250 2v in Xy GS, please help!!!!

[Anonymous]

Tom, where abouts are you located. Are you in NSW? Sydney area?

Hey Mkeily,

I am on the South Coast of NSW, But sometimes travel up to Sydney. why did you want to know?

Cheers
Tom

 

[aussie7mains]

tomxy
Why are you wasting your time trying to port with a drill, you wont be able to do any valuable work like this.
1 The 2v inlets are just fine as they are, any grinding is only likely to make them worse, BTW polishing is only cosmetic, it actaully makes things worse.
2 Exhaust are bad and need help, but grinding near the gasket face is next to useless, the valve needs to be bigger and the seat blended to match, with guide reduced.
3 The center exhaust port needs dividing and you must have matching divided headers, this can be done by cutting a piece if 12mm plate to fit an have it welded in.
The only way to do this work poperly is with a high speed grinder (20000rpm) and siutable cutters or for the amatuer stones.
I do have experience with this work and this head, just in case your asking.
A7M

 

[Anonymous]

tomxy
Why are you wasting your time trying to port with a drill, you wont be able to do any valuable work like this.
1 The 2v inlets are just fine as they are, any grinding is only likely to make them worse, BTW polishing is only cosmetic, it actaully makes things worse.
2 Exhaust are bad and need help, but grinding near the gasket face is next to useless, the valve needs to be bigger and the seat blended to match, with guide reduced.
3 The center exhaust port needs dividing and you must have matching divided headers, this can be done by cutting a piece if 12mm plate to fit an have it welded in.
The only way to do this work poperly is with a high speed grinder (20000rpm) and siutable cutters or for the amatuer stones.
I do have experience with this work and this head, just in case your asking.
A7M

Sorry, i should of explained whats going on.

For the inlet ports I have only just started blending in the bumps closest to the gasket which are pretty large imperfections. I still need to get some longer stones to get all the way in there, but i am not going to polish it like a mirror, just grinding it back, so it is smoother and cleaner, for better flow, I am just matching the ports to the intake manifold which should help a bit.

With the exhaust ports i am not really sure on what to do exactly, so i havent touched them yet, only removed the 2 cast marks in 3 & 4. How close is the water jacket?

I have a pair of normal 1v extractors and dont really want to get new headers, because i have heard that mine will work fine using the right gasket. How do you suggest i do port the exhaust , besides welding in a new plate, just port it out as far as i can go? What do you mean when you say grind the guides to match the ports, is that ok to smooth them out?

The drill works fine, and is doing a good job. It might look like crap but it does work properly.

Thanks if you can help

Tom

 

[aussie7mains]

Truly I cant stress enough that you will make the inlet side worse.
the 2v inlets are already too big, so DONT enlarge them at all, the shape just behind the valve is the most important area and without putting in larger valves there isnt much you can do, If I remember your car is a streeter, if so then just leave well alone. Its almost impossible to properly match the port to intake joint, without putting dowels into the face to align them.
The exhaust really beeds 1.5 valves then blending to match the new larger valve seat , the guides can be cut down and the port straightened up somewhat, you'll notice theres a strange bend just near the outside of the of the port on one side, this can be removed to starighten up the port. your 1v headers should work IF the centre port is divided right up to the flange, so you can divide the centre exhaust port and give a header with 2 groups of three cylinders
hope this helps a bit.
A7M

 

[Anonymous]

Truly I cant stress enough that you will make the inlet side worse.
the 2v inlets are already too big, so DONT enlarge them at all, the shape just behind the valve is the most important area and without putting in larger valves there isnt much you can do, If I remember your car is a streeter, if so then just leave well alone. Its almost impossible to properly match the port to intake joint, without putting dowels into the face to align them.
The exhaust really beeds 1.5 valves then blending to match the new larger valve seat , the guides can be cut down and the port straightened up somewhat, you'll notice theres a strange bend just near the outside of the of the port on one side, this can be removed to starighten up the port. your 1v headers should work IF the centre port is divided right up to the flange, so you can divide the centre exhaust port and give a header with 2 groups of three cylinders
hope this helps a bit.
A7M

Thanks A7M, all this info is very helpful, so i will not enlarge the inlet ports, i'm just removing the bumps near the outside, and cleaning them up.

How do you weld a plate into cast iron? Wouldnt you need to heat it up red hot, and risk cracking it?

 

[Anonymous]

Sorry Tom I've been a bit slack replying. I was asking where you live because I am always keen to catch upwith forum member if possible if they live in the Sydney area. I live in Cherrybrook which is in the north West of Sydney.

If you were driving up one day we might be able to catchup.

Mark

 

[aussie7mains]

The way i did it years ago is:-
Cut a piece cardboard to get the shape you need to fill the space right to the exhaust flange.
Then oxy cut a piece of 12.7mm steel plate to that shape and dress up so it fits fairly well, clean up edges ready for welding.
Get some special cast iron welding rods, you will need about 12 for this job.
Weld in about 4 tacks to hold the steel in place.
Now run each weld but only about 10 mm at a time, between each weld pien each weld to relive strees, if youve got a propane torch heat the head up somewhat.
Dont undertake this unless youve got the right gear and can do reasonably competant at arc welding.
A7M

 

[Anonymous]

Sorry Tom I've been a bit slack replying. I was asking where you live because I am always keen to catch upwith forum member if possible if they live in the Sydney area. I live in Cherrybrook which is in the north West of Sydney.

If you were driving up one day we might be able to catchup.

Mark

Hey Mark, No problems, next time i am travelling up there i will send you a PM, and we can catch up. It would be good to finally see your car.

The way i did it years ago is:-
Cut a piece cardboard to get the shape you need to fill the space right to the exhaust flange.
Then oxy cut a piece of 12.7mm steel plate to that shape and dress up so it fits fairly well, clean up edges ready for welding.
Get some special cast iron welding rods, you will need about 12 for this job.
Weld in about 4 tacks to hold the steel in place.
Now run each weld but only about 10 mm at a time, between each weld pien each weld to relive strees, if youve got a propane torch heat the head up somewhat.
Dont undertake this unless youve got the right gear and can do reasonably competant at arc welding.
A7M

Thanks again A7M, i will have a think about it and might have a go, but do you think it would help much, because there is still a risk of cracking the head?

To match port we used a bit of cardboard and put it between the head and the manifold, tightened it up and then took it off, and cut the holes out of the cardboard. I then put the cardboard on the the head to see if it matches up, then use a permanent marker to mark out where i need to take a little bit out.

Two more questions ,

- There is a small bump about 80mm into inlet ports 2 and 4, is this safe to remove because it is fairly big, i think it is on the sides of the ports closest to the centre of the head.

- Is it any help to shine the combustion chambers up like a mirror, to reflect the heat back down into the combustion, and to stop hot spots, or is this just a myth?

 

[aussie7mains]

To my mind it is worth doing the centre port, especially if you run a dual exhaust right trough al la jag 6.
The two bumps in the inlet port are just underneath the tappet cover screws, so dont remove tham or youll have a possible air leak, they wont after flow to any extent anyway.
Dont bother polishing the chamber it does nothing except let you comb your hair. How long does combustion take?
A7M