The 4" Bore Thread

[MeXX]

My 104 mm JE. 440 g with CNC copied dome from my E-Plus heads.
71 mm stroke.
5.325" rods

Hi

They look really nice; what CR to U get with this dome?
Low compression height means the need of a guard ring, the mounting of this pistons is a little bit
tricky.

MeXX

[Frallan]

The heads are bit tricky with deep chambers. Therefore custom domes.
I should be able to get up to 11.5:1 with a tight quench and 1.3 mm clearance.
I might increase that to 1.5 mm.

[58vw]

I have build one wbx engine with 101's for racing only , it has 280 hp with 51 carbs , he has run 10,9 in a street car this year . But i would never build this engine size with less hp for german street driving - autobahn -

Udo

very nice Udo

[MeXX]

Hi to all 4 inchers

some new pix from the heads from my kind of a 4 inch street engine

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bare casted inlet runner

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finished inlet runner

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ported inlet runner

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finished inlet runner

MeXX

[BeetleBug]

Mexx, do you have any flow numbers on your heads that you are willing to share?

[MeXX]

Mexx, do you have any flow numbers on your heads that you are willing to share?

Hi

I don't think that this heads will spend time on a flow bench.
As this is a street engine that is focused on torque they have not to big ports.
The flow numbers should be in the neighbourhood of 260 CFM @ .600 lift and 25".

MeXX

[Udo]

I have build one wbx engine with 101's for racing only , it has 280 hp with 51 carbs , he has run 10,9 in a street car this year . But i would never build this engine size with less hp for german street driving - autobahn -

Udo

very nice Udo

First WBX with an oilsump :-) I like it but a lot of work

Udo

[58vw]

Hi to all 4 inchers

some new pix from the heads from my kind of a 4 inch street engine

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bare casted inlet runner

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finished inlet runner

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ported inlet runner

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finished inlet runner

MeXX

nice

[MeXX]

Some more pix

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polished intake runner

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mirror finish closeup

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closeup actual size versus bare casting


MeXX

[58vw]

nice and shiny mexx....keep up the good work

[Eddie DVK]

Nice,

But very strange I always hear you should not polish your inlets, but the big guns always do? 

regards edgar

[MeXX]

Nice,

But very strange I always hear you should not polish your inlets, but the big guns always do? 

regards edgar

Dear Edgar

There will always be guys who say size doesn't matter 
There will always be guys who say polish isn't good 

But at least it looks cool 

Always thrust the Big Guns they know how to go fast

  MeXX

[Eddie DVK]

Hahaha...
thanks for the honnest answer mexx...

ok I will thrust the big guns from now on.

Regards Edgar

[richie]

In my opinion they shouldnt be polished, if you could see what the ports on really quick cars have,its a quite rough surface,you will rarely see this as they wont show you there own heads , the shiny port came about as "customers know best" and want it as it looks better not understanding the principle behind the rough surface,just thinking it doesnt look good so cant be good.
The shiny surface is supposed to encourage the fuel to fall out of atomisation and puddle which is bad,i have never seen a "big gun" polish heads to be shiny,they just do what is needed,no more as its wasted time and effort,and you the customer has to pay for that time and effort, just my opinion

cheers richie   

[MeXX]

In my opinion they shouldnt be polished, if you could see what the ports on really quick cars have,its a quite rough surface,you will rarely see this as they wont show you there own heads , the shiny port came about as "customers know best" and want it as it looks better not understanding the principle behind the rough surface,just thinking it doesnt look good so cant be good.
The shiny surface is supposed to encourage the fuel to fall out of atomisation and puddle which is bad,i have never seen a "big gun" polish heads to be shiny,they just do what is needed,no more as its wasted time and effort,and you the customer has to pay for that time and effort, just my opinion

cheers richie   

IMHO

You will not be able to gain CFM or HP with a rough surface intake port compaired to a polished one.
But it is true that if polishing helps it will definitely not be much.
The possibility that  fuel to falls out of atomisation will if ever take place with carbs not with EFI.

as I started IMHO MeXX

[richie]

Eddie,

as an example of what I am talking about,heres a picture of Johannes port work and finish on my 4inch heads


cheers richie

[Zach Gomulka]

A golf ball isn't smooth for a reason...

[Udo]

Hahaha...
thanks for the honnest answer mexx...

ok I will thrust the big guns from now on.

Regards Edgar

Eddy

I think i did your heads and they are right. You can trust me. i think it is not a question of big guns but different meanings... Those shiny ports are more for show and shine :-)

Udo

[John Maher]

IMHO

You will not be able to gain CFM or HP with a rough surface intake port compaired to a polished one.
But it is true that if polishing helps it will definitely not be much.
The possibility that  fuel to falls out of atomisation will if ever take place with carbs not with EFI.

as I started IMHO MeXX

Mexx, like Richie says, you won't see highly polished intake ports used by head porters who really know their stuff. A textured finish (within reason) will encourage any fuel that may have fallen out of suspension to rejoin the airflow, whereas a mirror finish surface encourages droplets or even small puddles of raw fuel to form and trickle their way down the port, independent of the main air/fuel charge. If I were you I'd flap the walls of the port with 40 or 60 grit emery cloth to eliminate the shine. CNC ported heads work just fine without polishing out the machine marks - assuming the port design is a good one in the first place! The golf ball comment by Zach is relevant too... a smooth finish can allow the formation of a boundary layer - that's why a smooth golf ball won't travel as far or as fast as a dimpled one.

You unlikely to see any difference in CFM between a rough and smooth finish on the flowbench but on the engine you could pick up some power with the rough finish as a result of burning more fuel and achieving a more evenly distributed air/fuel mix in the chamber. This applies to EFI as well as carbs but can vary depending on engine speed and injector placement.

There's a possible benefit to having a highly polished port on the exhaust side, where the small reduction in surface area will see the head absorb a little less heat from the exhaust gas. Whether it makes any appreciable difference to horsepower or not is debatable, plus the fact it'll carbon up instantly anyway.

The shape and size of a port is vastly more important than the finish.

PS  I've very much enjoyed reading about your car - a stunning piece of work!

[MeXX]

Hi

I did not want to start the discussion how to finish inlet runners as every engine builder has its own truth.
But its definitely not true that professional engine builders do not polish the intake ports.

For an example here are some pix of a high horsepower Moto GP intake from Ilmor.
I know that these are no air cooled VW's but you can see the injectors and it seems that they don't have the
problem that fuel to falls out of atomisation.

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So long MeXX

[John Maher]

Moto GP engines run up to 18,000rpm - that helps with fuel atomisation 

[Eddie DVK]

Hahaha...
thanks for the honnest answer mexx...

ok I will thrust the big guns from now on.

Regards Edgar

Eddy

I think i did your heads and they are right. You can trust me. i think it is not a question of big guns but different meanings... Those shiny ports are more for show and shine :-)

Udo

I know you did udo, i never doupt that.

But i have been trying to gain all the info I can get, and did some portwork (2 race engines) on a friend of mine circuitcar (alfa 2.0 twinspark engines) did not polish it, but made it bigger and rought it up after that.
Really strong engines he went 2 seconds faster (on a 2min lap) with those engines then before. and I liked doing this...
But have seen some same engines in raceshops with a lot of polishing on the inlets altough the onwers said it is not ok to do so..... so I get confused...

But I like to do everything myself, did my own engine (less the heads  )...
said it before, i am collectng parts for a new engine (also CU heads) and like to do the heads myself this time..

But thanks for sharing all those info guys... (also John and Richie)

Regards Edgar

[richie]

Hi mexx

interesting pictures,the injector on top of the velocity stack will no doubt give its own set of variables,and we cant see under the throttle plate,the stack being polished is another topic,but looking at the ports closely they don't appear to be polished to me,I may be wrong as its not 100% clear in the picture of the heads,I have marked in yellow the areas I am looking at

cheers richie

[Bendik]

A golf ball isn't smooth for a reason...

I learned that a golf ball is dimpled to be stable in the air. I talked to some guys from a pro cycling team that spent considerable time in a wind tunnel and they got no gains from a dimpled surface. But they also adhered to the idea of a boundary layer that acted almost like a roller bearing for the reast of the airflow. He would not rule out that some "texture" to the finish would help but said this would not be a great difference. As he was talking about the outside of bicycle frames and wheels he did not worry about atomization of fuel mixture..

[Andy Sykes]

I think we need mythbusters on the case

[John Maher]

I talked to some guys from a pro cycling team that spent considerable time in a wind tunnel and they got no gains from a dimpled surface.

An aerodynamic track cyclist can manage 60+kph...
Air speed in the intake port of even a modest street engine reaches more than Mach 0.5
A slight difference 

[Shag55]

 

I think we need mythbusters on the case

[Dead Dog]

I think we need mythbusters on the case

or just you 

[Bendik]

I talked to some guys from a pro cycling team that spent considerable time in a wind tunnel and they got no gains from a dimpled surface.

An aerodynamic track cyclist can manage 60+kph...
Air speed in the intake port of even a modest street engine reaches more than Mach 0.5
A slight difference 

Indeed..

[Udo]

I think everybody gets his own experiance and should do so . If Mexx got good results with the polishing he can polish the ports . I do not know any other head builder who does it like that ...

Udo