I think the smallest gasket they make is a .030.

This whole quench area thing is something I might be encountering myself on my 393.

When I did my 393, I got a shortblock from CHP, and did the rest. I wanted about 9.5:1 compression, but with my 64cc chamber heads and 15cc dished pistons I would need a thicker gasket to achieve that. The guy at CHP told me to use a .060 gasket and it would lower the compression. I didn't know about quench area at the time, but I have a pinging problem that is probably because of it.

I can change my timing on the fly with my SCT tuner chip, and it'll go from 28-32 advance (plus base of 10). It pings at WOT on the higher timing settings, hard, I don't even touch that because of it.

It's been chipped for 13ish:1 A/F on dyno
Has 93 octane gas
and only 9.45:1 compression...

My gasket is .060 + piston deck height of .017 = .077 quench area, I too was told afterwards that it should be below .050. I need a .030 gasket to achieve that.

I was told having the quench area over .050 will lead to detonation and can have an affect on power output from improper burn.

Heres a good link to Ford Head Flow Data...

http://home.isoa.net/~mharrisj/fordhead.html

 

Mustang i would atleast drop to a standard .041 felpro head gasket this will put you at .059 with the stated deck clearence and that will help termendously I thnk you will find a huge difference loosing that .019 of clearence.

 

Me too, but I've got more problems then just that.

I'd go change the gasket right now but that'll require new pushrods unless I was able to adjust the difference in my valvetrain but I don't believe I can.

 

You could put some shims under the rockers, if they are pedestal mount, should be little cheaper than new pushrods.

 

Do you guys have a reference for the quench height? Or, do you know the value for a stock engine? I have a hard time believing that 20 thou difference would cause that much difference in the quench characteristics of the head, although I can always learn something new. Right now, the only thing I have to go off of is replies on internet forums such as these, and I'm not sure I quite buy into it yet. It seems like it would be different for each cylinder head depending on the combustion chamber shape and size and piston top configuration, and would be too hard to generalize to a value, such as .050".

 

I just did a google search for "quench height" and pulled up a few good sites...

 

This is an article out of a cheby magazine (sp?) but the concept applys the same to ford motors.

http://chevyhiperformance.com/techarticles/94138/


This is another site that gives more of a racing view of it.

http://www.speedomotive.com/building%20tips.htm

 

Thanks, I'll give those a read!

 

I haven't looked through here since the other day, but I noticed that there were quite a few responses to my post. I am not positive about the pistons being that far below deck. I have heard of stock blocks having that much of a negative deck, and mine looked like it was a long way from zero. With 69cc chambers, a compression check shows 9:1, I run 87 octane and I have no problems with detonation, even when I lug the engine. I may do some more research on AFR's, I will keep you guys posted. Does anyone know where these heads could be had at a discount price? Since I am working with a limited budget, I have been thinking about pulling a set of gt40P's off an explorer and porting them. I am not sure but I might have to change my headers or modify them. If anyone knows anything about gt 40 heads let me know.

 

I think you can rev past 5000 or max hp in a truck, my friend has a 1978 chevy silverado 2500 4x4 34" tires single cab long bed with a 468 auto, makes 500 lbs of toruqe at 4000 rpm and 350 at 5500 rpm he says very conservative on the power, he makes up for it with 4.56 gears,

gearing is most important I think, with 31-35" tires

3.73-4.11 if you make max toruqe at 1500-3000

4.27-4.88 if you make your torque around 3000-4500 rpm

4.88-5.38 ect if you run bigger then 37" tires

If you run idle to 5500 rpm rrange which I think you will I would reccomend 3.96-4.11 gears if it is an auto and 3.72-4.11 gears if it is a manual with a 4.32 or so 1st gear and some 31-33" tires,
this is not the absolute answer, just the way I would go...

 

I have a set of GT40p heads that I put on the 5.0 I built for my Ranger. The ports are a different shape, they're oval rather than square, and the spark plugs are relocated a bit, they come out of the head at less of an angle. This can cause an interference problem with the header tubes, particularly on the driver's side head.

Many headers have been built over the years with oval ports at the flanges. I have several sets, some of which pre-date the GT40p heads. I modified a set to fit mine, rather than buy new headers. It was more of a challange to modify them to fit the Ranger than it was to fit the heads. The passenger side header gave me no spark plug interference problems, but it was a bit tight on a couple of the driver's side tubes. Different headers will fit better or worse. If you have any fabrication skills you can work around the problem, otherwise you'll need to buy some headers made for the P heads. Here's how my headers came out:

http://community.webshots.com/photo/...44654520kvtaxY

http://community.webshots.com/photo/...44662262KvqWdB

As you can see, the passenger side is just fine for clearance. I didn't get a good pic of the driver's side installed on the motor, due to a rather overcrowded condition in my shed...I had reached maximum density and it was a bit difficult to reposition the engine stand.

If you're up to it, the p heads can be made to work but you might be better off with some ported E7s.