Head Porting/Polishing

[GiJOr33]

Just wondering where in Melbourne you guys would recommend i take my RB25DE cylinder head to be ported/polished? It's going on an RB30 bottom end. I'm looking for between 300-400kw at the wheels.

Is there different types of porting for different applications? i'm quite new to this area so i don't know the ins and outs of it.

Be good if we could get everyone's thoughts and experience on it. Also how VVT will be effected and whether or not i should get rid of it and just use adjustable cam gears.

Thanks

Andrew

[Steve]

From what I have read, the head in stock form should be well and truely capable of that sort of power without porting.

Its not in melbourne, but Hillsmotorsport quoted me $895 for a head port including extrusion hone, might be worth sending it up there.

[GiJOr33]

yeah... at this stage, that's the power level i'm aiming at. Once i get more cash for a gearbox then i'll go for more. So i'd like to do it while the engine is in bits.

[Cubes]

but while its off why not clean it up a little...

[Steve]

Originally posted by -Joel-

but while its off why not clean it up a little...

All well and good if you have the extra dollars lying around - Its not just the cost of the port, but also the remove and replace of valves, springs, cams, plenum etc it all adds up - and if its not necessary I personally would sooner have the dollars in my pocket - bloody car cost enough to mod as it is:D

[Cubes]

Depends if you are getting the head re-co'd or not..

Mine is going in for valve stem seals, valve grind etc.. all the usual stuff so I may as well get it cleaned up.. Not ported just cleaned up. Any casting slags etc..

[GiJOr33]

Well the head is off sitting on the floor already. So i may as well do something with it rather than just put it back on. I figured spend a few $$$ now to save doing it later. I'll have the valves refaced and reseated, and change the valve stem seals and guides. I'll definantly have it cleaned up, but am wondering where the porting benefits in the rev range... i'm tipping more in the topend than down the bottom.

[Steve]

Think you will find increased off boost response as well - a good port is good across the range - its all about flow

[Ender]

Wouldn't you have to change the valve springs at least...I would have thought they may have been a bit soft, as well as old and used....I'll be putting someheavier valve springs in mine...Especially if you are gonna run higher lift or longer duration...

Cheers,

[GiJOr33]

well i'll be using stock cams at the moment, but i spose putting in better springs now before the head goes on will mean that when i do want to change the cams, i won't have to stuff around with valve springs while the head is still attached to the block.

Any recommendations on what springs to go for?

Thanks

Andrew

[Cubes]

The RB30 won't be reving over 7000-7500rpm so there really is no need for much more than stock valve springs I would think.

[GiJOr33]

just bringing up this old thread again... i am about to drop the head in for some work. I was told that with increased boost you need stronger valve springs as the pressure from the turbo is trying to open the valves. (that's on the inlet side)

This is what i have been told to get done.

Port inlet and exhausts ports

Taper valve guide protrusion into ports

Triple angle cut the valve seats

Match the combustion chambers so that all 6 are exactly the same volume

Match the inlet manifold and exhaust manifold to the ports

Flow bench to check results

As i'm not chasing 800hp, i don't see the point in spending $2000 on head work if it's only gonna get me 30kw more than a $1000 job.

I'm not too cluey on cylinder heads so i don't know what benefit each modification yields.

Has anyone had similar work done on their cylinder head and what was the cost?

Thanks

Andrew

[Steve]

Dude, that sounds mighty suspiscious to me. Boost pusing vavles open WTF? I dont think it would be necessary to get 2k worth done - thats just over the top. Have they given you a cost break down?

Lastly, if anybody told me that they would check the results AFTER the work was done I would run a mile in the other direction.

If they cant tell you up front what sort of flow they expect, and what it will cost to produce those results I just wouldnt touch them - and get it in writing.

[GiJOr33]

he was talking about running decent boost, 1.1bar+, not just ya stock.

i was told that for ever 1psi increase of boost , you should have an increase of 3psi of valve spring pressure...

the guy i spoke do didn't say i need to spend $2000, i'm just saying that i personally don't want to spend $2000, if it will only give me a few kw gain over spending $1000. He said that once i decide what i'm after he'll be able to tell me what i should get done, and what i can expect from that. They have a flow bench to test the work is done properly.

i was just looking to see what other people have had done and how much it cost them