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Discussion Starter #1
Hey all, I need to know what the cc's are of the combustion chambers on a set of E7TE's. Does anyone know?

I'm about to hog out the combustion chambers to lower my compression and would like to know what they were supposed to be.

Also, if anyone has a link to a site that does compression ratio calculations that would help a lot.

I'd like to hit 8.5 : 1 or lower with my TRW flat tops with 4 valve reliefs and E7TE's.

Is it possible? What would the CC's have to be?

Thanks,
Mike SVOR
 

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I'd like to know this to, I've read that they typically run 62-64cc but my cousin printed out head spec sheet at work for a 90 and that says they are 60-62cc so ??? Hopefully someone else has measured them.

I calculate that on a stock bottom end using a Fel-Pro 1101-1 head gasket you'd need a 69cc to get 8.5:1
 

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Discussion Starter #4
Mouse said:
Mike,

Should be 60 to 64 I believe, 62 nominal.
http://www.geocities.com/jjonibones/E7OV.html

Sounds like you will be adding a supercharger or turbo. While you are removing material from the chamber, you might want to work around the valves to unshroud them as much as possible to maximize your breathing as you remove material.

Good luck

John
Thanks for the help guys,

John,
Yes I have a vortech B trim which I am sending back to get the S trim upgrade. I am taking the heads off cause I blew the rear freeze plug out and can't get to it to hammer another one back in. I've tried rubber plugs but there's a webbing in there that won't allow me to put it in far enough. Sucks to be me. LOL.

These heads are already ported by me and have been on this engine for ~80,000 miles. This motor used to be carbed with an X303 cam and long tubes. Now it's EFI with stock cam and 36 pounders and stock intake.

The emmissions bumps are gone and I have ground off the valve guides smooth with the exhaust runner. Still stock valves and doesn't smoke a bit.

I'm in the process of building a front mount IC out of parts and plan to run 10 psi.

I'm looking at the Tweecer, but I don't know how to tune it. Is it easy? I'd be willing to buy the wide band O2 option if it is as good as it says it is. If so, I'll be going with the Tweecer.

Oh well, that's my plan.

Thanks for any tips you can shoot me with,

Mike SVOR
 

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Mike SVOR said:

I'm looking at the Tweecer, but I don't know how to tune it. Is it easy?

Mike SVOR
I know nothing about the Tweecer, but I am sure a lot of people who do will chime in.

Sounds like a fun project. Keep us posted.
 

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Spec on stock heads is 60.6-62.6, with most falling around 62. Some unshrouding of the valves can easily bring them to 64 if you want to drop a little compression.
 

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Sorry, but thats a very bad idea.... For one, 8:1 on a street car is only gonna give you lousy throttle response, unless your are planning high boost levels I'd stay closer to 9:1. The main thing, though, is that eliminating the quench area (that flat area where the piston comes close to the head) will result in huge detonation problems, far greater than the little detonation margin you would gain by dropping the compression. When the piston comes up the a/f mixture gets squeezed out of that area at high velocity, giving the mixture lots of motion that gives a better a/f mix. Even just opening that quench gap too far with pistons down in the hole too far results in less resistance to detonation, eliminating the quench area completely would be no good!
 

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Discussion Starter #9
TURBOX2 said:
Sorry, but thats a very bad idea.... For one, 8:1 on a street car is only gonna give you lousy throttle response, unless your are planning high boost levels I'd stay closer to 9:1. The main thing, though, is that eliminating the quench area (that flat area where the piston comes close to the head) will result in huge detonation problems, far greater than the little detonation margin you would gain by dropping the compression. When the piston comes up the a/f mixture gets squeezed out of that area at high velocity, giving the mixture lots of motion that gives a better a/f mix. Even just opening that quench gap too far with pistons down in the hole too far results in less resistance to detonation, eliminating the quench area completely would be no good!
Then a DISHED piston would detonate worse than a flat top if your theory was correct.


p.s. I have an 8:1 compression motor on the street and it has great throttle response. :D
 

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Mike SVOR said:
Then a DISHED piston would detonate worse than a flat top if your theory was correct.
A proper dished piston only has the dish under the combustion chamber, not the quench area.
 

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Here's JE's Ford listings, http://www.jepistons.com/pdf/2002-je20-23.pdf the dished pistons retain the quench area and are only dished under the chamber. Hopefully you aren't on dialup as its a .pdf file....should be easy to find other examples though.
 

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We're looking at the same pistons, but you're looking at them backwards... Compare the pistons with just valve reliefs and no dish, for instance the first picture on that link, see which direction the valves are moving? They are moving out into the chamber, the lower edge of the valve is on the left and they are moving down and out to the right. The chamber is on the right and the quench area is on the left. Now scroll down to the dished piston and compare, the quench area behind the valves is still there on the left, with a dish under the chamber on the right.
 

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Discussion Starter #15
Uhhh,

Spark plugs are in the combustion chamber, Right?

Valves are in the combustion chamber, Right?

Why would valve reliefs be anywhere other than under the valves in the combustion chamber?


See right where those valve reliefs are? That's where the combustion chamber is. The valves go down and towards the center of the piston when extended.
The spark plug is inbetween the valves in the combustion chamber, above the valve reliefs.

The dish area is under the quench area.
 

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ugghh...last attempt at this.... Here is a picture of a combustion chamber...



Here's a non-dished piston top...



Notice how if you completed the circle of the chamber the quench area would be rather small and look just like the area to the left of the valve reliefs in the piston picture? Notice how the valves and chamber take up most of the piston top, so there is no "this side" or "that side"? Notice how the edge of the valve on the bottom of the picture is very close to the deck surface, while the top of the valve is up into the chamber? Look at the piston and on the left side the valve relief is very steep because thats where the edge of the valve in the bottom of the chamber picture will enter the relief first. The relief then flares out to the right in a circular shape to accomodate the face of the valve. The right side is where the chamber is and the valves move out into the chamber.
 

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Discussion Starter #17
OMG, I have been horribly mistaken. I get the retard award for that one.
It's been a while since I opened up this motor.

Thanks for the pics.

I will try and keep the quench area as large as possible, but do plan on cutting it back a little.

The way I see it, I'll need to remove ~6 to 8 cc's out of the combustion chamber.

Any areas that have a decent amount of meat that can stand to lose some material?

Have graduated cylinder ready for cc'ing

Sorry for wasting your time again, :eek:
 

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You get the brain fart award for today.... :D LOL

Lay a head gasket on the head and scribe the outline of the cylinder, but when porting stay inside the line as the gasket is 4.100 while your cylinder is 4.00 or 4.030 or whatever. You'll be able to take a few cc's out while unshrouding the valves, I'd do that first and then measure to see where you are. If you get to 65cc that will put you at 8.5:1 (using a .047 thick Felpro 8548PT-2 gasket), personally I wouldn't go any lower unless you are planning to run over like 15psi, but thats your decision. It will take almost 71cc chambers to get to 8:1, IMO you would have seriously messed up the head if you tried to take it that far. Much better to just get a dished piston if you are dead set on 8:1.
 

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Mike you said you ground off the valve guides smooth with the exhaust runners, is it ok to do this or can it be a potential problem? I'm getting ready to port some E7's and the articles I've read said not to cut them down just to round it off close to them. Did you do the same on the intake valve guides also? Thanks
 
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