Headwork suggestions

[turabaka]

Alrighty guys. I've hit the point where it's time to start in on head work. After I get my paycheck next week I'm gonna grab CAH's old a20 head, and start working on it. Here's the plans

head cleaned(yay for old and dirty parts. heh)
Port & polish job
bisimoto valve springs
3 or 5 angle valve job
mill the head to increase compression
ARP head studs

my questions are on the last two. What is the advantage of doing a 5 angle valve job instead of just a 3 angle? Is it gonna be a pretty decent power increase, or is it just gonna be wasted money?

Also, as far as milling the head goes. How far can we mill them down before we start running into clearance problems? I'd really rather not have a valve hit a piston. Another concern is how streetable is this car going to be with an 11:1 compression ratio? I don't really care if it's super annoying to drive, hell the interior is completely gutted. But, if it's not gonna start up in cold weather or some major problem like that I'd like to know before I go ahead and find out the hard way.

The goal of this build is to have a fun autocrossing car that's also my daily driver. As it sits now I'm stuck in an open PAX class that's an anything goes class. So I need all the power I can get just to keep up.

With all that said, start chiming in guys. Feel free to mention anything I probably forgot to add, or tips/work I should do while I'm in there.

[LX-incredible]

I'm doing pretty much the same with my head. I had my shop replace the worn exhaust guides first and clean everything for $42. If you're doing the work yourself get a carbide tip, some sanding drums, and a few flapwheels for your dremel. Check out rjudgey's posts, there's a lot of good info there. Don't rush anything. I should finish with my P&P sometime this week.

[turabaka]

I'm doing pretty much the same with my head. I had my shop replace the worn exhaust guides first and clean everything for $42. If you're doing the work yourself get a carbide tip, some sanding drums, and a few flapwheels for your dremel. Check out rjudgey's posts, there's a lot of good info there. Don't rush anything. I should finish with my P&P sometime this week.

Yep. I knew I'd forget something. I'm going with all new valve guides, and probably new valves as well.

[2oodoor]

I thought these already had 3 angle cuts on them oem....
IMO p&P with a slight shave will do it plenty. You have a popping cam so I cant see a big difference with angle cuts as long as the porting is done.
This sounds like a great project!

[Hauntd ca3]

dunno if you'd gain a great deal with a 5 angle valve job eh.
sure there are slight gains in flow to be had there but its something that only a flow bench will really show up.
i'd only shave the head enuff to make sure its flat and true
as for the p & p, depends on the cam you want to use.
the proper way is to port the head then have it flowed and match the cam to get the best result
no point in having a cam with mega lift/duration if the head cant flow the air and vice versa.
if you want to get really silly bout it, you'd have to send the inlet and header with it so the whole package can be flowed
11:1 comp should be easy enuff to run aslong as you run the best gas yu can get at the pump.
and once you start getting serious enuff to be running a red hot motor and using it the way it should be, expect engine rebuilds to be alot more frequent

[lostforawhile]

um you can't hot tank aluminum parts, they vanish. only steel or iron. the chemicals eat the aluminum. at least in a true hot tank. i've always blasted them with plastic blasting media.

[2drSE-i]

a 5 angle valve job isn't gonna flow well enough to justify the cost over a 3 angle. It MIGHT be slightly better for combustion, and flow a tad bit better, but its really not going to make that huge of a difference. You'd be better of spending it on something else. As for shaving the head, i wouldn't do it more than necessary. You get too low youll have to worry about timing and thats just no fun.

[2ndGenGuy]

Screw a 5 angle, get radiused valve seats. That's the money shot right there. And yes, roodoo is right, they are already 3 angle. So if you don't get them done at least with a 3 angle cut, you're going to lose performance.

While maybe the 5 angle will provide "minimal" gains. It's all the little minimal gains that add up to one big gain.

[turabaka]

um you can't hot tank aluminum parts, they vanish. only steel or iron. the chemicals eat the aluminum. at least in a true hot tank. i've always blasted them with plastic blasting media.

Good to know. I'll be sure to remember that one when I get it cleaned.

So is the general concensus that it'd be a better idea to increase compression by getting new pistons?

[rjudgey]

ok ok I'm here don't panic!

Yes radiused valve seats are the best but a 5 angle is needed to make the radius as smooth as possible.
Who's doing this work for you most places can't do 5 angle as they don't have the expensive machinary needed for this? I would have 5 angle with matching valve heads done all day long there is a difference and the better the cam and exhaust system the bigger the difference you will see, most people don't understand why a seat is so important it's the biggest restriction in the head so the best seat possible makes the biggest difference it's just on a stock or near to stock engine it makes bugger all difference on a highly modded engine it's fooking huge!! But don't expect your seats that are 1mm big to last 100k miles!

As for compression I'd aim a little lower for reliability you don't need massive compression for big power, go maybe 10.5:1 then at least the felpro head gaskets will last 30k miles before blowing out between cylinders.

I would go with A20A4 oversized pistons at 83mm, shave some off the block, and then some of the head max 1mm still gives you a couple of light shaves if you have to pull the head for rebuild or head gasket thats blown.

But your biggest mistake will be to put new valves in and keep them stock in size! Go to SI and get them to make you up a set of big valves go 32mm inlet and 37mm exhaust that will give you huge boost in flow, you can go bigger but for a good 5 angle/radius seats you'll have to change the valve seats too for bigger ones which can be done but more cost. Also if your having new guides see if you can have some bronze ones made up it is possible to be done and doesn't cost as much as you think. If you don't know anywhere that can do this let me know i have a link to a good place stateside that should be able to handle that and the radius 5 angle seats too.

So with a nicely flowed head which includes chambers, big valve conversion, and compression increase, header, and 2.5" exhaust and collector on header you'll need a serious induction so what are you planning on using? If you go with twin Webers you'd be looking at potential power with say a 272 degree cam which i think is best for all round tractable power for autox and driveability to get there and back would be around 190-210bhp with a real solid amount of torque if you were to use ITB's about 195-215bhp with much better low end tractability. If you were to go with a bigger cam with custom lobes say 290 degrees duration on inlet with 12mm lift, and exhaust at 295 degrees and 12.5mm lift you could be looking more at 205-230bhp. But the power figures will vary hugely on the quality of the headwork and what valves and seats you go for as well as the induction used these figures are all based on R&D that I've done on my own ET/ET1 and A20 engines.

[turabaka]

Thanks for all the info rjudgey. I'd love that link that you mentioned since I haven't picked a local shop to do all this work yet. I'm still at the planning stage so I haven't gone around and asked for quotes at all the local shops.

[Tdurr]

good luck man. I need a extra block to start a real build...

[rjudgey]

http://www.cccylinderheads.com/main.html

Been used by 4th and 5th gens with good results seem to really know what they are doing off no ones approached them about A20's but I'm sure they could work there majic on ours as well!! Heads a head at the end of the day!

[turabaka]

http://www.cccylinderheads.com/main.html

Been used by 4th and 5th gens with good results seem to really know what they are doing off no ones approached them about A20's but I'm sure they could work there majic on ours as well!! Heads a head at the end of the day!

Awesome thanks man. I'll see what I've got for options here in Boise. I know there's a couple of good shops, but if they can't do the work I'm wanting then I'll prolly end up sending it out to them.

[MessyHonda]

sweet...i wanted to get a head job but now i have a ported and polished head with welded combustion chambers...i got to say its not a happy motor till it warms up