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Thread: unshrouding valves on bbc

  1. #1

    unshrouding valves on bbc

    What is actually done when check and unshroud the valve? I have a set of dart 355 cnc's and was wanting to check to see if they need it. Is this worth any real horsepower?

  2. #2
    Senior Member DYNO OPERATOR
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    To answer all your questions about this;

    Yes.

    If block is bare, put blue on the area surrounding the chambers and bolt heads to block. Use a scribe and reach inside and scribe the heads all around the cylinder.

    Remove head. Place head gasket to be used on head. Place bolts in the head gasket larger than necessary. Stick some 1/2 bolts in the gasket holding it in place so it can not move.

    Now mark with scribe around the valve relieved sections of the head gasket. That is the maximum you will go when doing valve unshrouding.

    Where the valve relief Extends past the cylinder wall where valve relief is it won';t do any good to cut head any farther back at that location. Unless you place head gasket on the block and also mark it where the valve reliefs are and grind those relief notches in the block. If you do be very careful and do not grind the notch too deep. If you do decide to grind notches in block only cut it for intake vlaves and not very deep. You will then need to debur where you cut the block in the cylinder wall area. Haven't done this in many years.

    Esay way to cut the valve unshrouding reliefs is to get a flap wheel for sanding that is a little larger in outside diameter than the valve that cuts only on the outside diameter of the flap wheel. I say this because there are also flap wheels used on a disc style sanding disc that cut on the falt surface.; You want the type that cuts on the outside diameter.

    As you sand with it at only the valve relief position, move it continously up and down and slightlyu side to side. Usually anytime I am sanding or grinding on a head i am constantly keeping the stone, sanding surface, cutter or grinding surface moving, usually in small circles. I keep better control by keeping the tool continously moving.

    Possibly someone else will come by and tell you an easier or better way.

    Ed
    " Let all things that hath breath, praise the Lord. Praise Ye the Lord" Psalms 150 vs 6.

  3. #3
    Senior Member RACING JUNKIE
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    I would think they are already done but unshrouding the valves is a process that opens up the combustion chamber in the heads on the short side of the valves to the head gasket or bore size of the motor. It definately helps if they are not done already. Also valve pocket porting to 85% of the valve dia. is a good thing.

    just my opinion.

    Zip.

  4. #4
    Senior Member DYNO OPERATOR
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    Zip,
    I have seen a lot of your opinions here.
    Thank you for trying to be helpful for others.
    I like your opinions.

    Ed
    " Let all things that hath breath, praise the Lord. Praise Ye the Lord" Psalms 150 vs 6.

  5. #5
    Senior Member RACING JUNKIE
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    Quote Originally Posted by edvancedengines
    Zip,
    I have seen a lot of your opinions here.
    Thank you for trying to be helpful for others.
    I like your opinions.

    Ed
    We were typing at the same time, and we both have the same conclusion. Your post entered before mine, but we have both been there and done that, we think a like, NO it's whats the facts are. I've been racing for over 50 yrs. and have tried most everything, some work some donot. At 68 yrs. old i'm still learning, and i read every post that has to do with performance and i have learned from people such as yourself who does it for a living. I am an amatuer compared to some of the engine builders here at RJ and that's why i read all the post, to learn what i don't know. I appreciate every post that i read and learn from a lot of them. I could act like i know everything from racing so long, but i would be lying to myself, because i will never know everything, nor will i ever know all the secrets where some people have pulled extra HP from the same engine that i have built. Funny story, back in 1966 i was at Oswego Dragstrip with my blown 56 t'bird. Chicago land dodge boys, was there to match race farmer Arney Beswick, Beswick had an accident on the way too the track, so the match race was called off . Since i was there they ask me if i would run them. I said no problem, bring them on. I had run 10.22 earlier and they run 10.43, easy clip. (who is the chicago land Dodge boys?) none other than Forconas,Memic and Coil, yep Austin Coil Forces tuner. well unfortunately it started raining at lunch break and we didn't race. I approached Austin Coil and a couple yrs. ago and we talked for a few min.raminising about the old days and he remembered the days.
    Just a day in history that i will never forget, and i will never know everything and will never stop learning until the day i die.

    Zip.

  6. #6
    Senior Member DYNO OPERATOR
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    Zip,
    What is your name?
    What part of Louisiana are you from?

    I am Ed Wilson.
    I arrived in Louisiana in the Lake Charles/Sulphur/Carlyss/DeQuency area in 1977. I raced in that area on the street/highways. and the tracks until 1979. That car was wrecked in a non racing traffic accident. In 1981 I brought out a different sort of Chevy Nova that got featured in a few magazines. I raced that car from 1981 till 1985. In 1985 We took my engine out and installed it into Doug Mead's old Top Fueler and ran it a year.

    Before the Louisiana tour I was in Houston racing from 1970 until 1977. lol. Prior to Houston I was in Ft.Worth Texas doing a little racing but mostly working. Before that I was in the APOSF area in S.Vietnam.

    Is there any chance you know me, or I know you?

    Ed
    " Let all things that hath breath, praise the Lord. Praise Ye the Lord" Psalms 150 vs 6.

  7. #7
    sorry if you get ofended but de dee deee don't spend over 3000 on a set of cnc heads and do any porting by hand or on any cnc heads for that reason if you want to really see if the valves need unshouding before you kill you combustion chamber send the to joe mondello have the wet flow tested and he'll tell you if you'll see any flow gain at all. theres no point in cutting the combustion chambers if they don't need cut are they cnc chambers if so don't worry about it just bolt them on either way you'll have to have them cc each chamber to be sure each cylinder has the same compression. i meantioned joe mondello don't get confussed with his site he doesn't just do oldsmobile he will work on anything but "BE WARNED" he is expensive but you'll never find a better porter in you life time if i had to pick between a set of cnc's from some other guy and a set of hand ported heads by him i'd take his hands down.

  8. #8
    but for a much shorter version if the valve is big enough and its a small chamber size then yes you'll definitly see more horsepower from unsrouding the valves call and ask joe he'll tell you all about it ask him about when he took .060 out of the chamber and picked up 24cfm

  9. #9
    Senior Member RACING JUNKIE
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    Quote Originally Posted by edvancedengines
    Zip,
    What is your name?
    What part of Louisiana are you from?

    I am Ed Wilson.
    I arrived in Louisiana in the Lake Charles/Sulphur/Carlyss/DeQuency area in 1977. I raced in that area on the street/highways. and the tracks until 1979. That car was wrecked in a non racing traffic accident. In 1981 I brought out a different sort of Chevy Nova that got featured in a few magazines. I raced that car from 1981 till 1985. In 1985 We took my engine out and installed it into Doug Mead's old Top Fueler and ran it a year.

    Before the Louisiana tour I was in Houston racing from 1970 until 1977. lol. Prior to Houston I was in Ft.Worth Texas doing a little racing but mostly working. Before that I was in the APOSF area in S.Vietnam.

    Is there any chance you know me, or I know you?

    Ed
    PM'ed

    Zip.

  10. #10
    Senior Member DYNO OPERATOR
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    TIMMYBOY,
    hOW DID YOU GET ALL THE INFO FOR YOUR RESPONSE OUT OF THE ORIGINAL QUESTION? i DIDN'T. (caps by accident)

    What is actually done when check and unshroud the valve? I have a set of dart 355 cnc's and was wanting to check to see if they need it. Is this worth any real horsepower?
    Maybe you know the situation better than we do, because we don't know zilch except what was written as a question. That question was amply answered along with methods to do it if needed.

    Understand that on all of these forums there are many people who see questions and the reponses to them besides the original poster of the question. Many of them do not own porting tools and a few who do are not sure how to do the work. My explantions should be clear and to the point and easy for anyone with some mechanical abilities who are not used to working with cylinder heads. If each valve is done exactly the same the chamber cc of all chambers will remain the same. It takes quite a bit of sanding to make a one cc difference. Also this modification can in no way harm runner flow as measured on a bench. It might help some but can not hurt any. There is no such thing as a valve unshrouded too much in any engine.

    I will agree with you 1000% that Joe Mondello is very sharp. Joe Mondello is not on this forum answering questions though and if the original poster had acess to him, that question should not have been asked here at all. Last I heard Mr. Mondello is very ill and is living in Tennessee. He is a member on SpeedTalk with us, but has not posted in a very long time. As a kid I greww up with Mondello Heads. I know very well who he is and his contributions and innovations.

    Ed
    " Let all things that hath breath, praise the Lord. Praise Ye the Lord" Psalms 150 vs 6.


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