Girdled Head and Domes Does Not Work on Big Bore?

motojunkie96

motojunkie96

AKA "The Paulinator"
All right, I've now heard mixed messages here and am slightly confused. I just got a Group K 780 big bore (85.5 mm pistons) I'm wanting to put on an ADA girdled head w/interchangable domes (want a lil more compression than 170). I've been told by several people that I can put on 86mm domes (cc size to be determined) and it'll work. But, I called Group K today to get their opinion and they said that a dome type o-ring head will not seal. They said to instead run a Pro-Tec half girdle kit. Which one is it? Anybody have a similar setup?
 
motojunkie96

motojunkie96

AKA "The Paulinator"
Actually haven't ordered that head yet...but I've got another non-girdled ADA I might...thinking about putting it on my Blaster though
 
SUPERTUNE

SUPERTUNE

Race Gas Rules
Location
Clearwater Fl.
85.5mm is max size on a ADA head for me, 86mm bore cylinder w/ADA head dome are very thin for sealing and the o-rings don't last very long. Use a R&D or Riva for 86mm and up as long as your not building a positive deck stroker.
 
Bonzia Bob

Bonzia Bob

Location
San Angelo, Texas, United States, 105590109474550,
R&D Head Pics

Here are the pics of the R&D head that NOSKIFORME told you about. The domes are marked 33cc. It has all the o-rings and girdle bolts included.
 

Attachments

  • Jun01_0001.jpg
    Jun01_0001.jpg
    62.3 KB · Views: 52
  • Jun01_0002.jpg
    Jun01_0002.jpg
    49.2 KB · Views: 40
  • Jun01_0003.jpg
    Jun01_0003.jpg
    61.9 KB · Views: 41
  • Jun01_0004.jpg
    Jun01_0004.jpg
    52.6 KB · Views: 34
  • Jun01_0005.jpg
    Jun01_0005.jpg
    51.3 KB · Views: 29
MTRHEAD

MTRHEAD

Location
MotorCity
Frist- Group K says that about every motor made.

Why ? Sleeves drop - that is why aftermarket sleeves such as WATCON.COM's have wide heads to fully capture the domes to prevent this problems on Yamaha's. Most dome to sleeve interferance's are around .003-.005 to prevent failures such as you have heard. However with this "pressure" point over time it actually makes the sleeves fall and then the dome can rock or leak. Also during the 2000-2002 era some of the aftermarket heads were machined slightly off and random failures occured. During that time the fix was to machine .002 to make sure the dome was kissing good.

This "falling" sleeve also happens in Kawasakis which dont have removable sleeves. That's why it's best to use a seasoned cylinder and deck for superstock applications.

Saying all of this I ran a domed SJ LIMITED class cylinder with 33's and never ever had a problem. I ran a SJ Superstock with 85.5's and also never ever had a problem. GPR's with domed heads and never a problem.
I also check/replace the rings and whipe the decks every so often.

I have also pounded sleeves in so deep the dome rocked and literally cracked on other motors - deto and bad setups
 
Last edited:
Rickster

Rickster

Matakana Menace
Location
Bay of Plenty, NZ
I'm currently running a 86mm flat top big bore with a girdled ADA head and 24cc domes.

In fact, I just removed the base gasket this morning and sealed her back up, and the o-rings are still nice and purdy.

Works with my engine.:biggthumpup:
 
aqua

aqua

the taco
Location
Jefferson City, MO
Rickster said:
I'm currently running a 86mm flat top big bore with a girdled ADA head and 24cc domes.

In fact, I just removed the base gasket this morning and sealed her back up, and the o-rings are still nice and purdy.

Works with my engine.:biggthumpup:
Click to expand...
rickster...how long have you been running that setup on those o rings. i am doing a bb setup and will be running an ada head also.
 
Rickster

Rickster

Matakana Menace
Location
Bay of Plenty, NZ
aqua said:
rickster...how long have you been running that setup on those o rings. i am doing a bb setup and will be running an ada head also.
Click to expand...

3 months with probably 50 gallons ran through the engine.

I was only running 165 compression with .065 squish. I removed the base gasket this morning, which should give me another 20-30 psi and lower the squish for a bit more bottom end..
 
Last edited:
G

Goose

Guest
im running 86mm pistons and havent had any problems with the 33cc 760 domes
 
Lucifer

Lucifer

Jet Junkie
Location
Croydon PA
Which head to use??

It seems like a lot of people are using the ADA heads on thier big bores. They were my first choice n they arent as expensive as some others.
Anyone running other heads? Pros? Cons?
I'm running 85.5's in a 61x with LA Sleeves....
 
Rickster

Rickster

Matakana Menace
Location
Bay of Plenty, NZ
I'm still running the 86mm Big Bore with ADA head for over a year now, and have had zero issues with o-rings.

:woot:
 
You must log in or register to reply here.
Top Bottom