Porting and polishing head?

19th April 2011, 22:08

Right quick ones guys.

Head is coming off in a couple of months when I'm next home to sort this $%*(£%$£($ ing oil leak out. Spoke to a company about skimming, not a problem, then he opened a can of worms and asked if I'd like the head porting and polishing whilst it was in...

... then he mentioned bigger valves and then I was like omg.

... but anyway, in your experience have you witnessed much gains or is this purely for when you're putting uber power down? Not fussed majorly for the gains, even if it improves fuel economy I'll be a happy chappy.

What are the typical prices for a port and polishing on a J4 head?

NB: Probably will be predatoring the car once the 3-plugs come on board so could take proper advantage of any mods there
NBB: Raunchz, I'll know you'll read this at some point. Thanks for sending those docs over (I know it's a bit late

) very interesting

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19th April 2011, 22:19

You can buy jp4 valves brand new for about £6 each
So why don't you think about getting the bigger inlet valves from the jp4?
Just a thought

But ive heard a few people porting there exhaust ports out the same size as the metal gasket
With no remap n they had good gains!

19th April 2011, 22:28

Could always go down the JP4 head route ladyboy.

Theres a few options, but ultimately depends if you are wanting to spend ££££ or not on this car.

19th April 2011, 22:40

the question you have to ask is, can the guy back up the work wth valid graphs??

any one can take a die grinder to a head, but only a few people can get good gains from it!!

19th April 2011, 22:55

Depends on how much he's charging to do it?

Might be a good idea to try and polish up the exhaust side to remove the old carbon deposits? Surely can only be a good thing to improve the efficiency of getting the gases out, could try and port match the head to your manifold?

Inlet side I'd be tempted to leave, as surely the rough port surface helps improve the atomisation of fuel? So efficiency wise, polishing up the inlet side wouldn't help. And bigger valves are not going to match up with the cut-outs in the inlet side of the piston, so any future choice on chucking a cam in there is going to be an unknown, valve clearance wise

No probs on doc's, not a huge amount on the ABS unfortunately.

19th April 2011, 23:03

As raunchz says port matching is a good idea. Though i have it done on inlet and zorst port.
Then make sure the inlet and zorst are opend out to match.

Its a job ill be doing shortly on my v6, wont give massive gains but every little helps.

19th April 2011, 23:05

bleeding heck, the sayer is alive..

19th April 2011, 23:06

my mate matched his inlet i think on his trophy....Is it worth doing on Saxos? its probably not worth it...i know...

20th April 2011, 00:22

Quote:

Originally Posted by Aaron

You can buy jp4 valves brand new for about £6 each
So why don't you think about getting the bigger inlet valves from the jp4?
Just a thought

But ive heard a few people porting there exhaust ports out the same size as the metal gasket
With no remap n they had good gains!

Can I simply stuff jp4 valves on a j4 head with the necessary headwork?

Quote:

Originally Posted by Ryan

Could always go down the JP4 head route ladyboy.

Theres a few options, but ultimately depends if you are wanting to spend ££££ or not on this car.

I've got two j4's man... I don't fancy adding a jp4 to the collections. adsayer's saxo inventory is far too big as it is. The plan was to just pop the new j4 onto the block in my car. Then I got chatting and ideas arose in my head, no pun intended.

Quote:

Originally Posted by swampy

the question you have to ask is, can the guy back up the work wth valid graphs??

any one can take a die grinder to a head, but only a few people can get good gains from it!!

He has a reputation for headwork on VW's, quarter mile beetle machines and that sort of thing. But as far I know I don't think he's touched j4... not as if it's going to be much different I would have thought. I'd be telling him exactly what I want, unless he knows for a fact he can get gains from a specific area.

Quote:

Originally Posted by raunchz

Depends on how much he's charging to do it?

Might be a good idea to try and polish up the exhaust side to remove the old carbon deposits? Surely can only be a good thing to improve the efficiency of getting the gases out, could try and port match the head to your manifold?

Inlet side I'd be tempted to leave, as surely the rough port surface helps improve the atomisation of fuel? So efficiency wise, polishing up the inlet side wouldn't help. And bigger valves are not going to match up with the cut-outs in the inlet side of the piston, so any future choice on chucking a cam in there is going to be an unknown, valve clearance wise

No probs on doc's, not a huge amount on the ABS unfortunately.

Haven't discussed prices yet man... this would be based on what I have done, which I'm glad you and aaron mentioned - this is where you lot come into it

I've always had a thing about the carbon deposits on the exhaust ports when removing the ex. manifold. It occurred to me but I never verified whether the ex. manifold had a larger area than the ex. ports... so if what you chaps are saying, then there is certainly a sound reason to spend some time tackling that region?

Good call on the valves.. forget that then.

I'm not sure about the inlet, I reckon it could be safely smoothed to almost mirror like conditions dude... This is purely speculation on my part but I reckon that the flow, even at low speeds, has been through a tube, a filter (Okay, which acts like a turbulence screen - so admittedly it'll be briefly laminar post filter), then turned 90degs, gone through a TB with an air temp sensor sat part way into the flow (and even worse at part throttle), into a butted plenum (phat pressure drop), then eventually sucked down port. Even if the air were able to settle in the plenum for a significant amount of time, I'd have thought the Reynolds number would be sky high in the ports anyway, so turbulent enough to support sufficient atomisation. Having super smooth ports won't return the flow laminar again but it'll give a much thinner boundary layer thus higher V.E right where it matters.

But as I say this is purely speculation so I'd been keen for a bit of brainstorming and head scratching on this theory

Quote:

Originally Posted by swampy

As raunchz says port matching is a good idea. Though i have it done on inlet and zorst port.
Then make sure the inlet and zorst are opend out to match.

Its a job ill be doing shortly on my v6, wont give massive gains but every little helps.

At a minimum surely removing the casting 'scars' would make even a DIY porting session worth while provided the DIY'er didn't go all jackie chan on the ports and open them up al the way to the oil/water galleries?

Cheers for the input so far chaps!

EDIT: Does anyone know what the diameter of the port where the valve sits on the inlet side? Might as well calculate the Re number at that point and confirm for sure.