Porting and polishing 16v KR head

[wcrado 0]

gonna have a go at porting and polishing my 16v head. Have a ready done one to go on, so was gonna port/polish the old one myself.

The one thats going on is another DIY job done by someone else, so no idea how effective it will be. dodgy thing is, the exhaust ports have been opened up about 2 or 3mm(i think port-matched) all the way around, and to about 5mm inside and then not at all blended in or smoothed. :roll: was wondering if this head would be ok, if it needs more work or if it needs to be binned.i did hear that opening up the exhaust ports was a bad idea. the inlet ports have not been opened up at all. i discussed the work the guy did, and i think he just smoothed out the valve seats and smoothed the air passage around the bends down to the valve openings. :D

Either way i'm gonna have a go at my current head, so if anyone has carried this out themselves and seen good gains, then can you give me some step by step advice please? have a semi-rough idea what to do as far as smoothing the air passage around the bends and valve seats, but not sure how far to go with the port matching on the inlet side etc or whether to even touch the exhaust ports

cheers

[LowG 0]

Overworking the floors of the ports could hurt flow. Porting is not something you could get step by steep instruction for but some things to look for on the 16v head when light porting the chambers is to keep a nice short turn radius on the inlet and exhaust ports. I have found good results by knife edging the exhaust dividing wall.

On the inlet keep it simple with a rough finish. The chances are that if you start digging into the ports removing material you most likley will hurt flow instead of increasing it. Another thing you could do is bowl work, to smooth the transition of the bowl to the factory machine work on the port.

 

Smooth the quench area where the combustion takes place, try not to damage the seats, use some tape to cover them, do not remove material here, just smooth rough areas to avoid knock.

Also important is to get a nice transition from the quench area to where the valve seat begins, try and get them as level as possible without removing too much material.

If you feel good enough you can try deshroud the valves using your headgasket mappig over the head seeing where you need to remove material to help the valves breathe better.

Last thing I would suggest to get 3 way angle cuts on the seats.

 

Without knowing where you are improving flow the only thing you could do is light work getting rid of the obvious defects.

 

Here is a pic of a 16v head i finished a few weeks back.

 

Hope this helps.

 

Regards.

[wcrado 0]

yeah it does! cheers. when your talking about porting the inlet/ exhaust ports,i'm a bit at a miss to understand what the short turn radius means, could you explain this in i've-never-done-this-before-and-i'm-from-cornwall terms please :iamwithstupid:

[flusted 0]

http://www.sa-motorsports.com/diyport.shtm

[wcrado 0]

cheers flusted. some good stuff on there. i noticed a while back you did your own head, how did that come out? did you enlarge/gasket match the inlet/exhaust ports at all? i'm a bit dubious to do this though. a while back i left my old corrado in the allegedly capable hands of a mate. while he was carrying out other work he insisted he knew how to port/polish a head, and all he basically did was open up the inlet and exhaust ports to gasket size. i had a 4-branch, so they matched, and the inlet manifold was also grinded out to gasket size to match the head. thing is, it ran like a bag of sh:)t afterwards! we did blend in the inlet porting using wet and dry, so there were no horrible steps, but that has left me very hesitant to open up the ports at all.

 

 

by the way, did you ever get round to fitting the old porsche TB?

[bighands 0]

Am currently doing this as well, what do u use to polish them? i have found flap wheels best on a dremel type tool with flexi shaft?

[flusted 0]

i ported a throttle body not a head.you want a slighly ruff surface on the inlet to cause turbulence but polished on exhaust to prevent carbon buildup.

[corradophil 3]

I did my own too. I used an electric drill and flexi shaft. A die grinder is a far better bet, but I didn't have my compressor then.

 

I used a combination of burrs and flapwheels on mine. I'd like to pull it off and do some more work on it, but it is running perfectly so i'll probably leave it alone.

[wcrado 0]

phil, did you open up the inlet/exhaust ports at all??

what sort of work did you carry out and how much difference did it make?

[corradophil 3]

phil, did you open up the inlet/exhaust ports at all??

what sort of work did you carry out and how much difference did it make?

 

I opened them out a little and matched them to the manifolds, I also spent quite alot of time on the exhaust and inlet manifolds. It didn't make a massive difference, probably similar to the difference the KR inlet cam made. It was a bit of an experiment and a learning experience so any gains were good in my opinion.

[wcrado 0]

definitely. it all adds up. and when you do it yourself for free it's all the better! i just really don't wanna mess it up. my last 'rado ran like an airy bag of poo, (until i had to replace the engine) and only put out 130bhp. always thought the dodgy diy head job had messed the flow up.

so i take it you just gasket matched the inlet ports, then matched the inlet manifold to gasket as well? and i guess the same with exhaust?

[corradophil 3]

I opened the ports out very slightly, tidied up casting marks and anything I felt would hurt the airflow. Before starting I did a lot of research on the net, plus read a book called "How to Buildm modify & Power Tune Cylinder Heads (ISBN 1-901295-45-1) which was useful.

 

I'm quite sure I could get more power with a head flowed by a proffesional, but it would have cost a lot more.

[wcrado 0]

for sure.... i've also been keeping a keen eye on ebay and have noticed a company on there that polish/port &rebuild cylinder heads, have noticed a couple of KR heads on there, at a starting price of £299. they seem confident that their heads are good, but haven't had the money to try them! plus i'd rather give my own a good go first.

thanks for the help phil, i've got a pretty good idea which way to go with it now

1 thing thou, i keep hearing the phrase '3 way angle cuts on the seats' and that i should do this....any idea what this means?

[corradophil 3]

1 thing thou, i keep hearing the phrase '3 way angle cuts on the seats' and that i should do this....any idea what this means?

 

The back of a standard valve and ir's seat are machined at a 45 deg angle, 3 angle seats are machine at 60 deg and 30 deg. Apparently this alone can give a very large inrease in airflow, up to 25%!!

 

It would appear to be very worthwhile. I didn't do this on mine, but if I ever pull the head off again I will seriously consider it.

[wcrado 0]

this is definitely something i'm gonna try and carry out then....

do you have to buy the 3-way valves then or can you machine down the standard ones?

i got a couple of spare heads i can test this out on first, so i think is got to be worth a go.

[sciroccotune 0]

once you have seen how untidy the casting marks are on the inside of teh ports you will see how you would have to bugger about quite a bit to hurt flow more. long as you dong go silly and just smooth and match the ports you should be fine.

[corradophil 3]

do you have to buy the 3-way valves then or can you machine down the standard ones?

 

I'm not 100% sure, but I think you get the originals machined.

[wcrado 0]

i can't seem to find anything on the 'net about 3-way valves so think i'll leave it for now and just concentate on basic porting etc. mite look into it at a later stage for one of my spare heads.

just stripped the current head that was a diy port polish job by someone else.

looks like he's done a good job, fairly smooth transition down to the valve seat and i can see where he's taken material away, although i would like to go over it with wet&dry and just smooth it out a bit more, especially on the exhaust side.

exhaust ports have been port-matched but not 'feathered' in, so i'd like to get that done too. according to the standard abrasives diy guide it's not recommended to open out the exhaust ports, but as this is already done oi think i'll just try and smooth it in a bit better

 

still in two minds over whether or not to open the inlet ports up to gasket size....... everything i've read suggests that this is a crucial part of the process, though i'm just scared it's gonna run like my old one if i do

[LowG 0]

3 way angle cut valves means that the valve seat its cut in 3 angles or sometimes 5 to increase flow, you dont cut the valves. This is something very important and increases flow by quite a bit as it decreases turbulence and its something you cant get wrong.

 

Valve seat cuts its something you CANT do youself, take it to a engine shop who specialises in this sort of work.

 

Make sure you know what you are doing before you damage the head.

[wcrado 0]

i don't think i'll touch that..... i can't believe i'd find anyone down here who could carry this out anyway.

 

i'll be happy if i can gain anything considering it'll be done by myself

 

was reading about exhaust valve shrouding in the standard abrasives diy guide and it suggests slightly cutting back the combustion chamber wall if the valve is too close, it suggests there should be 3/16' of an inch clearance ideally.

the exhaust valves on the valver head has a clearance of half a mil if that!

is this something i should look at or leave well alone?

[corradophil 3]

3 way angle cut valves means that the valve seat its cut in 3 angles or sometimes 5 to increase flow, you dont cut the valves.

 

Interesting, although I did not look in to this area too much as I was doing a D.I.Y. job, the book shows both valves and seats machined.

[LowG 0]

yes you can machine the valve also, most shops wont do the valves. I have used stainless steel valves which come ready cut also with a nice cut on the throat/stem reducing the diameter meaning less obstruction. Places like TSR should be able to do that kinda job, if you are local i know a few shops in london which do valve seat jobs.

[wcrado 0]

sorry i'm in cornwall.... so unless someone grinds down valve seats with a combine harvester i'm outta luck!

 

if you know anyone down this way who's cabable of grinding down the valve seats to 3-angles i'd definitely look to getting this done

 

so do you recommend de-shrouding the valves then?

 

also, in the combustion chamber there are alot of sudden angles on the transition to the deck/ quench area

should i try and smooth these out so they curve better or leave well alone?

i know i can't help airflow here as it's in the combustion chamber, but in the picures i've looked at on the net of before and after jobs on combustion chambers, some have had these smoothed out and some have not

[bighands 0]

 

I would be interested in these, sounds like a VERY worthwhile thing to do as its in peices anyways, any idea how much its gunna set me back?

Also on the inlet being slighty rough, is this really right for this head, as the only reason its done i thought is to help mix the fuel and air, but the injector sprays it almost directly on to the valve, so up untill that point, smooth would be better?!?

[bighands 0]

if you are local i know a few shops in london which do valve seat jobs

 

I would be interested in these, sounds like a VERY worthwhile thing to do as its in peices anyways, any idea how much its gunna set me back?

Also on the inlet being slighty rough, is this really right for this head, as the only reason its done i thought is to help mix the fuel and air, but the injector sprays it almost directly on to the valve, so up untill that point, smooth would be better?!?