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84 C30 Exhaust - Stymied

Discussion in 'Tech Discussion' started by RangerLee, Jan 26, 2021.

  1. RangerLee

    RangerLee Junior Member

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    Engine Size:
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    I am working on a 84 C30 that had a GM Crate engine put in it. The heads are 882 and only have the 6 hole exhaust stud config. The exhaust manifold on the passenger side has a 7 hole stud config. The people that put the engine in just never bolted the last stud. Both manifolds are over the sparkplug manifolds. The block only appears to have a left hand dip stick so the left manifold blocks the dipstick hole. I ordered below the sparkplug manifolds for a 79 C30 since they had the correct 6 hole stud config and would work on left side dipsticks. However when I went to mount them up, the motor mounts are totally in the way, not by a little.. but by a lot. So I am baffled here.. the motor mounts have not changed between 79 and 84 so what am I missing? I am in Cali so I changing the exhaust beyond OEM will result in a failure.
     
  2. DoubleDingo

    DoubleDingo Drain The Swamp, Completely

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    81-C20 Silverado Camper Special-TH400-4.10s; 65-C20 with 4:57 gears and Borg Warner Overdrive
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    Carb'ed Vortec 350; 1972 L48 350
    Pics. Need pics
     
  3. 80BrownK10

    80BrownK10 Full Access Member

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    Sounds like it has Ram horns on it now and he wants to go to the later style manifold. Why a manifold off a later truck won't work I have no idea. Let's see some pics as he said. These guys will point out real quick what may or may not be happening.
     
  4. AKguy

    AKguy Full Access Member

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    The obvious solition: Move out of “Call-ee-forn-ya”! Move up here, it is a free-for-all!
     
  5. RangerLee

    RangerLee Junior Member

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    OK.. Sorry for slow response in getting pictures.. but I was hit with a blizzard in the Sierra and had to wait for the truck to melt out some so I could get pictures. The first picture is the new passenger side exhaust manifold (6 bolt config) that will fit the 882 heads. The second picture is the exhaust manifold currently on the truck. It is the 7 bolt configuration and the 882 heads are not tapped for the extended bolt. The third picture is a close up the back side of the exhaust manifold showing the 7 bolt (sorry not very clear). The last picture is a close up of the engine mount that is in the way of the exhaust manifold. Per RockAuto, the new exhaust manifolds should fit a '79 C30. Although my truck is an '84 I selected the '79s because they had the 6 bolt configuration that would mount to the heads. I would not expect the motor mounts to be different between '79 and '84.. I kinda figured motor mounts are motor mounts on these trucks...

    20210202_092453[1].jpg

    20210202_092536.jpg

    20210202_092557.jpg

    20210202_092628.jpg
     
  6. Bextreme04

    Bextreme04 Full Access Member

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    No pic of what doesn't fit? It looks exactly like my stock manifolds on the 74 C20 and 80 K25 with 350's that I've had. What part doesn't fit? Yu should have heat shield on the inside of those curves so it doesn't melt the plug wires, but other than that it looks identical.
     
  7. RangerLee

    RangerLee Junior Member

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    It is the first picture.. that '79 exhaust manifold will not fit because the motor mount is in the way
     
  8. Bextreme04

    Bextreme04 Full Access Member

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    You tried to install it and it didn't fit? It looks exactly like mine and fits fine. The manifold rests on top of the upper clamshell and the plug wires go right on top.
     
  9. Bextreme04

    Bextreme04 Full Access Member

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    F1568233-4FE1-48A1-AE91-9C8CFB20D867.jpeg C2F18DAA-9049-46F9-8B47-C204B643F4F5.jpeg This is how mine looks installed. Factory 1980 K25 “M” code 350 with federal emissions
     
  10. DoubleDingo

    DoubleDingo Drain The Swamp, Completely

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    I have never seen a manifold like that one. It's like a ramhorn, but it exits out the back. Maybe from a 305? Why are you changing them? Edit: changing them because of dipstick. Wouldn't it be easier to get a dipstick that worked with those manifolds, instead of the extra cost manifolds and of course your time?
     
    Last edited: Feb 2, 2021
  11. Bextreme04

    Bextreme04 Full Access Member

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    Here’s the ones from my 74 C20 also a factory 350 engine with federal emissions. image.jpg
     
  12. DoubleDingo

    DoubleDingo Drain The Swamp, Completely

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  13. RangerLee

    RangerLee Junior Member

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    I also want to stop the exhaust leak since the manifold present has stud holes in the 7 bolt config. and my heads are only drilled for the 6 bolt config.
     
  14. idahovette

    idahovette Full Access Member

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    Are you sure the new manifolds are pickup manifolds? Passenger car manifolds usually won't work. Thee is a "flat" on the inside lower portion of the truck manifolds that will clear the clamshell, kind of "angled" like.
     
  15. bucket

    bucket Super Moderator Staff Member

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    Yeah, they were used in the 80's on some cars and trucks. They flow terribly.

    My hunch is that the mount clamshell bracket on the block is from a different vehicle. It has to be close to fitting though? I'd just trim the bracket a bit until the manifold fits. You can also grind on the manifold some, especially if there's a hump from a parting line in that area that interferes.
     

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