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.
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.