Thewhitebeast

I just purchased a set of low mi 317 heads. They are going on a 01 ss m6 with a MS4 and all the goodies. My question is how much should I get these milled and is the porting worth it? Should I get them milled and do the porting myself? What is you opinion on which head bolts to use? Thanx

Steve Bryant

iTrader: (1)

I would suggest that you do a search on home+port and some other terms like that. This question has been asked many times (me included).

What are your goals?
What is your plan for your car (future use, future mods)?
What is your budget?

Steve

Gunnar@Patriot

iTrader: (20)

We can CNC port them, do our 5 angle valve job, hand blend the valve bowls, and mill to your specs for $600.00. If you have any questions, please let us know.

N4cer

iTrader: (11)

What forced induction setup do you have?

Thewhitebeast

The car has no blower and will be that way for about a year.

muncie21

iTrader: (14)

I would stick with the stock heads until you go FI. The reason most people go with 317's is to reduce compression on FI motors; milling them would kinda defeat that purpose.

N4cer

iTrader: (11)

Then why do you want low-compression heads?

Cop Car

iTrader: (14)

if you are going to buy a supercharger later, just put the heads on a shelf. when you put your supercharge in and with a cam matched for FI have the heads ported, but not milled, that way you loose compression (which is good for FI)

if you just HAVE to have ported heads now, port some 241 or 243s

muncie21

iTrader: (14)

241's can be had dirt cheap and the 243's aren't far behind.

Thewhitebeast

The reason I went with 317's instead od 243's is I got them cheap less than $200. If the port design is the same I was just going to try and get these heads back to stock compression. If and when I go with FI it will all be different ...block, heads, cam, etc. So All I really want to know is how much to take off to get the compression back up and do they flow good enough as it is? thanx

N4cer

iTrader: (11)

I think you'll have problems if you thin the base of them that much. They'll be weak.

Steve Bryant

iTrader: (1)

The 317 heads are good heads and in my opinion. You can do very well even if they are not milled at all to increase the compression ratio. If you plan to go to forced induction in the future, your heads will still work. If you want them milled a few thousandths (maybe .030"), you may not even have to adjust your pushrod length at all. However, I would buy a decent set of aftermarket pushrods no matter what you do.

I can tell you from my own experience, home porting your heads takes a lot of time, patience and self-education. It's an interesting experience, but it's a very large challenge to get good consistent results from cylinder to cylinder. You also run the risk of breaking through to the water jacket while porting or getting the wall thickness for the port too thin and the head is more vulnerable to self-destruction in use.

Since you already have the heads, it would be nearly impossible to beat a deal like Gunnar is talking about for $600. Also, a good CNC program will beat anything you or I could do. I'm glad that I ported the heads that I have just for the learning experience. I got some nice gains by blending the bowls and smoothing the runners and not going much further. I didn't hog out a bunch of material in intake or exhaust. However, I don't plan to stick with these heads. I learned a lot and gained a lot of respect for just how much better a well prepared pair of CNC'd heads perform than what I could do on a single pair of heads.

Steve

Cop Car

iTrader: (14)

you will be loosing serious piston to valve clearance. 241s and 317s flow about the same stock ive heard. from everything that ive seen personaly it seems like there are 2 diffrent heads you want to use when porting, either 5.3 truck heads or 243 heads. i was told that because the 5.3s are such a bad flowing head, there is pleanty of material to shape the runners exactly how the porters want.

imo sell your 317s, you can buy 241 heads for 150 bucks (ill sell you mine if you want). for 300 or so you can have 243 heads, which bumps up your compression even more, without milling

Thewhitebeast

Is it or is it not true that stock 317'2 and 243's flow about the same? I read this awhile back in another thread that I cant seem to find now. I dont really care if you think it is to much workinvoled I just wanted to know how much to take off 317's to get the compression back and to keep stock push rod lenght. thanx

Cop Car

iTrader: (14)

317s and 241s flow the same

243s flow much better

Gunnar@Patriot

iTrader: (20)

035, 317, and 243 castings share the same intake and runner design. The main difference in the 243 heads and the other 2 castings in the combustion chamber size. All 3 of these heads will flow in the high 230's to low 240's in stock form. 241 castings will flow in the low 220's.

Cop Car

iTrader: (14)

interesting. what are 035 heads off of?

Gunnar@Patriot

iTrader: (20)

2002+ LQ9