Thank god for angle grinders

[Pumaracing]

It's a pain building engines when you don't have your own mill and lathe currently, (long story which I won't go into). There's always something you need to make which would be a five minute job with the right equipment and hours of grief if you don't. One of today's tasks was to make a port sizing tool from an old valve which is how I make sure all the ports in a head are to a specific size. Only works with round ports of course but most are.

For those starting out in porting their own heads if you decide on your target port size, turn down the head of an old valve to a bit under that size to allow for final polishing, keep checking the port as you open it up to see where the valve head will and won't fit through, eventually you'll get the whole port nice and round and to the right size without choke points which will hurt your flow and final power.

Anyhoo, I made a couple of sizing tools on someone else's lathe a while back but I hate pestering him for a loan of it and needed another sized valve turning down today for the exhaust ports I'm working on which I forgot to make last time. Angle grinder to the rescue though. Spin the valve up in a drill and angle grinder against the head of it until it's down to the right size. The poor man's lathe I suppose.

What size should your ports be though? Now there's a question although I have covered it previously.

[Pumaracing]

Talking about flapwheels, the price of those seems to have gone mental since I last bought some. I usually finish round ports off with little 30mm x 10mm 80 grit flapwheels on a 3mm shank and to gain extra reach I made up a couple of 4" mandrel extensions to fit the porting gear. Those have a 6mm shank on one end for the collet and a 3mm hole drilled in the other for the flapwheel. Loctite to hold it in and once that's set you're good to go and can reach all the way down most ports.

I used to buy those flapwheels for about a quid each from Cromwell Tools down south but since the house move I can't find any knocking about. Not sure if I'd used them all up or they went missing. Anyway a couple of weeks ago I tried to source some online to finish a head off and they're a ridiculous £30 for a box of ten now, even on Ebay. Still, emery roll wrapped round a stick does a similar job and at least I have plenty of that left over.

Edit.

PS. Yes I know you can get the 6mm shank ones cheap enough on Ebay. I guess there just isn't much demand for the 3mm shank ones.

Edited by Pumaracing on Friday 20th February 22:50

[Pumaracing]

PeterBurgess said:

Carbide burrs can be awkward to source, we use Master Abrasives and Merlin Tools and resort to having them made to our shapes sometimes, usually 25-50 burrs at a time ...

Peter

Struth. Just the other day when I was looking for my favourite carbide burr to work on a head it occurred to me I got that burr with my Foredom porting equipment 25 years ago, it's done every head and manifold I've ever worked on, it still appears to be as sharp as the day I got it and it's never chipped a tooth. It's a 3/8" diameter oval on a 4" long 6mm shank with a general cut tooth pattern. Not quite as fast as an open tooth burr on aluminium or a cross cut tooth pattern on iron but quick enough for me on either. Long enough to reach down most ports but not so long you lose control.

Occasionally I resort to one of the other 20 or so burrs the guy threw in for free to give me a good range to work with. One on a 6" shank if I'm trying to work all the down an inlet manifold and blend into the port, smaller diameter ones for tight radii, but otherwise it's all been done with that one apparently everlasting carbide since I started out.

[Pumaracing]

stevieturbo said:

I meant these, they're great

Hmmm. Don't think they'd quite fit down a cylinder head port though.

[Pumaracing]

We used the angle grinder to regap the new piston rings on a mate's race engine last year. At 12 thou gap they were a bit tight for my liking in an 83.5mm bore in something revving to beyond 8000. It was a bit heart in mouth but with my mate holding the angle grinder hard down on the bench and me holding each ring, sliding the gap over the grinding disc and then just dabbing one side carefully against the disc we knocked 4 thou off each ring and it all worked very nicely. I'm not sure I'm brave enough to do that on a daily basis though. I had visions of the grinder grabbing a ring, ripping it out of my hand and hurling it in bits across the workshop.

Those 1mm thick metal cutting discs are really good though. The sides are smooth enough to give you real control over how much stock you remove. I wouldn't have tried it with one of those old 3mm cutting discs with the spongy sides.

[Pumaracing]

I freely confess I've been far too hacksaw oriented for my entire life until recently. If a bolt needed shortening then I'd automatically use a hacksaw. I'd never even think to use the angle grinder. Not having a really good carbide parting off tool for the lathe when a piece of stock needed parting off then out with the hacksaw again. I've finally realised how much faster and easier almost any metal chopping activity is with a 1mm disc in the angle grinder. I've used it more in the last few months than for the previous 25 years.

One useful tool any race engine builder can make is a centre punch for marking piston crowns down the valve guides so you see where the valve centre is to check that valve cutouts are in the right place or if they'll clear big valves. Fit a rod and piston to the block, bring it to TDC, pop the head on with an old gasket and a couple of bolts and then you can fit the punch down the valve guides and make a little centre pop on the piston crown for the inlet and exhaust valves. Those points are the centering datums for the machinist if you need to send the pistons for the valve cutouts to be enlarged or deepened.

Make the punch from an old inlet valve with the head cut off and then machine a point on the end. I made a 7mm stem one for the engine I helped build last year and as usual grabbed a hacksaw without thinking. Valve stems are bloody tough though and I had to try a couple of blades before finding one sharp enough to cut through. Recently I had to make a 6mm punch for the current engine I'm working on. Now I'm finally savvy enough to get the angle grinder out instead. 2 seconds and zip, valve head off and in the bin. If you spin the valve stem in a drill you can even make the pointed end with the angle grinder although in my case I was able to do that on a machine.