Combustion Chamber Cleanup
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Combustion Chamber Cleanup

  1. #1
    Senior Member Josh@JBP's Avatar
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    Default Combustion Chamber Cleanup

    Didn't want to take the other thread too much further in this direction.

    Warp Speed made a comment/observation about a picture of D3 heads Paul(Lakes Only) put up.
    Quote Originally Posted by Warp Speed View Post
    Are these 460 heads? (sorry, I don't get out much so it's been like 20 years since I've seen any!)

    If so, i can see how they could be prone to detonation.....they're a mess stock aren't they!?!
    The reason I say this is the huge ledge dropping from the quench area to the chamber roof. Those grooves may be helping some, but with a little grinding and blending I bet they would be a differant animal!
    These are a pair of Edelbrock performer 460 (75cc) heads I acquired for an upcoming 512 Build.




    You can still see the imprint from the fire ring in the head gasket to give a general idea of the quench pad area. The chamber is completely open on the lower half. I believe, and Paul can correct me if i'm wrong(I know he will) that these were modeled after a D0VE head combustion chamber. So essentially the chamber design is 40+ years old.

    What can be improved here. I'm not worried about removing material I have compression to spare.

    Also does the answer to this question change if i told you the pistons have a D shaped Dish, it appears that the quench area on the piston mates up pretty well with the quench on the head as it is.
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    gn7
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    Its more than a little work, but it would look something like this. Your chamber won't allow you to get it esxactly like this, but you can see how much the chamber is laid back towards the quench pad. This camber is deeper than yours so you won't be able to lay it this far back, but the point is to soften the jump.



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    Quote Originally Posted by gn7 View Post
    Its more than a little work, but it would look something like this. Your chamber won't allow you to get it esxactly like this, but you can see how much the chamber is laid back towards the quench pad. This camber is deeper than yours so you won't be able to lay it this far back, but the point is to soften the jump.
    Alright i get the gist, and i don't mind the work. Another question, i remember seeing a formula a while back, or maybe it was a ratio, that would tell the minimal desired quench area.
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    Also Josh leave the area around the intake valve finished in 40 grit. . .nice and rough. . .as you transition to the the exhaust side of the chamber smooth that out to a polished finish..
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    Here is a couple pic's of my Blue Thunder Heads combustion chamber. Hope it helps!
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    Quote Originally Posted by Marcsrollin View Post
    Here is a couple pic's of my Blue Thunder Heads combustion chamber. Hope it helps!
    Those are nice, my SBF vic jr's look very similar in combustion chamber design to those.

    Maybe they had a reason but it looks like Edelbrock got lazy when it came to the 460 chambers. Alot of ppl have told me that edelbrocks arent the pick of the litter as far as 460 heads go, but I got a great deal on these and with a little work I think I can make them better.
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  9. #7
    www.highflowdynamics.com LakesOnly's Avatar
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    Quote Originally Posted by [email protected] View Post
    These are a pair of Edelbrock performer 460 (75cc) heads I acquired for an upcoming 512 Build. You can still see the imprint from the fire ring in the head gasket to give a general idea of the quench pad area. The chamber is completely open on the lower half. I believe...that these were modeled after a D0VE head combustion chamber. So essentially the chamber design is 40+ years old.

    What can be improved here. I'm not worried about removing material I have compression to spare.
    Those old Edelbrock heads do base their chamber design on the early 385 Series heads. Although based on a 40 year old design, when compared to the factory chamber designs that both Chevy and Mopar offered in their mass produced big block passenger car engines of that same era, the Ford chamber could be considered to be well ahead of its time comparatively speaking. (Please, no tangents on this thread. )

    There may be some significant gains by detailing the Edelbrocks, but BIG gains would require welding and not worth the effort in a lake-use hot boat build, or even in a drag boat where an engine with your heads could already be made powerful enough to need to back the boat into the zeros in many classes. Besides, you'd be "bastardizing" the heads and if you needed to replace one of them then duplicating it is that much more trouble. Further, chamber design has come a long way and so has port design, plug location, etc, that comes with the newer BBF offerings in aluminum heads, so just accept the Super Cobra Jet-based Edelbrocks for what they are and clean them up and run them with some good detailing. By itself, there is more to be gained from porting them than there is from reworking the chamber, but if they will be ported then chamber work often becomes part of the equation....just not completely redesigning them.

    The fact is that the early-style Ford chamber, by virtue of it's shallowness, offers some gains over the later/deeper D3VE chamber. (The "smogger" D3 head's job was simply to lower compression and reduce detonation through the re-introduction of the quench pad). On your Edelbrocks I might lay back the chamber wall around the intake valve so as to unshroud it slightly, by laying back toward the fire ring, starting where the adjacent chamber is closest and continuing this lay-back around the perimeter of the valve toward the quench pad, but blend your way out where the quench pad has straightened and begins move further away from the intake valve. That quench pad is your friend and I don't think that the gains in this particular chamber design would be as great as the chamber that GN7 has posted, for example. On the crescent side of the chamber (where the plug is) there is some stuff that can be done there but don't get too happy, just "even out" the chamber shape.

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    Quote Originally Posted by LakesOnly View Post
    Those old Edelbrock heads do base their chamber design on the early 385 Series heads. Although based on a 40 year old design, when compared to the factory chamber designs that both Chevy and Mopar offered in their mass produced big block passenger car engines of that same era, the Ford chamber could be considered to be well ahead of its time comparatively speaking. (Please, no tangents on this thread. )

    There may be some significant gains by detailing the Edelbrocks, but BIG gains would require welding and not worth the effort in a lake-use hot boat build, or even in a drag boat where an engine with your heads could already be made powerful enough to need to back the boat into the zeros in many classes. Besides, you'd be "bastardizing" the heads and if you needed to replace one of them then duplicating it is that much more trouble. Further, chamber design has come a long way and so has port design, plug location, etc, that comes with the newer BBF offerings in aluminum heads, so just accept the Super Cobra Jet-based Edelbrocks for what they are and clean them up and run them with some good detailing. By itself, there is more to be gained from porting them than there is from reworking the chamber, but if they will be ported then chamber work often becomes part of the equation....just not completely redesigning them.

    The fact is that the early-style Ford chamber, by virtue of it's shallowness, offers some gains over the later/deeper D3VE chamber. (The "smogger" D3 head's job was simply to lower compression and reduce detonation through the re-introduction of the quench pad). On your Edelbrocks I might lay back the chamber wall around the intake valve so as to unshroud it slightly, by laying back toward the fire ring, starting where the adjacent chamber is closest and continuing this lay-back around the perimeter of the valve toward the quench pad, but blend your way out where the quench pad has straightened and begins move further away from the intake valve. That quench pad is your friend and I don't think that the gains in this particular chamber design would be as great as the chamber that GN7 has posted, for example. On the crescent side of the chamber (where the plug is) there is some stuff that can be done there but don't get too happy, just "even out" the chamber shape.

    LO
    Great info, just what i was looking for. My next question was going to be about unshrouding the intake valve but you beat me to it. Also these heads have already had some port work and opened (nicely) to SCJ ports. Most of the work looks to be done on the intake side, and from what I read on Reincarnation Automotive, the exhaust need only a little blending which it appears to have. Not sure what they flow yet.

    Never wanted to make these heads something they're not(ie welding etc..) but if theres room for improvement, i'm all about that. thanks guys
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    Good luck , and keep us posted on the numbers and the rest of the build!
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    Quote Originally Posted by LakesOnly View Post
    Those old Edelbrock heads do base their chamber design on the early 385 Series heads. Although based on a 40 year old design, when compared to the factory chamber designs that both Chevy and Mopar offered in their mass produced big block passenger car engines of that same era, the Ford chamber could be considered to be well ahead of its time comparatively speaking. (Please, no tangents on this thread. )

    There may be some significant gains by detailing the Edelbrocks, but BIG gains would require welding and not worth the effort in a lake-use hot boat build.

    LO
    It pretty common knowledge that the Ford early chamber is less detonation prone than the BBC. And you can't get even close to a modern chamber heart or fig.8 shape and slope without some serious welding. Only posted the pics so Josh could get an idea of what direction to go.
    And Josh, you Victor Jr. SBF heads alongs ways ahead of your BBF heads. The Eddy BBF heads are more of a performance "replacement" head. The Victor Jr are little more towards the "race" side, with the assumption that aftermarket pistons and cam will be used.



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    That old Ford chamber is basically a hole in the head to contain the valves and spark plug, and a place to squeeze the mixture. There isn't much thought if any to manipulating the air for any performance reasoning. The best you can do is just do some unshrouding and eliminate any sharp edges to help prevent detonation. Put the head on the block and scribe the bore around the spark plug side of the chamber and lay it back to the scribe line. A good quality valve job will make a bigger difference than anything, and blending the bowls just under the valves would be next.
    Last edited by scott foxwell; 11-19-2009 at 03:46 PM.
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    Quote Originally Posted by gn7 View Post
    And Josh, you Victor Jr. SBF heads alongs ways ahead of your BBF heads. The Eddy BBF heads are more of a performance "replacement" head. The Victor Jr are little more towards the "race" side, with the assumption that aftermarket pistons and cam will be used.
    Yeah I got spoiled early by the vic jrs, first set of heads I ever bought (17yo).

    Quote Originally Posted by steelcomp View Post
    That old Ford chamber is basically a hole in the head to contain the valves and spark plug, and a place to squeeze the mixture. There isn't much thought if any to manipulating the air for any performance reasoning. The best you can do is just do dome unshrouding and eliminate any sharp edges to help prevent detonation. Put the head on the block and scribe the bore around the spark plug side of the chamber and lay it back to the scribe line. A good quality valve job will make a bigger difference than anything, and blending the bowls just under the valves would be next.
    Good tip, makes more sense than using the gasket

    I didn't pre-load this question with a lot of information about my build because i was looking for more generalized answer/s, the 460 head served as a good example and much of the information above will be aplied to them soon. I believe there's a lot of good information in this thread, a lot of which is universal and will apply to future builds also.

    This engine will be 512 inches with 28cc dish srp pistons, relativley mild cam and will be forced to breath through aluminum log manifolds (the better long bolt manifolds). With the large dish's the static compression (with the chambers at 75cc), is still 10.28:1±. With a cam small enough to work with logs (with out fear of water reversion) my dynamic compression is high enough to make me second guess pump gas.

    It sound like alot of the work mentioned above will help considerably with detonation control, and perhaps the "fire jet" or quench groove will give me a safe margin.

    As far as perfromance gos this thing wont have to work hard to kick my 460 pack-a-jet's ass, and i love my pack-a-jet it a great engine 31 years and still running strong.
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    Quote Originally Posted by [email protected] View Post
    Yeah I got spoiled early by the vic jrs, first set of heads I ever bought (17yo).



    Good tip, makes more sense than using the gasket

    I didn't pre-load this question with a lot of information about my build because i was looking for more generalized answer/s, the 460 head served as a good example and much of the information above will be aplied to them soon. I believe there's a lot of good information in this thread, a lot of which is universal and will apply to future builds also.

    This engine will be 512 inches with 28cc dish srp pistons, relativley mild cam and will be forced to breath through aluminum log manifolds (the better long bolt manifolds). With the large dish's the static compression (with the chambers at 75cc), is still 10.28:1±. With a cam small enough to work with logs (with out fear of water reversion) my dynamic compression is high enough to make me second guess pump gas.

    It sound like alot of the work mentioned above will help considerably with detonation control, and perhaps the "fire jet" or quench groove will give me a safe margin.

    As far as perfromance gos this thing wont have to work hard to kick my 460 pack-a-jet's ass, and i love my pack-a-jet it a great engine 31 years and still running strong.
    Unless your worried about noise, don't let the wet logs scare you away from some duration. You just have to think outside the box and you can run more duration than many think. Depends on what is on the ass end of those logs. Thru or over transom, "U" traps etc. I run as much as 288 @ .050 in a FE Ford and wet logs with no problems.



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    Quote Originally Posted by gn7 View Post
    Unless your worried about noise, don't let the wet logs scare you away from some duration. You just have to think outside the box and you can run more duration than many think. Depends on what is on the ass end of those logs. Thru or over transom, "U" traps etc. I run as much as 288 @ .050 in a FE Ford and wet logs with no problems.
    They're risers opend to 3.5" hose (3" id) and are at if not below the water line, i'm also lookn to make power at 4600-5200 or there about. Planing to start with a 9.5" impeller. ought to be a stump puller.
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