gains from milling a head worth it

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Landrew -> gains from milling a head worth it (9/27/2008 9:49:37 AM)

 I have my head out on my 07 Rancher 420. I'm getting it bored as it got sunk and there is some piston/ring/cylinder wear. Since it was out I took the head over to the shop as well as the cylinder.  I was wondering if it is worth milling the head 10 to 20 thousands and increasing the compression? I know the timing will be retarded becasue of this.

Am I going to make gains with this or will the change in timing hold it back.



kleinwild -> RE: gains from milling a head worth it (9/28/2008 9:30:40 AM)

Very large gains if done right!



Landrew -> RE: gains from milling a head worth it (9/29/2008 1:07:09 PM)

The shop doing it does a lot of the performance mods around here. What can I expect or what should I look for in doing it?



engie -> RE: gains from milling a head worth it (9/29/2008 1:39:40 PM)

The rancher engine is still a pushrod engine, correct?

You can achieve virtually unlimited compression out of doing this to a pushrod engine because the valves open straight up and down, whereas they come in at an "angle" on overhead cam engines.  It has nothing at all to do with timing on your engine, since you don't have overhead cams and thus no timing chain.  You'd just have to adjust your valves to work with the pushrods which will now essentially be "longer" in comparison to head height.  Worst case scenario, the pushrods may need to be shortened... 

Compression is essentially a linear gain.  If you have 10:1 compression and increase it to 12:1, and then match timing and fuel to it, you stand to gain 12/10, or 20% more power....[;)][:D]



VT_Grizzly -> RE: gains from milling a head worth it (9/29/2008 1:41:02 PM)

To do this correctly - you should measure you piston to valve clearance.  In order to do this, you need to put some putty (form an auto store made for this application) on your piston and re-install everything torqued properly.  Turn the motor over and check how thick the putty is where the valve comes down near the piston.  Then you know how much you can shave without hitting a valve on the top of your piston.  When I bored mine out, I had them take off 10-15 thousanths, just to gain a little and have a clean head surface.  I don't think 10-20 thousanths would pose an issue, and it should gain a little compression. 



Landrew -> RE: gains from milling a head worth it (9/29/2008 4:59:38 PM)

Thanks for the help. I'll go ahead and get it done.

Cant wait to see how it runs after a new HMF pipe, Optimizer, porting and milling the head along with a 25 thou bore job.



longdude17 -> RE: gains from milling a head worth it (10/5/2008 11:57:31 PM)

i dont think the rancher 420 is a push rod engine.....



Landrew -> RE: gains from milling a head worth it (10/6/2008 8:10:35 AM)

It is. When I took it apart I was surprised to see pushrods on a vehicle from 2007. Sure makes it easy to do the cylinder as I dont have to worry about a timing chain etc. Though with the milled head the valves shoudl be re-adjusted.



toyazman76 -> RE: gains from milling a head worth it (10/6/2008 7:50:13 PM)

Just a question. Why wouldn't you just go with a high compression piston?



Landrew -> RE: gains from milling a head worth it (10/6/2008 11:01:53 PM)

They dont make one. At least after a day or searching the web. I suppose Wiseco could custom make one for hundred of $ or more but that is to much for the return on investment.



longdude17 -> RE: gains from milling a head worth it (10/7/2008 7:51:59 PM)

well ill be danged....it is a push rod engine....i just looked at a parts fitche and man that is surprising! talk about making it easier to rebuild!



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