Thank you... well on the thread anyhow, hopefully the rolling road will show what the head is doing. If for some reason is does'nt work the way I want it too I'll just start again.
Ok, as it's you Dom... Right, exhaust mods... The standard exhaust throat is even worse in standard form than the inlets... just look at the horrible seat shape... Well, we can fix that with a bit of re-shaping like the inlet seat... See the ridge just below the seat work in the pic above... thats the short side turn which needs blending into the port.."VERY" carefully.. as its a very short turn and you dont want to make it shorter, just brake the edge at this stage, like so... The rest of the throat work is as per the inlets at the start of this thread. The exhaust ports are however a different ball game to the inlets. Due to the shape, you cannot use a dummy valve to help shape them as you dont want them round (though I have seen round exhaust ports on some race engines). What you need to do (at least for road use) is scribe around an exhaust gasket (make sure you have it the right way around as they're offset), and grind around the top half and halfway down the sides only, blending the sides into the lower part of the port so you end up with a shape something like this... Note in this picture without all the swarf how the port is wider at the top (remember the head is upside down to work on)... As you cant use a dummy valve you'll have to resort to measuring and a good eye... And here with the good ol guide boss gone... And here, close to the finished shape.. and this time the correct way up. The idea of shaping the port this way is because most of the flow happens in the top part of the port. This has worked fine before on other Golf heads and I've used it to good effect on A-series (Mini) heads before, so I'm doing the same here. Remember out nice new valve seats further back in the thread... well they need some more work now to open up the valve area... The pic above shows how much material is cut back. You need to grind back to "just" below the edge of the main seat (shown by the thin grey rim).."BE VERY CAREFULL"... and stop short just before where the seat insert joins the throat. The rest of the insert is cut away and blended into the throat and "carefully" smoothed into the seat at a slow speed with some emery tape. More to follow later...
Top Work mate! I've got to say you have some serious control of hand tools to be getting results that look that smooth. Pics are getting better too! like the one with the red back light! I was wondering what you were going to do with the valve seats, didn't expect you could get that stuck into them though. How far before they drop out on you? Cracking thread that i'm sure every body is getting a good understanding of head work from. There are always going to be a mix of opinion one way or the other with guys that do this for a living. But i'm taking your lead for a head of my own once you have this all drawn up. Especially as my new project had yielded another spare DX head for me to have a proctice on. Nice work Jason, Cheers Domma..........
Cheers Dom. Yeah if only the pics were as consistent !.. The trick with the finish is in the speed control. You cant get a finish like I've got with a single speed die grinder, I'll go through that when I summarise at the end. I've been lucky in being able to use a very good friends air grinder for some of the work. The valve seats and throats are where a lot of the work and gains are from. As for them falling out, I was a little cautious about this at first myself. But according to those in the know, as long as the depth is there they'll be fine. Plus, I hav'nt gone back as much as it looks, the later pics where I grind back to the seat only really takes away material from the insert that is'nt used, and again, I'm told by friends that have been doing this very sucessfully for many years that they've never had a problem. I'm glad you brought the expert bit up really Dom. Theres no secret to it, I can read a book or magazine like anyone else... ... and have been doing for nearly 25years since I started taking an interest in making cars go faster in my mid teens, so you tend to absorb a bit of info along the way. Part of the trick though is being able to apply that info into reality. None of the experts out there are born with a die grinder in their hand and knowledge of air flow, its something they've all learnt along the way, something you could all do if you really put your mind to it. Its a bit like me and some technology, I "really" cant be bothered to read the instructions for my camera, hence the ify pics at times! .. though as I have an interest in making cars go faster (as a lot of you out there do), I have enough interest to be bothered to learn how to make heads work better. I've also consulted with a couple of proven experts in their field, one of whom did all the guide and seat cutting work for me, the other who can extract over 300hp from a 2ltr 16v Vauxhall.. so if they're happy, I'm happy. I hope it inspires more to "have a go" like you Dom, or at least understand what it takes and what work goes into a modified head.
When you are prepared to "have a go yourself" you tend to take for granted what you learn over the years don't you. The interesting thing here on this forum, is the likes of you and this thread who are prepared to share the knowledge and pictorally show how to do it from their experiences. You don't get that buzz from buying sombody elses work in my book. Although it does take time and alot of money to pick up all the tools and experience along the way. I've just been trying to get a die grinder off one of the old boys in the mould shop! Find one thats into his cars and bingo, they can't do enough for you. Good point made about knowing your limitations and paying for the services that are key like the seat grinding though. P.S i still don't think you do enough work in that garage if the walls are still that white!! Laters Domma...........
Thats very true.., though we should never stop learning and trying to improve. Yeah it's good 'ere innit ! I've seen many book and mag articles over the years, but most have a distinct lack of detail, either because of poor journalism, or the consulting experts reluctance to share too many tricks, which is understandable.. so why do the article in the first place? Yeah some of the gear is'nt cheap, but can be picked up second hand in most cases... or if you know someone.. Yeah, you cant really cut the seats or skim the head at home, I'm not planning on buying a Serdi seat cutter or a surface grinder any time soon.. There's a trick to the white walls, I'm fairly carefull when I work.. and I've only just built the bench and painted the walls to do this job !
How did you go about refitting the valve guides ? I've ross sectioned a few 8v VW heads, the amount of meat left to hold the guides in after youve removed the whole boss is scary !
Really nice bit of work Mr H. I'm not sure about the wisdom of removing the whole guide boss on a road engine, but it should be fine for your competition purposes. It's also worth noting that the early solid tappet heads have smaller guide bosses than the hydraulic tappet ones. So in theory you should be able to take the hydraulic ones down to a similar size at least. I'd be interested to see some flow figures for with/without guide bosses... as it's on the outside of the curve the effect might not be so much.... could prevent a bit of 'fuel dump' round the boss though... Based on talking to someone 'in the trade', if it was a road engine that was going to do a lot of miles I'd leave some meat there, or there's a risk of the forces from the cam lobes causing movement in the guide, over time... could lead to cracking.
Thank you mr Hillclimber for this thread... i very much appreciate you taking the effort to take pictures of this and sharing your experiences ! If only the internet held more of this quality information... Very tempted to have another go at it now (with proper tools that is)
The guides were fitted by a pro. I'm not scared ! If a problem does arise from it I'll publish the details here.
Thanks Mike. This head is for a road engine, though a low milage one. The race head on my own engine (though not done by me) does'nt have bosses either, and that has survived many years of abuse without issues. Though it does'nt do the milage, it's always been subject, in theory, to a "lot" of loading from the radical cam. Interesting point on the hydro/mech guide boss. Yes flow figures would be worth compairing... if I can get a better deal than Superflow Europe have given me then flow figures may not be that far away.. I certainly did have concern about removing the boss, and maybe on any future road heads I may consider leaving some matrial there. The issue of the cam loading was one thing I considered (rightly or wrongly) to be in my favour. As it's a direct acting bucket, there should be little side movement, of which even less is transfered to the valve and subsequently the guide. The guides also have a shoulder on them so theres no chance of them falling down through, and the spring seat stops them coming up, and also reducing/virtually eliminating any potetial movement where the top of the guide fits snug into the spring seat... that my theory anyway Plus I'm told by my friends in the trade, as long as the guide length is'nt shortened there wont be a problem. Any thoughts on the above more than welcomed.
Aw thanks... Thats the spirit, though wait until I sum up at the end (not long now) regarding some equipment etc.
On the topic of removing the guide boss's i think i have found the perfect excuse!!! When i had this head refurbed by a respected old boy in my area about 12 years ago he informed me the job would take a little longer as he had to get in oversized valve guides for some of the ones on my head. Turns out about five of the new guides are over sixed from the factory by about 2mm in diameter. No great shakes other than four of the five have these cracks about 3-4mm in lenght running from the edge of the hole. May have been to much interference on the fit. Wont know till i press them out and have a look but i think i'll have them away with the grinder. Cheers Domma...........
Thats the spirit... Mind you, maybe worth checking availability of those guides again before you start.. or using another casting to make things simpler. Just come back from the machine shop, head skimmed and valves back-cut.. pics over the weekend.
i'd like a close up of the valves before they go into the head if you have one? I can wait!!!! Domma..................
