Things I learned today while polishing my CC's

[Anlushac11]

1) Even though I had no problem porting a set of heads for my dads 289 with his help 20 years ago, I seem to have forgotten all the important stuff.

2) 20,000rpm Electric Die Grinders will get hot enough to burn your hand.

3) Dont move the grinder so your on the debris exit side unless your wearing a dustmask over your nose(fortunately I was or I would be on a high iron diet about now)

4) Even at 6'4" and 350lbs I cant control the grinder to keep it from leaving chatter marks.

So a nice breezy low humidity 85 deg day so I setup outside on the ex hospital table and decide Im going to polish the combustion chamber.

After an hour I am not done with the first chamber, I still have pinholes in the cast iron and I have chatter marks intead of that nice even polished look.

I was planning to use the grinder to do all the cutting and material removal and then using either a Dremel and a some silicone rolls or one of those paint strippers to buff the combsution chamber smooth.

How do you guys get that smooth finish that looks like the chamber is baby butt smooth and even.

A few times the grinder escaped onto the deck surface to leave a trail that I can only hope will clean up when I get the head milled(should not be a problem). I thought the polishing would go alot quicker. Either that or I am being really cautious (yeah thats it)

I also laid back the combustion chamber wall away from the valves. Isnt it supposed to be 3/16" from edge of valve to edge of combustion chamber wall? The intake is about 1/4" from edge of valve to edge of combustion chamber wall.

I quit for today only because the electric grinder was getting to hot to hold and it takes too long for it to cool down. As in 1/2 hour or more and its still fairly warm to the touch.

Any pointers would be appreciated.

Thanks

 

[Anonymous]

You might be suprised by this but if you have a couple of hours of more to spare you could get a very good result do them by hand.
Recently I polished my exhaust port by hand took 2-3 hours and looked like a glass mirror when finished with a few slight imperfections still evident (nothing that would make the slightest differntce to flow)
Get different grades of wet and dry from 200 all the way up to 1200 grit and use each by hand until you get a good polish. maybe a bit harder with chambers than runners. Flap wheels for drill are good if you can get them fine enough.

 

[Anonymous]

hm, doin it by hand or usin a grinding tool w\ all its gyrating, proly neither is gone help the hands and wrists : \
I dont know what matieral u r usin as grinders, maybe a "softer/ finer" grinding wheel is what u need, Kinda like using those red or blue discs in a metal grinder, they r kinda like sandpaper instead of a "stone", they still grind well but arent so harsh. I was jus wondering if u were using those metal grinding/ cutting spools, as opposed to sandpaper type spools.

I'd say for safety, another good thing to have is a face shield, it does so well at keepin debris from smackin u in the face as if it were welding sparks, ear protection, as well as your mask and some leather gloves.

 

[addo]

Weight and height haven't a lot to do with hand tool control. It's how used you are to strong manual tasks. It also sounds as though you're using too much pressure. I'm guessing it's a stone, not a carbide burr. Consider a couple of these - new - they are spendy but will pay you back well.

Feeding into the stock will cause the bit to try to "dig in", feeding away from the material will give a much lighter cut. There's no rush really!

Adam.

 

[Anlushac11]

8)

I am using a set of 5 new carbide burrs. After reading up some more I will need to use grit drums or a buffer wheel to get the final smooth finish.

I dont think the chamber is bad, just was having difficulty figuring out how
to get that nice finish.

Basically I am doing the following

1) Smoothing and polishing the combustion chamber.

2) Laying back the cylinder walls to unshroud the exhaust valve, The intake valve is already unshrouded, possibly by previous owner.

3) Chamfering the edges to reduce hotspots.

After the chambers are done I will do the 4 outer exhaust ports, saving the center port til I get a port divider.

 

[Anonymous]

I said exhaust port in above I meant all the exhaust posts in approx two hours. This was after I worked it to about 250 grit first with a power file.
Used small pieces of wet and dry sandpaper and didnt use one piece for long (would clog) before changing to next. Ended up with a incredible finish this way (probably more than was necessary).
Standard abrasives supply a porting polishing kit and they reccommend using the right flap wheel I think the finest they suggested was 320 grit on the chambers.

 

[Anlushac11]

8)

I had intended to finish the one chamber today but there was auto racing, naps, the heat and humidity..where did the day go?

 

[simon]

Careful when doing grinding work on the combustion chambers, they are just like intake runners: surfaces shouldn´t be polished to a mirror like finish as fuel separation may result.

on the other hand, a high luster mirror polished finish is best for exhaust runners.

 

[rbohm]

8) actually a mirror polish in the combustion chambers reflects heat back in to the chamber.

 

[Anlushac11]

8)

Not that big a deal. Im doing it mostly to eliminate hotspots and to unshroud the exhaust valve wwhich is badly shrouded. There is about 1/16" from edge of valve to chamber wall and that is after grinding. There is a little room but Im hesitatnt to go any farther. I want to leave room for error in head gaskets.

If I can afford it later before I assemble engine I want to get head dry film coated with a thermal barrier. This reflects majority of heat back into combustion process. That in turm leads to greather combustion effeciency, more pressure sine the heat is kept in and that means more power. You also have to have face of pistons thermal coated also.

By coating the combustion chamber and quench area and face of pistons you also greatly reduce chances of detonation and pinging.

 

[Anonymous]

Go down to the hardware store and get a Router Speed Controller and use it to control the dremel. It will still have the same torque but be slower.
Mine cost $25 at Harbor Freight.

John

 

[Anlushac11]

Go down to the hardware store and get a Router Speed Controller and use it to control the dremel. It will still have the same torque but be slower.
Mine cost $25 at Harbor Freight.

John

I have been working out how to build my own using a room dimmer switch but im not an electrician. A router speed controller would be great!

Thanks for the info.