Page 1 of 2 12 LastLast
Results 1 to 10 of 13

Thread: difference between heads

  1. #1
    Forum User Not Verified Feedback Score 3 (100%)
    Join Date
    Nov 2010
    Owner Since
    2007

    Location
    Midland,MI
    Posts
    175
    Thanks
    0
    Thanked 1 Time in 1 Post

    difference between heads

    What is the difference between the DOHC NA heads and the Twin Turbo heads?

  2. #2
    The one. The only. verified
    supporter
    Feedback Score 14 (100%) stealthee's Avatar
    Join Date
    Sep 2010
    Owner Since
    August 28, 2002

    Location
    SWPA
    Posts
    4,012
    Thanks
    169
    Thanked 682 Times in 513 Posts
    TT heads flow better.

    [06-05, 19:29] OhioSpyderman: Brian, finding a woman is NOT the answer, you need to shop for a good VACUUM

  3. #3
    Forum User verified Feedback Score 1 (100%) Amphiron's Avatar
    Join Date
    Sep 2010
    Owner Since

    Posts
    513
    Blog Entries
    1
    Thanks
    8
    Thanked 12 Times in 10 Posts
    I believe the TT heads are ported a bit more, or the valves are a bit bigger. The exhaust cam has more duration as well.

  4. #4
    The one. The only. verified
    supporter
    Feedback Score 14 (100%) stealthee's Avatar
    Join Date
    Sep 2010
    Owner Since
    August 28, 2002

    Location
    SWPA
    Posts
    4,012
    Thanks
    169
    Thanked 682 Times in 513 Posts
    Valves are the same size.

  5. #5
    Forum User Feedback Score 0
    Join Date
    Nov 2010
    Owner Since

    Posts
    37
    Thanks
    1
    Thanked 0 Times in 0 Posts
    Can you bolt TT heads on to an NA has an upgrade?

  6. #6
    Forum User Feedback Score 0
    Join Date
    Sep 2010
    Owner Since

    Posts
    30
    Thanks
    0
    Thanked 4 Times in 4 Posts
    yep the ports are different between turbo and NA heads

  7. #7
    Banned Feedback Score 11 (100%) J. Fast's Avatar
    Join Date
    Sep 2010
    Owner Since
    - O - SIX -

    Location
    Colorado, USA
    Posts
    2,755
    Thanks
    412
    Thanked 203 Times in 143 Posts
    The parts and internals are identical from the 1st gen N/A and TT heads, valves, lifters, springs, etc.... The exhaust ports are slightly larger on the TT heads but can be matched with about and hour or so of port work. I would say they're identical as according to Jeff Lucius' findings from bench testing their was a flow variation of 3-5 cfm.

    On to the 2nd gen heads. The heads are completely different between the 2nd gen's. There was a revision on the mid 1994 models as the intake and exhaust ports are dramatically different. There is no way to port match 2nd gen N/A heads to the same spec as the 2nd gen TT heads as the water jacket on the N/A is to close to the wall to port to the same spec. The internals are nearly identical on all models with the exception of the cam profiles.

    Awhile ago at co3s we had a dicussion involving N/A heads and TT heads being identical. I stated they were. I based that off of comparing a set of 1st gen N/A and TT heads. After comparing a set of 2nd gen TT heads with a set of N/A heads, Gary Melcher had at MHM, I realized there must have been a revision, hence the dramatic change in the exhaust and intake port shape and size.

    I would suspect the reason why first gen cams were found to make more power with 2nd gen heads would be the result of the INCREASED PORT SIZE ON THE INTAKE AND EXHAUST combined with the difference in lift duration/overlap between the 1st and 2nd gen cams. Ofcourse it's a big assumption however I'll throw a guess out there and say 1st gen heads have a smaller port so the cam profile was more agressive to make more power. When mitsu increased the ports on the 2nd gen they changed the profile to a more economical profile, hence swapping a set of 1st gen cams on 2nd gen heads resulted in IPO's discovery of 25 more hp.

    2nd, there's a few threads in some closed forums with cutaways of our engines I can't point you to them but if you use your google finger you may be able to dig them up 8)

    I can't say anything about 3rd gen heads as I've never seen a set of NA or TT heads from that generation so I have no idea if they modified the design again for those years.

    Jeremy

  8. #8
    Twin Turbo verified Feedback Score 5 (100%) GTOJOE's Avatar
    Join Date
    Sep 2010
    Owner Since
    2007

    Location
    Melbourne, Australia
    Posts
    2,155
    Thanks
    79
    Thanked 92 Times in 76 Posts
    If you take the time to read the post that Steve linked it is a question I asked about JDM NA and TT heads and the differences. The pics he posted show the differences. Obviously the USDM heads are different to the JDM heads. But worth a look.

  9. #9
    SKADOOSH!!! verified Feedback Score 1 (100%) J_Parker's Avatar
    Join Date
    Sep 2010
    Owner Since
    2008

    Location
    Prince George
    Posts
    1,302
    Blog Entries
    4
    Thanks
    47
    Thanked 49 Times in 42 Posts
    I think I'll have to take a wild stab at a downgrade man. We all know that N/A's like their backpressure.
    Photobucket

  10. #10
    The one. The only. verified
    supporter
    Feedback Score 14 (100%) stealthee's Avatar
    Join Date
    Sep 2010
    Owner Since
    August 28, 2002

    Location
    SWPA
    Posts
    4,012
    Thanks
    169
    Thanked 682 Times in 513 Posts
    Backpressure is a myth. You want free flowing heads with the highest velocity.

Page 1 of 2 12 LastLast

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
The 3000GT/Stealth/GTO Web History Project
3000gt.com
3000GT / Stealth International WWWboard Archive
Jim's (RED3KGT) Reststop
3000GT/Stealth/GTO Information and Resources
Team 3S
3000GT / Stealth / GTO Information
daveblack.net
3000GT/Stealth/GTO Clubs and Groups
Michigan 3S
MInnesota 3S
Wisconsin 3S
Iowa, Nebraska, Kansas 3S
North California 3000GT/Stealth
United Society of 3S Owners
3000GT/Stealth/GTO Forums
3000GT/Stealth International
3000GT/Stealth/GTO Event Pages
3S National Gathering
East Coast Gathering
Upper Mid-West Gathering
Blue Ridge Gathering