Milling the Heads How much?

Discussion in 'Small Block Mopar Engine' started by 64X2, Jan 29, 2011.

  1. 64X2

    64X2 Mohel at your service.

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    Ok, so I have had my car in hibernation for close to 3 years, which has just about killed me. I have been starting the car and letting it run on a regular bases, last year I got the floors put in and was able to drive it temporarily. On a short trip the car started acting up and running poorly, lose of power, slight engine ping and generally not operating properly. So I limped the car home and discovered that the dizzy was toast, the shaft was worn badly and it decide that on my trip it was going to take a crap. So I managed to pick up a fairly new dizzy out of a wreck in the salvage yard. I got it all wired up and fired up the car and I now have a horrible miss at an idle, that even when you rev the engine it is still there. I double checked everything and it seems to be coming from number 5 cylinder. I can't drive the car, because the first/reverse rod also broke on the trip, and lucky I have one on its way. So my question is does it sound like a burned valve, still need to do a compression check. If it is a burned valved, which is an excuse to pull the heads. I want to mill the heads to bump up compression, how do I figure out how much to remove from the heads, how do you figure out how much to take from the intake side of the head, what about pushrod length. The block has about 50,000 miles on it so it does not need a rebuild, I just want to get a little more power out of the motor. I know I need to figure out how far the pistons sit down in the block and the cc of the combustion chamber, I have never done anything this complicated on a engine so I need help, and or advice. I want to thank all in advance

    This what I have:
    72 318 Block .30 over
    79 Heads not sure of the casting number
    1.88/1.60 valves
    purple cam 276/284 .444/.453" 112
    LD4B Edelbrock intake
    650 Edelbrock carb
    windage tray
    double row timing chain
    Mopar Electronic ignition with and orange ECU box
    Dakota Manifolds

    Thanks
    Pete
     
  2. 72 slant 6 swinger

    72 slant 6 swinger Well-Known Member

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    i had 60 thousandths took off my 79 318 heads. i'm gonna need new pushrods tho. i don't think it helps out compression on 318's much. maybe if i'm lucky it'll help about 1/2 a point, or maybe 3/4 of a point c/r.

    it definately helps, but i don't think its a "bang for the buck" mod. it was a 100 bucks to mill my heads .60, then i had to pay 75 bucks to have my holley street dominator milled so the bolt holes would line up ok. now i'm lookin at around 100 bucks for custom length push rods. +, milling more than that can really throw off the geometry of the valvetrain. i could have bought a set of kb pistons for the same amount of money and had more compression. it has stock pistons now, i'm going with kb's and the milled heads hoping for around 9.5:1.

    you could mill your heads around .30 thousandths for now, your intake and pushrods should be fine. then in the future go with some kb's. is the heads ported? if not milling it .30 and a mild port job will wake it up. hope this helps...
     
  3. Mrmopartech

    Mrmopartech Well-Known Member

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    here is a few options.
    For every .006 you remove 1 cc of chamber volume
    Use a steel shim head gasket,normal gaskets can be .045-.060 thick,the steel ones are .025
    Replace the valves with thick margin valves to reduce the chamber volume
    If the motor is stock,and has never be apart,you could remove the crank and have it offset grinded on the rod journals .030,depending on the amount of deck height you have.This is the distance from the piston at TDC to the deck surface which needs to be checked with a micrometer,and check all of them.
    A set of bearing is cheap,100-150$ for good ones,steel gaskets are 30-40$,the crank grinding is about 150$,which will get you the most bang for the buck,as you will gain a .060 stroke advantage,mrmopartech
     
  4. TurdFerguson

    TurdFerguson Banned

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    Mill .0048 for every 1 cc on a 360 head, .0053 for every cc on a 318 head.

    http://www.mopar1.us/mill.html

    Have you done a cranking psi test yet?

    What were the results?

    Those sound like they either have small 360 valves in them or you have a set of 360 heads.
    The open chamber 318 heads come out to around 68cc
    The open chamber 360 heads come out to around 72cc

    If using the 72cc 360 heads, removing 8 cc's would be what I would do.
    BUT I would also cc the heads 1st to be sure....then determine the amount to mill.

    Start with finding the cast number of the heads, then report back.
     
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    • needsaresto

      needsaresto Well-Known Member

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      Next time have the intake face of the head milled. That way the intake can still be used on any motor,plus you wont need to have a new intake milled. Milling the heads is a great idea,just dont go over board. 9:1 is o.k with an open chamber and no quench. It's a big improvement over 7.5:1 or 8:1! You can also have the crank offset ground which will raise comp slightly as well as giving a few more cid. For the crank it will mean being maxed out as far as grinding go's,but I think 10:1 is achievable with offset grinding,head milling and a thin gasket.
       
    • 64X2

      64X2 Mohel at your service.

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      The heads are 79 318 heads, I have done some mild porting and went with a bigger valves. I have not done a compression test which is a must do to really get a better direction to go. I am toying around with ways to make what I have a little better. Believe it or not the combo I have is only putting out 200 hp and about 275 ft lb torque. I want to wring what I can out of this combination. I am on a very thin budget, almost transparent and can only afford certain things and really don't have the cash to do major things. So I was just seeing if there is anything I can do with what I have and get a little more out of it. Before the dizzy fiasco the car was dead reliable I could drive it any where and got about 20 mpg out of the motor. I am running a 10 1/2 inch clutch with a kevlar disc and 3000 LBS pressure plate. The weak link is the 7 1/4 axle with 2:76 gears. I have a 8 3/4 out of A 100 that I would love use as a trade for a 8 3/4 SBP rearend with possible 3:23 gears. So any suggestions......maybe a junkyard turbo??????
       
    • RustyRatRod

      RustyRatRod Just another dumbass. FABO Gold Member

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      Milling heads is not a very efficient way to raise compression. Let me give you an example. Using the compression calculator on the United Engine website, you can see that it takes a bungload to make a 1 point difference. Using 72 cc as a starting point with the head and 6 cc for the pistons I came up with 7.7:1 compression. That's probably fairly close. In order to move that compression up one full point, I had to decrease the cc's of the head to 60. That's 12 cc's. That's also a .072" cut on the heads. That's a lot to have to worry about intake alignment, pushrod length and valve train geometry. I don't know where different head configurations come into play. It does not make a difference what style of head you have or what shape the chamber is. "X" amount of cc's equals 1 compression ratio point. PERIOD. it is a mathematical equation. It will work out on paper the same as it would on any given engine. I've seen people try to make the comparison using different head shapes and chambers and on and on. It's the same kinda equation as 32 ounces makes a quart. It doesn't make a hill of beans difference what shape the glass is. Never has. Never will.
       
    • needsaresto

      needsaresto Well-Known Member

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      Good point Rob. There are always unforseen complications when changing a stock part. Rasing the comp with a piston is the best choice. Or you could use a set of heads that already have small chambers,like the 302 and magnum.

      I do like the idea of a blowthru turbo setup but they can be difficult to get running right. Be patient and it'll work out eventually.
       
    • 64X2

      64X2 Mohel at your service.

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      This is brilliant, exactly what I needed to understand. So that makes me wonder if it would be cheaper to pick up a set of pistons, rings, bearing. So now to look into pulling the engine out and changing the pistons, it makes sense I got the engine as a rebuilt engine that had been ran once and I guess it broke, then it was pulled and set in a corner for 12 years , and it has been in my car for the past ten years , so thats about 25 year old rebuild..there where a few things that where not built correctly when I went through the engine. . All lefthand rockers, bent push rods, bent rocker shaft. It was a mess, I went through and corrected all the defiecnces I found. I wonder if when it was built that they threw in cheap pistons also. Anyway time to rethink things....thanks for the science...


       
    • 72 slant 6 swinger

      72 slant 6 swinger Well-Known Member

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      @ 64x2. i would definately spend the extra cash on pistons. intstead of milling a lot off the head. just like stroker scamp said it's not a efficent way of gaining comp. the money,time, and extra is not worth what i have in mine. your better of to buy a decent set of pistons to up the c/r and be done with it. i'm gonna break down and buy a set for mine i'm tired of losing the compression ratio fight lol. its a losing battle all the way around. seems like no matter what you do your still gonna have crappy comp, when you try to go budget performance on stock pistons..
       
    • 64X2

      64X2 Mohel at your service.

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      well it loooks as though it will be next year before I can pull the engine and change things out. Any suggestion on what is the best bang for your buck as far as pistons go..forged, cast, hypereutectic.......would it be wise to change the rods also......
       
    • needsaresto

      needsaresto Well-Known Member

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      KB 167 or similar speed pro etc. Hypers are great pistons for the $$. Stock rod is fine to about 6500 rpm and after that you should go aftermarket.$$ wise the stock rod is alomst as much. I'd just go aftermarket,but there are refurbished stock rods available at PAW for a very reasonable price.They are resised,shot peened etc.
       
    • 72 slant 6 swinger

      72 slant 6 swinger Well-Known Member

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      ^^ actually i don't think you can get much from PAW anymore. i was on their website a couple months back and it said they would only be selling early hemi parts from now on. they had some of their left over stock on ebay for pretty cheap prices. i bought 2 new small block mopar cams off of em cheap. i dunno if anythings changed yet tho. just thought i'd throw that info out to u guys.. they could be selling all the different motor parts again for all i know lol.
       
    • needsaresto

      needsaresto Well-Known Member

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      Well thats a shame. Was a good buy on those rods,but the aftermarket stuff is better anyways,lol! It's usually much lighter and stronger.
       
    • TurdFerguson

      TurdFerguson Banned

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      Milling the heads for compression is just fine when dialing in quench or working on a budget.

      Preference is unique to all of us.

      When I milled 8cc from my open chamber 360 heads, I picked up a full point.
      It all depends what you are working with, slant sixes are a testament to this.
       
    • 64X2

      64X2 Mohel at your service.

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      So I have done more reading than I think should have. I have decide to rebuild the engine and this what I have figured out so far. KB167 pistons, scat rods and 302 casting heads. I will zero deck the block, on the heads I will build them with 1:88/1:60 valves. I will reuse the cam I have 430/444 lift and 268/276 duration. If I used the compression calculator correctly this should yield me about 9.1:1. I figure I should be in the nieghborhood of about 300 hp. I have alot of planning ahead of me, since this will be done next year..........
       
    • needsaresto

      needsaresto Well-Known Member

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      Good idea planning ahead! Write it down somewhere so you dont forget.
       
    • RustyRatRod

      RustyRatRod Just another dumbass. FABO Gold Member

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      The best thing to do is to blueprint everything. Don't take the specifications at face value. MEASURE them. All of the specs given on parts I have always considered as a "guide" if you will. Because of variancies in machining process and the mere temperature of the air, when you get down to measuring CC's and thousandths of an inch, almost anything can make a difference. I would invest in a good CC kit with a nice burette and the whole shoot and match. They aren't expensive and they are literally worth their weight in gold when it comes to seperating the bullshit of bench racing from reality. You will see for yourself exactly how many CC's will make "X" amount of difference and what it takes to get there.
       
    • 64X2

      64X2 Mohel at your service.

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      I have gone back to the books, and started rereading blueprinting. I will post my progress once I start on this. Thanks to all that responded........
       
    • mullinax95

      mullinax95 Well-Known Member

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      I was more or less on the same road you're are now except my engine was a 273. I had already had the "302" heads cut also back cut valves. I still wanted more torque/hp but the 273 was already bored .060 so that was that far as the engine. I had a friend make a suggestion that made a since so I did it. I bought a blueprinted 360 short block and never looked back. The longer stroke of the 360 made a big difference. The total cost was $900 the cam bearings was already installed so I installed my MP .474 cam, installed my small valve 302 heads, performer intake, carb, etc... off the 273 engine and off I went. Just a little suggestion that I will more likely get flamed for but it beats the hell out of a short stroke 318. lol
       
    • dartfreak75

      dartfreak75 Well-Known Member

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    • Wyrmrider

      Wyrmrider Well-Known Member

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      classic camshaft should be obsolete POS- and there cheaper sources
      there is another thread where the poster claims milling ruins flow
       
    • dartfreak75

      dartfreak75 Well-Known Member

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      Sorry i didn't mean to post that there i clicked on the wrong thread!!
       
    • RustyRatRod

      RustyRatRod Just another dumbass. FABO Gold Member

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      Deadgummit. Thread back from the dead.
       
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      • dartfreak75

        dartfreak75 Well-Known Member

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        I'm sorry. I had two tabs open I was reading this thread and another at the same time and I went to comment on the other thread and opened the wrong tab!