DIY porting and polishing?

[Phatz]

Evening folks,

As I am soon to start rebuilding an M20 and doing the 2.8 conversion, I have been wondering about various performance upgrades I may add.

Certainly a cam springs to mind, possibly a manifold... I'm not sure! One thing is for sure I'll be getting my ECU re-mapped!! But what of work on the actually cylinder head? I've thought of splashing out on getting the head ported and polished or even gas flowed, and then I recently came across this website: www.sa-motorsports.com/diyport.aspx and it got me thinking.... could a task like this be carried out on an m20 head?

It seems to me that this would be a long and labour intensive tasks that will likely produce hardly or no gains at all, but I'm intrigued as to whether anyone on hear has done this kind of thing before!? If anyone has any input on this, I'd be keen to hear as I'm quite interested in this as a project wile I wait for funds for other parts.

Waste of time or not???

[maxfield]

To get it done properly you need a flow bench!

You couldn't do it on your dining room table on a Sunday afternoon!

You will more than likely lose power doing it yourself.

[Phatz]

Yeah, I suspected as much... just wondered if anyone had done it before. The people on that website seem to think its possible, though they are talking about yank lumps and I'm heard the standard M20 head is pretty good anyway....Oh well.

[maxfield]

I'm not sure if anyones done it with successful gains.

But someone who knows there stuff and has a flow bench you should get power.

Especially with a cam, decent 'zorst and maybe ITB's.

[Turbo-Brown]

I reckon you could safely enough smooth out the intersection between the valve seat and the port on the inlet side on the kitchen table.

Whether it would make a real difference remains to be seen, but you'd feel like you've achieved something!

As Max says though, you could stand to lose power by doing the wrong thing

[ian332isport]

Matching the manifolds to the head, and removing any flashing/casting marks is about the limit of home head work.

Ian.

[Phatz]

And roughly how much would I be looking at to get it done professionally?

[Gunni]

from 300-1000pounds.
And quality would very likely lie in the price.

[Phatz]

Blimey, that much money would be better spent on a BTB manifold.... or a Hottuning.... but thats a whole oher thread right?

Well I may leave that aspect alone and probably focus funds and time into other areas of the project.

[scotty86d]

just smooth of casting marks at the very least. always best to find an old boy from back in the day. theres one near me, doens't charge the earth and has been porting heads for 40 years.

[Phatz]

Okay then, say I were to get someone to do the work for me. Realistically, what sort of gains can I expect from a decent job?

Cheers

[DaveD]

this guy reckons on 10-15%...interesting article

http://www.pumaracing.co.uk/gentune.htm

but there has been a thread on this before ... Templ8e30 had it done

[Phatz]

And what were his experiences with it? Is there a link to a thread about it all?

[fuzzy]

my experience of p+p heads is not on e30's but it definately made my cossie engine feel more responsive and urgent instantly. i was told in my application it would be good for +20bhp ish but whether thats true or not i dont know as ive not had it rolling roaded since. i bought a complete recon p+p head though and didnt do it myself as i was told unless you know what you are doing it could end up in disaster if you buff right through a thin part of the casting.

[Phatz]

Wow! 20bhp!!! Would definately get it done if it were to produce that kind of gain. Even if it was just a claim, you still felt a difference in your engine so it must of been worth it. What we need is someone who'se had this done to their M20 powered E30.....Anyone?

[maxfield]

Just cause it might make 20hp on fuzzy's engine (YB) doesn't mean it will make any gain on an M20.

[Phatz]

Yeah, thats why I want to hear from anyone whose had it done. I have read a lot that p+p or gas flowing does give good results on many engines, but I've also read that the M20 head is pretty good standard.

[maxfield]

I can't say I've red up on many gains from the M20 head.

He who dares, wins?

[march109]

Just cause it might make 20hp on fuzzy's engine (YB) doesn't mean it will make any gain on an M20.

If its done properly there is a gain to be had from an M20 head, they are not as efficient as you seem to think. Only heads I have every heard of that no custom work could get any extra out of were the older porsche heads.

But you need someone who knows what they are doing to do the work, IIRC there is a chap on the zone who had his b20 ported and polished and noticed a massive difference, and I would reiterate Ants comments on the following thread, for cars of the era BMW were well ahead in terms of head development, but weve come along way since then, porting and polishing (I hate that term since its hardly every done anymore!) is not a magic pill and must acompan other mods to help the engine breath efficiently.


http://www.e30zone.net/modules.php?name ... ic&t=87664

[cypriot_boy_2k7]

my mate dad done his alpina 2.7, with nice results

[bottlecapE30]

I have port and polished a few m20 heads. I do have a flow bench at my disposal so i can do it right.
I have found best results with the 731 head and 200 head, mainly because they don't flow as well as the 885 head stock. as for the 885 head gains are small and only noticable in the higher rpms. to take advantage of the port and polish you should run a port matched and bored intake manifold, BBTB,headers and cam,. I have never put one of the motors on a rolling road but you can feel a difference, smoother power delivery and pulls harder when the cam kicks in.

To do it yourself i would recommend to practice on a junk head frist, and read a lot on the topic. Metric mechanic used to have a lot of info about port and polish of the m20 head on there site. It has since vanished i'm sure a call and a chat with IIRC Mike would shead a lot of light on what needs to be done to make it right.

I know i read and studied a lot after i messed up my frist head. Note bigger is not alway better!