Not just nice its beautiful. You're work Hugo or do you have a man in your shed ? Would it flow any better if the valve sleeves were flush ? Or does the benefit not warrant the time and effort / cost ?
Design is HPR exclusive, different specs were tried and tested, but machining is outsourced... For the best flow make the valve guides flush.... but it depends on what head as you need a minimum lenght / accuracy to get good valve guiding also the purpose of the engine, rebuild interval, etc need to be taken into account... there is no need for what you want to achieve though..... doesnt mean nothing cant be done to make improvements ... like tapered guides 4 Stoke performance and tuning .....its a very good book, a must have.. to build Power
A. Graham Bell - 4-stroke Performance Tuning in Theory & Practice This is a continuation of 4 stroke performance tuning.
thanks for the books to read tomsdubs, I am downloading a copy of Graham Bells - 4 stroke performance tuning book now, if you don't mind sending PDFs to me that would be great yeah, maybe we can post a sticky with them in the main area? Admin guys, is this possible? seems like a good idea. I need more information, before I do anything else on the port venturi to valve diameter ratio, this from what I have read needs to be quite precise at around 85% of the valve ouside diameter, to keep good port velocity & flow and removing material in this critical area can be bad for performance. The article I just read spoke about radiusing the valve seat into the port, but not making it flat to ensure this venturi is retained. Thanks for the pictures and words of advice HPR, your work looks fantastic.
85 % sound very conservative to me, as this means 27.2 mm on 32 mm valve ...thats about std size.... 88- 90%... this in function for what purpose the engine is used... The valve seat should seal on the outer edge of the valve, this way your still able to get a nice radius and opening the troath
little read about seat and throat blending, and the throat valve ratio too. he is fitting bigger valves but the principles are the same. http://www.pistonheads.com/gAssing/topic.asp?h=0&t=1430327&mid=0&nmt=Valve+to+throat+ratio.+Is+a+bigger+valve+always+better%3F I measured up the valve in my head, they are: Inlet - 31.9mm Inlet seat diameter - 28.5mm Exhaust - 26.8mm Exhaust seat diameter - 21.7mm The exhaust side seems a very low ratio compared with the inlet.. thoughts on the reasoning for this? I am presuming it is so the seats act to relieve the exhaust gas temperatures? What would you do about porting the exhaust side throat? open it up into more of a chamber, then widen it out a down the port. I downloaded the 4 Stroke Performance manual and read the section on the cylinder head, it shows the port ratio to be about 90% too. Pic below is taken from the book. Also one from the porting section.
I wanted to see how big the ports are now, so with the exhaust valve, I put it in the inlet port inplace of the inlet valve and it went into then port about 10mm, but when I tried it from the injector side it wouldn't even go down the runner. I measured the diameter of the runner, and the narrowest part, just infront of the valve guide is only 25mm wide, 3mm narrower than the valve seat diameter this to me suggests the need for porting it out, as it must be loosing velocity further down the port runner as the opening gets wider, it doesn't make sense not to? Bernoulli Theorem says that if the opening is narrower velocity/flow increases and pressure drops, and the opposite when it widens. Isn't the idea of increasing port velocity more desirable in terms of flow? I am thinking of making it the same size as the exhaust valve all the way down, I can use it as a guide to get a nice round port I was thinking, I would only be taking material from the port roof and sides as the image shows above. What do you think guys?
Velocity will increase in order to maintain the mass flow rate . There is an optimum velocity to achieve id imagine to suspend fuel/aid mixing. I think the main issue with the vw 16v heads is valve/port angle which there isn't much you can do about. CFD helps but a flow bench would probably be better.
I was looking at the head again and think that it already has had 3 angle valve seats cut on it.. Can you see from the pic this lower seat cut? I lapped in the valve to show where it makes contact with the seat and you can clearly see a lower cut into the valve seat. I cant see it as clearly on the top cut into the combustion chamber though. I will try to get some better pictures tonight anyway. When I bought the head with a set of Schrick cams a few years ago I was told this head was a Stage 1 Bill Blydenstien jobbie, but never had any proof that it was. Given peoples views that this is the first area to modify for gains it would align to this claim? I lent my Valve Spring Compressor to by mate, otherwise I would have stripped my other head down to check for differences.. can you tell from this picture?
lovely job on the ports ive seen a fair few top quality heads and they have all been finished smooth and sharp with varied detail and angles around valve seat area . the best one I seen was a vw motorsport head . finished just like hpr ,s one in the picture
Certainly sounds interesting that it might be already. Out of interest though, who did you buy the head from? I had a similar conversation about what you describe, Blydenstien head with Schrick cams.
I went and borrowed my mates 16v 051 cylinder head as I wanted to compare the one he has. Well worth the trip as I have now found out some good bits about my head! The seats I have look to have the 3 angle cut and it appears that the throat has also been widened too. The picture I put up the other day about putting the exhaust valve into the intake ports, well I tried it in the standard head and they would only go as deep as the valve seat, where as on mine they go in atleast 15mm. I took a video, will try and upload it in a little. After this I thought I would CC my head, so with a 5ml syringe we got the following results. Cylinder 1 - 48ml Cylinder 2 - 47.5ml Cylinder 3 - 48.2ml Cylinder 4 - 48ml Not too far out at all which I was happy about, can anyone confirm normal un-skimmed head CC? is it 49ml? I would still like to unshroud the valves slightly, just radiusing the tiny lip where the valve seat has been machined & pressed, I was wondering before I do this these lips aren't here to help tumble into the combustion chamber are they? to me they only look like they are an unsightly ridge disturbing flow past the valve. Surely this is a sensible mod, to further improve flow off the seat, especially at low valve lift levels. I also thought it was worth CC'ing the intake port runners, as I have been grinding a little I wanted to see if they all held a similar volume, as if one was a lot bigger I would more than likely have problems as they aren't balanced to each other. With the valves still greased up in from CC'ing the combustion chambers, I filled the ports in order, left runner, then right runner, then all the way to the top of the inlet manifold flange with a bigger 50ml syringe. Not quite as accurate as with a 5ml syringe but I just wanted to get a rough idea of what they were like. I filled the each runner up to the devider just about to where it over-spilled into the other side, then filled the other side to the same point. Once that was done, I filled it all the way to the manifold flange again just until it looked like it would spill. I had already levelled the head out on the bench, and did all of the runners before i moved the head again. The results were scarily close actually. All of the intake runners are very similar. Intake Port 1. Left Runner - 29ml Right Runner - 28ml Total Vol - 114ml Intake Port 2. Left Runner - 29ml Right Runner - 29ml Total Vol - 115ml Intake Port 3. Left Runner - 29ml Right Runner - 28ml Total Vol - 114ml Intake Port 4. Left Runner - 27.5ml Right Runner - 28ml Total Vol - 114.5ml Has anybody else done this? or know what is standard? I must have removed a few ml when grinding and with the throat mods being done this will have added addition cc's. What do you reckon guys, clean up the work I have done now and leave it or carry on with the porting mods. I will be getting a set of DTH Jenveys from Badger 5 shortly so all improvement in the head will definitely be utilised.
Yeah I couldnt find my one in between the 5ml and 50ml one i had, will get another one and give it another go but they are quite similar. This is the video i took yesterday showing the 3 angle valve seats and slightly enlarged throats on my head, when you compare the normal valve seat to the 3 angle / radius'd cut seat you can see why everybody says it flows alot better. they look completely different. [video=youtube;3Hs-DH0duUE]https://www.youtube.com/watch?v=3Hs-DH0duUE[/video] Thanks Toyotec - will give it a whirl a little later.
I think it came from Mike H from the Scirocco Register, he didnt build it, he got the head with a car i think he said? Cams I have are Schrick 268's.
