target cc??

[falcon fanatic]

Hi,
I'm sure this has been asked a million times, but here is once more. I've had this head that I've been porting (for like two years now) and I'm getting motivated to finish it and send it to the machine shop. It currently has 63cc chambers. Engine is a totally stock 200 (stock except for thousands of dollars of bolts-ons!) from a 69 falcon.

Short of removing and cc'ing the head that's on there, any ballpark idea on what my stock compression chambers are, or suggestions on a target cc that will give me somewhere between 9:1 and 9.5:1? In other words, enough more compression so that I don't actually lose any bottom end power from bolting on a head with bigger valves and a bigger manifold, but not so much that it pings. 52cc seems to be thrown around a lot.

 

[CZLN6]

Howdy Back:

We would need to know-
*What is the casting code of the '69 head you are working on?
*what block is it going on?
*What head gasket will you be using?

Early 200 heads typically have a chamber volume of 52 cc. Later 200/250 heads, after '69 "M" castings have about a 62 cc.

All 200/250 came from the factory with a steel shim, .025" compressed thickness head gasket. These gaskets are no longer available. The gaskets available are .045" to .055" thick.

The ratio we use to estimate cc reduction through milling is .010" mill cut reduces chamber volume by 2 ccs. That gets us into the right ball park.
Then remeasure for accuracy.

Adios, David

 

[pedal2themetal45]

If I remember corectly its about 2cc's per .10 removed.
tim

 

[falcon fanatic]

Hi David,
The current head, the one I'm going to replace, is C9DE-3090-J.

The block is C8DE-6015-B.

The point is to find out what size the chambers are on the current head, and make the ones on the new head smaller so that I get maybe 1 point higher compression. That, along with bigger valves and the big flat top and milled log should be a big bonus.

The gasket I have is a FelPro, but I'm not wedded to using it if I can find a better one. I can't tell what gasket is on the engine.

 

[powerband]

please delete

 

[falcon fanatic]

David, any comments. According to the chart on this site, it's all probably '68 or '69 Falcon, although there was no reference to a head casting ending in J. Does that mean 52cc chambers?

I tried using the compression calculator on your site, but there are too many variables I can't anser, like dish volume, or the compressed thickness of the gasket (If I use the Fel-Pro).

Finally, let's assume for instance that I have a target cc of 50. At 2cc per .010, that will require approximately .110 to be milled off. Can I do that safely? I guess I should refer to your book, which is on my shelf somewhere...

 

[addo]

No! If you start with 52CC and want 50CC, only take ten thou, or 0.010"

0.110" would remove 22CC.

 

[falcon fanatic]

addo, the head I'm going to install has 63cc chambers. I want to reduce by 13, i think.

I'm tossing the head that's on there. My new one has a large, flat top log, with all the advanteages that implies.

 

[addo]

63-50=13

13÷2=6.5

6.5×0.010=0.065

So - remove 65 thou if the head is pretty mint on the gasket face.

 

[CZLN6]

Howdy Back FF and All:

The C9-J head casting is likely to be a 52 cc chamber with a 1.5" carb hole. You said the chambers are 63cc. While that is a bit of a mystery, it does not surprize me as this is the beginning of the EPA change years to lower CR and other issues. The only '69 casting that I was aware of with a flat-topped log and 62 cc chambers are the castings with an "M" casting suffix. I am assuming that you measured the chambers yourself(???).

The compressed thickness of the FelPro head gasket is aproximately .050", depending on the amount of torque on the head bolts. The stock OEM head dish volume is 6.5 ccs. Calif Emmissions engines would have a 13 cc dish. The typically, on a '69 block, the pistons would be down in the bores .025".

You would be wise to check with Mike to see if the new .038" compressed thickness Cortico head gaskets are available yet. They would help to minimize the lose of quench effect due to the thicker head gaskets and also minimize the thickness of the mill cut on the head to gain back CR.

I will run these numbers on the Compression calculator and get back to you. In the mean time, would you measure the volume of the chambers to varify that they are 63cc chambers?

I'm going to be gone over the weekend, so don't be surprized if you don't hear back til Monday.

Adios, David

 

[falcon fanatic]

David, sorry to cause so much confusion. We are talking about TWO different heads. The one that's on the car, and the one I intend to install.

The one I intend to install is an M head with 63cc chambers. I just wanted a best guess at the volume of the head that is currently installed (apparently 52cc, so I could go ahead and send the other head to the machine shop without having to disable my car). At this point, I think I have all the answers and I'll run this info through the compression calculator.

Thanks for all the help!

James

 

[CZLN6]

Howdy:

I'm back sooner. You got my thinker going.

First, '68 - '70 200s are advertized at 8.8:1 CR, yet, every one checked has the same internal dimensions as the earlier 200's with an advertized 9:1 CR. .025" thick head gasket, .025" deck height, and 6.5 cc piston dish. We suspect the change was just a marketing issue or possibly a more true reflection of CR.

250s of those years were advertized at 9:1. Which cause us to think that chamber size was not increased until the '72 casting change. In the '68 - '71 years, 250 CR was held to 9:1 by adding the huge deck height typical of 250 engines.

Second, if your '69 head has 63 cc chambers and all else typically stock dimensions, the CR would be 8:1, Which Ford doesn't advertise until the '72 250 engines.

All stock 200/250 heads can be safely milled to about .090". Any more than that and it becomes wise to do some sonic testing to verify that enough material is left to maintain structural integrity.

Adam gave you the generality to get from 63 to 50 cc chambers. Remember, that is only a generality. To get hard data, you must remeasure.

If you did have 63 cc chambers and you reduced them to 50, and installed the head with a .050" Fel Pro headgasket your new CR will be 8.8:1, assuming a stock OEM piston dish of 6.5 ccs and a .025" deck height.

Please do some more measuring and checking to verify, for sure, what you have. Please know that I am not questioning your facts, but curious as to what FoMoCo may have done. These years are a big question mark in trying to nail down specifications. Please add the diameter of the carb inlet hole to the measurements.

Adios, David