Page 1 of 2 12 LastLast
Results 1 to 15 of 16

Thread: Porting question on exhaust bowl - pic attached

  1. #1
    Join Date
    Apr 2002
    Location
    Westminster, CO
    Posts
    1,192

    Porting question on exhaust bowl - pic attached

    I disassembled a spare head today and was thinking of trying my hand in lightly porting a set.

    The intake valve seat looks to be pretty well blended into the intake bowl in stock form.

    The exhaust valve seat, not so much.. Is this a casting flaw of this particular head, or is this pretty typical? (see picture - seems the exhaust valve seat is smaller than the bowl.)

    Obviously I can't just take the dremel/porting bit to the valve seat.

    Is this something that a machine shop can taper in when doing a performance multi angle valve job? or is the only way to correct this by going with larger valves and seats?

    Jeramie
    Attached Images Attached Images  

  2. #2
    Join Date
    Apr 2002
    Location
    Westminster, CO
    Posts
    1,192
    In case anyone wondered, that is not a supercoupe cylinder head.. it is off of a 1995 ford Windstar, and has a D-shape combustion chamber.

    Stems measured in about .341"

    Intake valve diameter is about 1.782"
    Exhaust valve diameter is about 1.464"

    So they appear to be the same valves as SC heads, or any other 89-95 3.8 head for that matter.

    Jeramie

  3. #3
    Join Date
    Jan 2003
    Location
    Woodbridge, VA
    Posts
    4,642
    Its a typical bowl.
    ~Chris
    SCCoA Member #1826
    Riding jack stands.

  4. #4
    Join Date
    Jan 2004
    Location
    Outside KC MO
    Posts
    5,790
    i will edit this tomorrow because I am drunk ritgt now. You need to have the machine shop do that work, but it is no t necessary. It depends on the speed of which the engine turns and the volume of air you use when youre ngine is runnning. If you are looking for the best bang for your buck, it looks like some pocket porting would do some good with some larger valfvs. If you blemd the valvea bowl you willl seee the better gains sfrom what it appears.

    SWS

  5. #5
    Join Date
    Dec 2009
    Location
    Toronto
    Posts
    1,956
    As mentioned, they can be fly cut be a shop down to the valve stem.

    Come back in the other side to smooth the transition.

    Paul

  6. #6
    Join Date
    Jan 2004
    Location
    Outside KC MO
    Posts
    5,790
    Hmmm...Little more sober now so lets try this. Is the area in question in Pic #1? If so, you may want to consult a builder. There is a number of percentage that the seat needs to cover. Not sure what it is, but I too think you could vastly improve on that hole in and of its self. By pic #2 and #3, you can see the other parts I have circled. They need to be blended and smoothed for the best results. As far as the seat goes from the first pic, each head can have a bit of that or maybe even none of that depending on the core shift. I would see how much you can get away with by using a larger valve seat. Check the measurement of that and see if it is still a problem. If it is, get another head.

    SWS
    Attached Images Attached Images    

  7. #7
    Join Date
    Apr 2002
    Location
    Madison, Ohio
    Posts
    16,925
    First check your guides, most likely they are shot. Then put in bigger valves. All the farting around you might do trying to blend and port is going to be mostly wasted without properly installed, larger valves. You can't build a proper bowl when the valve is too small in the first place. I've seen plenty of "ported" heads that flow no better and sometimes worse than stock, and in contrast a properly done set of valves with no porting at all can improve flow nearly as much as all the porting in the world with stock valves. But the biggest plus with bigger valves is that you can now run much more lift which is the real key to making any flow/power.

    For an efficient combination, stock heads but with bigger valves and a short duration, high lift cam will absolutely smoke a set of highly ported heads that are limited by stock valves to .520" lift.
    Quote Originally Posted by Miller View Post
    Ya thats why i tape mine down. People think its bc i dont have a moonroof seal (which is true) but its really to keep my roof from ripping off .
    Email me here.

  8. #8
    Join Date
    Apr 2002
    Location
    Westminster, CO
    Posts
    1,192
    When you say high lift, and short duration.. how high and how short are you talking?

    This weekend we are tossing an old DR fred .520 regrind into my old '94 SC (sold to local GTP buddy). .520/.520 212/218 112 LSA, using crane 96803 springs. If you recall, this car has a '96 N/A 3.8 bottom end, with stock police package cylinder heads. (about stock SC compression ratio due to D-shape chamber)..

    Due to these heads having an open chamber, a local engine builder told me they are more efficient than the heart chamber heads, and will make the most of a lower lift cam, as the shrouding is greatly reduced.

    We'll see, and we'll also see how long the powdered metal rods hold up, the .520 cam isn't a super exciting cam, but does make a lot of torque.

    Only thing I don't like about those police heads are the swiss cheese deck surface. Have you ever thought about taking an SC head, or 96-98 mustang head and milling the combustion chamber to an open D-shape? I wonder how that would affect flow numbers, real world?

    I should have one of these flowed, or send one to you to play with

    Jeramie

  9. #9
    Join Date
    Apr 2002
    Location
    Westminster, CO
    Posts
    1,192
    Pics of intake and exh valve opened about .520...

    I bet an open chamber design would really help out for bigger valves, as shrouding becomes more of an issue. At least it would help low-lift flows?

    Jeramie
    Attached Images Attached Images   

  10. #10
    Join Date
    Jan 2004
    Location
    Outside KC MO
    Posts
    5,790
    Wow...it seems the more questions I answer, the worse my answers look.

    SWS

  11. #11
    Join Date
    Apr 2002
    Location
    Westminster, CO
    Posts
    1,192
    Wow...it seems the more questions I answer, the worse my answers look.
    Forgot to thank you for your input in my reply - drunk or sober, LOL..

    Truth is, porting is a lot of work.. dirty work. These heads need a valve job and new guides anyway, so big valves probably won't add too much to the cost. I'm starting to think bigger valves and some very mild portwork to clean up casting imperfections might be ticket..

  12. #12
    Join Date
    Apr 2002
    Location
    Madison, Ohio
    Posts
    16,925
    The unshrouding has a minimal but significant effect on flow. 95% of the flow occurs against the wall toward the plug in the open side. You can see this by the washing that occurs at that point. Because the heads have very low intake ports and a sharp short turn, very little actually happens on the short side of the intake other than turbulence.

    The amount of unshrouding that is done on that chamber is similar to how a performance head is ported anyway, so basically it's just a step in the right direction, but nothing that a properly massaged SC head doesn't already accomplish. The only thing we don't normally do is remove the heart shape because the heart is beneficial regardless. I don't know why Ford took out the heart shape for the police head. Any performance head is going to have a heart shape because it promotes swirl and it helps reduce reversion.

    If I was going to make a wild guess, I'd think that the police heads might be an earlier design? Out of curiosity, what is the casting #?

    A cam making torque is all about event timing and has little to do with lift except that more lift at the same timing means more flow and more torque, all other things being equal. Fred stuck with the .520 number just because he surmised that most people wouldn't want to go to a bigger valve. I don't question Fred's knowledge, but I think his emphasis on the stock valves was misplaced. A set of SS valves that maximize the available seat area cost like $120, and for barely more than the price of a set of 96803's you can get some 99893's.

    I've taken the best stock valve ported heads I was able to get and compared them to a set of totally stock heads that had the bigger valves with a few minutes of attention to the bowls and short turns and a port match at the intake manifold they flowed within ~5%. But when you compare the fact that the aftermarket valves offer you the ability to go to .600" lift, then they actually perform better than the fully ported, stock valve heads at .520" lift.

    All without what I would call "porting".

    To give you an idea on lobe design and lift vs. duration, for example an old CMRE SI cam was 210/220 .491/.491" lift. Fred pushed the lift to the max on the stock valves with his .520 cams, but the thing is you could order a .520" lift cam with duration anywhere from 206 all the way to 240 duration. Hence the confusion about people running ".520 cams" and getting all sorts of different results. Generally speaking if you want something with 100% drivability you are going to want to stay in the 206-220 range, 224-240 starts to cost bottom end and starts to really be a hiperf cam, at least in typical SC terms.

    That being said, if you can go high lift and keep the duration you like, then there is no reason not to do it. Just make sure you have clearance and the right valve springs! I run .580" lift on the cam in my wife's grocery getter. It gets 24mpg if driven easy and idles dead smooth with 18" of vacuum. To get specs any more specific than that you'd have to buy one.

    Seriously though, everyone knows how much I like to discuss cam stuff on the boards so don't take it personal, but I'm not going to go into any more detail on cam profiles than that.

    Chris, I didn't mean to seem like I was dissing on your comments. Everything I've learned about the SC heads is pretty much backed up on a flow bench though so while I don't have the last word, I do have some inside info as to what the heads need more than anything. All the sharp edges in the exhaust port really bother people but the truth is they don't really cause too much of a problem. I actually think Ford may have done some of that on purpose because they new that the exhaust was going to build pressure on these motors and they wanted to prevent reversion. If you flow a stock exhaust port both directions you'll find that the flow much worse backwards than forward. If you blend and smooth all that stuff away without addressing the real bottleneck (valve size first, short turn second) then what you end up doing is dramatically improving the reverse flow characteristics of the port without significantly improving the forward flow.

    There is a lot more to it than that, but you start to get the idea. Common sense and logic don't always prevail.
    Quote Originally Posted by Miller View Post
    Ya thats why i tape mine down. People think its bc i dont have a moonroof seal (which is true) but its really to keep my roof from ripping off .
    Email me here.

  13. #13
    Join Date
    Apr 2002
    Location
    Westminster, CO
    Posts
    1,192
    Casting number is RF-F35E-6090-A20A, these heads came off a 1995 Ford Windstar. The only year windstar to have a single port 3.8L

    The other set I have on the car is F15E something.., off of a 1991 Lincoln Continental 3.8L - but appears to be identical.

    HP rating for engines with these heads was 160@4400 and TQ was 225@3000

    HP rating for regular taurus 3.8L was 140@3800 and TQ was 215@2200

    Both engines had the same cam, same intake/exhaust components, possibly different tune.

    Although the pistons were different and had a 3 cc dish vs 9 cc dish for the heart shape heads.

    Replacement pistons for D-shape head vehicles now cross references to standard 3.8L pistons, no aftermarket company (sealed power, KB, silv-o-lite) has ever made the correct pistons for a D-shape head motor ironically.

    Went through this when helping my uncle rebuild his '95 windstar... Ended up with lower compression, ~~~~~~ gas mileage and no power.

    Vehicles using this head are 91-94 lincoln continental, 91-95 police taurus, and 95 windstar

    Jeramie

  14. #14
    Join Date
    Dec 2009
    Location
    Toronto
    Posts
    1,956
    Jeramie

    Just curious what power levels were you hopeing for.

    Many changes since you last updated your build.

    Paul

  15. #15
    Join Date
    Apr 2002
    Location
    Westminster, CO
    Posts
    1,192
    Well, no build planned for me in the immediate future.. Just was looking at a spare set of heads I had in storage, that I recently disassembled.

    Seeing a few local guys doing some builds and mods, i've been getting the mod bug again though..

    For my old '94, I sold it to a local GTP buddy, and I'm guiding him through the way to make it faster. Right now the plan for that is to toss this .520 cam in this weekend, add all the bolt-on (mpx, headers, FMIC) and big injectors and E-85 possibly. Push it hard and see how much abuse this N/A motor bottom end can take. When it breaks, he wants to do a 4.2 forged stroker build.. Not his daily driver anymore, so we got the green light to turn up the heat, LOL.

    I keep telling him to get on here, he' a cool guy.

    Only project I had going on possibly for my new '94 was the application of a 1.95 roller rocker package using aftermarket GTP parts. Kinda put that on hold, as I need an engine out of the car to mock it up.. At this point, I think we are going to run into pushrod/head clearance issues. The geometry looks ok though. If that goes through, will dyno before and after to see the change.

    Jeramie

Similar Threads

  1. Exhaust question
    By ORION in forum Super Coupe Club of Ontario
    Replies: 14
    Last Post: 09-05-2010, 05:07 PM
  2. header porting question
    By scxr7 in forum Technical Forum
    Replies: 12
    Last Post: 05-26-2010, 06:40 PM
  3. exhaust question
    By white90sc5spd in forum Technical Forum
    Replies: 4
    Last Post: 10-27-2009, 02:49 PM
  4. Need a pic of Exhaust
    By fastsc92 in forum Non Technical Forum
    Replies: 9
    Last Post: 02-02-2005, 10:10 AM
  5. another exhaust question (I'm sorry)
    By moore89 in forum Technical Forum
    Replies: 6
    Last Post: 11-05-2004, 06:40 PM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •