Slant Six Forum
https://slantsix.org/forum/

Porting and Matching
https://slantsix.org/forum/viewtopic.php?t=22361		 Page 1 of 1
Author:  dakight [ Thu Mar 22, 2007 4:40 am ]
Post subject:  Porting and Matching
I am getting ready to start on my head - just have to get it examined first. :? I am planning on some mild smoothing and port matching and oversize ( 1.7 / 1.44 ) valves. I have a couple of questions. Given that valve size above, is it necessary or helpful to relieve the valves? If so, how much? Can it be done by hand or do I need to have the machinist do it? Also, when matching the ports it is almost impossible to get a perfect match and probably as difficult to install everything in a matched position. So that leads me to the second question. If there is a step or transition is it better for the step to be toward or away from the valve. In other words, should the smaller port be in the head or in the manifold? I'm assuming that the exhaust is the most critical but I could be way off there too. Any advice would be appreciated. This will be my first try at porting a head.
Author:  flatiron [ Thu Mar 22, 2007 5:06 am ]
Post subject: 
Be careful. I'm doing the same thing you are and I went thru a Exhaust port into a water jacket glad I have another head. I sprayed dykem laid the gasket and scribed aline around each port. I don't know if I hit sand or what. The next one I start on tonight I'm just gonna remove the flashing from the port entrances chamfer the intake ports and polish up the short turn radius's
Author:  dakight [ Thu Mar 22, 2007 5:13 am ]
Post subject: 
I've heard of that happening. I'm not trying to do anything radical, just smooth out the passages for better flow and make way for the larger valves. Oh, I forgot to mention originally; my cylinders are bored .060 which will have some bearing on valve shrouding and the need for relief. I just don't know how much.
Author:  Dart270 [ Thu Mar 22, 2007 6:57 am ]
Post subject: 
If possible, get your open 0.060" over block and drop the head on it to see if the edges of the combustion chambers hang outside the cylinder. You can also shift the head forward or rear to correct bad block dowel locations by grinding the dowels on one side or getting offset dowels.

Relieving is good to do, and can be done with a die grinder and 1-1.5" diameter stone and/or carbide cutters. Blend any sharpish edges into the chamber contours.

You will gain a lot by just opening up under the valve after you hog out the seats. Do not take any material off the floor of the port except to smooth the transition to the port from the valve. Smooth out the guide bosses and you can take the exhaust one mostly off.

Lou
Author:  slantvaliant [ Thu Mar 22, 2007 7:09 am ]
Post subject: 
Be careful about gasket matching - a little gasket sticking into the flow can mess things up. A small gap (head-gasket-manifold) where the port is a little smaller than the gasket opening won't hurt. Good flow is more important than port volume.
If there is a step because of a port mismatch, you want the flow to go from smaller to larger. The airflow should not hit a dam or wall. In other words, would the airflow "trip" on the step?
Where the intake port in the head meets the intake manifold, aim for a good match. If anything, make the head side a little larger.
On the exhaust side, the exhaust manifold openings can be opened up slightly to ensure a smooth transition.
Remember: It's usually easier to go back and remove a little more than it is to put some back.

Here's some more Porting Info
Author:  mpgmike [ Thu Mar 22, 2007 7:29 am ]
Post subject: 
I leave the floors mostly alone, only smoothing things out a bit. I take a little material from the side wall that equates to the outside of the cylinder. Most of the material I remove is from the ceiling of the port. Here is what I did with the OS valves:

http://powrehaus.com/2006/12/05/old-sla ... new-power/

Mike
Author:  icaneat50eggs [ Thu Mar 22, 2007 9:31 am ]
Post subject: 
I just finished porting my head. It went pretty smooth. What I did to match the intake ports to the head was to place painters tape (several layers) over the ports on the head, place the intake on the head and tighten it down. I left it like that for a bit, remove the intake and could see where the intake flanges contacted the head (compressed tape). I think using prussian blue (even lipstick) on the flanges of the intake would help visibility of contact, as it was hard to see after some grinding. I did not match the exhaust ports too much. The exhaust ports on the head are almost 1/4 smaller than the ports on the exhaust mainifold, at least on mine they were.
Author:  dakight [ Sun Mar 25, 2007 8:58 pm ]
Post subject: 
OK, I drug the head out today and cleaned it up the best I could with water and simple green. Will take it to get it tanked and magnufluxed later. I pulled out all the casting wires that I could see and reach - at least 6 up to a foot long. I removed the valves, studs and temp sensor and took some pictures. Here's what I have:

Here's the middle 3 chambers. Note that it has been machined and bronze valve guides installed.
Image

This in a close up of one chamber. Note the remains of the bump where the original valve guide would have been.
Image

A couple of questions. I assume I should remove the remains of the guide hump and blend everything in under the valves? Is there any "meat" to be removed from between the valves - especially in the exhaust runner? It just seems the the port walls are really in close to the perimeter of the valve seat and it seems that would disturb the flow but i don't know. I'm putting in the 1.44 / 1.70 valves so the seat will be even larger. Should I try to do something now, wait for the hardened seats to be installed, or do nothing at all? I blieve this is one of the later heads with the better chamber design.
Author:  dakight [ Mon Mar 26, 2007 6:11 pm ]
Post subject:  A Start
Here is after a few minutes with a die grinder and stone.
Image
Am I on the right track or have I just destroyed the head? My main concern is that if I go much deeper the edges of the bronze valve guides will be exposed. Would that be a problem?
Author:  sandy in BC [ Mon Mar 26, 2007 6:32 pm ]
Post subject: 
Thats quite the crack between the water holes!
Author:  mpgmike [ Mon Mar 26, 2007 6:55 pm ]
Post subject:  Re: A Start
Quote:
Here is after a few minutes with a die grinder and stone.
Image
Am I on the right track or have I just destroyed the head? My main concern is that if I go much deeper the edges of the bronze valve guides will be exposed. Would that be a problem?
You're on the right track. Now flow your clean-up from the valve stem to the rest of the port. Then go and do the intakes as well.

I ended up doing most of the work that I could, sent the head to the machien shop and had the seats opened up for the OS valves, got the head back and cleaned up the machine marks, then sent it back again for a final tanking.

Mike
Author:  emsvitil [ Mon Mar 26, 2007 8:29 pm ]
Post subject: 
Exposing the bronze guide isn't a problem.

This is a motorcycle head:

http://www.head-quarters.com/html/sportster.html

with a very exposed guide.
Author:  Dart270 [ Tue Mar 27, 2007 10:09 am ]
Post subject: 
It looks like you've barely started to me.

Lou
Author:  dakight [ Tue Mar 27, 2007 10:52 am ]
Post subject: 
Quote:
Thats quite the crack between the water holes!
To be honest I didn't even see that until just now. I'll have to look at the head when I get home but I don't think it's a crack; more likely a scratch.

Yeah Lou, I am just getting started but I wanted to be sure I was doing the right thing before putting too much more time and effort into it. Besides, it was dinner time... first things first.
Page 1 of 1 All times are UTC-08:00
Powered by phpBB® Forum Software © phpBB Limited
https://www.phpbb.com/