The V8 Owners Forum -

after gavs post regarding the exhaust ports,
if i want to open the exhaust port out to match the gasket do i need to go right into the head , or can i just do say like the first half inch of the port opening and blend back into the original porting??? or with this cause problems???

reason i ask, the exhaust port openings on my 4.6 heads are a lot bigger than my stg2 ones,

Hi Tony
a basic question here, does the exhaust manifold exactly match the gasket or will you be taking this out to match the gasket aswell?
If you end up enlarging both to the gasket then you will end up going narrow to wide at the gasket to a narrowing in the exhaust pipe, this is not good.
If you are going from the exhaust gasket face to a wider exhaust pipe then opening out the port in the head half an inch then blending will probably be the best answer.
if it is a sudden step immediatly after the exhaust flange face to the actual pipe then as long a blend into the port you can manage would probably be best.
The aim is to avoid rapid changes in cross section and small to large to small changes in cross section. Often people fing that a step change (small to large) in sectional area at the bottom of the port where it meets the exhaust flange/ pipe is a good thing as it prevents the exhaust returning into the cylinder during overlap, it can efectivly bring you on can a couple of hundread revs earlier on a hot cam.
Best of luck
Mike

Hi Mike,
my gaskets match the manifold flanges, thus why i was thinking about opening up the head ports a fraction

OK in that case I would open up the first 1/2 to 5/8ths of the port in the head to the gasket and then blend it as smoothly as posable, might be worth leaving a step at the bottom of each port and see if this helps bottom end (if it is working you will probably find you can lean out the bottom end on light throttle (you are using FI aren't you). job for the router then?
Mike

yeah using a fully mappable fi system mate,

UPDATE

Camshaft is now ordered and will be here wednesday/thursday, i bit the bullet and went for the crower 50233 and Paul (v8tuner) recommended the crane hi rev lifters over the rhoads to go with them,

I just need some ones help in making this notching tool and i can get to work

I'm going to open the exhaust ports out a bit so they are slightly smaller than the gasket 2-3mm ok???. fingers crossed will start that this weekend,


I will contact Neil at caprisport to see if he can take a pic, or lend me so i can take a pic of the manifold flanges he used when he made the manifolds,

Mike how high should the step from the head out to the manifold be at bottom of the port?????

Hi Tony
I would try 3-4 MM to start with, if there is enough on the floor of the port to start with I wouldn't build up the floor of the port just to create the step, just don't grind it out. You can always fully match it later if it doesn't seem to do anything. Used to do it on Minis and it used to make the old 285 cams just about drivable in a 1300 on the road.
Best regards
Mike

kiwicar wrote:Hi Tony
I would try 3-4 MM to start with, if there is enough on the floor of the port to start with I wouldn't build up the floor of the port just to create the step, just don't grind it out. You can always fully match it later if it doesn't seem to do anything. Used to do it on Minis and it used to make the old 285 cams just about drivable in a 1300 on the road.
Best regards
Mike

This used to be common practice on bike engines to the point the port got welded up to leave a flat floor so you had a D on its back. Really not sure if it will have the same effect on the rover as the port is at 45 deg to the piston and not 90 like the bikes and the mini. That said the bikes at any road had steeply inclined valves so the angle would have been reduced there too. It is important though to have a step into the port to catch the reflected wave so don't gasket match like you would the inlet.

cheers guys,
so leave around 3mm of the exhaust port round the inside of the gasket

Got home from work today,
and came face to face with a parcel from Paul at v8 tuner,
was well impressed as only phoned him monday afternoon,
in the box was a crower 50233 camshaft, and a set of crane hi-rev anti pump up lifters

Just got off the phone to Rob, (v8 dev) i do enjoy talking to Rob,
and these are early v8d heads (can't find any records for them though) BUT this is the best bit
They are not stg2 but stg3 whoop whoop
he has advised me to open the exhaust port slightly, the reason the port is left a bit smaller is to aid the torque,

well this weekend is the start of my upgrade,
fingers crossed after this weekend every thing goes to plan, otherwise i will have a non moving car again

its going to be a gamble to get every thing done in 6 days.

Old parts to be removed from engine (trying not to damage the sump gasket where it meets the timing cover)
then.....
pistons reliefs to cut,
new cam and timing gear to fit and dial in,
new lifters to fit and set preload,
new heads to fit (remove servo to aid removal and refit)
new throttle shafts to fit the twin plenum,
A/F gauge and egt to fit (wiring to do and bungs to weld in exhaust manifold)
water pump to change,
uprated rubber engine mounts to change.

test and map the ecu for the above mods,

??? so what are you going to do with the other 5 days of your 6 day holiday then.

if only it could be done in a day mate

Remove the servo? Cant you just unscrew the head studs and lift them out of their holes and the head will come out.

Just had a thought, you've got that rear bolt on the drivers manifold to do snigger snigger!