Roger H Posted June 5, 2007 Report Share Posted June 5, 2007 (edited) Hi all I read with interest Iain Rollo's thread on his new Racetorations machine and noticed the following... (Quote) "BTW the head made 90CFM at full lift on the flow bench". It got me thinking..... How does this, or any other figure for that matter, compare to the stock 150 bhp head design? Is there a magic figure that one hopes to achieve when embarking on this process? Are there down-sides to simply achieving the highest possible volume flow? While I have had some work done on the head, it has so far been a seat-of-the-pants approach and is yet to be "benched" so I would appreciate any guidance. ....then I may be able to have a half-intelligent conversation with the fellow who will do the work when the time comes! Cheers Rog Edited June 5, 2007 by Roger H Quote Link to post Share on other sites
marvmul Posted June 5, 2007 Report Share Posted June 5, 2007 90 CFM : at least, the vacuum used on the flowbench should be mentioned : not all benches are working with the same vacuum. "The higher flow, the higher the bph " doesn't apply. Perhaps, it's much like bph figures on rolling roads : interesting when back to back comparisons can be made on one and the same flowbench. In the 'Speed Pro Series' "How to build, modify and powertune cylinderheads" is a very interesting book, written by Peter Burgess, who has a lot of experience with MG and Triumph cylinderheads. It's about cylinderheads, but also about carburettors, exhaust systems, manifolds etc... Quote Link to post Share on other sites
marvmul Posted June 5, 2007 Report Share Posted June 5, 2007 PS : it's the modifications on the combustion chamber that are most labour intensive = expensive. Experience of specialists has proved that the widest possible inlet tract is not the best : the entrance of the inlet tract can be made as wide as 43mm, but wider than 41mm does more harm than good (according to people who I believe). Stage 3 heads have slimmer valve stems : with special valveguides, exhaust valvestems with the same diameter as the standard inlets can be used : about 7.9mm instead of 9.4mm. The valve guide bosses are removed, the guides are mostly not shortened. The lower part of the inlet guide is tapered. Some specialists relocate the valveguides : 1 or 1.5mm towards the middle of the cylinder, and inlet and exhaust valve guide are also 1mm wider apart; and the valve stems are slimmer : 7mm is about the minimum. The law of diminishing returns does apply! Quote Link to post Share on other sites
Roger H Posted June 6, 2007 Author Report Share Posted June 6, 2007 (edited) Thanks Marvmul, there's a bit to digest there..... 90 CFM : at least, the vacuum used on the flowbench should be mentioned : not all benches are working with the same vacuum. I guess this means that comparisons can only really be made when the figures are compared to the original, unmodified head, tested on the same bench prior to the work being done. Do you have any figures, say in percentage terms, that one should be aiming for when the modified head is tested? Thanks Rog Edited June 6, 2007 by Roger H Quote Link to post Share on other sites
Bald Rick Posted June 6, 2007 Report Share Posted June 6, 2007 Rog Here's an article by Chris Witor on the 219016 head which gives some info on gas flow in cylinder heads and goes part way to explaining the significance: 219016 Head Hope this helps Tony Quote Link to post Share on other sites
Roger H Posted June 7, 2007 Author Report Share Posted June 7, 2007 (edited) Tony - thanks for your input. I have seen it before and my head was ported, but not flowed, along similar lines in the early 90's - and therein lies my problem!! The problem is that I have no baseline reference as to how good it is at the moment. If I have it 'benched' , the figures I get (apart from balancing each chamber) don't tell me much without knowing what is the flow of a stock head. I suppose I have answered my own question to some extent as the only way to properly do this is to compare a stock head to mine on the same test bed. The trouble is there are not many unmodified heads lying around here waiting to be tested. Also I don't know what figures to be aiming at. I was hoping that someone would have guidelines as to what figures are stock, (say) Stage 2 and Stage 3 modified. With these figures, they could be translated into % improvements which would enable me to then see how good my modified head is and whether it is worth doing any more work on it. still left wondering... Rog Edited June 7, 2007 by Roger H Quote Link to post Share on other sites
ncoll Posted June 14, 2007 Report Share Posted June 14, 2007 I am assuming that the 90 cfm cylinder head mentioned in this thread is one that i have modified. If this is the case, then it would be tested at 10" test pressure. If anyone is interested, today i will check the flow of a standard head and then put the results on this site along with the figures of a modified head. Neil Collingwood Quote Link to post Share on other sites
scotty Posted June 14, 2007 Report Share Posted June 14, 2007 Sorry to go off on a tangent but anyone know if any of the suppliers will be able to sell uprated heads at Malvern ? What type would they need in exchange - I have a couple in the garage . Quote Link to post Share on other sites
Roger H Posted June 14, 2007 Author Report Share Posted June 14, 2007 I am assuming that the 90 cfm cylinder head mentioned in this thread is one that i have modified. If this is the case, then it would be tested at 10" test pressure. If anyone is interested, today i will check the flow of a standard head and then put the results on this site along with the figures of a modified head. Neil Collingwood Yes, please Neil - that's exactly what I'm after . Cheers Roger Quote Link to post Share on other sites
ncoll Posted June 14, 2007 Report Share Posted June 14, 2007 dont have technical know how to put graph on here, so sent you a message Roger. Neil collingwood Quote Link to post Share on other sites
ncoll Posted June 14, 2007 Report Share Posted June 14, 2007 Roger after a bit of head scratching her is the chart i hope The three lines on the chart were all done on the same flowbench a superflow 110 @ 10" test pressure. Neil Quote Link to post Share on other sites
Iain Rollo Posted June 15, 2007 Report Share Posted June 15, 2007 I am assuming that the 90 cfm cylinder head mentioned in this thread is one that i have modified. If this is the case, then it would be tested at 10" test pressure. If anyone is interested, today i will check the flow of a standard head and then put the results on this site along with the figures of a modified head. Neil Collingwood Neil. It was good to meet you today and thanks for the great job you did on my head. The cars really flying now after the session on the rollers and I've booked a day at Cadwell for Tuesday so will be able to see what it can really do. Iain. Quote Link to post Share on other sites
Don Elliott Posted June 15, 2007 Report Share Posted June 15, 2007 Neil - Is your graph showing the flow as a total for all six cylinders or only for one ? Do you check if all six have the same flow rate as a function of valve opening ? Do you also do 4 cylinder TR engines ? Quote Link to post Share on other sites
Roger H Posted June 16, 2007 Author Report Share Posted June 16, 2007 That is spectacular Neil - thankyou, from me personally and also on behalf of the other Forum members who will benefit from this. Thanks also to Iain, as I have a feeling that Neil's membership and contribution here may have been prompted by him. Cheers Guys! Roger Quote Link to post Share on other sites
Bald Rick Posted June 16, 2007 Report Share Posted June 16, 2007 Neil I would like to add my thanks for a very usefull and informative bit of information. Excellent! Tony Quote Link to post Share on other sites
ncoll Posted June 17, 2007 Report Share Posted June 17, 2007 Neil - Is your graph showing the flow as a total for all six cylinders or only for one ? Do you check if all six have the same flow rate as a function of valve opening ? Do you also do 4 cylinder TR engines ? The graph shows flow of just one inlet port. Each port is checked until i get the flow i am looking for. Yes i do do 4 cylinder triumphs, i will put a flow chart on the forum tomorrow if i can find one. While downloading the latest version of port flow analyser 3.5 it took information i had on the version 3.0, i know i should have backed them up but i didn't, so i will look on some floppies to see if i have the information on one of them. Neil Collingwood Quote Link to post Share on other sites
ncoll Posted June 18, 2007 Report Share Posted June 18, 2007 This is a chart of a TR3, it is the cylinder head that Phil Britton used on his 2.4 litre engine that he used in the mid 1990's before he totalled the car at Mallory Park. The race head on the TR6 chart is the head that Joe Henderson has been using for the past two years. Neil Collingwood Quote Link to post Share on other sites
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