Head Port and Polish

[Steve]

Ok boys and girls

after finishing reconditioning the 155 head today i had a look at the ports, and there is so much to take out.

the head garage i use said it would take about 40 hours to do it justice. Thats cutting out, polish and gas flow.

I cant afford to do it on mine at the minite and i need to sell the 155 due to cash flow, but it would be an interesting thing to try.

Also a fair bit of power increase bout 30-40% i recon.

Has anyone had it done???

 

[Tom]

30-40% LOL!!! They are pulling your leg!

5-10% maybe if its been done carefully with the aid of a flowbench. Simply hacking at the ports and especially polishing them usually results in a loss in power.

A perfectly smooth surface is what you DON'T want, it slows airflow down. No good tuner will recommend polished ports.

 

[Steve]

really ???

Where is your info coming from cos i purly pollished (to a mirror finish) the ports on my Astra GSi and i deffo noticed a considerable difference.

 

[Tom]

Got any figures to back up a 'considerable difference'?

Look at any pro engine builder, the ports are always left a matt finish. And I'm talking proper racing engines used on race tracks in races rather than someone who has a 'race' engine in their road car.

http://www.gcroft.com/page5.html

Check out the ports, matt finish.

A perfectly smooth surface results in the air/water sticking to it. They put a textured surface on the hull of the US America's cup yacht many moons ago and it reduced drag by something like 15%. The technology was quickly banned.

 

[Anonymous]

couldnt afford a dyno or rolling road test but a particular stretch of road that i use to "test" my cars saw an increase of 15 mph at a given point to a previous attempt.

i know race cars that go in to this guy for head work, Porsche turbos, Calibra turbos and special projects:

Ford KA with vauxhall 2 litre turbo lump, with motorbike throttle bodies, revs to 12,00 no probs. has a ported and polished head, lightened and ballanced rods, crank, fly and pulleys ect

CRAZY LOL

Tom have you had it done yourself ??

 

[Tom]

Had it done or done it myself? Yes, I've done it myself. I don't let other people do engine work for me.

2 ltr turbo vaux lump with bike throttle bodies revving to 12k? Sorry but thats B$.

 

[Anonymous]

he spent about 20k on the engine work i have seen it

its not bull

(i had to see it to belive it)

he uses it for grass racing ???

 

[RaB hImSeLf]

12k???? Boooooooooooom!!!!!

Why bike throttle bodies??

 

[Tom]

No idea why you'd use them on a turbo engine.... big single throttle body is best for that.

 

[Anonymous]

carbs not bodies

bike carbs (and engines) can rev to 14k where as car ones tend to only get to about 8k

thats what was wanted when they built the engine i suppose

 

[Anonymous]

Tom - the fact that it revs high was the deciding factor i recon.

also there is no need for ECU ect the engine runs itself essentially not sure how reliable it is though lol

 

[Steve]

sorry my browser keeps logging me out lol

 

[RaB hImSeLf]

You sure it ain't just a BIKE ENGINE? Unless you had a 2.0 bike then bike carbs would be too small. My uncle has a Westfield with a RS2000 motor up front from a '94 model. Thats decatted and all life support removed, twin webber dcoe 48's specialy made in-let manifold and exhaust and that'll go to 7500 before it starts to cry.

 

[Tom]

But a bike engine that revs that high is only 600-1000CC. Putting bike carbs or TBs on a 2ltr engine won't allow it to rev that high, its flowing twice as much air as the 1ltr bike engine and the carbs restrict it.

Simple physics.

Bike CARBS on a TURBO engine revving to 12K? Utter B$.

 

[Anonymous]

its like catchphrase............"say what you see"

ive seen it so i say it

i have no reason to "B$"

 

[J]

30% that's comedy . I have done all this work and believe me you can't open the ports up that much as you will just end up putting a hole in the water jacket. In order to research the 20V head we cut a cylinder head in half and carefully evaluated every aspect of the cylinder head in terms of how far we could go with the port sizes etc. A mirror finish is the last thing you want that just makes things worse and also if you over port the head you will get less power. It took us hours of labour and flow benching to get the correct cfm. The 20V head is very delicate I would recommend you be very careful in terms of you does the work. A standard head will produce 90% efficiency. A good modified head will produce 95-96%. Our specially developed race head produces 102% as you can see this is an overall increase of 12% and that is it.

 

[J]

Guy Croft is one of the best engine builders in the country and I know him personally.
So you're saying it's a 2litre 16V turbo Vauxhall engine with throttle bodies no ECU which revs to 12,000rpm and inside a ford KA?
To find out weather its B$ or not tell me the length of the conrods. Also can't see why you would have throttle bodies on a turbo??!!??!!

 

[Tom]

J, some kids will believe anything they are told.

And some 'tuners' will spout ANYTHING to make people give them money.

"Ooohhh dem portz is polished, ain't dat kewl!"

VXR might be interested in a lump that runs at 12k RPM and only cost £20k, would be cheaper than their multi-million pound R&D that only gets them ~9k RPM.

 

[steve]

I don't think its possible to get a 2 litre car engine to 12k revs is it?

certainly not a std car engine based one.

There is a limit to how fast you can make big valves move etc

I know f1 cars peak at 17k or something like that, but they cost considerably more than £20K to build and are not your average car engine to begin with

The new R6 from yamaha only revs to 15500 or somat even though it claims 17000rpm and thats with 4 tiny 150cc pistons and a 42.5mm stroke

No way you'd get 500cc pistons to move at them sorts of speeds.

For example a cosworth engine has a stroke of 76.95mm(according to the internerd) Assuming all things are equal, the stroke is 1.8 ish times longer than the R6 so the piston would need to weigh 1.8ish times less than the R6 piston just to give 15500rpm with the same stresses and strains.

I don't know for certain, but it sure smells a bit whiffy in here. Just a hint of bovine fecal matter

 

[Anonymous]

i'd love to see a vauxhall engine rev that fast. i'd think it would throw a rod or two before it reached that speed though

actually, it'd be total destruction, top to bottom