Anyone here ported/polished a head themselves?

[ezi]

Been thinking about trying to port/polish heads at home, I've been looking it up online for a while and really there doesn't seem that much to it.
You can get a very high quality dremel tool for around £100-£130 and bits aren't expensive enough to note. I was going to start by just picking up a few heads off eBay that have come from stripped engines and restore them at home in my main time, if I managed to pick up the skill well I might make a bit of profit along the way if I start knocking them out for my owners club etc but nothing massive, amazes me that good condition bare heads can be had for less than £100 yet to buy one ready ported and polished you're talking £1000. Am I missing something as to where they are getting this seemingly massive markup?

Any tips/advice much appreciated

[HustleRussell]

Without a flow bench it's all pure guesswork. I suspect there is more to it than you imagine, hence the £100 vs £1000 disparity.

[anonymous-user]

In the old days, you could get good results by eye, because the ports where to terrible to start with. These days, any engine built in the last 10 years will have CFD optimised ports. Now of course, you can lower the mean intake velocity, to push torque up the rev range, but you stand a good chance of loosing more down low than you gain up top! tbh, these days, unless you're also fitting bigger valves/seats, i'd say that porting a head is almost pointless (sure someone will disagree, but if you consider the time you spend vs the gain, and factor in the chance of a big loss (without a flow bench) )

If you really want to get into it, then you need a flow bench. Plenty of people have made their own, and it's not really that hard of expensive to do. Google it for more info!

[anonymous-user]

BTW, with direct injection engines becoming more common, you stand a very good chance of really screwing things up if you mess with the port geometry!

[DVandrews]

A Dremel probably doesn't have the torque or size/reach of cutter to do a proper job. Experience counts for a lot when assessing a head prior to porting, a good eye and understanding of head design can get you 95% of the improvement you are looking for, the rest normally requires a flow bench, but as ever a flow bench is just a tool, it is your intuition that leads towards the modifications that may yield an improvement. Modern 4 valve heads are fundamentally good in their design, but production compromises often result in sme poor machining in vital areas or a mismatch between the casting centre and machining centre resulting in misalignment of seat inserts with valve throats.

Detailed work around the valve seats is the most productive area and can greatly I prove low and mid lift flow. The profile of the valve seat can have a profound affect on the discharge coefficient of the seat aperture.

One particular 4 valve head that I often modify has an I itial peak airflow of 75cfm, when properly modified this rises to over 110cfm with commensurate increases in low and mid lift flow.

Golden rule, it is easy to remove metal, putting it back on is more of a challenge.

Dave

[Evoluzione]

Never ever polish a head, aside from what the others have said, that's my advice.

[anonymous-user]

DVandrews said:

Modern 4 valve heads are fundamentally good in their design, but production compromises often result in sme poor machining in vital areas or a mismatch between the casting centre and machining centre resulting in misalignment of seat inserts with valve throats.


Dave

Those "misalignments" are most often done deliberately these days, (in the old days port core alignment was less controlled, these days most port geo is +-0.15mm for a DI engine)

[Steffan]

Max_Torque said:

DVandrews said:

Modern 4 valve heads are fundamentally good in their design, but production compromises often result in sme poor machining in vital areas or a mismatch between the casting centre and machining centre resulting in misalignment of seat inserts with valve throats.


Dave

Those "misalignments" are most often done deliberately these days, (in the old days port core alignment was less controlled, these days most port geo is +-0.15mm for a DI engine)

Max Torque is spot on with all his comments on here. With modern ECU complexities and modern manufacturing improved tolerances meddling with the porting is very likely to upset rather than enhance the porting. I come from the old school like Clive Trickey and David Vizard who were excellent engineers who built upon racing know how on the backs of giant pioneers like Harry Weslake.

I started on A series polishing and altering porting and then the potential improvements were colossal given the dire condition that manufacturing then achieved. The amateur could not go wrong in getting some improvement with a bit of port polishing and massive improvement with serious head work.

That is no longer the case: I fear those days have long since gone. I would leave this to experts in the particular modern engine concerned.

[DVandrews]

Max_Torque said:

Those "misalignments" are most often done deliberately these days, (in the old days port core alignment was less controlled, these days most port geo is +-0.15mm for a DI engine)

That has certainly not been my experience, I am familiar with the devices used in ports to promote swirl and tumble and have seen a great number of modern multi valve heads, 3, 4 and 5 valve. Many of them suffer with machining misalignments, sometimes quite badly despite modern production methods. Some of the 4 and 5 valve Audi heads have a large shift which gives a measurable lip at the edge of the seat which is prevalent on the long turn on some heads and the short turn on others. This is not a 'deliberate' misalignment, it is just poor production control.

Any production head will be full of compromises both of design and production.

Dave

[CrutyRammers]

I fail to see how any reading on the subject can give you the impression that there's "not much to it", or that a dremel would be up to the job...

[Mikey G]

Ive done a few heads for friends and my own cars over the years. Had some reasonable results but I don't go mad on them, just tend to clean the ports removing casting marks and match the manifolds, and reduce any large lumps around the valve stem, and slim down the Siamese inlet bridge between the valves.
Heard so many people wanting them polished, it does little for a road engine apart from look pretty in pictures.

[anonymous-user]

DVandrews said:

Max_Torque said:

Those "misalignments" are most often done deliberately these days, (in the old days port core alignment was less controlled, these days most port geo is +-0.15mm for a DI engine)

That has certainly not been my experience, I am familiar with the devices used in ports to promote swirl and tumble and have seen a great number of modern multi valve heads, 3, 4 and 5 valve. Many of them suffer with machining misalignments, sometimes quite badly despite modern production methods. Some of the 4 and 5 valve Audi heads have a large shift which gives a measurable lip at the edge of the seat which is prevalent on the long turn on some heads and the short turn on others. This is not a 'deliberate' misalignment, it is just poor production control.

Any production head will be full of compromises both of design and production.

Dave

I would say that the audi 5v engine is now an old engine (development finished in mid 1996 iirc!)

Since everything went DI, chamber charge motion has to be so much better controlled and hence the port tollerances have improved dramatically. For example, take a look at the ports on a AJ126 V6, and by eye the port looks terrible for flow! (which to some extent it is), but those features are required for mixture positional control across the load/speed range. Remove them and under some conditions the engine will actually misfire because the fuel is nowhere near the spark plug at the moment of firing......)

Edited by anonymous-user on Monday 12th August 12:53

[DVandrews]

Max_Torque said:

I would say that the audi 5v engine is now an old engine (development finished in mid 1996 iirc!)

Since everything went DI, chamber charge motion has to be so much better controlled and hence the port tollerances have improved dramatically

But the 4 valve is current. In any event, it is much more likely that older engines will be modified by the amateur tuner than very recent ones.

Dave

[harleyE30]

Polishing the intake ports to a mirror finish is completely pointless. Flow velocity is practically zero at the surface and it takes a considerably rougher surface finish than what is found on production heads to have any effect upon the faster moving air above the boundary layer.

Moreover the intake port should have a uniform roughness in order to prevent fuel from pooling on the port surface on carbureted and port-injected engines.

Polishing the exhaust port can be advantageous in terms of preventing a build up of combustion by-products.


The highest gains in terms of air flow can usually be achieved by replacing the single angle valve seat common to most cylinder heads to a multi-angle seat. On a 8V Renault Head I managed to achieve a 13% increase in peak flow just be installing multi-angle intake seats.

[Mojocvh]

Some great info coming out here

[reggid]

dremels are rubbish, nothing more than a gimmick really.

porting is all about sizing certain points in the port according to the engine specs and application to achieve proper velocity for good VE across the required rpm band. then just shaping it to help the problem areas of the port at hand (e.g. getting air to turn the short without separating, getting air to go around the valve efficient with nice valve job, getting velocity gradients relatively uniform and using all the volume etc). in some ways if you do this as best as you can then the CFM numbers will look after themself. CFM only tells you a ballpark peak hp potential but in most applications its next to meaningless

it pays to look at fuel preparation and mixture motion but this a much more complex area.

[rolymo]

Back in the very early 60's when the Mini and Anglia first estabished themselves on the motorsport scene it was a terriffic boost to the average enthusiast and almost immediately we saw every Tom, Dick & Harry start applying their talents to modifiying cylinder heads to achieve power upgrades and make all sorts of spurious claims about their power outputs. The problem at that time was---there was no certified way of checking, verifiying or if in doubt contesting their claims. Today it is a whole different story mainly due to the advent of " Rolling Roads" and computor diagnostic analysis, back in the day one simply paid your money and took a chance on what you had purchased power-wise, very often the results were disappointing because no academic study or experience had been applied only a beautiful mirror like finish ( pscho -ops inducement to purchase because it looked good ! )
Prior to this surge in cyl- head business I had been employed at BMC Longbridge as a service engineer and had recieved lots of exposure to "Dyno's" in the factory. the senior management had been advised that we were losing ground in the retail repair sector due to poor fault diagnoses in dealers workshops not keeping up with the latest improvement in technology. This was a Lord Nuffield (William Morris) initiatative although he was not actively involved in managment, he maintained a healthy interest in the corporate business and often tabled opinions at board meetings,By this time he was considered somewhat of an irrittant to the senior managers (grumpy-old man syndrome) but his observations were upheld in my view and could be substanciated by analizing the returns of complaints in the Warrantee Repair Claims Dept. But this was BMC( to become) British Leyland Ltd and that would be far too easy, I was sent out to investigate the market and report back knowing the result of my endeavoures would be consigned to a file marked " Cobwebs ! " I devised a plan to overcome my bosses lethargic attitude to this project which had not produced much support and would struggle to get approved leave alone reach functionality.
Arrangements were made for me to team up with a west of England main distributor who had been quite successful marketing modified cyl-heads ,twin -carb and other tune-kits for Morris Minors & Mini saloons however I suspect that progress was being purposely diverted by persons behind the scenes as the Chief Financial Officer (accountant) constantly proclaimed that there was insufficient funds to undertake such an enterprize.It turned that the modified heads were being "bought -in" from another company and no one had requested certification or verified the actual performance gain in flywheel BHP. The whole deal revolved around a national automobile magazine endorsement quoting
these cyl- heads were :- best buy of the month! without issuing any power figures.
Returning my report direct to the "Boss" was deliberate but did not go down very well with many of the senior managers and subsequently resulted in me being fired, my actions had prevented them from voting for a < NO- veto> at the birth of project "rolling road". Several months later the CFO attempted to initiate my plans in order to rejuvinate his failing company and take the credit, but being a numbers man and not an engineer he made a few fatal miscalculations and the whole scheme crashed in the early stages of introduction taking him and the tuning side of the business with him.
Sometime later in early 1965, I opened my own first "Rolling-Road " and Dynotronic testing center available to the general motoring public as a service item. previously
they had only been in the hands of manufacturers, laboratories or very up-market main dealers who used them for a different purpose .Shortly after becoming established the production of modified cylinder heads commenced and we discovered that we were immediately in a world of trouble.A large percentage of the heads tested proved to be defective, down on expectation/claims and in general a bit of a "dogs dinner"
Our trading motto was :- "Testwork not Guesswork" so in order to create a reputation we had to live up to our customers expectations, the answer was to engage some very special talent in the form of Mr (automotive genius) David Vizard, Author and Technican extraordinaire. After many hours spent on the Dyno we had produced some pretty spectactcular cyl-heads all certified and garranteed to meet specifications, plus David generated huge quantities of data that proved invaluable while compiling his technical books, ensured that they were extremely accurate and based on repeatable exercises, Dyno proven. Even today he still uses the term "Testwork not Guesswork" 49yrs later.
My advice to anyone wanting to get into the cyl-head business would be to invest heavily into the Vizard liberary of knowledge,forget the Dremal ( too lightweight, its for hobbies not commercial use) and team up with a Dyno operator to begin a very long learning curve.Or alternatively take up metal- polishing ? another needed skill.

[GavinPearson]

Good post rolymo.

David Vizard has had a long and distinguished career and got his reputation by academic work and considerable experimentation and practice.

A first time amateur thinking they can achieve near or similar results is being incredibly optimistic.

[PeterBurgess]

Hi Shaun

I got into the business cos of a vocation, from the first time I played with model aircraft engines to reading the Cyl head mod book by Vizard when I was 15 to spending hours in a shed messing with porting tools, making a flow bench work, meeting people and learning how engines really work to 27 years down the line of running my own tuning business and investing all I have in lathes, millers, compressors, £500 die grinders, £27,000 on a modern rolling road for rapid data acquisition..... learning to try and be holistic....I don't think I will ever earn any money! If you just want to earn some money there must be an easier way I reckon......says you are South Yorkshire, you are always welcome down on a weekday to see what we do.

Peter

[anonymous-user]

Fast forward 40 years, and i'd recommend that budding cylinder head port modifiers pick up a laptop and copy of some decent CFD software, rather than the dremel!

How things change eh!