Porting and polishing 16v KR head

[LowG 0]

Ok if you are local Burton Power in Ilford Essex will do them for you, they work around 120 pounds for the 16v head.

I think you should still leave the rough port becasue the air will start to mix before it meets the fuel and once it does it will mix it better, maybe it will have less time to do so but I think there should be some effect. It has been shown that mirror polishing will lose flow, you want to do this on the exhaust ports as it will help reduce carbon buildup on the ports.

 

wrcrado maybe you could take a pic of the combustion chamber, you should only smooth it over, taking out obvious bumps which are not part of the design and which will cause hot spots and detonation.

Have you used your headgasket to check out the area around the chamber? Be aware that most gaskets bores are larger than you actual bore size.

 

regards

[wcrado 0]

wrcrado maybe you could take a pic of the combustion chamber, you should only smooth it over, taking out obvious bumps which are not part of the design and which will cause hot spots and detonation.

Have you used your headgasket to check out the area around the chamber? Be aware that most gaskets bores are larger than you actual bore size.

no haven't got to that yet! have just finished the exhaust ports, smoothed them out and polished them up.

was going to start the combustion chamber next. the plan was that i was gonna open the combustion area up just a few mil to help the valves breath better. wasn't gonna gasket match it, i thought that would be too extreme! but the valves are very close to the side walls, so i was gonna machine them back a bit....unless this is a bad idea???

 

 

still after advice on which way to go with the inlets....

 

like i said, i let my mate touch my last rado with the dremel and he opened up the inlets to gasket and port matched the manifold, but afterwards the car would never start on the button like before, it ran like a spluttery bag of poo and only made 130bhp!!!!

is it common practice to open up the inlets to gasket on a valver?

cos my plan at the moment is to grind them out to match the gasket, and then gradually feather them in to about 1.5 inches inside the port. obviously do the inlet manifold to match as well.

the short side radius has already been smoothed nicely, so don't wanna ruin the work thats already been done.

just a bit scared, don't wanna screw up another head....!

 

anyway, heres the exhaust ports....

[jezzaG60 0]

I can get any machine work your head needs sorted for you. Can also give you some pointers on where to concentrate on with your porting work. I've got a 16v head that i'm working on at the moment (when i get time) Probably best if you were to pop down some time and i can show you whats what. Can't give all my secrets away online :D

[sublime 0]

What LowG has said matches the experiences I've made so far.

 

Generally, the way a port has to look like depends on the camshafts you're going to choose. The inlet port diameter behaves antiproportional to the air speed. Opening up the diameter means reducing the air speed at the same rpm. The optimal airspeed is reached at a higher rev. (Keep in mind, after reaching the optimal airspeed, burning efficiency (or the equivalent, torque) will start to drop and bhp rising will start to slow down. When torque is dropping faster than the rev, bhp starts to drop). While going for a mild street race camshaft (speaking of arround max. 268° and max. 0.45in of valvelift) it's good advice to avoid opening up the port too wide. I whould concentrate on optimising bottlenecks, as it is with the valveseats (get the 3-angle vlave seat cut, although you should get noticeable benefits with a 2-angle cutting job, without the last 5° cut) and the area arround the valveguides. The original vw head layout isn't that bad, at least the inlet. If you plan on using camshafts above approx. 276° and 0,49in valvelift (which I whould not recommend while using the original KE-Motronic/Jetronic), you can consider widen up the inlets. Those camshafts open longer and earlier and therefore need a greater air speed to be able to use those gas dynamic effects generated by the mass inertia of the airflow. Yes, on the first view, it looks like opening up the ports and reducing the airspeed is the wrong thing to do. But as the port opening results in an optimal airspeed appearing on a higher rev and the sharp camshaft pushing up the ideal airspeed even higher ('cause it needs those gas dynamic effects), the max. torque lies on a rev a lot higher. And as bhp is a product of rev and torque, this is the reason why sharp camshafts and wide inlets often lead to high bhp numbers.

So where's the drawback? It the rev range below the ideal airspeed. It's way wider than the rev range on mildly modified engines. That's why those race engines need to be operated permanently in high revs. Low rev torque drops a lot on those engines (at least with OEM injection/ignition and intake manifold). The air is to slow and in addition to that, the intake valves close to late. So gas-fuel mixture is lost that whould otherwise be burned. It's a little complicate to explain without any pictures. For those who do have some experiences with engines I whould like to recommend the book "Four Stroke Performance Tuning" by A. Graham Bell. I've read a lot of books in the last years, but this is definitly the most detailed one and reads like Mr. Bell really knows what he's talking about.

 

A short comment on a personal experience I've made: if you do not modify the outlet and use a very mild intake camshaft, even with modified intake ports (at least on the 1.8l 16V) you can go on without changing the OEM outlet camshaft. It doesn't effect the max. bhp a lot, just about 1-2hp and it slightly lowers your bottom rev torque up to mid range rev.

 

Just my personal erperience.

 

Greetz

Chris

[wcrado 0]

While going for a mild street race camshaft (speaking of arround max. 268° and max. 0.45in of valvelift) it's good advice to avoid opening up the port too wide.

i'm currently using the kr exhaust cam mod, so where would this fit in? i was planning to open the inlets up to gasket size and then matching the inlet manifold, as it's only about 2mm(roughly) larger, so i would not have to remove to much material. would this be advisable, or would you personally leave the inlets as they are?

i'm also possibly gonna want to change back to the standard kr inlet cam in the future, as at the moment the exhaust cam is just too aggressive. it doesn't pick up til almost 5k revs! will wait to see what affect the head has first though

[flusted 0]

that exhaust cam cant be fitted properly if it doesnt come in till 5k mine comes in at 2k,

Reckon when the head was taken off,it wasnt timed properly when it was refitted hence the bad running

[wcrado 0]

i did want to bring this up with you actually, cos it's been getting on my nerves and i know you know this mod inside out. from 5k onwards it does shift, but there is just nothing until then. it is very slow to pick up under 2k, i mean dangerously slow, then from 2k to 5k it feels flat, got to really red-line it to get anywhere.

 

i'm not convinced the cams are in time actually, but i'll wait til i put the new head on until i check it, i'm not driving it at the moment anyway.

but the cams could be out of time with each other, or slightly out with the bottom end. i know how to check that, but i've no idea where the two exhaust cams should line up, because obviously you can't use the original timing marks.

 

with this mod, how many teeth do you have to count back from the original timing mark to get the cams to line up right?

[flusted 0]

Are you using the modified chainwheel which corrects the timing allowing you to use the standard timing marks?

Sounds like your a tooth out of cam to cam timing

 

Just to rub it in,mine flys from 2k then goes mental at 3.5k and again at 5k!

[wcrado 0]

i bought the car with the mod already done, and the guy said he never modified the chainwheel, he just counted back the correct number of teeth, and then marked a new timing mark.

 

but the question is, did he count back the correct number of teeth at all?

it could be that both the cams are out of time with the bottom end, but i have check that the cams are in time with each other before i check that.

 

so if you can help me out and tell me how many teeth back from the original mark it should be then i can eliminate this.

 

would the exhaust cam mod sit at the same timing point as the original kr inlet cam? cos if it would(and i guess it should) i can grab a spare kr cam i've got, and then turn the engine over til the two timing marks match up(the actual exhaust cam one, and the new timing mark old boy marked himself) and hold the kr cam up to the engine in-line with the actual exhaust cam timing mark, and see if it is a the same angle as the new exhaust inlet cam.

 

would this work, or does the exhaust cam mod have to be timed slightly differently to the orginal kr cam?

 

either way if you know how many teeth back it should be from the original timing mark this would help me out.

never know, it could be the dreaded keyway sheared again!

 

my old rado, which was standard bar a 4-branch and system, had way more pull at low revs than this one, although this one revs its tits off! but like i said, up to 5k revs, it feels like i'm running about 85-90bhp. once it gets to 5k it pulls all the way to the redline.

 

 

btw a 2.0 16v corrado has just cleared at combellacks vehicle recyclers in cornwall if your still after a 2.0 bottom end! they'll take it out of the car and i'm pretty sure they deliver as well

[flusted 0]

Nah got a 2l now! You cant use the mod without the chainwheel as it will be 6 degrees out which is bad.

I have a chainwheel here which you just press on and all the original marks will line up and you will have silky smooth idle and huge power increase!

If you dont want to go that route then this is what it should look like without the modded chainwheel at tdc

[jezzaG60 0]

You certainly need the adjustable cam gears... and ideally a vernier pulley as well if you have had the head skimmed at all.

 

It is possible to get the original gear machined with a new key slot in the correct position. I seem to remember 6 teeth and 4 degrees for some reason.

 

If you buy a set of the adjustable gears they come as a pair so i'm pretty sure you could just use one of them and sell the other on to someone else interested in doing the mod...... I'll tell you when i give the set i've got sat here a go!

 

No reason why this mod shouldn't give a good power gain without being too cammy.... the profile of the exhaust cam is still pretty mild when compared to some of the piper and kent offerings!

[wcrado 0]

I have a chainwheel here which you just press on and all the original marks will line up and you will have silky smooth idle and huge power increase!

If you dont want to go that route then this is what it should look like without the modded chainwheel at tdc

 

so even if i time it correctly, as in your photo, it will still be 6 degrees out? thats pretty rubbish.

and the chainwheel you have will just press on easy and i'll be able to time it perfectly?

 

cool. is it up for grabs? i'll defo have it

[flusted 0]

yep always be 6 degrees out,the chainwheel i have here is on a cam already modded but both are up for grabs

[wcrado 0]

its already on a cam? cos i could send you my chopped down exhaust cam and you could send me the whole lot if thats easier than me farting around changing the chainwheels over etc. or just fit the chainwheel to mine and send it back! just dubious to change the chainwheel myself, reckon i'll end up being 12 degrees out!

 

either way i'm interested, even if i have to buy the whole thing and sell mine on.

 

pm me or something and we'll talk about it

 

cheers

[flusted 0]

yeah thats cool,il dig it out and go from there.

I want to get it sorted for ya so you can see the benifits it has when done properly!

[wcrado 0]

sweet cheers!

[wcrado 0]

ok so i've finished the head! here are some photo's, please speak up if something doesn't look right!

[davidwort 0]

ok so i've finished the head! here are some photo's, please speak up if something doesn't look right!

 

OK, so I watched Topgear on the web at lunchtime so my eyes are a bit sore but it's all a bit blurry, try fixing the focus on the camera at something less reflective at the same distance first.

[flusted 0]

Mine has knife edged dividers right up to the entrance of the port? will try and post pic 2moro

[wcrado 0]

i did think about knife-edging the dividing walls, but couldn't be bothered in the end! i was just sticking to what i thought i could do.

 

davidwort! i may not know how to flow a head but i can take a photo! the camera is crap, it has trouble focusing on anything thats relatively close.

 

flusted--- any news on the exhaust cam chainwheel?

 

cheers

[flusted 0]

Got the whole cam for £75 if interested? Stealth used to charge £75 plus vat just for the chainwheel and they doont make them anymore!

Only downside is the chainwheel has the pointy teeth but it will fit and work fine.

Let me know

[Bobby 0]

i've done the twin cam mod without using the adjusted chainwheel just marked the cam using a guide i was emailed, have to admit it easy to get a tooth out but when its done right makes the car pull alot better at low revs with no loss on top end.

[wcrado 0]

flusted p.m sent.

 

bobby- power at low revs is just what i'm after! the cam doesn't kick in until about 4.5 - 5k rpm. when it does though you can actually feel it open up and pull harder all of a sudden, kinda like power valves opening up on a bike, (or a weak shot of N20!!!) but until then it's just sluggish.

[flusted 0]

Dont worry,you will have low down power again soon

[sublime 0]

Sorry for having kept you waiting....

 

As modifing an exhaust camshaft to an intake camshafts involves adjusting the timing, I guess something went wrong. The exhaust camshaft is far from beeing aggressive. Even a Schrick 260° is somehow mild, it provides widespread torque an peakpower increases smoothly around 2500-3000rpm. But talking about 16V, using a 1.8l PL it makes a big different if you use KR ignition controller oder PL ignition controller. If you use KR modell, you loose knock controll, but you gain a far more ballanced power output. Using the 2.0l 9A Modell, a modified Chip does the job.

 

To answer your question, mildly open the intake ports at the bottle neck, but driving a 1.8l it isn't necessary while using an exhaust camshaft as intake. I whould advise you reconsider replacing the mod. intake camshaft by a mild sportscam or checking again if the modifing job has been done propperly.

 

Oh, damn, i just realised something. Of course I always spoke of the 1.8 KR cylinderhead, whose intake ports are somehow quite well contrukted. While having a narrow 2.0l cylinderhead, widen up the ports isn't that wrong. But I whould advise going for a 1.8 KR head, I saves a lot of work.

 

Greetz

Chris