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post #1 of 23 Old 09-29-2007, 07:02 PM Thread Starter
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Valve Questions ...

The '98 3.8 V6 come w/1.78 intake & 1.46 exhaust valves. I have heard that the '99+ 3.8 V6 (split port) comes w/larger int/exh valves. Can anyone confirm this? What size are the '99+ valves? And can they be installed into the '98 cyl heads by merely opening up the existing valve seats ... or do you also have to upgrade the valve seats?


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post #2 of 23 Old 09-30-2007, 11:23 PM
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Quote:
Originally Posted by Geezer View Post
The '98 3.8 V6 come w/1.78 intake & 1.46 exhaust valves. I have heard that the '99+ 3.8 V6 (split port) comes w/larger int/exh valves. Can anyone confirm this? What size are the '99+ valves? And can they be installed into the '98 cyl heads by merely opening up the existing valve seats ... or do you also have to upgrade the valve seats?
They are indeed larger. I believe 1.84int/1.5exh but dont quote me on it. As for swapping the two, I dont think so. The positions of the valves are different.
-Thomas

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post #3 of 23 Old 10-04-2007, 04:20 PM
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You can swap the valves just fine, you just have to grind down the seat like you already stated.

Typical 97 vert with 8-point roll bar.
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post #4 of 23 Old 10-07-2007, 06:50 PM Thread Starter
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homank76 ... "You can swap the valves just fine. You just have to grind down the seats like you already stated."

Thank you ... Thank you ... Thank you!!!

'98 GT equipped w/Koni, Eibach, Cobra R rims w/Yokohama tires, Cobra brakes all around & 3.73 gears. Also a Boss330 4.6 Cobra block w/PI heads & stuff from Accufab, ARP, Centerforce, Comp Cams, Fidanza, K&N, Mahle, Manley & Borla exhaust w/Mac Pro Chamber thrown in for grins & giggles.
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post #5 of 23 Old 10-20-2007, 10:09 PM Thread Starter
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homank76: "You can swap the valves just fine."

OK, just thought that I would get back to you on this whole valve thing. It appears that you cannot interchange '96/'98 valves w/'99+ valves. The earlier valves have 11/32 valve stems while the '99+ have 7mm valve stems. If you want to install the '99+ intake valve (1.86 vs. 1.78 or 9.2% increase in area) into the '96/'98 cyl head, you'll have to install the 7mm valve guides also. BTW, the exhaust valve remains the same size at 1.46 (tho stem size differs as indicated above). The "upgrade' for day-to-day driving probably won't buy you much of anything, but on a track car w/increased cam lift, the additional flow will be good for a few HP.

'98 GT equipped w/Koni, Eibach, Cobra R rims w/Yokohama tires, Cobra brakes all around & 3.73 gears. Also a Boss330 4.6 Cobra block w/PI heads & stuff from Accufab, ARP, Centerforce, Comp Cams, Fidanza, K&N, Mahle, Manley & Borla exhaust w/Mac Pro Chamber thrown in for grins & giggles.
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post #6 of 23 Old 10-21-2007, 05:24 AM
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The valves are 7mm across the board. Where you getting you info from?

Typical 97 vert with 8-point roll bar.
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post #7 of 23 Old 10-22-2007, 02:24 AM
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On the topic of valves, my 1999 had them let loose at 127K miles. Also had the rings in #3 cylinder burning 1 quart of oil in 100 miles.

Traded that in for a 08 GT Cal Special

You forgot about the ramdom gun fire in the streets, RPG's, and the cackle of Klashnikovs on all the major holidays.

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post #8 of 23 Old 10-22-2007, 06:33 PM
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wow thats weird. Thats the first time Ive heard of that happening. I had 150k on my motor, 10 runs of a 75hp dry shot, always ran conventional oil. No problems at all.
-Thomas
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post #9 of 23 Old 10-26-2007, 11:30 PM
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Well, that #3 cylinder had been an oil burner since new. I checked the plugs for the first time at 12K miles and it was fouled then. Also I did a valve job at 55K miles when I ported the heads. So I think this was more of a ring problem that created a valve problem.

Anyways, lesson learned, V6's are for transportation V8's are for evil grins.

You forgot about the ramdom gun fire in the streets, RPG's, and the cackle of Klashnikovs on all the major holidays.

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post #10 of 23 Old 10-27-2007, 06:05 PM
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Quote:
Originally Posted by 35thPONY View Post
Anyways, lesson learned, V6's are for transportation V8's are for evil grins.
Well now youre just asking for an argument.

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post #11 of 23 Old 10-29-2007, 07:23 AM
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I'm willing to argue that point as well.

Typical 97 vert with 8-point roll bar.
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post #12 of 23 Old 10-31-2007, 11:16 PM
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Ill join that one too- I have a 300HP flat tappet 3.8/4.2 conversion

http://www.fquick.com/garages/Ford/Mustang/1983/10315/

engine pic is night before install

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post #13 of 23 Old 10-31-2007, 11:17 PM
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lots of possibilities

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post #14 of 23 Old 11-01-2007, 10:09 PM
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Quote:
Originally Posted by homank76 View Post
The valves are 7mm across the board. Where you getting you info from?
I will tell you the valves are NOT the same across the board . My stroker is using 1985 heads with 4.2 valves form 1999 and the stems ARE different . I got mine together by using a custom made set of guides from Brodix. I dont know where your info is from, but Ill let you measure mine.

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post #15 of 23 Old 11-02-2007, 05:34 AM
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85 heads are different, that I will admit. Only 1% of the people with v6's use those heads.

The 96+ all use 7mm.

Typical 97 vert with 8-point roll bar.
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post #16 of 23 Old 11-06-2007, 08:53 PM Thread Starter
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homank76 ... "The valves are 7mm across the board. Where you getting your info from?"

I pulled the valve sizes & application dates directly from Ford service manuals. I will soon be tearing down my '98 V6 so we shall see.

'98 GT equipped w/Koni, Eibach, Cobra R rims w/Yokohama tires, Cobra brakes all around & 3.73 gears. Also a Boss330 4.6 Cobra block w/PI heads & stuff from Accufab, ARP, Centerforce, Comp Cams, Fidanza, K&N, Mahle, Manley & Borla exhaust w/Mac Pro Chamber thrown in for grins & giggles.
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post #17 of 23 Old 11-07-2007, 06:29 PM
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all of the fuel injected heads have 7mm valves. I'll be right back to prove it.
-Thomas
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post #18 of 23 Old 11-07-2007, 07:11 PM
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OKAY I went and measured my 89 SC heads and my 93 NA heads and they both came out the same. 11/32" So I was wrong. I don't, however, have any 96+ plus heads to measure, so maybe someone else could chime in on that one.
-Thomas
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post #19 of 23 Old 11-07-2007, 08:32 PM
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I will check my CFI valves too they may be different still

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post #20 of 23 Old 11-07-2007, 08:43 PM
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yes it is a "fuelie" but it does not have the injector bosses in the heads.
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post #21 of 23 Old 12-04-2007, 05:48 PM Thread Starter
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Thomas: "OK, I went & measured my '89 SC heads & my '93 NA heads, & they both came out the same ... 11/32. So I was wrong. I don't, however, have any '96+ heads to measure ..."

I just (finally) got around to measuring my '98 V6 valves, & they are 7mm. The question now seems to be: When did the 11/32 stop & 7mm begin? I would guess '94, tho it could be '96. Anybody?

Also, it appears that a cheap valve upgrade for the 7mm folks would be to get some '99+ intake (1.86" vs. 1.75") & exhaust (1.46" vs. 1.34") valves. This would increase the intake area by about 13% & the exhaust area by about 19% (assuming my math skills haven't gone the way of my memory).

And, if there is no difference in the OA valve length, the 11/32 guys might also be able to take advantage of the '99+ valve upgrade. However, they would also have to install 7mm valve guides. The narrower valve stems (11/32=0.344 & 7mm=0.276) will provide for slightly increased flow thru the ports. The more mods done to the engine, the more significant the hp gain.

Thomas: "As for swapping the two, I don't think so. The positions of the valves are different."

I would think that if the OA valve length, keeper location & valve stem diameter are the same (or correct valve guides installed, if not), the valve location w/in a given cyl head should not matter. It would merely involve opening up the existing valve seats to accommodate the larger '99+ valves.

'98 GT equipped w/Koni, Eibach, Cobra R rims w/Yokohama tires, Cobra brakes all around & 3.73 gears. Also a Boss330 4.6 Cobra block w/PI heads & stuff from Accufab, ARP, Centerforce, Comp Cams, Fidanza, K&N, Mahle, Manley & Borla exhaust w/Mac Pro Chamber thrown in for grins & giggles.
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post #22 of 23 Old 12-04-2007, 07:23 PM
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are they the same size as the 99-up 4.2 valves? if they are larger, this is also a viable upgrade. you will need vave guides if you have early (83-88)

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post #23 of 23 Old 12-05-2007, 05:14 PM Thread Starter
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Valve Info ...

plstktnkr2: "Are they the same size as the '99+ 4.2 valves? If they are larger, this is also a viable upgrade."

Sorry, but did not check out the 4.2 at all. Interesting point tho. I wonder if the 4.2 has even larger valves than could be installed in a 3.8?


plstktnkr2: "You will need valve guides if you have an early Fox ('83-'88)."

If the '83-'88 has 11/32 valve stems, then, yes, you will have to 'upgrade' to the 7mm valve guides.

'98 GT equipped w/Koni, Eibach, Cobra R rims w/Yokohama tires, Cobra brakes all around & 3.73 gears. Also a Boss330 4.6 Cobra block w/PI heads & stuff from Accufab, ARP, Centerforce, Comp Cams, Fidanza, K&N, Mahle, Manley & Borla exhaust w/Mac Pro Chamber thrown in for grins & giggles.
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