Winston I... that looks incredible! Do I spy a dizzy blank? Don't even get me started on the cam cover. Amazing.

May as well share my personal failed ambition: always wanted to make a HK/AAU to replace my Golf's aging GG engine. I bought a HK head off Yeti about 2 years ago, and got as far as installing double valve springs, and... yeah I suck.

PS - pretty sure I have another set of the KR springs kicking around (bought 16), if any of you schlepphebel freaks want them gratis, drop me a PM

I thoughts NA tuning rule of thumb was 100hp/1000cc should be achievable

I know thats considered a rule of thumb for Pintos. Not sure about other engines. Depends so much on design. I guess anything is possible with enough work, but I think the pinto figure is for a mildly tuned engine rather than fully reworked head

I reckon a 1272cc Polo with 11:1 compression and single 36mm inlet 29mm outlet valves (and 11.9mm lift!) and 296 cam needs to be at 7600rpm to achieve 74Kw (100bhp).

At 5800rpm it only gets 57kW.

If you want to play along

http://dairally.net/daihard/chas/MiscCalcu...rs/DaiPipes.htm

I'm cutting up the spare head in the hope that i have enough room to move the ports up. Will get some nice cut throughs etc while I'm at it. Unless anyone already has any good photos like this?

I'm trying to reduce the angle of the port and make it as close to a downdraught head as possible. I've seen and helped out (slightly ) with this sort of work done on ford 105e engines, so I'm hoping to repeat it on a polo.

wont really matter as the valve angle will deflect the flow, better off aiming directly at the back of the valve and let the flute do the rest, filling downwards across a valve works better on turbo'd engines, also, massive charge area (silly big port area with small in and out) is useless on an aspirated engine, its aimed at turbo's as flow is irelevent with forced induction, aspirated you want everything working with the shape of the port/back of the valve.. the ford pre crossflow engines you speak of drop the valves almost completly virtically downwards.. for maximum power and most consistant recharge of a cylinder the port MUST point in the direction the valve moves... unless your trying to sacrifice hp for torque, in wich case the [port entry will want to be bigger than its exit (compresing in port tract)

I was also thinking about doing this. Following on from what the old ford works boys did with the cross-flow engine, they managed 100bhp/1000cc.

They filled in the old ports and bored through at 135* (Standards being 90*). I think they managed to braze in brass tubular manifolds, that were then resin matched to the valve throats, awesome bit of engineering.

Problem is you start to create hot spots, as some of the coolant and oil galleries may be effected, this can lead to failure from over heating and/or cracking, as the head has different levels of expansion and contraction.

You'd have to do something about making sure it was all nice and cool, lubricated.

alot of the crossflow and precrossflow boys are running larger sumps and oil coolers for that exact reason. the hot spots will be exhaust side, you can counter this by decompressing the exhaust gasses, the valve is usually the bottleneck in the exhaust, thus this heats up, the inlet port is obviously too big or the exit diameter of the exhaust port is too big in comparersen to the valve dia... but these sort of engines are close to drag spec, valves close to touching, rizla between valve seats and so on, your gonna get hot spots lol... I've seen bolt on cooler extentions used in exhausts (basicly a giant spacer thats water filled, bolted to the head with the exhaust bolted to it) theres ways round everything, but the engineering becomes pointless when replacing the engine is less work.

but ye, its still useless pointing a valve downwards in an aspirated engine, the valve flute and combustion chamber profile should all be central at full open valve, meaning there should be an equal distance from the top of the chamberl to the valve as the cyl wall to the valve, all central, so it fills downwards diagnally, as a straight down drop creates a turbulent charge.. turbulent air obviously takes power to disrupt.. thus you loose bhp and gain a little torque. forced induction your just moving the valve the hell out of the way so the charge can be pushed into the cyl without the valve getting in the way, aspirated engines need the flow to be massaged into every nook of the barrel.

I was also thinking of bolting/welding on a coolant jacket, and maybe tapping into the existing coolant reserviors, but obviously another head would have to be sacrificed to find them.

Its certainly got me thinking!

machine from one section as a solid, machine out around the port's (leave a good size wall) then match the outlet outer diameter, a flat peice seals it off, obviously leave some material in the jacket for seating and bolting in the cover (recessed lugs) trace out an exhaust gasget and ill do a tech drawing in 3d of it if you like, seal's and all. as for getting water to it, just nick the heater matrix piping, or t off ether end of the rad.. it may need a balancing pipe routed to the header tank and it would all have to sit way below the level of the lowest pipe on the header tank to prevent airlocks. you could even run it inline with a heater matrix but relocate to beside the rad, thus it becomes a second cooler..

Edited 7 February, 201313 yr by MiNoR cOnFuSiOn

I have access to all the neccessary software, but thanks anyway.

Wouldn't be hard to do tbh, as you say, just machine a shadow flat onto the head, that the block can seal against.

Regarding tapping into the head galleries, i meant that not for a feed/return system, but to help cool the water that actually makes it into the head. But i suppose it would be important to make sure the coolant is all flowing in one direction.

You'got me thinking about doing this again, on my mechanical head.

wont really matter as the valve angle will deflect the flow, better off aiming directly at the back of the valve and let the flute do the rest, filling downwards across a valve works better on turbo'd engines, also, massive charge area (silly big port area with small in and out) is useless on an aspirated engine, its aimed at turbo's as flow is irelevent with forced induction, aspirated you want everything working with the shape of the port/back of the valve.. the ford pre crossflow engines you speak of drop the valves almost completly virtically downwards.. for maximum power and most consistant recharge of a cylinder the port MUST point in the direction the valve moves... unless your trying to sacrifice hp for torque, in wich case the [port entry will want to be bigger than its exit (compresing in port tract)

Please next time could you split up your words so its easier to read.

I'm not following what your trying to say here?

Who said id be going for a silly port area, and for the record port diameters are crucial for forced induction both inlet and exhaust. Contary to what alot of crap is banded about, turbos arnt immune to the laws of physics, you need sensible sized ports for a decent spool up, massive ports = horrendous lag.

Mixture quality is also just as important on forced induction as it is to any engine. Forget how much air can you cram in and how much fuel you can inject, getting power is about how you can extract as much energy out of the fuel/air mixture that your engine has got. Theres no point getting loads of fuel and air in if it doesnt mix well.

I'm not moving the valves on the polo head, and the ford heads I've seen didnt move them either. I'm moving the port, which enables a better distribution of flow over the valve face. I've found this crude drawing on wiki instead of me doing it.

By allowing the 'dead' or lower side of the port to flow better you can get a better mixture and it provides space for more mixture to be crammed in.

Your last sentence... A port MUST point in the direction a valve moves? So a polo port must go vertical? Right through the valve train then?

And ports tend to have a venturi right before the back of the valve around 0.88 times the valve o.d. This speeds up flow right before the valve to help with combustion.

Edited 7 February, 201313 yr by shaun_89

I have access to all the neccessary software, but thanks anyway.

Wouldn't be hard to do tbh, as you say, just machine a shadow flat onto the head, that the block can seal against.

Regarding tapping into the head galleries, i meant that not for a feed/return system, but to help cool the water that actually makes it into the head. But i suppose it would be important to make sure the coolant is all flowing in one direction.

You'got me thinking about doing this again, on my mechanical head.

Id like to run an external coolant feed by the exhaust ports like what they used to run on this

Doubt its practical and or feasible, but we can only imagine

Need to get cutting up!

my bad, I'm thinking your changing the valve angle, not the port tract angle.. as for turbo's, the smallest diameter opening is always going to bottleneck your flow, but forcing air through any shape wont affect it, so can be any shape, its area as you say is more important, turbo's will deal with corners alot easier than an engine trying to suck through a hole. flow bench shows this (change atmospheric pressure inside flow chamber to simulate boost conditions) an engine sucking mixture needs as unrestrictive a port as possible, as the only thing getting air in is vac. if you have massive voids between bottlenecks it will mean lopts of dead air, with a turbo this becomes a stored compressed charge, you want as much compression in as many areas as possible as the turbo wont need to recompress mixture thats already bursting to get back in the cyl, its heavily discussed by alot of the bigger names, and theres controversy ether way, i tend to find that when using forced induction, flowing is irelevent and mearly increasing the diameter of the bottlenecks in the inlet tract will make the same power as flowing a port with the same dimentions, where as on an aspirated engine flowing and removal of bottlenecks both produce power.

my bad, I'm thinking your changing the valve angle, not the port tract angle.. as for turbo's, the smallest diameter opening is always going to bottleneck your flow, but forcing air through any shape wont affect it, so can be any shape, its area as you say is more important, turbo's will deal with corners alot easier than an engine trying to suck through a hole. flow bench shows this (change atmospheric pressure inside flow chamber to simulate boost conditions) an engine sucking mixture needs as unrestrictive a port as possible, as the only thing getting air in is vac. if you have massive voids between bottlenecks it will mean lopts of dead air, with a turbo this becomes a stored compressed charge, you want as much compression in as many areas as possible as the turbo wont need to recompress mixture thats already bursting to get back in the cyl, its heavily discussed by alot of the bigger names, and theres controversy ether way, i tend to find that when using forced induction, flowing is irelevent and mearly increasing the diameter of the bottlenecks in the inlet tract will make the same power as flowing a port with the same dimentions, where as on an aspirated engine flowing and removal of bottlenecks both produce power.

All of the principles applied to n/a engine apply to fi engines thereabouts with a few exceptions. Physics is physics you cant change that.

I know what your saying, the problem is on fi engines people just up the boost to get more power. They cant be bothered to do the same things an n/a would need to make great power. You want to look at race series where boost restrictions are enforced, thats where some good development work takes place.

I'm not saying it does nothing, but the gains to be had are minimal when compaird to a na engine... where the same work will equal bigger gains. the above picture is pretty self explanitory, I've moved 2 stroke reed windows from barrel to case befor just to get a better flow direction. if your using a turbo on the above tho it will be more work than the gains would be worth. but ye, I'm probably waffeling off topic anyway so will shut up now lol

How are you going to about welding?

I've just had an idea...

If you went for the brass tubes as ports (Holes bored at the correct angle, then brass tubes inserted and brazed in)

You could then use the original inlet manifold ports as coolant jackets? Basically bolt on a water jacket, use this to aid cooling of the cylinder head?

tbh you could get away with the std stud position and a *&^%load of devcon... ali welding/filling that much in is asking for something to warp.. the stock stud position could be used. the alternative is to cut a step into the existing gasget seat and add an extra p-eice of ali you then machine to shape/requirements.. you can use the stock stud holes and weld on new flanges.. little involved, but alot less work/zero welding to the cyl head really.. ill tryu dig out some pics of similar stuff I've done... be amazed what a little devcon, a mill and a big ol lump of ali can be turned into...

may be worth poking about other manufactors to see if theres a head thats close enough a fit.. theres loads of diff 16 valve engines about these days so I'm sure theres something usable out there somwhere that would work with a little machining. I've heard of people nocking up an adapter plate, cut a motorbike head back and bolt up to car engines in the past, same with zetec or redtop heads on the wrong engines.. shame i dont ask more questions racing/at shows...

Can any mechanical gurus shine some light on this please......

http://www.clubpolo.co.uk/forum/index.php?...p;#entry2487234

I like to revive this topic as I’m really interested in gaining the maximum power from a mech headed GT engine on Twin 40’s.

Especially with the head and valve works and cam choices (my knowledge is lacking in this area)

And what was this head.

http://www.clubpolo.co.uk/forum/index.php?...p;#entry1801171

You all are very knowledgeable and i'm really impressed

Does anyone have cam detail sheets for mechincal cams for 1.3 engine.

reading through this it look like a newman 284 cams with some head work

I have a HK head with 34/28.1 widening the inlet to 36.2

Edited 10 April, 201313 yr by residentmelon

Can someone help me with cam selection or point me in a good direction with a mechanical head / GT bottom end

And do mechanical camshafts fit hydraulic head as the parts number as very simalar.

Just need to know a little more so I can order the correct one and not confuse the guy at the other end of the phone.

Edited 31 May, 201313 yr by residentmelon

There hydro and mechanical headed cams are not interchangeable I'm afraid.

What else would you like to know?

thought so is it the dizzy end thats different.

I've chatted with newman and catcams

newman suggested 272 but was too sure about mech heads. he thought they only had hydraulic heads

catcams suggested 269

have you got the pn for your cam that you used.

Its not just the fact that the dizzy drive is different, all the dimensions are too!

Newman should be able to supply you a data sheet.

I try again I think I need to speak with someone different at newman.

anyone used this company for camshafts etc

dbilas dynamic