Topic: Need some advise on head mods

[Beachbum]

Soon I plan to install another cam, and have the head freshened up. Can oversized valves be installed, if so is the gain worth the expense? How much can the head be milled? I realize that oversized valves and high lift cams can cuase clearance problems, I'm looking for the maximum amount of compression from milling, I've had very good results with milled heads and cam changes in the past ( on Harley's and chevy's )and consider this mod one of the better bang for the buck mods you can make. Any help or anyone's personal experience who has made similar mods in the past to the 2.5L would be greatly appreciated.

[wrangler387]

How extreme of a cam are we talking? I'm not to sure if oversized valves can be put into the head without new seats.. But i think you would be better off porting the head and getting a really good valvejob. A good valvejob is probably the most important thing.

[joe-joe]

I am interested as well. Can those knowledgeable on the subject please speak up?

[supryj4]

It was recomended that I not do a full port job just match port and polish I was told I would loose too much bottem end with a full port job.I will be reciving me cam on friday it is a hesco rvob with 470 lift 264 duration 214@ .050 and center line is 110 deg.I am having my head machined for the sping hight of the new double spings,milled,match ported and polished,a race valve job,bronze guides,and better valve seales it should be done next week.I cant wait.When I was checking into it no one ever talked about larger valves so I dont know about that.

[wrangler387]

I dont know what that guy considers a "polish" but i just think of the things people do to make their heads "look pretty" for their customers. I'm assuming he is doing basic portwork also though. Definately don't polish the intake side, leave it ruff. Have you tried searching the internet about headwork? there is a lot of stuff on the actual ports (bowl, throat, deshrouding etc.) but most good headporters won't disclose their valvejobs since thats the most important part to headwork.

[Beachbum]

Hey supryj4 will you let us all know how your jeep runs after you get the head and cam installed, I've been researching the Hesco and clifford cams but can't find much info on the performance increase after they have been installed. Did you mill the head? As I stated in the previous thread I've had very good results doing this on other engines, is the .470 lift to much lift to allow for milling? Good luck and let us know how it turns out !!!!!!!!!!

[supryj4]

Sorry to that guy for the poor choice of words.I have done two stroke motors before and thats what the guys I worked with called it when we ported and polished a motor.What is being done to my head is match porting to the intake/exhaust gasket and all the rough edges and casting imperfections smothed out to get better flow in and out of the motor with less turbulance.It has nothing to do with making it look pretty sorry!I got the cam today but still wating on the head I will let you know how it turns out as soon as it is done.Bennie from hesco said that a 2 or 3 angle valve job would be fine unless you are building an all out race motor running a constant 6000 RPM then you would want a 5 angle.Bennie also said that taking 3 to 4 thousandths off of my head would bring up my compresion and not  cause any problems with heat or valve clearence but I would have to run premium gas wich I already do.

 http://www.cylinder-heads.com/pages.asp?pageid=22988
 wrangler387 see bottem of page were they talk about port and "polish"

[wrangler387]

i dont know if you took what i said as being a dick, i was just trying to make sure you weren't paying to have somone just polish the ports... I've seen it done, shiney ports do sell haha. I was just trying to help you out  :wink:  I think i need to use more emoticons... What they are doing is good (thats what i meant by just do a basic port job), i plan to do the same thing to a head alittle down the road. As for the valvejob, not all 3 angle valvejobs flow the same or work the same. You can have a 3 angle outflow a 5 angle... Just depends on what angles you combine together (When a head porter finds what angles/combos he likes the most, he normally doesn't tell anyone). And one set of angles isn't the best for every motor. I wish i knew more about head porting, i looked into it alittle bit a year or so ago when I was looking to port one of my Honda heads.

[snowbrew]

Two Years ago when I rebuilt the engine I put a Clifford cam with a 264 duration.  I found that mopar makes oversized valves for both the intake and exhaust.  I talked with several drag racing guys here locally and they said that I would benefit from enlarging just the exhaust side.  By leaving the intake small causes a greater velocity in the air-fuel mixture, so more air-fuel is put into the cyclinder.  I had a three way valve job and polish and ported the head myself.  With the cam, Clifford sent me stiffer valve springs.
Driving inpressions: The engine really comes alive above 2500 rpm's.  The engine will make hp untill 5500 rpm's.  I pulled a 20' boat over a pass here in WA doing 65 all the way, but I was running 4800 rpm's in third gear.

Two months ago I put a banks header on.  Wow this made a BIG increase. I also increased the exhaust pipe all the way back to 2 1/4, with a flowmaster 50 series.

One month ago I put on roller rockers.  The engine rev's up much quicker now.
Hope this helpes.

[dragon51]

snowbrew

How is was your gas miliage after those engie mods.

[BK2LIFE]

looks like im building pretty much the same motor as described up there..
as far as compression, "3 to 4 thousandths off of my head " will only raise compression about .1 -the factory compression is 9.2:1.  i am milling .010 off the head, and .020 off the block, static compression should be 9.8:1 - will have exact compression once i get the head gasket and measure the thickness (not all gaskets compress the same amount)
the block has been bored .030, and my head has a full port and polish job.
( http://s2.photobucket.com/albums/y36/BK2LIFE/jeep/ )
porting the head is a great idea on any motor, metal casting is rough, porting smooths out the roughness. you dont want any smoother than an 80 grit finish on the intake side, now the exhaust side you can make super smooth, like mirror finish. (intake charge has fuel, too smooth and the fuel sticks to the sides of the ports, exhaust is just gas so smooth ports to help it out) now i could go into detail about port matching, opening the runner size, unshrouding valves, but heres a link to check it tells the basic good stuff to know: http://www.sa-motorsports.com/diyport.shtm

-james