The Head Page

LOL, got some of you guys attention!

I just put up my page on Head CCing, let me know if you see anything wrong or I said something wrong and I will fix it.

formatting link
click link to "CC your head"

Thanks!!

Reply to
TerryB
Loading thread data ...

Pretty good.

A few notes:

1) measure each chamber three times, and calcluate the average. There's always room for marginal error.

2) if you uses a clear plastic you would see the trapped air bubbles easier. You can peel the CD metal layer off and there you have it. It's easy to miss small bubbles near the edges but they have a big difference.

3) really do try to get them all to same volume. Remove material from near the valves, on the vertical surfaces. If you can avoid it, don't make the chamber wider than any of the others.

That's a good start you have there, into a successful engine rebuild.

Here's a calculator to help you determine your CR:

formatting link
Note the choice of metric and archaic, obsolete imperial systems :)

Jan

Reply to
Jan Andersson

------------------------------------------------------------

Dear Terry,

Nice job. You'd be surprised how many people don't bother, ending up with inappropriate compression ratios.

-------------

Couple of comments:

If your valves are properly lapped they will not leak, hence no need for any grease. Or to say it another way, if your valves are ALREADY leaking, it's time for another valve job :-) (After lapping and cleaning things up, the usual test is to pour a small quantity of kerosene or WD-40 (ie, something that WON'T RUST) into the port while holding the valve closed with your hand. If you see a damp spot, lap them again.)

In a similar vein, you don't need to install the valve springs just to cc the chambers. If the valves are properly lapped a THIN wipe of grease on the frosted edge will hold them closed.

The reason the VW factory service manual shows using a thick plexiglas disk pierced with five holes is because plexiglas and most other plastics are close to the weight of water. (Specific gravity of Acrylic sheet [ie, 'Plexiglass] is about 1.17.) That means it doesn't take much of a bubble to cause the thing to float out of position. The multiple number of holes (see the drawing in the service manual) helps defeat the bubbles and the thicker the plex, the better it seals. (The holes also serve as a handy level gauge.)

Speaking of seals, there's no need to grease the entire disk, just its edge. But when forced to use a THIN sheet of plastic, glass or what-ever, wiping a thin layer of grease around the edge of the combustion chamber should be enough to give you the required seal.

Also, while liquid detergent does a good job of defeating the surface tension of the water, if you use more than about ONE DROP PER QUART it will tend to PROMOTE bubbles.

Jan's advice about measuring each chamber several times is another of those pesky details most chose to ignore, probably because they find it difficult to DRY the chamber between tests. (It's especially tough to get all the fluid out of the spark plug.) The secret here is to use compressed air. And alcohol. A blast of compressed air will get most of the fluid out of the nooks & crannies but to get it all you'll need to give the chamber a slosh of alcohol. NOT rubbing alcohol. Rubbing alcohol, which is usually only 70%, contains dissolved solids (usually alum and other nasty-tasting stuff) which can leave a residue. Wood alcohol (methyl methinol ?) is 90% or better and leaves no residue. (Look in the paint the dept.; tell them you want to thin some shellac.)

The reason for using alcohol is that it 'dissolves' water :-) And once the water has been dissolved into the alcohol, a blast of compressed air will blow it away. (Real air works best but you can use 'Dust Off' or similar. [Canned 'air' is actually Tetrafluorethane.. or similar stuff].)

Back in the Good Ol' Days, whenever that was... we used kerosene for the fluid and gasoline for the solvent. Nowadays, the stuff they call 'gasoline' is toxic and kerosene runs better than $5/gal, so colored water has become the fluid of choice.

------------------------------------------------

Finally, to everyone who has NOT cc'd their chambers nor balanced their engine, the loss due to any imbalance of mass or volume is effectively DOUBLED by the engine, since it must consume that amount of power to overcome the losses resulting from such imbalances, which is why relatively small adjustments can produce some impressively large increases in power output. Another of those 'unimportant details.' :-)

-Bob Hoover

PS - There's nothing magic about petroleum jelly (ie, 'Vaseline') other than it's not as messy as most other greases. In a pinch I've used chassis lube, Crisco and even butter (!)

Reply to
veeduber

There's

Thanks Jan, I will go back and do the ccing again and take fresh pics using some plex or a clear cd. I think I trashed the DVD.

Removing material from the head just plain scares me to death, truthfully. But I am willing to do it if coached correctly. Would this be better done by using a file or a rotary file on a Dremel? Feel free to use one of the pic on my site if you want to do some drawing aids.

Thanks again Jan, your VW knowledge and willingness to share is most welcomed!!

Reply to
TerryB

plexiglas

doesn't

Rubbing

(usually

shellac.)

What can I say, two of the Internets BEST VW authorities (IMHO) have looked at my work and did not find major fault with it. No, I am not bragging at all, nor would I. I just want to do my part for the continuing of our beloved VW's and want to give good info as these gentlemen do!

Thank you Mr. Hoover, your input is always of great value. I have been reading your sermons and all since the early 90's, don't mean to make you feel old or anything like that, just appreciate you sharing your years of knowledge with those of us who need experienced feedback.

Now I need to go lookup valve lapping, I know it has been discussed and should be able to look it up.

Thanks again to ALL who looked at the web page and took time to read my ramblings!!

Reply to
TerryB

--------------------------------

You're welcome.

The use of a CD is ingenious and while it is not the most appropriate material for a cc plate, the data it will provide will be close enough to prevent you from destroying the engine with a CR that is too high. Overall, your efforts do you credit.

--------------------------

---------------------------------------

That's okay. Like it or not, I *AM* old... and you will be too, one day :-)

-------------------------------------

-------------------------------------

I suggest you go find Mark Langford's web site...

formatting link
This is a HUGE site so give it time. Find the section covering his overhaul of the Corvair engine. There you will find some excellent photographs and well-written narrative as he laps his valves, cc's the chambers, checks the rocker geometry and so forth.

Pay particular attention to the eccentricity Mark discovered in the valve guide and seat. This is one of the first things you need to check for when lapping in your valves. (Yes, even when the heads have just come back from the shop.)

Also note the 'wiggle' test for guide wear. You'll find the spec's for this in the factory service manual.

Should you need to replace your guides, be advised that VW guides are a shrink fit -- you'll need to heat the heads and freeze the guides before installation. Also, VW guides are usually cored-out with a special step-drill before being driven out of the (heated) head. This is worth mentioning because many shops don't bother, simply hammering the things in & out with a pneumatic tool, which usually causes the valve-guide boss to crack.

Replacement of the guides is not difficult but as with cc-ing the chambers it calls for keen attention to details most folks deem 'unimportant.' Of course, the culmination of all those 'unimportant' details is an efficient, more powerful engine that is stone-reliable... a terrible idea to the go-fast/make-noise crowd :-)

-Bob Hoover

Reply to
veeduber

enough

Thanks again, Jan had the idea to use the cd and it is a good idea.

I ain't as young as I use to be. 39 and still going. I have quit worring about the years, just enjoy every minute I am given.

This guy must be related to you Bob, he covers it all in great detail. Is this Mark Langford in Alabama? He mentioned Birmingham, just wonder if that is Alabama..... hmmmm.

I bought the stuff to do the valve lapping yesterday and did one head last night. You don't want to know what I used as a spring compressor....LOL. I used two of my bar clamps that I have for wood gluing. I will take some pics of that as well and put them up on my site. I did not want to spend the $30 for a compressor at the store, so with necessity being what it is, I improvised and it worked quite well.

After I got through lapping each valve, I tested it with water to see if they leaked. With NO spring attached, just put the valve in the hole and by its own weight it held with no leaks!! Just like Mr. Hoover said it should. Nice, very Nice!! Not that I ever doubted Bob's word or anything. LOL

Now, I just need to finish the other head and get syc'ed up to grind on the chambers to equal out the CC's. A new frontier for me, but so have these other things been as well. I am learning loads and enjoying every minute, well with exception of dropping the bar clamp close to my foot!!

Reply to
TerryB

MotorsForum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.