They normally do... have a look on the Kent or Piper website, I think even Catcams show it. Most radical cams have around 4-5mm lift at tdc, some show 6mm but only if the cam is radical with a lot of advance... but never much over the above. In a chamberd head it's not normally an issue. They found more power when slotting rather than just conventional cut outs... possibly due to disturbed combustion, but the difference was only a couple of hp... but a gain is a gain. In effect, you'll need to follow a Ford Crossflow (Kent engine) style piston... you'll need around 30cc in the piston with around 100 thou deep cut out's. You'll have to juggle the numbers subject to the cam, c.r required, valve diameter. A dummey build will be essential to check clearances regardless of how close you can get the machining.
Couple of things from my dabble with rallycross heron 1588's in the middle 90's. I tried a few cams and ended with GS6. Lots of lift on overlap, but a great power band. On std pistons you had flippin massive cutouts. I still have a set under the bench. They were heavy, but they worked, providing you used the best oil. I then moved to mahle forged pistons, which came with an unfinished crown. You had to machine the bowl and the cutouts. Easier to keep as much compression as you can get. Another thing, don't just worry about the depth of the cutout, but the side clearance. Just as important. It always took me flippin ages to get them right, but that might just be me...
This is my sort of favorite thread. Mr H has already answered your last questions chopperoli and to be fair knows far more about the detail than I do, but I'm enthusiastic . However, have you been following the "F3 Spiess engine in Ireland" thread in this section (my favorite for a while, oh... and the crossflow one)? Spiess seem to have decided that the piston weight issue was best resolved by ignoring squish and piston pockets and simply using a flat top piston run down the bore by enough to not need any cut outs. To my understanding squish is important to get the mixture centralised to control flame spread etc. but it would seem, and you must assume Spiess know what they are doing, that given the choice it's more important to reduce rotating mass. Obviously F3 engines are very specialised but certain criteria relate to all engines and I would think this issue would broadly apply to any race engine The problem with this option, aside from the squish, would seem to be that the cylinder walls at the top of the bore will be exposed to flame constantly and that could lead to a number of problems. Spiess seem to have gone to lengths to get cooling around the top of the bore by adding addinition cooling channels (it could be a ringed block but it appears to be part of the cooling to me). My reason for the interest is I would like to use the Spiess top end I have on a 1400/1600 engine. Ideally it would be a 1600 but that would be for tarmac rallying but the long term cooling of the cylinder as mentioned above is a worry (and I don't have access to the money/equipment/R&D that Spiess have to develop that). The 1400 option is for sprinting/hillclimbing (all to do with classes) but I'm not sure how to get the capacity. I would need to keep the 1600 gti bore std to get enough area to fit the valves etc in but what crank/block/rods? Needs to be a block that was used in a MK1 golf for the regs but my thinking is, given the flow on a spiess head and a very short stroke, that it would make a wicked 1400cc class racer and should sing top end. Anyway I'm still developing my current 8v engine but the plan is to go crossflow at some point which is when I will have a spare Spiess induction system to mate up with the head and valve gear, I will then have a choice of engines and classes . In summary, for race engines, maybe running the pistons down the bore is the way to go, anyone any experience of this? Good to have a look at both options but I don't see big revs and heavy pistons being a match made in heaven and with modern ECU's any timing/pinking issues should be easy to dial out.
Always better to take your time Jon... it's easier to remove material than put it back. Got any pics Jon?... a central bowl with "bunnies ear's" cut outs no doubt? Got some pics of mine somewhere... I'll have a hunt to give an example.
Tony's made a valid point here... a lot of Ford Kent Crossflow's are done this way, but tend to need a fair bit of ignition advance to help with the lack of squish to get the burn going, but seem ok that way, though can lack low end torque... but the above can also be engine spec driven. There are two ways to look at the weight issue tho... If you start with a piston with a thick enough crown and then machine the required cut out's & a nice deep bowl, do you then end up with a lighter piston (which you technically do), or a piston with unnecessary weight stuck on top?.... chicken or egg... The F3 engines would have been built with inertia in mind due to the restrictions, which obviously arnt there for most of us running open induction engines. It's that old word again.... compromise!
Mr H, thanks for the figures. So would you agree that the factory EG engine probably only had such a large squish band (3.3mm + gasket) for reasons such as: no valve pockets req'd, full 360 squish band, lighter piston (i.e. shorter piston = less bowl req'd for nominal C/R)? John, I like the sound of these forged Mahle semi-blanks you once used, do you have any other information on them? Long shot I know, since it must've been a while back. I found these pictures of some (they look like cast) Mahle pistons with a taller compression height and valve pockets, apparently 10.5:1 in a 79.5 bore for a 308 cam with 12.3mm lift: Found some good images of Crossflow/Kent pistons with valve pockets on Page 3 of this: http://rcma.free.fr/escort/ford_kent_crossflow.pdf Tony, I personally don't like the idea of the Speiss F3 flat piston & head combo. Are you thinking of replicating it or would you stay with a conventional piston with combustion bowl? From what you say about cylinder cooling, it sounds like they ran into problems. Here's a link to an interesting article on Heron heads & combustion from a Moto Morini bike point of view. It seems to mention that exhaust valves and ports on the smaller side of things can be a good thing for torque as the velocity is higher. http://www.northleicestermotorcycles.com/rut/page2.htm Interestingly, in the 4-stroke performance tuning book (by Graham Bell- who seems to despise the Heron design) he mentions that on flat heads, inlet port diameters should be on the smaller side to gain velocity as well. Oh and I found some nice valve pockets (5th picture in slideshow) http://www.racemagazine.com.au/index.php?option=com_content&task=view&id=24&Itemid=1
I'm in two minds on the flat top or dished psiton options. My gut instinct is that 'back in the day' when ignition and fuel were controlled by springs, bob weights and jets it was far more difficult to 'iron out' ignition and fuelling glitches caused by design compromises. Therefore difficult to work around the extemes of ignition and fueling created buy the less than perfect flame sperad/heat range etc. I'm wondering when Jason last saw a kent engine being set up was it by using springs, bob weights and jets? Obviously once set to work at a certain point it is difficult to make them jump from one setting to another and back again, if you see what I mean. With electronics you can jump from one setting to another and back again as the revs increase, not ideal but it lets you disguise problems much better. If you look at modern race engines pistons and cylinder head designs they seem to just make them suit what valves, angles, pistons, injectors they squeeze in at the desitred angle. They don't seem to worry about squish, swirl etc. to much. Road engines seem to be a little more interested in this but I assume that is because emmisions/fuel consumption/longevity are primary objectives. With a race or high performance engines this isn't so important. The Spiess engine I refered to above is a late version running electronic fule injection, I wonder what the early ones had for pistons? Super vee engines I have seen all ran chambered pistons with cut outs but the were on clockwork injection and ignition! All that said I think a flat top piston is favorite given an ECU controlled fuel and ignition system. The only unknown is the heat issues I outlines above. On a hill climb and Sprint car not a problem, they don't run for long enough. Rally or race engines may be more of an issue. Only one way to tell I suppose!! Jason, did the Kent engines you mentioned above have any issues with overheating?
Bought these recently, Spiess Inlet manifold Group A exhaust manifold Then found my spare Judd 8v Supervee head and this and this Thought it would be a good place to start,to build a sqishy /non sqishy 1600 flyer, have got a couple or standard 1600 Gti engines that could be stripped for other bits ???
Looks like you've got the makings of a very nice engine. You staying 1600 bottom end? And cam/valvetrain-wise? If you haven't got the tappets, Arrow precision sell the shim under bucket type ones in 35 or 37
Very interesting to see the sump Ray. Rather than divert this thread, more here: http://www.clubgti.com/FORUM/showthread.php?t=229100
Agree 100%, I reall like the idea of a screaming 1600. I've got a late Spiess head (much the same). The injection system is currently on my 2.0ltr race engine but I'm intending going cross flow on that and have a Rowland manifold ready to take some Jenvey throttle bodies so they will be available again. The sump is pretty but alloy sump scare me so would probably go steel (although I do like items with a history . I used to use an Autotech/Automech? sump but the windage tray stress fracture resulting in a lot of debris in the sump. I cut the one way flaps out and welded them in to a std VW 2E sump, fabricated a front plate to stop the oil riding up the front of the sump under braking and then used a VW windage tray. Inexpensive and effective. I would go dry sump as I like the idea of it but to be honest I just to hillclimbs and sprint and it's overkill. I use an Ashley manifold with the port flanes/down pipes machined out and then welded back up (they end up with holes every where so you have to plate them back up). Takes a lot of time but needs to be done. Word of warning to others - NEVER use an Ashley manifold standard. Always port match them as they are miles off. Probably loose you 5bhp over std. Not saying thay are bad, I would buy another for the price, but like most cheaper parts (and many expensive ones) you need to spend time getting them just right if you are looking for power!! I also modified the collector to take a 2.5" system by cutting the std 2" pipe off and welding a 2.5" one on. On the std Ashley you need to use an adaptor to use their 2.25" system . So you go from the headers down to 2" then back up to 2.25", doesn't sound like a recipe for BHP to me . In addition the 2" pipe extends in to the collector by about 1", well it did on mine?? Like I said for the money I don't mind doing a bit of work but I have the facilities and kit to do that but some people do, or aren't aware that additional work needs to be done to make them work properly. The Group A one should be right out of the box, so to speak, plus the primarypipe and secondary lengths will be pretty close to ideal (was talking about this on another thread). Out of interest what is the measurement from the port to the end of the 4/1 collector and the length from there to the first silencer? BTW I'm in the market for a 1600 GTI bottom end for my 1600 engine project if you have any spare. Still not sure if I should go squishy or non squishy although I'm leaning towards non squishy and a very short stroke for revs, revs, revs
Managed to get this VWMS dry sump from ''sunny california'' no longer available ? would be nice to fit on the 1600 screamer and sit it even lower in the car
Need to dig some old hardware out so I can provide the requested info, to contribute something to this thread. Enjoying where its going. Have an EG race build on the bench now. Been there 5 years.....
Indeed, stumbled upon them really. Their background appears to be the BMW Alpina M10 motors, so for use with with mechanical injection http://www.alpinabmw2002.com/2012/04/schrick-bmw-m10-slide-throttle.html Seen them used in a few Mk1s with Supervee spec motors
Hi guys, currently restoring my series 1 GTI and want to keep the original engine because of matching numbers but want to increase its power. I have acquired a US spec 86.4mm stroke crankshaft that has the EG spec 46mm big ends, was thinking of mating this to some 81mm wosner Pistons to get 1781cc. Would this work?
It will yes with a little work. Off the shelf pistons won't be any good as they'll either have the crown height to suit a std 1781 which has 144mm long rods so will be too shy of the block deck or pop out the top with the long crank and the 136mm 1600 rods. Also if it's for high power/c.r use don't use wossner pistons...Ok ish for road use/moderate performance. The block needs a very close inspection too as the suffer badly from cracking between the head bolt holes and water jacket.
Holy thread revival! Which is ythe better distributor for a race EG? (which has the most advance swing?) mk1 EG one: 0237 023 001 (067 905 205) OR mk1 DX one: 0 237 024 016 (026 905 206) Got one of each here and the engine is nearly complete, ready to drop into the hole..... Searched and haven't found the info I need. I'm guessing the EG one would be best Ta Jon
