To polish, or not to polish

[float_6969]

So I've been super busy with work, but I've been making time here and there to work on the CA. The bottom end is done and I'm on to the head. I've got the old 4 port head torn down. I was hoping that it wouldn't need a valve job, but it does. I had the 8 port head nicely port matched, and polished as well as the lower manifold and as much as the upper manifold as I could get to.

I have enough stuff left to be able to port match and polish this head as well, but I wonder how much it's going to help. The turbo is a T04E. Not too many big HP CA ppl in here, but I thought I'd ask. If I'm only gonna gain 10hp, it's not worth the trouble. If it's more, then I'd be more likely to put the time in it.

Input? Opinions?

[beans33]

I say if you got time and the supplies to do it why not ?

[blownhemi]

I don't think anyone is able to tell how much hp it will gain... I personally don't believe in porting a turbo engine, UNLESS it is seriously $h1te to begin with, like old US V8s, or old two-valve engines in general. I would like to believe that the head of the CA, being on a turbo engine out of the factory, is not $h1ite enough in its stock form to justify serious port work, and unserious port work will not yield any difference that is measurable on the "a** dyno" (which is the only measurement I find relevant ).

But if you know how, have the time, patience, then why not. At the very least it will give you peace of mind, that you've did everything that you could....

I wouldn't polish, though,I'd leave it very slightly coarse. It might sound like Regurgitated Internet Bull, but I've found some really good explanations online, that were based on physics of fluid dynamics, instead of folklore, and I was convinced. Just throwing that out there.

Boost_boy probably has *some* experience he can share about what he typically achieves with what headwork.

[float_6969]

The reason I'm hesitant is because it is A LOT of work. Probably around 20-25hrs. of work. But I found some better info after I posted this last night. I went over to another forum where they have more experience with modifying the CA and the most common answer was that it was more of a percentage change in power. The general consensus was that it was good for around a 10% increase in power, but it's hard to tell, as nobody ever JUST does a port match and polish to compare results.

They basically said that if you're making less than 350hp, and you're paying someone to do it, it's not worth it. If you're doing it yourself, it's always worth it. So I guess I'm gonna have to make some time at one of the shops I have available to me to work on it. My little 5 gallon air compressor isn't quite up to the task of running my rotary tool for more than a few seconds, LOL!

[boost_boy]

Ahhh, good 'ol porting and polishing . It wouldn't hurt to port and polish to remove the imperfect factory castings and gain a little extra flow. If you're going to be removing large chunks of aluminum to gain maximum flow, I strongly suggest against that, especially if you're porting and polishing isn't your area of expertise. The most important thing with the CA's head is that you have valves that are sealed when closed and that comes via a competent machine shop. If you're going to be hanging around the 8000+rpm range on a regular, then there is no need to get a sick port and polish job. There is a noticeable difference with a ported and polished head, but barely noticeable with the use of the buttefly system activated and the smaller turbochargers. If you're using your butterfly valve system, don't even waste your time porting anything. Bigger turbo, valve train upgrades, high flow manifolds and big exhaust systems all compliment the ported and polished head for upper echelon performance areas. Again, low boost (7-15ps), stock ecu, stock injectors, stock turbos or slightly bigger ones for the most = no need for a ported head.

[float_6969]

Not changing the size of the ports, just cleaning up the casting lines, matching the ports to the gaskets, etc. This is a 4 port head, so no butterfly valves. I've got some HKS 264 cams that will be going in, so I will be spending a bit more time in the higher RPMS, and with the big T04E turbo, that will be running up there too.

[themadscientist]

It spun up nice on a bone stock engine with weak compression. You should be fine.

[float_6969]

It spun up alright for the short time I had it installed. I'm not necessarily looking for a whole lot quicker spool, but with the combination of the 4 port head and the cams, I'm hoping that the divided turbine housing will help me gain back a little of the bottom end I'll loose from those changes.