays stationary. You need to check all combustion chambers. They may not all be the same. You set up your burrette directly above the chamber that you want to check with a hole in the plexi on the head directly below the tube opening from the burrette. I think atf would be a good choice for measuring liquid, alcohol with some dye in it would also work. You might even try thinning atf with alcohol. Fill your burrette to the top measure, not to the top of the glass. You will get your cc measurement by subtracting the amount of liquid left in the burrette after you fill your combustion chamber from what you started with. You want to fill the combustion chamber slowly and carefully until the medium just comes up to the bottom of the plexi, but not into the hole you pour through. You will need to calculate how much space the gap created by your crushed head gasket will add to your heads, but I don't know how to do that. That last step has more to do with figuring out your final compression ratio. If the heads are flat, and the block deck is flat, and the pistons come up the same amount in relation to the deck height in each cylinder, then your combustion chamber cc's will all be the same. One last thing you need to check. Do your pistons come up flush with the block deck? If the pistons are slightly below the deck at top dead center, the area from the top of the piston to the block deck will have to be added to your combustion chamber cc's. If the pistons come up above the deck at top dead center, the amount of space the pistons take up will have to be subtracted from your cc's.

Regarding your question of where to get a burrette, I don't know, but I would check with your local high school or junior college science dept. They use them in science classes, and can probably tell you where they get theirs.

 

I found a website that talks about it...

Its for a corvair though! http://home.hiwaay.net/~langford/corvair/valvejob.html

I'm just trying to figure how you get a complete fill of the chamber! That and where do you drill the holes in the plexiglass for the vent/fill!

 

I forgot about the need for a vent. I don't think the location of the vent and fill holes is critical. The vent doesn't have to be nearly as big as the fill hole to work. I would just make sure that both holes are at least 1/2 inch from the edge of the combustion chamber.

 

I think I'm going to have to build a bench... Gotta clean out some of the garage first... dont think the kitchen counter is a safe place to CC some heads!

So they have to be perfectly flat. is a bubbel level good enough?

 

I would say so. Just make sure to check flatness in every direction. Regarding the kitchen counter, if your single living alone and the landlord doesn't find out, go for it. If you are married, using the kitchen counter is probably a good way to become single.

 

I'll have to see if I can clear a spot in the garage... and see if one of the hardware stores has some scrap plexiglass!

Found a chemistry/biology supply store not far from here, going to give them a call to price one of those burettes.

 

Hardest part is trying to measure the liquid properly, I tried syringes beakers etc. but could not get an accurate measurement. The proper burette to use is a long thin tube that is marked in 1cc graduations ( I think ) and has a stopcock on the end.

I was not going to spend the money on that to use a couple of times so I took my heads to a local speed shop, the guy only charged me 20 bucks and then forgot about it when I picked up my heads as I had other work done at the same time

 

I'll price em!

Either that or measure the amount that fits in a shot glass...

Then have a bartender price out how much my bill is...

Wonder if they'd let me use their bar as a workbench?

 

That's just it any wide mouth beaker will have surface tension and you will not be able to get an accurate measurement. If you want to know whether your not your heads are 76cc or 64cc then it will work but if you want to know the exact measurement you need one of these long burettes in the pic below everything is there grease, plexiglass,isopropyl rubbing alcohol and food coloring

 

It doesn't have to be perfectly flat as the plexiglass will hold the liquid in and force it to go wherever it's needed. Fill and vent need to be the highest points so they fill last. Go by a veterinarian's office and pay him a few bucks for a couple of 60cc syringes and big needles. Grind the points off of the needles and you're set. When you draw your liquid into the syringes, don't fill them completely full. I leave enough air at the top to "zero" it out at the 5cc mark so you don't have to account for volume of the needle and top of the syringe. That means that if you zero the liquid at 5cc's and the plunger is at 45, you have 45cc's of liquid. I use Vaseline to seal around the valves and it works well and is easy to clean up. I use cheap isopropyl alcohol since it's non-corrosive (evaporates too fast to do any damage), it's cheap and reusable. I've done it this way for several years and am never more than 1 - 2 cc's off from what the shop finds when they use a $200 burette on a test bench. My vortecs came out at 62cc's, exactly the same as the shop.

 

Cool stuff!