couple of questions from forum noob

[bluezone]

hi, i've tried the seach fuction and could'nt locate the infoermation i was looking for.

1st there seems to be 3 styles of intake port in the mk3. has anyone compared all of them together? e.g. long divider, short divider(blunt) and even shorter divider shorp.

2nd Vf voltage under boost. ii've been having a discusstion with someone experimenting with this and it dosent seem to vary under boost. "0" volts? is he doing somthing wrong?
or is it a closed loop open loop question?

thanks ahead of time

brian

 

[jetjock]

It's a closed loop/open loop question....

 

[bluezone]

thats what i thought.
should of come here 1st.

thank you.

 

[jetjock]

S'ok. I'd have answered your first question but frankly I have no idea what you're talking about...

 

[Poodles]

Think he's talking about the revisions in the head design. As far as I know, there isn't enough difference to worry about it, especially if you have port work done...

 

[bluezone]

yes thank you.the port revisiions. guess i should of been more descriptive in what i was askiing.

i'm not planing on high hp numbers 300-350hp. just trying to make what i working with responsive.
i've got a good 88 7mgte that needs a head gasket and has a good turbo. plus all the parts to convert a n/a auto to turbo 5-speed.
i'll be adding
mhg
apr studs
bicc divoriced down pipe(closed system)
3" cat
george's cat back
apexi filter
n/a intake cam

where this put me was wondering which head to tackle with some port work. i do my own port work.
any suggestions as to what to stay away from when porting the 7m head? i've heard feedback that there are anti-reversion dams in the ports. if so i did not want to mess these up.

also thinking about blue printing the turbo, or i should say optimizing the turbine and commpressor wheel clearances.
i've talked to some of the garret engineers and they felt this was important. i work in a machine shop so doing something about this is not a problem.

and thank you

 

[IJ.]

There are at least 16 port/casting revisions excluding the Group A heads.

 

[bluezone]

I did not know that there were so many different castings. group A's might as well be avaliable on the moon, not very likely that i'd find or be able to afford one of those. be over kill in my case but sweet.

is this by the casting number on the intake port side?
i have a 3, 9, 11 and i think the junk one was a 15.

 

[IJ.]

The numbers sometimes appear in behind the CamBelt tin cover as well.

I've had a #1 and the last new casting I bought was a #16, keep in mind most were probably only casting revisions to make them demould easier or save material.

I'm not aware of any studies on port flow to determine if the Long/Short dividers make any difference.

I just had my new casting opened up +1mm for it's full length and some work done on the short turns, I also sawed a head into pieces to make sure of the wall thicknesses so there wouldn't be any wet surprises.

 

[bluezone]

thanks IJ. you've helped remove some of my worries.
from pic's i've seen on EDS.EU and another site i forgot to bookmark the port floor of the newer heads appers to be higher.i haven't set my three heads down together to see for sure. this might help the short turn radius flow abit. hard to tell without testing it though.

i'm still leaning to the early long divider heads though.

which ever way i go, looks like i'll just pocket port and smooth things up abit. that and make sure i have a nice 5 degree tapper to the valve opening.

your info and input are appreacated.

brian

p.s. someone posted on the SM site here that the newer short divider ports flowed a little better(2cfm) at stock lift and much better at higher lifts. they didn't provide any more info than that though.