Diy Porting

[mmt 15]

Hi guys,

 

I´m about to do some work on my mi16 head.

 

Any closeup pics and pointers very welcome.

 

Thanks

[welshpug 1,675]

personally I'd leave it alone! can be good for over 200 bhp stock, you need to concentrate on the bottom end and cam choice

[unariciflocos 49 1 Cars]

From what I've read all over, the standard Mi16 head is good for well into 250 bhp, please don't ruin it. Find something else to tinker with .

[DrSarty 99 1 Cars]

As above. It's not worth wasting your time, effort and maybe money; the head doesn't need it.

[mmt 15]

Ok guys....I surrender...I´ll leave it alone!

 

Then what Cams do I need? Race/track only on 45 webers.

Edited September 30, 2009 by mmt

[Saveit 0]

Pipercams 285 in my opinion. I believe 300, which is the next step, is too much without higher compression if you want some low down power and driveability also. Otherwise compression should be raised a bit. Pulling out of the corners on a race tracks is far more important than pure top end power.

[paulsupervts84 0]

No dont go there bud, leave it to the pros, i get a set of cams and throttle bodies myself and you get big bhp gains

[Baz 421]

Do a search for a flow graph, the Mi16 head flows very well as it is.

 

No dont go there bud, leave it to the pros, i get a set of cams and throttle bodies myself and you get big bhp gains

 

No you don't, not necessarily.

 

 

Somebody wants quick Driver status don't they...

[paulsupervts84 0]

Do a search for a flow graph, the Mi16 head flows very well as it is.

 

 

 

No you don't, not necessarily.

 

 

Somebody wants quick Driver status don't they...

 

I'm just learnig about these engines as i just got my first 205 and putting a mi16 engine in, but most engines you get them ported for better flow, if there flow good a standard less money i have to pay for mods

Edited November 18, 2009 by paulsupervts84

[Lan 24 1 Cars]

but most engines you get them ported for better flow

 

...... yes we know

 

I'm just learnig about these engines as i just got my first 205 and putting a mi16 engine in

 

If you're actually learning then you would be letting other people who have the knowledge answer the question, and as they have done so your opinion on this matter is well useless

[B1ack_Mi16 67]

Removing the ridge between the valve seat and port can't be the worst thing to do though....

 

Some early heads actually had this done at the factory, while laters don't have any machining work in this area.

[James_m 0]

Im sure the heads cant be that optimal, i mean lets face it they hardly make spectacular power/torque figures as standard. If you actually know how to make improvements is another matter however... But if you are prepared to read up extensively on the subject then why not!

Edited November 19, 2009 by James_m

[kyepan 291]

think some of the replies on this are a tad harsh.. I personally think a bit well thought out home brew work should not be sniffed at.

 

Check out Pumaracing.co.uk for one slant on how best to modify the Mi head.

 

There is also a fairly epic thread on here covering the topic of whether big valves actually help make the mi head better

 

Also you might want to read david vizards how to tune your A series engine as that explains in detail how to tune the Aseries head... some of the approaches may be transferable.

[woodsy 0]

I recently fitted my mi head with uprated inlet cam and whilst at it i got the dremel out and removed the excessive ridge

where the inlet gasket goes up against the head and the manifold too so it makes it bit more smoother.I didnt want to get carried away too much and go right inside the ports.

[richsmells 2]

Mi Big valves topic: http://forum.205gtidrivers.com/index.php?showtopic=31290

[richsmells 2]

Mi Big valves topic: http://forum.205gtidrivers.com/index.php?showtopic=31290

 

DB was a bit condescending

[Sandy 191]

I'd forgotten how bad it could be!

 

Since it's been dragged up and "I couldn;t let it lie Vic", as far as I know, no big valve Puma Racing engine has yet exceeded the 281bhp/204lbft (2.2, on engine dyno) I've had on standard valves, or even go near it for that matter! I know for a fact that i'm still at least 30bhp short of what can be done on those valve sizes.

[Galifrey 1]

DB was a bit condescending

 

 

Sorry I don't believe you, he was never like that

[kyepan 291]

I'd forgotten how bad it could be!

 

Since it's been dragged up and "I couldn;t let it lie Vic", as far as I know, no big valve Puma Racing engine has yet exceeded the 281bhp/204lbft (2.2, on engine dyno) I've had on standard valves, or even go near it for that matter! I know for a fact that i'm still at least 30bhp short of what can be done on those valve sizes.

sandy is probably a good chap to listen to about this, as he has built a fair few high performance engines.

 

sandy - was only suggesting the thread because it may give a good indication of how "opinion" is divided. It's good that you're getting to the facts about big valves.

 

Without giving too much away, are there any simple home brew improvements that can be made to the head... including 3 angle seats?

 

Cheers

J

[brumster 135 1 Cars]

My engine is also on standard valve sizes and specced to 250bhp, so I do not doubt what's being said above. Most people I've spoken to whose opinion I hold valid have said the same thing, no real need to go big valves for big numbers. Granted, Longman have worked my head, and there are new 3-angle valves in there, but they are not *bigger*. A chap with a same-spec engine as me had his dyno'd at 257bhp, so clearly it can be done (and ours is far from the "mutts nuts" in terms of what can be done).

[Sandy 191]

Without giving too much away, are there any simple home brew improvements that can be made to the head... including 3 angle seats?

 

I don't tend to use Mi16 or S16 heads, so I'm quite happy to tell you what I know! 3 angle seats nicely blended on the inlet side, inlet port untouched and open up the exhaust side a bit and it'll be pretty much as good as you're ever likely to get it. I've seen around 230bhp and impressive mid range with that on different engines from 1.9-2.1litre. The inlet ported and big valve ones I've run up have all been peaky and struggled through mid range bar one, a 2.0 built by a friend of mine, which had 37mm inlets and very violent cam profiles, it made about 275bhp (rolling road, so estimated) and had decent mid range and responsiveness. But, he really knows what he's doing and we agree that it could have done that on standard valves!

[kyepan 291]

I don't tend to use Mi16 or S16 heads, so I'm quite happy to tell you what I know! 3 angle seats nicely blended on the inlet side, inlet port untouched and open up the exhaust side a bit and it'll be pretty much as good as you're ever likely to get it. I've seen around 230bhp and impressive mid range with that on different engines from 1.9-2.1litre. The inlet ported and big valve ones I've run up have all been peaky and struggled through mid range bar one, a 2.0 built by a friend of mine, which had 37mm inlets and very violent cam profiles, it made about 275bhp (rolling road, so estimated) and had decent mid range and responsiveness. But, he really knows what he's doing and we agree that it could have done that on standard valves!

super...

 

I guess that begs the question... when doing xu builds.. what heads do you use?

 

he he

[DrSarty 99 1 Cars]

super...

 

I guess that begs the question... when doing xu builds.. what heads do you use?

 

he he

 

I suspect XU10J4R, RS & perhaps XU7JP4 heads too (if the latter are different?).

 

This topic was about DIY porting/flowing though really rather than big valves.

 

What PeterT explained and showed to me was that the porting in cast Mi/S16 head is larger than the valve seats anyway, so unless you fit larger seats (which naturally would accommodate larger valves), then you're not going to get beyond the 250bhp that it approximately flows for straight out of the factory.

 

Sandy & BlackMi have mentioned a couple of minor improvements, but they wouldn't supposedly give you access to more bhp, rather better throttle response and perhaps a tad more torques.

 

Triple cut valve seats - or even quadruple as PeterT also encouraged if possible - definitely seem to bring an improvement.

 

But beyond this, I would say cleaning up any factory produced anomalies or obvious mismatches in your inlet and exhaust manifold choices are worth the effort sorting out.

 

Although ultimately the original answer, however worded, is probably closest to the truth, i.e. it's just not worth bothering. T/C valves seats, new stem seals, new oil filter mesh insert, refurbed lifter and a fast road cam (timed correctly) and off you go.

 

Getting close to the 250 factory capable horses is gonna take a damn-sight more effort than just a few hours with a Dremel. In fact as go as far as to gamble it would unleash close to zero extra power.

[unariciflocos 49 1 Cars]

The point of the thread was if DIY porting would improve things and I think we can all agree that it would be either a waste of time or a waste of a head. Maybe gains can be seen after extensive calculations, tests and work on a flowbench, but not diy.

[DamirGTI 345]

I always fancy a little bit of "tying" and careful re-work job on heads , and i'm pretty confident in myself (been investigating this subject for a long time now trough books etc. ..) so im not going mad with grinder and i always ask competent person for advice for particular head , ten times if needed before attempt to do the job myself ... theres a few things which are almost unique bad spot for most of production heads ..

 

Anyway , few examples of S16 head preparation :

 

http://www.guy-croft.com/viewtopic.php?f=2&t=150

http://www.guy-croft.com/viewtopic.php?f=2&t=149

 

Damir