Race Engine Forum UK

Hi Guy !


my first post so hello to everyone! I have 205 1.9 8v D6B engine and been doing some D.I.Y head porting so can you tell me is this of any good ?

Please comment is this of any good ? This is my first time doing this so basically I didn't remove too much metal in any part of inlet or exhaust port but concentrating on generally tidying sharp edges and casting imperfections.

I didn't modified or enlarge inlet port entry, just smoothed the short side radius on inlet and exhaust port, removed lip where the valve seat meets the port, the ridge outside the valve seat between the valve seat and combustion chamber, and started with polishing combustion chamber today.

Can you advise me? (Without the flowbench and by myself )

Thanks and sorry if I write something wrong , I'm doing my best,

Damir

Hi Damir,

well done, much better photos.

I have read your notes carefully and yes, all the work you have done so far is good.
You won't be able to do any more useful work to the short side radius on the inlet without a flowbench unfortunately, it is very sensitive to shape on that head.
Smoothing of the inlet port and ex port next - 80 grit is fine enough.

Do you have valve seat tools?

The heads shown below both made over 170bhp in full spec rally trim, on Piper cams - with standard valve sizes, on throttle bodies (Jenvey/DTA).

GC

Hi Guy !

Are you thinking on tools for cutting valve seats ? if so , no i don't have one , but i can take the head to machine shop they can do this for me i think .

What seat angle is best for this head ? Wow 170bhp is great output ! how much hp can worth this what i have made ? is it possible around 5 hp ?

Thanks !

Damir, hi

Now - My recommended valve angles are given in the captions with the photos. I suggest you print the thread.

Your work - well, it is going to develop a gain, but without putting it on my flowbench and measuring the increase in flow & with the valve too, I have no idea at all. I do my best to help but sorry to disappoint you. I bought the flowbench for that reason you understand. What you have is the right kind of work with the tools you have and that's great by me, but the bhp result will be, well, guesswork. I won't do that really. The gain will be better with a good valve seat job for sure. I wish for good results for you.

GC

Hi Guy !

Thanks very much for all your help ! and i will post some pictures when i finish with that job .

Damir

Hello Guy !

I have some new photos that i wish you to comment :

also i have finished with the head porting , just need to make three angle seats and that's done .

Thanks !!

Damir

Damir, hi

nice of you to publish your pictures. That's all looking OK!

GC

Hi Guy !

Just one more thing i wish to ask you , can you advice me wath back cut on valves should i do ? traditionaly at 30 degree or something else ?

tahnks !!

Damir

By far and away the best valve shape is a penny-on-a-stick, almost flat on the back with a modest radius where the head joins the stem, see photo. You can produce that shape (grinding carefully) from the OE valve (at right).

I found this out for myself when testing a range of valves on a head I was overhauling (originally prepped by UK's Richard Longman and Co.). The head had 'dropped a valve' when the crank key sheared. I tested several valve profiles out of curiosity but - to their credit - the Longman race valves were way better than anything I could dream up, so I bought from them. First time I had seen a true 'penny on a stick' valve work.

A good race valve for that head would be very similar (close enough to make no difference) to my dummy valve in the picture, maybe just a bit flatter on the back.

GC

hello Guy !

Great thanks ! but is there some limit of how much material can be removed from valve stem (undercut) and from that area where the head joins the stem ?
Can that kind of modifided valve be dangerous in some way to break , bend or something else ? because i have a plan to fit flat top pistons from 205 1.9 DFZ engine (same type pistons as ones in the 205 1.6 engines) in my 1.9 D6B engine ( i have a dished pistons now , see photo below ) prior to raising the CR from 9.6:1 to 11.5:1 will that modified valve stand excessive heat of higher compression ?

Damir

Damir, hi

you'll have to try and copy my valve, gauge the reduction in thickness from the OE valve. I cannot give you a drawing sorry!

Provided you leave a radius like I have and don't make the valve head any thinner than mine they won't cause any problems. The inlet valve is being cooled on every intake stroke, so they don't get anywhere as hot as the ex valves and can be much thinner sectio. Don't modify the ex valves, OK?

GC

Hello Guy !

Yes i know , didn't plan to modify exhaust valves in any way . Ok! i will try to work on the inlet valves to look similar like yours on photo .

thanks for advices !!

Damir