Porting/polishing T7 head

[Si]

Hi, has anyone got any pictures of porting done to a T7 head?

Also on one side of each pair of the inlet ports there is a bulge running from the bottom corner down to the valve entrance, does anyone know what purpose this bulge has?

I will get some pictures of the head i'm working on later to show what i mean, i was really wondering if it could be removed when i clean the cast lines and smooth out the inlets. I'll also probably round off the area where the valve stem comes out of the head.

[John Z Williams]

I p/p and entire t5 head, the inlet side has a divider to help the air/fuel mixture seperate and flow better. Maybe that is what you mean.

The short radi side is the most important and most of the gains happen there and I spent a lot of time flowing the bowls. In and out of the canals to the valve bowls.

You want to port match, clean up the canals and maybe open them up a little, then flow the short radi side and clean up the bowls, some clean up the valve guides too and then leave the intake side fairly ruff, 80-100 grit and polish the exhaust side to a mirror finish to help carbon build up. I also polished the combustion chamber to help with carbon build up and detonation.

John

[Si]

Is it worth smoothing down the cente section between the valve inlets so it's more like a knife edge, or keep it fat? you can just make out the bulge in the first photo, it's on the lower LH side of the port.

[John Z Williams]

Some people knife edge that divider and smooth out the imperfections and any sharp lines or edges that disturb airflow. I am not sure what that hump is, maybe a casting piece, I would try and smooth it out or get rid of it entirely.

Look for some pictures of guys that have done these, they look great.

John

[Martin_9-5t]

T5 head. still sat in the garage...........

[John Z Williams]

Nice picture of a t7 ported canal, John


http://www.maptun.com/cars.php?id=161

[Si]

Thanks Matin/John, you can see on the T7 head that they have removed most of the bulge, so i'll do the same, looks like on both heads they have opened out the EFI port a little too.

[mike saunders]

be careful...

there's a water passage under there...

[John Z Williams]

Yea, you don't want to go too far and I have a spare junk t7 head that I might cut open to see how far you can go before you get into trouble.

On the next head I do, I want to really open her up on the intake side and there is a lot of black art that comes into play with venturi effects and flow dynamics.

I wish someone had some cnc porting for our heads. It seems abbott is one of the few doing gas flow measuring for the saab heads. You can port the head for better torque/midrange or upper end hp or a little of both and that takes time and trial and error to get all that information right.

If you take too much out, you can lose bottom end torque and only gain a hair of top end. You need to know what you're goals are and if you want a little of both, midrange and top end, I would recommend just cleaning up the ports and getting rid of the imperfections and straight edges. Try and keep the shape the same on the intake side and maybe knife edge the divider a little. Port match the intake and exhaust sides and open the canals up to match those. Spend most of you're time on the short radi side of the bowls and flow the valve guides and open the bowls up.

Good Luck,

John

[Si]

It's going with a bit of a mad combo, I'm modifying the T7 header to fit a B201 block/pistons with 7.5:1 compression ratio, then tubular header & a T 3/4. Inlet side will have an integrated chargecooler/plenum, single inlet from the turbo then 4 outlets to 45mm throttle bodies on each runner.

I'll either use Megasquirt, custom tuned T5 or DI/APC to control it.

[mike saunders]

7.5:1?

Why so low? Wouldn't you need to be on boost ALL the time to make any decent power?

The rest of the combo sounds like pure evil genius!

[Si]

7.5:1 = Loads of Boost

The intention is to create a nice smooth boost increase up to 2-2.5 bar, extend the rev range enough to accomodate it safely and hopefully not splinter the gearbox in the process.

If it all goes to plan the short inlet and big fat chargecooler will couteract the slow spooling of the big turbo so it's not too laggy, on/off throttle once it's going should be quite interesting with the throttle plates about 4-6" from the valves!

As i'm using motorcycle ITB's i've got the option of between 4 and 12 injectors aswell

[John Z Williams]

That is still too low in my opinion, stock is 9.2/1 and I have run 33psi of boost with no issues and Dave-ship runs around the same I think and runs 30psi+ and some guys have gone down to 8.5/1, but that creates lag and low performance down low in the rpm band and you will not start making power until you are under boost and that would have to be past 4500rpm with a turbo big enough to maintain 28psi+

I would consider 8.5/1 to 8.8/1 or even the stock 9.2/1 to run 2 bar. With a gt35r, you could make 600bhp and run 30-35psi all day long at 8.8 to 9.2/1 with no issues, especially if you run forged pistons!

Good Luck,

John

[NickTaliaferro]

You need the higher compression to get the VE up. It will hurt efficiency and make it a really hard car to drive. The higher compression will stabilize combustion especially at high revs.

[Si]

If the engine had 600bhp just turning it over would probably be enough to lunch the c900's gearbox

Ooopps, 7.5 is for the older 8v, it should be 8.5 for the one i've got.

It was supposed to be with an 8v head and very much like the 99 turbo rally car, but i got my hands on the T7 head cheap and the itb's line up better with the 16v inlet ports.

It's only going to be for track day use aswell, i don't want to kill the car in my avatar with too may more days, if i don't get this engine built I'll be doing another 3 or so this year in it.

I could go really high comp ratio and low boost as an alternative as i've got a B202i aswell which is 10.1:1, i'm sure sooner or later a B202t block/pistons will come up so i can experiment a bit to see which suits the set-up best.