Every chance... I've seen many horrors over the years, so called "hi torque cams and chip conversions" from "pro" tuners that gave no extra power but lightened the owners pocket but many hundreds of pounds. Said "hi torque" cams later found to be original std items!.... fortunately not a VW.
Unless its an 8v head like this, where valve layout favours gas path on overlap. But, ours are not this layout.....sadly... Ferrari308. BG
no its an APK which is the 2l so i believe. It does seem to be rather low on power though being only 10bhp more than George's, with all the extras like throttle bodies and portng. It has got 20ft/lb's more torque though according to the mag. It does say the owner was hoping for 200bhp and was dis appointed with the achieved power.
I have to admit, i was surprised by the figure george has acheived, for what isnt a highly modded engine. i hope to get the mapping finished soon on my engine to see if all the work in it can acheive some similar figures, or if i should have a change of direction. the problem is i have a good reason not to go cross flow... a set of supervee ITB's whether they could ever fit in a mk2 remains to be seen
I "think" George's is only 8hp & about the same in torque behind. I had a look at the article earlier (professional curiosity and all that!)... great car, bit too much clutter inside for me but very well done. Looks like it has a lot of good bits, but no mention of C.R, forged pistons, RPM, cam spec or valve size. Torque is a bit low for a 2ltr... my 1800's make similar as his claim (148 v's his 149ib-ft). I recently saw a 2ltr 8v with a big valve head, sub 320 degree cam, 13:1, 45 t/b's, long primary manifold etc, make 165ib-ft, which is about right scaled up from my 1800's, both engine size's having very similar spec apart from capacity. I would say his cam is'nt as special as he thinks, the c.r is a bit low, and the mapping/cam timing not quite right. Either way, it's a top effort of a car... but dont let the power/torque put you off 8v's or crossflow's.... they can make a lot more than that example.
George's is about right given the flow of a std crossflow, and the inlet he has done. Porting the head on std valves would see it as near dam it to 160hp.
Do all tall block 2.0lt 8v's share the same valve sizes, be they counter or cross flow? By chance has anyone compiled a list of 8v tall block engine models (AGG, ABA, - - ?) Are there any standard production valves, vw or other make, which could be adapted to a "big valve" cross flow head?
The mk2 GTIs used 40mm inlet and 33mm exh valves. But the mk3 / 4s use a 39.5mm inlet and 33mm exh. The later mk3s dropping to a 7mm stem. The mk3 / 4s are all hydro tappet so use the shorter valve like the late mk2s. Basically valve choice is similar to the usual mk2 hydro tappet choices with the advantage of the 7mm stems. There are subtle differences in the heads that mean what works on one may not be ideal on the other. Port angles and swirl inducer on the inlet, and larger exhaust port on the mk3 / 4 heads as std when compared to mk2 heads.
The crossflow exhaust ports I've tested to date flow very similar to the old style head at peak, a little better at low & mid lift Dan, swirl type, whatever MK that is. But, exhaust flow is not where the power is made, and not the biggie that a lot go on about... I'll explain that in another thread soon... you'll be surprised at how little exhaust flow some off the big power engines have. A little of the extra flow that the crossflow head makes could be from the thinner 7mm stem, but I've done heads on 40.5mm/8mm stem that arnt far off 41-42mm heads on 7mm stems, so I'd say very little in the stem size. The std 40mm hydro inlet may fit on the 39.5mm crossflow seat (it should "just"), so a cheap upgrade... flow figure to come soon when I fit one.. Just looking at the flow figures now... the only modded crossflow inlet port I've done to date, still on its std size 39.5mm inlet valve, out-flows the best road heads I've done to date on their std 40mm inlet, and is also better than the best of others I've tested apart from a couple of cfm right at the top of the flow curve. The crossflow always has better mid lift flow over any of the 40mm inlet heads to date, and on it's smaller valve... looks like an interesting development path coming up... Looking at another test... the mild crossflow port is very close to a very good 42mm inlet head I tested, and that engine went on to make 200+hp
Cross Atlantic shipping; membership drive - - ? Thanks Dan & Mr H - - was aware of the later 7mmd stem valves but not the progression from 39.5 to 40.0mmd intake valves Are there any standard 7.0mmd stem VW valves, that are or can be readily adapted to say 42 - 43mmd intake and say 35 - 36mmd exhaust? Any heavier duty/better suited-to-enthusiast use collets, keepers, springs, & spring seats likewise interchangeable? Not sure at what year/eng. model, but Nth American cross flows started with a straight forward long runner intake generically similar to the 9A 16v then changed to an even longer runner model which squiggled diagonally across the front of the engine, both ending with a single butterfly TB Haven't mastered the black art of digi photos & posts, so no visual examples "yet" Wikipedia claims Nth American 2.0 liter tall block 8v models are designated ABA, AEG, AVH, AZG, BBW, BDC, BEV, and BGD - - last I looked there were plenty of heads at our local used engine parts recycler - - if they're all but unobtainable in the UK, there's sufficient club interest, the UK landed price was considered acceptable, and participating members' payment was upfront to ClubGTI administrators, I could be persuaded to bundle a heap together and send them by slow boat - - (Note to ClubGTI administrators - - earlier this year and again Dec 1st, I applied to become a paid member, stating my preference of remitting through internet bank transfer or mailed certified MO rather than dodgy alternatives - - still no response - - with neither ClubGTI phone number nor mailing address to contact, and being reluctant to pm administrators for advice and distract them from their technical denouements, maybe a member can alert the appropriate shekels minister to my approaches? - - wonder how many other prospective members may have experienced something similar?)
No way will 43mm and 36mm valves fit! you could maybe get away with 42 and 35mm. Some people seem to think that 42mm inlet valves will fit the stock seats, but i very much doubt it. maybe some people can shed some light?
40.5mm is the largest optimised size on the oem inlet valve seat. You possibly could fit a larger valve but the actual seat area would still be 40.5mm at the outer perimeter of the seat. IE no point in going larger. LCT. Plenty crossflow heads here in the UK now as the Golf mk4 and similar cars using the engines are effectively disposable due to repair costs. Modern plastic pish.
Thanks guys - - depending on oe valve seat material, o.d., and depth, have seen a number of successfully modified different make heads with valve diameters at or within a mm. of valve seat diameter, and was assuming oversize seats were necessary if seeking maximum flows Don't have a head in front of me to measure, but what are the valve centers? Remain interested in valve train parts swapping and becoming a paid member too! (edit: whoopsa - - of course, since cross and counter flow head cams are interchangeable, will check one of the latter)
Would you not have a problem with shrouding if you were to go for bigger valves? Meaning major work opening up the combustion chamber to suit and then skimming of the head to get a decent CR again?
Hi madas (was tempted to transpose a few letters there - -), yes, maximising a crossflow head's potential surely requires larger valves and seats, and I've little doubt delicate recontouring of both combustion chamber and piston crown; the latter assumes custom or oe pistons with sufficient deck height and crown thickness to tolerate the reshaping necessary to decrease squish height to approx. 0.50mm whilst enhancing both compression ratio and burn rate, without the compromises otherwise created by skimming head or block alone
You may be just the man i need to speak too, i am actually the person who mapped the car you are talking about, as far as mapping goes i have done everything i can but the engine just does not want to give anymore ( it actually made 150 on the rollers atf) unfortunatly as far as the engine build goes we dont know a great deal what was done, it has standard internals fully lightened and ballanced but there were massive ammounts of work done to the head but still uses standard valves. the cam is a massive unknown and possiably a problem area, i know its an 8v but it really does not like to rev by 6000 its nearly all over and to me this just aint right, the car continues to be a work in progress and any ideas or possible cam profiles ect would be a great deal of help
Well as discussed earlier on in the thread it could be down to several things, theres no mention of CR any where, for all anyone appears to know it could be running std compression which is not going to help at all. I cant believe the guy fitted a specially ground cam without even knowing what profile or duration etc it was, if it will not rev past 6000 rpm it seems like the cam is of a fairly low duration for what is needed. To get the power he quoted he wanted of around 200bhp, i would expect the head needs some larger valves in it and a lairy cam such as a 300 deg plus duration with solid lifters and a CR of around 12:1 which would involve forged pistons as a minimum. There is a JRE built 8v for sale at the moment with 212bhp from a counter flow 8v, running the same jenvey bodies so it can be done
i really cannot understand why bigger valves were not fitted at the time especially with the ammount of port work, solid lifters have also been fitted, the cam is a total unknown to us but it does look like it has a long duration, i will see if i can get some pics up of the headwork
