200 head leaks oil/coolant - what now? also 250 swap notes

A

Anonymous

Guest
Hi all, thanks for the excellent advice over the past several days. I took the 200 head to the machine shop to get magnifluxed and checked for warping. The story is that the "newly rebuilt" I6 has bit the dust. I bought the 65 stang about 8 months ago, put 500 miles on it, and noticed smoke from under the hood. Whoops. Openned the hood and what a surprise. A watery mix of cooland and oil had filled up the intake manifold recess around the carb area and was running down the back of the engine. There were even air bubbles perculating up from underneath the head bolts! hmmm. The radiator showed a nice foamy froth in it, like the head of a beer, the dipstick had that milky oil/coolant mixture on it. All the symptoms of a blown head gasket?

I previousy checked the torque on the headbolts so that was not the problem. When I pulled the head, the engine builder had not used thread sealant on any of the head bolts (tsk tsk, at least the numbers 2 and 6, passenger side headbolts should have had thread sealer on them, according to my service manual). The numbers 3,4, and 6 compustion chambers had goop in them, like burn oil crud. I took it to the machine shop today to be magnifluxed and checked for warping. The shop looked at the head gasket and said it looked ok to them (huh? visual inspection to detect a blown head gasket? Is it that obvious. I thought we were talking .010's here.) What do you supposed could be wrong? Would a cracked block produce this clump of symptoms?

OK, I figure its time to swap up to a 250 head. Hey, out here in CA not all post-78 250 heads are created equal. There are the "smog" heads with a smog tube internal to the intake manifold, according to one salvage yard, and heads without that. Perhaps this guy is thinking of the 300? Is this correct for a 250?

Now I am talking to the shop about milling .050 off the 250 head. Whoa there little pony, this shop says only take off .010 or run the risk of warping the head. As I understand it, the factory head gasket is .025 and the newer felpro gaskets are .045, necessitating milling .020 just to stay even. Then, I would need to mill off an additional amout to get the compression ratio to a respectable 9.5:1 With a difference in combustion chamber cc of about 10cc, I figure I got to take another .020 or so off.

My questions are:
what is the factory compression ratio on a 65 200? Is the combustion chamber size 53 cc on the 200?
What is the combustion chamber size on a 78 or later 250? 62cc?
Is there a formula that would tell me how to calculate how much to mill off the 250 head to yield a compression ratio that would not require permium gas, but still make efficient power.
Is the machine shop being too conservative with wanting to mill no more than .010 off the 250 head?
Lastly, are my numbers correct on the headgaskets?

Thanks for all your help to this newbie. I've been playing with the V8s for about 5 years, but now it is time to learn the I6's. I am way impressed with having 7 main bearings! This is an engine that begs for nitrious or forced induction.
 
where are those darned Schjeldahl brothers when you need them?
On their website
http://falconperformance.sundog.net/
They have tons of interesting information about the ford sixes
http://falconperformance.sundog.net/facts.asp
and a handy compression ration calculator that is set to the 200 specs by default.
http://falconperformance.sundog.net/compcalculator.asp

Now don't go milling anything until you figure out what size your current combustion chambers, the new head CC's, and try to find out from your parts store how thick your head gasket is going to be when compressed. They are not all created equal .045 is what I think most people figure when adjusting for a new headgasket but not necessarily what yours will be. When I was shopping for a head gasket for my buddy's '66 coupe the Felpro book had compressed thicknesses for 300's and 2.3L 4cyl (both listed at .045), but not the small 6. Others have said that you can assemble a motor, torque the head to spec and then measure the thickness, provided you do not put any type of sealant on the gasket when doing the test fit.

Mustang Geezer has a page that shows how to check your CC size
http://www.geocities.com/mustang_man_1966/head_modifications.html without measuring you could be flying blind on your milling effort. Measure twice cut once.

Also on Geezer's page look at the port divider, most if not everybody who ows one of these swears by them, and as long as you are having machine work done anyhow, maybe you should get one installed.

Aside from clifford there was one other manufacturer that had this part, I will look for it later.
 
Hi there Fastback,

You've done your research pretty well. Your machine shop works with delicate V/8s too much. If they don't want to mill your head .060, tell them to go .070. It's fun to watch their jaws drop open. Just FYI, when we put a '75 200 head on my son's 144ci we milled the first .090 straight down, and then angle milled another .030 (to just reduce the combustion chamber side).

Yes, you'll want to mill your head more than .010. Generally speaking, you'll take off about 2 cc for every .010 you mill. CoupeBoy did you RIGHT by telling you to "don't go milling, until you measure the old and new head. Listen to him.

It is easy to cc a head. Put a light coat of Vaseline around the valve seats. Put a spark plug in. Put a coat of vaseline around the combustion chamber. Drill a 1/4 inch hole about 1 1/4 inch from the edge in a 5x5 inch piece of plastic. Press the sheet of plastic onto the Vaseline around the combustion chamber with the drill hole over the sparkplug.

Now use a syringe to inject fluid into the 1/4 drilled hole - keeping track of how much you inject. Any drug store will sell you a 10 to 15 cc syringe, or you can go to a "ranch" store to get a 20 to 25 cc syringe. Now goto our web site to calculators and put in your numbers.

The '65 head should have 51 to 53 cc - assuming it has not been milled.
The '78 head should have 62cc - assuming it has not been milled. That's why you need to cc it. To KNOW. If you have them mill the head .060 and it's already been milled .060, you'd be in deep... well, you see my point.

A good rule of thumb is to use no more compression than 1/10 of your gas's octance. If you can get 92 octane then 9.2 is a good "streetable octane.

Good Luck
 
Hot 6t Falcon":hsoq4al9 said:
Hi there Fastback,

You've done your research pretty well. Your machine shop works with delicate V/8s too much. If they don't want to mill your head .060, tell them to go .070. It's fun to watch their jaws drop open. Just FYI, when we put a '75 200 head on my son's 144ci we milled the first .090 straight down, and then angle milled another .030 (to just reduce the combustion chamber side).

Yes, you'll want to mill your head more than .010. Generally speaking, you'll take off about 2 cc for every .010 you mill. CoupeBoy did you RIGHT by telling you to "don't go milling, until you measure the old and new head. Listen to him.

It is easy to cc a head. Put a light coat of Vaseline around the valve seats. Put a spark plug in. Put a coat of vaseline around the combustion chamber. Drill a 1/4 inch hole about 1 1/4 inch from the edge in a 5x5 inch piece of plastic. Press the sheet of plastic onto the Vaseline around the combustion chamber with the drill hole over the sparkplug.

Now use a syringe to inject fluid into the 1/4 drilled hole - keeping track of how much you inject. Any drug store will sell you a 10 to 15 cc syringe, or you can go to a "ranch" store to get a 20 to 25 cc syringe. Now goto our web site to calculators and put in your numbers.

The '65 head should have 51 to 53 cc - assuming it has not been milled.
The '78 head should have 62cc - assuming it has not been milled. That's why you need to cc it. To KNOW. If you have them mill the head .060 and it's already been milled .060, you'd be in deep... well, you see my point.

A good rule of thumb is to use no more compression than 1/10 of your gas's octance. If you can get 92 octane then 9.2 is a good "streetable octane.

Good Luck
Click to expand...

Thank you very much for this information. This is valuable info that I could ruin a couple of heads trying to figure out on my own. Outstanding. I checked out your site (nice). Is your book for sale offline - Barnes and Noble? or simply at your site? Thanks. Sorry about the quote, can't figure out how to relpy without the quote.
 
Usually orders go to David, but with him on vacation, can we get the book from you Dennis? or is there somebody back in Idaho that will send the book? or are we relegated to wait?

Sorry about the quote, can't figure out how to relpy without the quote.
Click to expand...

at the very bottom of a message thread there is a
reply.gif
button it will open up the reply button. Or you could just delete the quote before posting, whichever works out best for you.

ron
 
David will be home to Idaho by the time you read this.

But I usually tell people that they can order through me if I know he's is going to be out of town for several weeks. His daughter checks the mail and forwards any orders to me.

Did you see we were review by Mustang Monthly?
 
It appears from the advertisement that if I am using a 1978 250 head/exhaust manifold combination on my 65 200, the exhaust manifold is already corrected for this and I do not need the dividier. Am I interpreting the ad correctly? Thanks
 
Howdy 65Fastback and all:

I'mm Hooome! Great trip! Sorry for the wait on getting orders out. I think all is caught up now.

65fastback- No, the Handbook is currently only available through us. We are doing it that way to hold down costs and to eliminate middle men problems. Sorry for the inconvenience.

You do not "need" to install the port divider, but while the head is off it is easier to install and may be worth a pony or two. It seperates the two center ports and equalizes flow on all ports. It is probably less important with a manifold, but would still be helpful in improving performance.

Do specify to your head builder to do a three angle, performance valve job, and inquire about having the intake valves back cut.

Once you sort out the milling issue, let me add that is is important to use hardened washers on the head bolts on reinstalling the head. This compensates for the milling and the risk of blots bottoming out in there holes and giving false torque readings, and spreads the torqueing force more evenly. Head warpage is a rare problem on these heads once properly torqued into place. Now flatness from the factory is another issue.

Given your locale, I'd caution you on going above a 9.2:1 compression ratio.

Enjoy the journey.

Adios, David
 
You must log in or register to reply here.
Back
Top