diy head modification

8/7/2019 DIY Head Modification

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DIY Head Modification

Sideways Technologies Forum

Neil Collingwood

Tools and Workspace

Figure 1 Required Tools Figure 2 Depth Gauge Figure 1 shows the tools you will need to complete the work. You will obviously need some form of

power tool, the one shown is a Makita with a six mil collets, and will rev to 22000 revs which I run

through a 600 watt light dimmer switch to control the speed. You will need a grind stone like the one

shown; it is a 60 grit silicon carbide stone. The one shown is an inch diameter, but if you have a worn

one that would be better as the inch one will collide with the valve guide unless you cut it down to

size. I prefer to start the modifying with the rotary burr shown, but these can be expensive. If you

look at figure 2, you will see a little tool I am holding, this is a depth gauge and should be shaped to

fit the short side radius, drilled, a self tapper screwed in and the tip of the self tapper ground off. I will

tell you what depth to set it at later. The other important things are a face mask, and a vacuum

cleaner to suck all the dust away.

Just thought I would show this picture, just to show you

where I work and that you don't need a really large

workshop to modify heads. Some stands to put the head on

are a good idea, that way you are not chasing the head

around all over the bench. The other important thing which

is just out of picture is the vacuum cleaner to suck all the

dust away, or you are soon going to have your work area

full of iron dust. Also in the picture is a valve re-facing tool,

it's a Black and Decker which I paid £110.00 for, which had

been reconditioned. Although it maybe old it¶s a realsubstantial cast piece of equipment, and does a good

job. Behind that is a press for which I use for pressing

valve guides in and out and other small jobs. In the far

corner is the Super Flow 110 flow bench. Also not shown I

have a Serdi valve seat cutter which I use to cut three

angled valve seats. That's about it, you don't need all this stuff but I find it helps me and saves me

farming work out. Most engine shops are capable of cutting the 3 angle valve seats for a reasonable

cost.

Figure 2 Workshop





Neil Collingwood

Port ModificationsTo start your DIY mods you need to have made a depth gauge and set its depth to between 2 -

2.5mm. If you look at figure 3 you will see the piece of metal we are going to remove.

Figure 3 Short Side Cut Depth Now you need a rotary burr

something 25mm x 13mm with

a flame shape will do the job

spot on. Remember the shape

that you saw on the cut away

head, so start shallow and

steadily go deeper to the depth

of the depth gauge following the

radius round the port and finish

shallow. This is the depth youare going to go too. DO NOT GO

ANY DEEPER.

Figure 4 Cutout Shape in Port





Neil Collingwood

Now you need a ball shape grind stone,

but before you switch the grinder on

make sure the grind stone will followthe short side radius without crashing

into the valve guide. This is the difficult

part for me to try and describe how to

do it, starting at the centre of the short

side radius and to the right hand side

towards the outside of the chamber you

need a long radius, the port well laid

back. To the left hand side you need to

grind straight down from the valve seat

and form a small radius blending it all

together across the port. Difficult I

know, but you need to look at the phototo see how I¶ve done it. The small

radius and the long lead into the back

of the valve seat are for the low lift

flow, and the large radius port laid

back, is to improve the high lift flow.

You now just need to tidy it up a bit to

make sure there are no bumps and

lumps and it all flows together as well

as you get it.

Figure 6 Matching the Short Side Radius Profiles

Figure 5 Radius roughed in using 60 grit stone





Neil Collingwood





Neil Collingwood

Figure 7 Tidied Up Port

Now you need to get someone to cut your

valve seats, the top cut is 30 deg. the

second is 45 deg. 1.6mm wide, the bottom

cut is 60 deg. The valve will need a 45 deg.

seat 1.6mm wide with a 30 deg back cut.

On the photograph this is my valve seat

cutter a small Serdi also you will see at side

of the head the vacuum cleaner pipe how I

set it up to extract grinding dust out of the

port whilst I was grinding.

This is a before and after graph, it was

ground as I would think you would grind

them at home, no attempt has been made

to improve it.





Neil Collingwood





Neil Collingwood

Further ModificationsAfter looking at the flow chart, I was a bit disappointed with the flow from 250 thou onwards. So

instead of grinding some more I thought I would try a different valve, I had an odd TT1714 valve

but this needs a bit of work doing to it to get it to work properly, you need to cut the 45 deg seat a

little wider and then put a 30 deg backcut on it to bring it back to size. The picture should shows, from

left to right, standard valve refaced with a 45 deg seat, middle standard valve refaced and a back cut

and TT valve refaced and back cut.

Because the TT valve is a few thou bigger, I decided to cut a new seat, 30,45 and 60 deg as normal

but 1.3 mil wide.

After these two jobs were done it was back to the flow bench,

the flow here is now very similar to one of my full race heads

developed back in 1996, it went on to win many races and set

lap records until 2004 some of which still stand today. If the

valve throats and the ports were cleaned up I am sure this

head would flow two or three more cubic foot than it has here.





Neil Collingwood

Figure 8 before and After Images





Neil Collingwood

Figure 9 Final Port Finish

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