Top End Rebuild Question...

[420a16g]

Well im almost done buying parts but im stuck on what to do with my top end. So i needed some advice from some knowlegable DSMer. Im planning on buying the top end kit from Howell Automotive and rebuilding my factory head rather then buying a new head and then buying the kit as well (someone let me know if this is not the best choice).

But i was just wondering how neccessary it would be to:
-have the head port and polished
-decked
-what kind of valve job to get
-and if i should get stock size valves or +1mm?

Also, one of my friends that has a 1g GSX said that stock valves in the 420a are strong enough to hold high boost, i didnt know if this was true or not. So do you think i should buy aftermarket valves?? If so what kind??

i know most of these answers will depend on my setup, so ill give you the basics. Running a Hahn Super 16g, fully rebuild bottom end, portfueler, planning on pushing 20lbs on high boost maybe more depends on tuning. Thanks in advance for the help.

 

[BigRand]

But i was just wondering how neccessary it would be to:
-have the head port and polished
-decked
-what kind of valve job to get
-and if i should get stock size valves or +1mm?

Also, one of my friends that has a 1g GSX said that stock valves in the 420a are strong enough to hold high boost, i didnt know if this was true or not. So do you think i should buy aftermarket valves?? If so what kind??

Well if you are going to do your head, you are definately on the right track.
The machine shop I used spent 6hours on porting/polishing the head and it looks so beautiful and so clean. (I'll be honest and tell ya I don't know what decked means), but the machinest did use the terminology of setting the stem heights of the valves so that everything is timed right as the pistion is coming up.
I got a 3 angle vavle grind, the reason being is that is I was told that a 5angle valve grind is better for performance, it is far from it for durability. And considering that I left the stock valves/springs in there I thought better safe than sorry.
ONe thing the machinest did find out is that the valves in our cars are really stong to begin with. so we left them (I also left them out due to money issues as well so if you got the cash get em).

The one thing I didn't get is cams/cam gears, but I didn't have the cash to do it at this time, and probably won't for a while, but if I ever want just a lil more power, thats where I have to go.

Whatever you do is up to you depending on how much money you want to spend on it, Or do you want to spend that money else wear.

 

[dr1665]

Im planning on buying the top end kit from Howell Automotive and rebuilding my factory head rather then buying a new head and then buying the kit as well (someone let me know if this is not the best choice).

Not that it's a bad idea, more so, you could probably find a used head on the Trader or 2GNT for around $100. Have it rebuilt while you continue to drive the car. Less down time for you. Less stress over "how long this is taking." Remember, you can have it fast, cheap or right and you can only pick two, so I'd go for cheap and right.

-have the head port and polished

I know a guy with some mild port work done to his head and Bill Hahn told him that he makes more power on the same turbo with less boost than he does himself. If you have the head off, I would go for broke now. Portwork is not something you do in an afternoon out in the garage. You want an experienced hand to handle the fine details to get the best results. If you have to, wait on things like lifters and rockers. Get the hardest processes out of the way now, and then do the simpler installs later. A turbo is little more than an air compressor. The easier it is for the turbo to flow a lot of air through the head, the more power you should make. Keep in mind, the same principles apply as I mention below about the valves. You don't need to hog it out or anything extreme (unless that's your goal), but your primary concern is the smooth flow of air into and out of the combustion chambers.

-decked

Deck it. You don't want to put it back on and have the HG leak on you. Make sure your shit is flat and ready to go above all else. This should be the first priority of any headwork imo.

-what kind of valve job to get

I've never heard anything saying that more angles contributes to decreased longetivity. In fact, I think I remember hearing BigRand getting fed a line of bullshit by a shop once upon a time too (then again, I could be wrong too). The more angles you get, the smoother/better the head will flow. Most common are 3, 5 and full radius. Full radius obviously provides the smoothest surface for things to enter/exit the combustion chamber, however it is the most expensive. When I bought my head from Exile Racing Technologies (ERT), they told me that any valve job is going to be an improvement. 3 angle will be great and a 5 angle will be a bit better. Does the cost difference between a 5 angle and a full radius job justify a couple more ponies on a normally aspirated street car (which mine is)? Not hardly. I went with a 5 angle. I thought it was a nice compromise considering everything else I had done to the head. Think of it this way: You can order a Big Mac meal in the small size with small fries and a 16oz drink (3 angle). They offer you the large size with twice the fries and a 32oz drink for a dollar more (5 angle). Then they ask you if you want the SuperSized meal with the same sized fries and a 40oz drink for double the original cost. Does it still seem worth it to you?

-and if i should get stock size valves or +1mm?

Some food for thought: Keeping the smaller, OEM valves will provide slightly better low end performance, due to the same amount of air being forced through a smaller opening. When you are NA, maintaining good intake charge velocity is important for making low end power. Were you to hog out the entire intake path and remain NA, you could likely make a shitton of power up top (relative), but it might come at the cost of a slowtard daily driver under 3000rpm. Introduce a turbo to the mix, and you now have a way to force more air into the cylinders. Larger valves mean you get more volume (I would think) per intake charge. More air = more fuel = more power. I don't know how this would affect off-boost driving. You have a S16g, so I doubt there's much of that going on.

Also, one of my friends that has a 1g GSX said that stock valves in the 420a are strong enough to hold high boost, i didnt know if this was true or not. So do you think i should buy aftermarket valves?? If so what kind?

I have +1mm SS valves in my head right now. Don't ask me what brand, because I don't honestly remember. I know they're Stainless Steel, swirl polished and back cut or something, but aside from that, I just know they're a quality part from a trusted vendor and they do what they were intended to do.

depends on tuning.

It all depends on tuning. Good luck with it and have fun above all else. Hope I was some help. I spent the better part of a year talking with Michael at ERT about odds and ends for my head and the finished product is something I'm rather proud of. Now, if I could just get the damn thing to run for more than a month.

 

[DSMcrazy3]

I'll be honest and tell ya I don't know what decked means

Just making sure that it is perfectly flat, so that when the Head and the block meet there won't be a gap anywhere. Sometimes they can warp, due to temperatures.

Josh

 

[420a16g]

Think of it this way: You can order a Big Mac meal in the small size with small fries and a 16oz drink (3 angle). They offer you the large size with twice the fries and a 32oz drink for a dollar more (5 angle). Then they ask you if you want the SuperSized meal with the same sized fries and a 40oz drink for double the original cost. Does it still seem worth it to you?

that was an awesome metaphor.


dude thanx so much for answering all of my questions. ok so i guess what im going to do is get the kit from Howell, have the head decked, 3 angle valve job, buy some +1mm valves and port and polish the head.

- since im on the port and polish shoudl i get both intake and exhaust side or just exhaust because a guy at Hahn said it really doesnt make that big of a difference but the more air you press out the better hp youll get, or something like that??

i mean money isnt a big issue to me, i already have about 4k invested in parts so i might as well go all out, but i dont wanna go broke. i just want this done right the first time and i want it to be able to operate at full capacity. And the down time isnt really an issue, i drive my daily all the time now anyways since im waiting on my brakes to come in and when i take it to have it built iv already prepared myself to leave it for about a month or so. Thanx again Dr1665 for the help and if you could answer that last question for me i would really appreciate it.

 

[dr1665]

that was an awesome metaphor.

Haha. Thanks. I wasn't entirely sure.

i guess what im going to do is get the kit from Howell, have the head decked, 3 angle valve job, buy some +1mm valves and port and polish the head.

Keep in mind that installing oversized valves will increase the cost by a couple hundred. I think it ran me about $250. They have to open things up to accept the larger valves, then give them the valve job. Otherwise, sounds like a good plan to me.

since im on the port and polish shoudl i get both intake and exhaust side or just exhaust because a guy at Hahn said it really doesnt make that big of a difference but the more air you press out the better hp youll get, or something like that??

I am in no position to dispute anything you were told by an official representative of HRC. They have far more experience in things than I do, however I can tell you that one of the things Bill has taken pride in over the years is making all this power on a pretty much stock head. That means, no port work, valve work etc.. I think he has cams, as I don't know how you could run 10.8 on a bone stock head. If you are running a larger turbo (or plan to), you could make use of port work. Like I said, I would keep it mild if you get any. No need to hog it out. The faster the air leaves the cylinder, the faster it will spool the turbine/compressor. Remember what I said about gas velocities - given the same volume flowing through a pipe, if you reduce the diameter of the pipe, the velocity/pressure will increase, but if you increase the diameter, the velocity/pressure will drop. (Think FMIC pressure drop, here.) Turbos give you some slack in this department, but if you're unsure, it's best to use moderation in your plans. Like a hair cut, you can always take more off, but it's a lot harder to put it back on once it's gone.

Thanx again Dr1665 for the help and if you could answer that last question for me i would really appreciate it.

No worries. It's why we're here.

 

[BigRand]

Like a hair cut, you can always take more off, but it's a lot harder to put it back on once it's gone.

True Say