hey i am think of tryin to port and polish a head and wanted to on if any one has info on port and polish heads
thanks aidan

See Head Porting. There's some brief comments, but lots of photos

The first tip would be don't polish the intakes. It might look nice, but it does not actually improve the gross flow at all. In fact, when dealing with a liquid fuel (finely suspended drops) believe it or not a rough surface finish actually creates just the right effect to discourage fuel from dropping out of the flow and clinging to the port walls. Avoiding this improves power, and also means that every drop (or at least most of it) of fuel is actually burned, so you don't have ro run stupidly rich to use up all the air in teh cylinder, so economy is better, and bfsc (the amount of hp per pound of fuel burned) is much higher. That might not initially worry a lot of people, but the other benefit, besides fuel costs, is that less 'extra' fuel that is needed means there's less of it ending up on the bore walls washing away the microscopic oil film, and contaminating the oil. Result? Your engine will last a lot longer. All from doing 'less' work and not polishing the ports.

Theoretically, a polished exhaust port will be less likely to pick up as much carbon deposits (unlike the liquid intake situation, where the liquid would cling to the wall but eventually flow in, the rougher exhaust theoretically gives more texture for the solid to bite onto. . that's theory, and it also 'theoretically' would reflect a little bit of the heat too, but in practice I'm unaware of ANYONE who has ever legitimately measured a tangible difference.

So essentially it is one area to save time/effort and win big.

I'll also say this - with 95% of heads out there, especially older 2 valve heads, 75% or more of the potential gains will be in ONE area - the valve seat and the bowl/valve guide area. that small 1/3 of the entire port is responsible for all the flow restriction on any head. It makes good sense - the other end of the port is a straight open passage, air has no trouble flowing efficiently through there, but to make it turn a sharp corner, past the vqlve and valve guide, then through a valve/seat that is only open for a short time (and spends most of it's time whilst open at modest lift ranges) That's where the 'magic' is and you need to know what seat shapes and short turn radius' work with a given combo. I'd argue that relatively speaking, shaping the valve guide boss area is fairly straightforward compared to that.

If it sounds like I'm trying to discourage you, frankly I am, as it's very easy to drop velocity and end up with a worse result. If you are prepared to do trial and error testing, you'll get there, everynne will, but the first head you do won't be anything close to ideal. About the only exception to this rule is holden red motor 9 port heads - someone could probably take a dump in their intake ports and improve the flow - they really are that bad.

If you really want to do it, I'd seriously suggest building a flowbench. It can be done with some vacuum cleaner fan motors and some plywood/glue/sealant) - it's about the only way you'll be able to test progress and get a good result. it doesn't matter if it is 100% accurate (the flowbench) as long is it is consistent. If it reads the same amount for the same flow, and more for more flow, the numbers aren't as important as the fact you can definitely track improvements. if you want to get really into it, you can find a scrap head and port one port/valve, and if you go too far, re-build the port with body filler fibreglass/metalmend and re-try till you find the general shape you need, then make small stencils up and duplicate them all on the 'real' head.

Apart from that - personal preference here - only trim the valve guide/guide boss as much as possible WITHOUT shortening the guide itself. you can definitely pick up flow by shortening the guide in a lot of heads (not massive improvements, but measureable) but the catch is that shorter guides lead to shorter valve/seat life as they can move around a fraction more, and hammer out the seats sooner, which means some or all of that work has to be repeated (depending on what it might take to re-claim the seat.

Good old jmac. Very good read there.
Well, actually all your posts are good reads for me.

For a self port job you can do small things and pick up a lot. I did my own with some supervision after each stage; First where the valve seat is pressed into the head the seat sticks out into the port, smooth that. Around the valve guide has an abrupt transition and you can smooth that, on the exhaust I semi polished it, on both ports I smoothed out the rough casting marks. After that I gasket matched the manifold...................the car picked up 6 mph at our local track. Nothing radical and I had a good valve job done at the same time. Worth doing but I bet I put 40 hrs in it, as I went slow because you can't put metal back :)

Tom

I dunno if I suggested this, but you could consider speaking to a head porter, telling them it's a not a million dollar budget job, maybe they'd be willing to do the work on one intake and exhaust, and let you copy them for the rest, then they'd do the valve/seat/throat cuts as a final thing. Probably save aboout 3-4 hours of labour charges (a basic pocket port probably takes around 30 minutes per port on these sort of heads for a very experienced person)

Quote:

Gold!

JMAC..............having someone skilled do one set and then matching those is an excellent idea. I was lucky in that I have a tuner friend who walks me through this stuff.

Tom

ill just cut the seats and face the valve myselt at work, i do a bit of head reco's at work just we dont port head so i was goin 2 try it out
thanks for all ur help

So how dose the home made flow bench work, would,nt you need some way to measurer the change in flow.....?