RK Posted July 13, 2009 Share Posted July 13, 2009 well, it might depend on the expectaions :-) on the 6-cyl engines the chamber is different from the spitfires - that's what I'm referring most :-). On the short side there is not a lot of valve shrouding anyway on the 6-cal heads. But on the long side (i.e. plug side) there is still something to do. But you might see the effect rather at high revs and high gas velocities. I consider triple cut seats and backcut valves to be standard anyway, easy to get, and more or less "bolt on", compared to real chamber and port mods. cheers, Reinald Link to comment Share on other sites More sharing options...
Mother Teresa Posted July 13, 2009 Share Posted July 13, 2009 I added my surmised summation of the entries against this thread, given that it was a thread started for DIY porting your own head. The benefits of reducing valve shrouding are indeed self evident; given the proximity of the valve to the combustion chamber wall etc. but I felt that working in the combustion chamber is potentially another step-up in accumulated knowledge, and would be wary of my unwittingly introducing more negative than positive attributes, for the additional work involved :-/ :-/? Link to comment Share on other sites More sharing options...
ncoll Posted July 13, 2009 Author Share Posted July 13, 2009 When i decided to do this DIY cylinder head, it was to enable people to do as little as possible for the highest gain. I did try some chamber mods, but ground the chamber to a similiar shape to the big valve race chamber but in the confines of a standard head gasket. It did not show any increases in flow. I therefore couldn't see the point of grinding metal out of the chamber to only have to machine it off the face. This already is a high flowing head compared to other peoples i have tested over the years. If its not too hot in my workshop tomorrow, i'll grind another port and try some more chamber mods, not as drastic as i did before. I'll put some graphs and info on of the results tomorrow night. RK: The 1300 spitfire head does benefit from chamber mods near the spark plug, but just because that does, it dosen't mean to say the 6 cylinder would do. You cannot generalise, each cylinder head is slightly different, the only way to find out what effect it has on flow is to put it on a flow bench. Many people who modify cylinder heads including professionals modify them to what they think a modified head should look like, without the slightest idea whether they have got an increase in flow or otherwise. Happy grinding Neil Link to comment Share on other sites More sharing options...
ncoll Posted July 14, 2009 Author Share Posted July 14, 2009 Good evening all' I am sorry but i haven't got much done today, iv'e checked the flow of a standard port, i have modified the seat and the short side radius to the DIY spec. I have also done a small mod to the chamber and the results are on the graph attached. neil Link to comment Share on other sites More sharing options...
ncoll Posted July 14, 2009 Author Share Posted July 14, 2009 This is a photo of the chamber which i modified, i first scribed round the inside of a head gasket, and then ground up to the scribed line. I also just slightly radius the edges of the two intrusions in the chamber, you can also see a valve that i have cut on the valve refacing tool to fit on the seat flush with roof of the chamber. This protects the valve seat when you are grinding. next episode hopefully tomorrow Neil Link to comment Share on other sites More sharing options...
Nick Jones Posted July 14, 2009 Share Posted July 14, 2009 That's very interesting. Something going on at .350 lift? That area of least gain is unfortunate as it is right where two of the better std Triumph cams peak (Vitesse/GT6 Mk2 & early PI saloon @ .329 lift and TR5/early TR6 @ .357 lift). Still demonstrates that unshrouding does have a positive effect although much less than the SSR mod. Nick Link to comment Share on other sites More sharing options...
ncoll Posted July 18, 2009 Author Share Posted July 18, 2009 I have spent some time working on this port and chamber, trying to move the flow around 350 thou. The red line is where i am at the moment. This is a little bit more chamber mods and a change of valve seat. Unfortunately i did two mods together, so i don't know which one gave the improvement shown. They weren't done like this intentionally, i ground the chamber, then went and collected my son off the school bus, gave him his tea and then went back into my workshop after emmerdale and not thinking just cut the seat. So if you look at the percentage improvements over standard for simple DIY mods, i don't think thats too bad. In fact i think there bloody good :D Neil Link to comment Share on other sites More sharing options...
ncoll Posted July 18, 2009 Author Share Posted July 18, 2009 This is a photo of the simple chamber mods where you need to grind. But, you must not grind further than your scribed line, or your head will be scrap. And yes i know there is more than one scribed line on there, but this was to try and make it stand out in the photograph. If i get time next week i'll see if i can make some templates that give the shape of the short side radius as the photographs don't make it clear how it's done and i just cannot explain it to be honest. Neil Link to comment Share on other sites More sharing options...
ncoll Posted July 20, 2009 Author Share Posted July 20, 2009 just to add to the above post, modifying the chamber by removing the ridge adjacent to the spark plug didn't increase nor decrease flow. And the same for the port and valve throat, cleaning them up didn't alter flow at all. Fitting a larger valve might be a different story. I ran the 2 litre engine on the engine analyser pro and a TH5 cam shaft to check the dynamic compression ratio. With a static compression ratio of 10.5-1 the dynamic compression ratio was 8.46-1 and with a 10-1 it was 8.03. Please note, at both these figures there was a possibility of detination. If the head flows more, this would aggrivate the situation and the opposite if it flows less. Hope this is useful information for you Bruce. neil Link to comment Share on other sites More sharing options...
Mother Teresa Posted July 21, 2009 Share Posted July 21, 2009 Hi Neil I think i'm with you so far Neil :-/ ! I wonder what drop off in efficiency the static and dynamic figures would be on a standard unmodified head in relation? . Link to comment Share on other sites More sharing options...
RK Posted December 14, 2009 Share Posted December 14, 2009 Hi Folks, I stumbled over a picture I took some years ago on a slightly modified head. At the time I took the picture it ran just a few hours. It is showing pretty clear, where you have high gas speeds. Draw your own conclusions :-) Reinald Link to comment Share on other sites More sharing options...
ncoll Posted December 14, 2009 Author Share Posted December 14, 2009 The whole idea of the DIY head, was to modify the chamber as little as possible. This was to save having large expensive amounts machined off the face. I have never found a flow increase grinding in the area you show, the reason being, that the air coming in the port has to do a u turn, and at high air speeds it is very reluctant to do this. Iv'e included a photo of one of my development race heads (38 mil inlet valve) as you can see there is very little work done in the area you have shown. A recent engine built with one of my race heads produced 251 bhp @ 6900 rpm and 219 lbft torque @5300 rpm. ncoll Link to comment Share on other sites More sharing options...
RK Posted December 15, 2009 Share Posted December 15, 2009 Hi Neil, the TR6 / GT6 heads do not suffer from valve-shrouding to the extend the Spitfire heads do, especially when you use big valves. I think you can't compare that. Good result for your race engine, congrats! What's the displacement? Reinald Link to comment Share on other sites More sharing options...
ncoll Posted December 26, 2009 Author Share Posted December 26, 2009 as promised sometime ago shortside radius shapes for DIY head. It would probably have been better to cut the head up into sections , but instead i have used some solder strips to show the shape, then put this shape on some paper and drawn round the shape. Hope this is useful neil Link to comment Share on other sites More sharing options...
ncoll Posted December 26, 2009 Author Share Posted December 26, 2009 drawings of the shortside radius shapes neil Link to comment Share on other sites More sharing options...
ncoll Posted December 26, 2009 Author Share Posted December 26, 2009 this photo has the 1, 2 ,3 which correspond to the 1,2,3 on the drawings neil Link to comment Share on other sites More sharing options...
ncoll Posted December 26, 2009 Author Share Posted December 26, 2009 this is the finished DIY plus head ports, i will put some more info on about them later neil Link to comment Share on other sites More sharing options...
ncoll Posted December 26, 2009 Author Share Posted December 26, 2009 this is a finished DIY head plus, it just needs painting to finish neil Link to comment Share on other sites More sharing options...
GT6Steve Posted December 26, 2009 Share Posted December 26, 2009 That is remarkably pretty. I've not seen such a sheen on our cast iron before. Now I'll go back and study those pictures in detail as "babes in the wilderness" have so much still to learn. Thanx Neil! Edit: Is that a TR6 head? the chamber walls look tall Link to comment Share on other sites More sharing options...
ncoll Posted December 26, 2009 Author Share Posted December 26, 2009 Hi Steve i have just been out to the workshop and the numbers on the head are 516816, i think before i had it machined it was 3.410 thick and i have had .065 thou machined of it. The chamber depth looks about .475 thou. I will check the cc's tomorrow or in my case the mililitres neil Link to comment Share on other sites More sharing options...
GT6Steve Posted December 26, 2009 Share Posted December 26, 2009 Thanx so much Neil! I'm dithering on whether to jump in to a head job just now with so much else on my plate. You make it look so easy but in my little shop that's about a three week excercise. Gotta get moving soon though...season starts in March! Link to comment Share on other sites More sharing options...
James Posted December 27, 2009 Share Posted December 27, 2009 It might help if Neil send that piece of paper to someone - we could then scan in and make a 1:1 scale drawing to print out (I'm happy to scan in a piece of paper) Link to comment Share on other sites More sharing options...
ncoll Posted December 28, 2009 Author Share Posted December 28, 2009 Hi Steve I know what you mean, it takes me a long time as well, i only get three to four hours a day on the days i have chance to do them. The actual grinding to increase the flow dosen't take too long, its making them look like a modified head that takes the time. Unless you do the polish and bullshit at the end, people think you haven't done anything. ;D ;D Hi James The actual shapes aren't that critical, i just tried to show what short side radius shapes were like as the photo's don't make it clear. But if people would find it easier to have a template then i have no objection to you scanning them or whatever, let me know what you want to do. neil Link to comment Share on other sites More sharing options...
Mother Teresa Posted December 28, 2009 Share Posted December 28, 2009 Hi Neil- top work here . Do you have any direct before/after shots of the work? Particularly the SSR area? Link to comment Share on other sites More sharing options...
ncoll Posted December 28, 2009 Author Share Posted December 28, 2009 Hi Neil- top work here . Do you have any direct before/after shots of the work? Particularly the SSR area? Hi Bruce No i haven't got any photos of the above head before i started, but if you wish i can take some photos of the standard unmodified SSR on another head ! neil Link to comment Share on other sites More sharing options...
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