Porting!

[noidea]

Ive got a dremel, that takes 3mm (1/8") shafts, and was going to borrow a die grinder which takes 6mm (1/4") shafts. Should i just buy a few stone bits and stick to the dremel?

 

[Mack]

The dremel will be ideal. Use 1/8 aluminium cutters like these

View attachment 55View attachment 56

should be able to get them from bunnings. Use your stones on the guide, and 60 grit sanding rolls for the rest. Most of your work will be done with the sanding rolls. Shaping and tidying the port. Bunnings sells dremels with the extension handpiece for a little over $100. The extender makes it real easy to use. If you have this you'll be laughing.

 

[noidea]

mite go have a look see what i can find. Im going to try a sand blasting method for the final finish of both the exhaust and intake ports. Put a vacum on the valve end of the port, then aim sandblaster down the intake... should get rid of all the little rough edges.

have you got any idea on the aluminium cutters, and what are the sanding rolls u talking about? Those little rubber bits that you slip a roll of sandpaper over?

 

[Mack]

The blasted intake is a very good finish on the intake and should be fine on exhaust. The theory behind the polished exhaust is to reduce the surface area of the port as much as possible to limit heat retention and recirculation of heat back into the head. This is the reason for the insulated exhaust washer as well and the fine gap between the collar and header pipe. All designed to get the heat to the pipe and away from the head.

Any tool shop with dremel bits will have the cutters. Also the sanding rolls which go on the rubber drum as you say. You will need a pack of them. About $10. Before blasting make sure you take the iregularities out of the port. They are pretty bad.

Don't think you have to finish with the bead blasted port. I think its more asthetic than practical. Many top tuners leave the 60 grit finish.

 

[noidea]

cool. Well i got my hsc trials this coming week and next so i probably wont have time to get much done... In between studying ill pull the head off my spare engine and see how i go. thanks for all the help ... should see about getting this thread stickied.

 

[noidea]

Got the head off finally. Took the rocker gear and cam out. Whats the trick for the valve springs and valves?

Im taking plenty of pics so when i get some spare time ill make a tutorial.

 

[Mack]

The springs are really quite soft in these. Just use a tube or long socket to compress the springs while you hold the head upside down. You may have to pump them up and down a few times. The retainers will just drop out.

Make sure you hold your thumb on the valve head to stop it opening while you compress the spring. Also choose a socket large enough to allow the retainers room to fall out.

 

[noidea]

ill have a crack now, and reply if i cant get it done.

(mack to the rescue yet again lol)

cheers

 

[noidea]

wow, that was easy. Do they come stock with two springs??? not looking forward to putting them back on lol.

edit instead of another post:
All cleaned and ready to port now.

It looks like someone has done some work to the ports, do they get machined before the leave the factory? Its just the top of the intake port, looks like its been opened up by a big grinding bit the diameter of the port... also is the double valve spring setup stock?

 

[Mack]

Yep, the two springs are stock. I'll warn you now, the only major drama doin this without a spring compressor is gettin those little barstard retainers back in. It needs great patience or save yourself the drama and when your ready go to any bike shop and get them to pop them in. Its 2 mins with a compressor.

Yes the ports have a bit of machining from the factory at the opening. The ducars I have seen have been opened out wide in this spot but then use a way undersized gasket and block the flow.

 

[noidea]

yea, thats the same. The intake manifold is nowhere near the diameter of the begining of the port!?

Good news is there definantly alot of room for improvement in the shape and surface of the ports

 

[noidea]

hey mack,
Got most of the intake port done tonight, definantly more fun than studying!!

All looks good, except i can feel a bit of a ridge after the valve guide on the bend in the port before teh valve seat. from the shape of it it would direct intake charge to hit the valve, is this what we want?

Anyway i took some pics, can you give me some tips on what you usually do this this area, and any other comments on my progress.

area behind guide/infront of seat: http://www.mypicpal.com/jarvie/My Photos/photos/CIMG2801.JPG

Intake port before: http://www.mypicpal.com/jarvie/My Photos/photos/intake before.JPG

Intake port after: http://www.mypicpal.com/jarvie/My Photos/mypics/intake after.JPG

 

[Mack]

Is this a Ducar head? The opening to that port looks huge. How wide is it? Does it match the intake manifold?

Well I normally would grind down the valve guide flush but that means breaking through and dealing with that. If you don't want this extra difficulty you could grind it down and leave it 3mm or so proud of the port roof. If you don't want to break through I would not grind any more from the surface leading up to the guide. If you look carefully at the previous pics you will see as regards shape that the standard port is a tall oval. After porting these ports end up a flattened oval or D shape. This will give you a clue as to shape. The ridge your talking about I'm not sure what area you mean.

Also if you are getting the valve seats redone, cool. If your not, then be damn carefull with the tool around those seats. If you nick 'em theyre stuffed.

 

[noidea]

yea, im going to get them redone.

Thats what i was saying about the port. Its been opened up heaps by some sort of milling machine. Its alot bigger than the intake manifold... I might take the head off my bike and see if its port is a bit smaller.

The area im talking about is the red area. I marked the port with a red texta and then ground it on the same angle as the inside of the seat. You can see the corner isnt smooth, the valve seat is smaller than the corner of the port and so there is sort of a lip there.

ive changed ur diagram a bit, the lip im talking about is this, http://www.mypicpal.com/jarvie/My Photos/photos/untitled.JPG

I think ill take a bit more off the sides of the lump infront of the guide and also a little more on the very top of it, thats if i continue with this head. Yea its a ducar.

edit for link to pic.

 

[Mack]

Oh, ok I see what you've got there. It is not ideal that the bowl area before the seat ring has a big scoop out of it. Nor that the port opening is so damn huge. I have seen this on Ducars. The ports have been ruined by the factory. Basically they have not left you anything to work with. There are three options open to you if you want to persist with this head.

The first is ignore the problems and do the best you can to clean up without enlarging.

The second is to install a larger seat and valve. That way you will reclaim some workable material and be able to rectify the bowl area and be able to shape the port to a preferred shape. This will mean though following up with a big bore kit and cam and bigger carby to make the whole thing work. This is exactly what is done with the big hp motors. It is the best option as far as power goes, just know that it is a very committed path in money and time.

Or number three, you can use a filler to reduce the oversize areas and shape to your liking. This way you can improve the flow and stick with stock valving and carb if you want to. The easiest way to do this is with JB weld. All you have to do is clean the port surface up like you have already done. Then drill with a tiny drill a few holding holes into the areas you want to fill being carefull you have meat behind those spots. Then gouge the entire surface to be JB welded with your alu cutter. It is then just a matter of mixing it up and building it up all through the areas you want. It can then be sanded to any shape you want.

 

[noidea]

Yea... sounds like this head isnt really a good base to start with then. I might leave it as is and possibly save it for a big hp motor or something. When i finish my exam today ill have a look at the head on my loncin and see if its better. I would imagine that head would perform better than a stock head, might give it to one of my mates or something.

cheers and ill let you know how i go.

EDIT:
Took the manifold off my loncin engine today. The head is untouched, looks like i will be taking it off tonight/next moment i get spare. Ive been looking at the pics of ur ports and i cant see the squished oval or D shape your talking about. Seeming as ive got a bit more meat to work with on this head i might try for a good port shape. Can you fill me in a bit about this process.

thanks heaps for your help so far man

Edward

 

[Mack]

While you've come this far with the ducar head you may as well grind that guide down a fair way before you put it back together. You have to make sure you have no burrs in the mouth of the guide too before re-inserting the valves. Also once done porting fill your laundry tub with hot soapy water and clean the head thoroughly with a toothbrush and force water through every passage. Also clean down the guides with cotton bud. Then dry with compressed air (or hair dryer if no compressor). Make sure you inspect in every cranny for crap. Then thoroughly oil everything with fresh oil as you put all the top end back together.

As far as shape goes you just have to look down into the port at the shape of the port at the far end. If you look at before and after shots you can see the differences.

 

[noidea]

well, after comparing them, i think your JB weld idea is going to be the better one.
Except that it seems the head volume of my loncin is ALOT more than the ducar head. But im thinking the valve sizes and port sizes will make up for the loss in compression... but now im going to have to think about a high compression piston... Heres a comparison of valves an ports:

Ducar head -Intake- Valve: 27mm
Inside Seat: 23mm
Manifold end of port: 29mm
Manifold: 22mm

-Exhaust- Valve: 22mm
Seat: 20mm
Pipe end: 24mm

Loncin Head -Intake- Valve: 23mm
Seat: 19mm
Manifold end: 21mm
Manifold: 24mm

-Exhaust- Valve: 20mm
Seat: 17mm
Pipe end: 20mm

So the ducar has a 4mm bigger valve and seat than the loncin. But the opening to the port is a bit too big, and there is that little lip just before teh valve. But that lip is even bigger on the loncin coz of the tiny seat.

The ducar also has a 2mm larger exhaust valve and 3mm larger seat than the loncin. I have also done about 1/2 the porting work on the ducar. How ever the loncin head has alot of metal to play with in its ports, but there is about a 2mm step from the port surface to the seat.

But the ducar has a higher head volume and therefore will give the engine less compression as opposed to the loncin head. but i think overall the gains in port and valve size with the ducar will outweigh the loss in compression which i will eventually regain with a high comp piston or machineing of stock head and barrel.

I think i will stick with the ducar, go and get some of that JB weld and close up the port a little and reshape it to a good size to suit the manifold.

Is there anything im missing with these small valve heads that might be better than the ducar?

 

[noidea]

hey mack,
found that cam grinding outfit for you.

http://www.tighecams.com.au/bikes.htm

 

[SIK50]

After reading this thread in its all ive decided we should start a new one dedicated to MACK the ledgend.............. all your information is so good ......... thanks for the help and thoughts