ever open up a combustion chamber on a milled head

hoggyrubber
hoggyrubber Expert Adviser
edited November -1 in HUDSON
i have a couple of previous posts about the 262 head i had on my 308. it has been milled .040" so i have some concern about running it as is. there is a 308 locally that the owner may sell parts off if he doesn't sell it whole in a month or so. it's head in in unknown condition.
i was thinking about this today, doing my usual thing of not wanting to wait. hate the thought of dust/ rust starting on my new valves/ seats. then it hit me... why don't i just open up the combustion chamber a little to compensate for the shave. i have a bridgeport style mill but an just a amature machinist. this seems like it could be pretty straigt foward. anybody ever done this? would it work? would it weaken anything.
i don't have the head in front of me cause i'm at work but best i remember it slopes down fron the valve side. i was thinking about hogging some out of the piston side. could i make what i take out flat or would i need to keep the roof at the same angle as it is now to help flow? or is this whole thing a bonehead idea? at close to $100 a pop i hat to buy another head gasket and my time is free right. :blink: any thoughts.

Comments

  • Ol racer
    Ol racer Senior Contributor
    fyi

    The only problem Ive encountered milling any Hudson head a lot was the Exh valves may close sparkplug gaps so I installed shorter reach plugs or dbl washers. Ive also 'fly cut' above the valve pocket for increased clearance, especially for hilift cams. Sugest get some 'play dough' & place on valves, install old gasket and cyl head with 'some' bolts then rotate by hand to determine your clearance. Higher compression may cause timing to be retarded slightly to elim ping.
  • hoggyrubber
    hoggyrubber Expert Adviser
    thanks oldracer for the info. after a little measuring and brain work today it looks like the combustion chamber is about 5.30 cuin. figured .020" back on the head would be 0.16 cuin more in size. if i take .035 off the intake valve area, which is flat, that will get me back to where i need to be. sound correct to anyone? is this a lot of trouble for nothing. since the head is flat set up will be easy. any other thoughts feel free to shoot them out at me, hr
  • [Deleted User]
    [Deleted User]
    FWIW Many long years ago when flathead fords were being hotroded it was common practice to releave the cl. block between the valves and cly.
    This gave a better flow between the valves and cly.also reduced compression some.I would think work on the head in the same area would work also.
  • [Deleted User]
    [Deleted User]
    one outher thought.how thick is the metal to the water jacket?will there be enough to take the running presure?
  • hoggyrubber
    hoggyrubber Expert Adviser
    well i did it this morning, pretty easy- took about 30 minutes. i don't know if it will do much, might have been fine without it. i guess feeling good about it is worth it. ha. took about .035" off the intake portion. i will put up a picture. i should be able to get the head back on this afternoon. thanks everyone for input. as usual, i need all i can get.
  • Ol racer
    Ol racer Senior Contributor
    edited May 2011
    :unsure: FYI
    Be sure to check the Exhaust clearance closely though.. If not enough depth will close the S/plug gaps.
  • hoggyrubber
    hoggyrubber Expert Adviser
    i will check them. thanks for letting me know. i like the idea of adding a extra washer.
  • lsfirth
    lsfirth Expert Adviser
    Hey Hoggy,

    Read through your post....interesting idea you have here. Judging by your picture, it looks like the intake valve area is about 1/4 of the whole combustion chamber area....therefore if you took 20 mils off your head, then you'd need to take around 80 mils off the intake relief to keep the same combustion chamber volume and therefore compression ratio (approximate numbers). But keep in mind, if your head was off of a 308, then it could have a larger combustion chamber to begin with. This is because the larger swept volume of the 308 cylinder would need a larger combustion chamber to have the same compression ratio. So, decking the 308 head by 20 mils could have put it right in the ballpark of your original 262 head's combustion chamber volume. You might be able to adjust the compression ratio with different thickenesses of head gaskets if available....seems like some old hot-rodders out there could give some experience/advice on that. Good work! Keep us posted on how it turns out!!

    Lee
  • hoggyrubber
    hoggyrubber Expert Adviser
    i don't know how good i was on my math.:blink: i thought it was around 1/3 of the area but my methods weren't highly accurate. i took .035 off so i hope that will be good enough. i was a little concerned about getting in the water jacket, though so i am glad i didn't press my luck! i was told about extra head gaskets but at a little under $100 a pop i would hat to stack too many up on there. prob one extra would do. well if i blow the gasket i might try 2 or hunt a extra head. i will let you know how she goes. i am working on the electric now.
  • hoggyrubber
    hoggyrubber Expert Adviser
    i found a aluminum 308 head with .020 milled off locally. wonder if i should pick it up seems like i read the aluminum ones would warp. what do you guys think? if the price is right?
  • Ol racer
    Ol racer Senior Contributor
    FYI
    I wouldnt double up Head gaskets. Stick to flycutting chamber if nebessary...I currently drive two Hoenets with aluminum heads, and raced with aluminum heads with Studs back in the 60's using any gasket available(McCord/Victor. etc).Just lucky I guess never blew one... Today, the BEST Permond is the only Gasket to utilize.
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