1.840 exhaust valve
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1.840 exhaust valve

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    custom member raped southwind's Avatar
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    Default 1.840 exhaust valve

    I just pulled my bbc 858 heads down and was a bit surprized with the exhaust size. I read that gm used these in there early alum heads but thats all the info i can find! Im guessing someone else put these in along the way. Any options other than going 1.88 any help greatly apreciated

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    gn7
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    Quote Originally Posted by raped southwind View Post
    I just pulled my bbc 858 heads down and was a bit surprized with the exhaust size. I read that gm used these in there early alum heads but thats all the info i can find! Im guessing someone else put these in along the way. Any options other than going 1.88 any help greatly apreciated
    The 1.84 was used in 68-69, 074 alum heads.
    That valve might actually have been a upsize for the 858 by who ever installed them. Those heads came with 1.88 and 1.72 valves.
    If they are OK i would just leave them. If you need to replace one or two, I go with 1.88.



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    Quote Originally Posted by gn7 View Post
    The 1.84 was used in 68-69, 074 alum heads.
    That valve might actually have been a upsize for the 858 by who ever installed them. Those heads came with 1.88 and 1.72 valves.
    If they are OK i would just leave them. If you need to replace one or two, I go with 1.88.
    Thank you. I figure these were done awhile ago. Unfortunately i think that takes some value away.

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    Quote Originally Posted by raped southwind View Post
    Thank you. I figure these were done awhile ago. Unfortunately i think that takes some value away.
    Not really. Those heads were came with 2.19/1.88 valves. So if you were to install 1.88 exhaust if you decide to sell them, no one good say they were not "original".

    Those are fairly rare castings. GM only made them for 2 years as I remember, and then they only used them on high performance engine like the 375 HP/396 and the 425HP/427. The restorers will pay a pretty decend price for them.

    DON'T PORT THEM!!!!



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    Quote Originally Posted by gn7 View Post
    The 1.84 was used in 68-69, 074 alum heads.
    That valve might actually have been a upsize for the 858 by who ever installed them. Those heads came with 1.88 and 1.72 valves.
    If they are OK i would just leave them. If you need to replace one or two, I go with 1.88.
    I would guess someone may have just put a 1.84 in place of a ``1.88,, maybe he didn't own a pair of calipers,, who knows. I took some SBC heads off my friend's flatbottom engine one time that had several different size valves in them.

    I had told TJ a few weeks ago to sell the heads to a collector and buy better ones for his engine.

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    Quote Originally Posted by gn7 View Post
    Not really. Those heads were came with 2.19/1.88 valves. So if you were to install 1.88 exhaust if you decide to sell them, no one good say they were not "original".

    Those are fairly rare castings. GM only made them for 2 years as I remember, and then they only used them on high performance engine like the 375 HP/396 and the 425HP/427. The restorers will pay a pretty decend price for them.

    DON'T PORT THEM!!!!

    Someone has already taken a grinder to the intake side unfortunately!

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    Quote Originally Posted by obnoxious001 View Post
    I would guess someone may have just put a 1.84 in place of a ``1.88,, maybe he didn't own a pair of calipers,, who knows. I took some SBC heads off my friend's flatbottom engine one time that had several different size valves in them.

    I had told TJ a few weeks ago to sell the heads to a collector and buy better ones for his engine.
    Heads are for sale Barry . I guess I'm not listing in the right places. I've put them up on a few vette forums . only pulled two valves to make sure valves were stock size. Unfortunately not!

    As for the motor build..... It's on hold due to the wife needing a second surgery on her hand! That's the main reason I couldn't buy ur crank.... Thanks for all ur help as always Barry

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    Quote Originally Posted by obnoxious001 View Post
    I would guess someone may have just put a 1.84 in place of a ``1.88,, maybe he didn't own a pair of calipers,, who knows. I took some SBC heads off my friend's flatbottom engine one time that had several different size valves in them.

    I had told TJ a few weeks ago to sell the heads to a collector and buy better ones for his engine.
    Like I said though, alot of them were fitted with 1.72 valves.



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    What size is the intake valve? There is no reason to worry about a 1.84 ex valve. Most of the really big-flowing, big intake valve heads these days have a 1.84 ex valve. They gladly sacrifice a little ex. valve diameter to make room for a bigger intake valve. My guess is someone who knew what they were doing did it for a reason.
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    Quote Originally Posted by steelcomp View Post
    What size is the intake valve? There is no reason to worry about a 1.84 ex valve. Most of the really big-flowing, big intake valve heads these days have a 1.84 ex valve. They gladly sacrifice a little ex. valve diameter to make room for a bigger intake valve. My guess is someone who knew what they were doing did it for a reason.
    To my knowledge all 858 heads have 2.19 intakes. I've heard that they had 2.06 as well but I have no first hand knowledge of that. They are the original 65-67 BBC rectangle port heads. Early ones had 1.72 exhaust valves, later ones had 1.88. There is a possibilty that the 1.72 heads were used on early 375 HP 396. Like you said, somebody may have just put in valve no larger than needed, and the 1.84 was the next size up from the 1.72 that was in the heads.



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    Quote Originally Posted by gn7 View Post
    To my knowledge all 858 heads have 2.19 intakes. I've heard that they had 2.06 as well but I have no first hand knowledge of that. They are the original 65-67 BBC rectangle port heads. Early ones had 1.72 exhaust valves, later ones had 1.88. There is a possibilty that the 1.72 heads were used on early 375 HP 396. Like you said, somebody may have just put in valve no larger than needed, and the 1.84 was the next size up from the 1.72 that was in the heads.
    No one that I know of stocks a 1.84" BB Chevy ex valve in standard lengths. If I want one I have to cut it down from a 1.88.
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    Quote Originally Posted by steelcomp View Post
    No one that I know of stocks a 1.84" BB Chevy ex valve in standard lengths. If I want one I have to cut it down from a 1.88.
    Yeah, but you're looking 40 years after they were a stock GM part number for 074 alum heads. You have no way of knowing when the valves were installed in a set of 45 year old heads.



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    Last edited by gn7; 04-02-2013 at 07:28 AM.

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    intakes are the standard 2.19. I just thought it strange for the 1.84 but gn7 has a point. 40 something yrs ago the 1.84 was easiely available due to it being a factory part number. the heads are dated early 66 so my guess now would be that someone built these looking for extra power back in the day, and used what he had at his disposal!.

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