Deck, head, piston and cc'ing ?

[LameHoof65]

So, I've got my old 65 head off, what is the best way I can clean up the deck and tops of my pistons? And I have read how to cc the head for compression, but with these dished pistons how does one best measure the volume to add to the corresponding combustion chamber?..... fill it up using the plexiglass as is done with the head comb. chamber? I know I read it somewhere here back when, but I can't find it. I know the perf. handbook gives the formula, I just want to get my measurements right.

 

[xctasy]

I have access to better equipment than most here. First step is to realise most 200's have a 7cc dish, which is made up of a 2 " rebate in the crown on the piston, which has chamfered sides. Thats about 6.5 cc, with around 1 cc from the annular edges of the cylinder to block area. All up, about 7 cc of dome and annular displacement.

The rest is a drop of about 25 to 40 thou beolw the block deck. I haved measured this with feeler gauges and a straight edge, but its better to use a depth caliper and straight edge if you can find one. Basically, I'd to that first, and use math to suss out the area of dish from the piston.

Cross check with a measuring cylinder from the vetinarians...the kind used for animals etc. Then that should confirm your calcs. I fill the piston up, and then measure the volume by adding water with a couple off cc's of dishwashing liquid to get a less of the dome that water exhibits. Get a straight edge rule, and keep adding until the water touches the rule.

You'll find that there is most around 5.2 cc for 30 thou of piston drop. Each stock 200 cylinder has 544.8 cc of displacement from Top Dead Centre to bottom dead centre. With 5.2 cc, plus 7cc of piston dish, thats a below block volume of about 12.2 cc in most cases.

 

[Hot 6t Falcon]

Darwin,

The easiest cleanup of the carbon on the head and the piston is a rotary wire brush in a drill. Get several sizes of the rotary brushes to get into the crevices. COARSE wire is quickest.

Are you removing the pistons, or are you checling them in the block. Do you have a dial caliper?

Good Luck

 

[LameHoof65]

Thanks for the response xecute, but now I have more questions. When you say, annular are talking about the space between the piston and cylinder wall down to the ring? And the dish is pretty constant at 6.5 cc's. Then use a depth gauge to find the volume from the level part of the edge of the piston to the deck, right which is normally .030 to .040. ?? And Dennis is it better to use brass brushes or fine steel brushes? I don't want to score the head or piston, if that is a possibility? And yes I'm leaving the bottom end completely intact, it has already been rebuilt and isn't really broken in yet. And, no I don't have any precision measurement tools, but can see I need to look into getting them...would some with .001 to .003 tolerance of accuracy be okay? I think I can get those for a relatively nominal price at a wholesale tool store in my area. : I don't want to look stupid but I would hate to get this part wrong.

 

[xctasy]

Yes, you are on the right track over measurement. In practice, you'll never get it perfectly measured, so jusy use what is at hand unless you plan to do more of this kind of stuff.

The annular volume, your correct. It's the cravas between the ring lands and cylinder and piston.

The 30-40 thou, check. Its the highest part of the piston. Bang on.

The dish is the volume of the 'swiming pool' or dish, if you were on Honey, I shrunk the Kids (While Modifying my 200 i6). You've got that sorted too!

And Hot 6t Falcon will possibly say steel. As long as its spinning, it won't gouge strips out.

 

[Hot 6t Falcon]

Yup, Steel.

Here's a thought for you about cc'ing.

To cc the head I have a 1/4 inch thick Plexi-glass plate about 4" x 5" with a hole drilled off to one side. The reason for the hole off to the side is so I can slightly tilt the head from level and then put the hole on the high side so the air bleed out.

I put a THIN layer of Vaseline around the valves to seal them. It makes a REAL mess when they leak all over the floor. (Maybe you should do the head on the picnic table) I then use a thin layer of Vaseline around the combustion chamber and set the plastic firmly into it to hold the plastic in place. Only on hot days do I need any sort of clamp.

You might also try the Vaseline in the annular gap and just put you plastic on top of the cylinder for the Total cc of the deck and piston dish.

Where do you live?

Good luck

 

[LameHoof65]

Thanks a bunch for the clarification, very nice to have guys who don't mind answering my questions no matter how lame they may be.

I live in OKC Dennis, lived in Okla. all my life except for my time in the service.

Thanks again