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Technical 283 head gaskets

Discussion in 'Traditional Hot Rods' started by slug, Nov 30, 2020.

  1. slug
    Joined: Sep 1, 2007
    Posts: 222

    slug
    ALLIANCE MEMBER
    1. West Virginia Mountaineers

    Where can I find 283 steel shim head gaskets for a 283 Chevy? I had them on back order with Summit for three months and they finally closed it out saying they can't get them. Thanks
     
  2. lake_harley
    Joined: Jun 4, 2017
    Posts: 1,427

    lake_harley
    Member

    I deal with a warehouse that shows as having over 40 in stock. I could arrange a drop ship if you're interested. The P.N. is FelPro 7733SH-1 and they show a compressed thickness of .015", but they do have a bore diameter of 4.100" which means that they are actually intended for a 350, so they wouldn't right at the edge of a 283's bore. I'm planning on eventually using a pair on a 283 I'm tinkering with. FWIW....they'd be about $11.00 each plus the shipping charges from Michigan.

    Lynn
     
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  3. triumph 1
    Joined: Feb 9, 2011
    Posts: 575

    triumph 1
    Member

    Have you tried calling cometic?



    Sent from my iPhone using H.A.M.B.
     
  4. AHotRod
    Joined: Jul 27, 2001
    Posts: 11,365

    AHotRod
    Member

    Summit has more than 16 available right now
     

  5. squirrel
    Joined: Sep 23, 2004
    Posts: 48,727

    squirrel
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  6. RockAuto has Mahle brand steel ones, 4" bore, for under $10 each. Is the steel shim or bore size critical to you?
     
  7. flamedabone
    Joined: Aug 3, 2001
    Posts: 4,923

    flamedabone
    Member

    Why are you using a steel shim gasket rather than a regular over the counter head gasket?

    Just curious, -Abone.
     
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  8. Roothawg
    Joined: Mar 14, 2001
    Posts: 21,410

    Roothawg
    Member

    Jeff, on the early 265's, 283's the compression ratio is pretty sensitive to head gasket thickness, due to the small bore. A .040" composite gasket designed for a 350 or 400 would lose 1/2 to a full point of compression.
     
  9. slug
    Joined: Sep 1, 2007
    Posts: 222

    slug
    ALLIANCE MEMBER
    1. West Virginia Mountaineers

    Thanks to all. What ROOTHAWG says is why I don't want the big bore 350 types or the composite ones. I will start checking again but want the small bore ones.
     
  10. slug
    Joined: Sep 1, 2007
    Posts: 222

    slug
    ALLIANCE MEMBER
    1. West Virginia Mountaineers

    Thanks squirrel, I sent the person on e-bay a message to mic them for me.
     
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  12. 56sedandelivery
    Joined: Nov 21, 2006
    Posts: 6,695

    56sedandelivery
    Member Emeritus

    ^^^This is the best way^^^. Occasionally, you can fine steel shim head gaskets on that auction site meant for the 262, 267, 305 engines. Also, look into marine applications for them with the same engines. And yes, stay away from the "universal fit" head gaskets. I have a supply for my 265 and 283 project engines. I am Butch/56sedandelivery.
     
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  13. slug
    Joined: Sep 1, 2007
    Posts: 222

    slug
    ALLIANCE MEMBER
    1. West Virginia Mountaineers

    The above ones show 3.960 bore size on the package but on Jegs site their description shows bore size at 4.090. I guess I could contact the manufacture. Thanks again for the expertise!
     
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  14. slug
    Joined: Sep 1, 2007
    Posts: 222

    slug
    ALLIANCE MEMBER
    1. West Virginia Mountaineers

    Just checked with SCE and they say no longer available. Maybe in the spring. That's the problem everyone wants to sell you stuff for a 4 inch bore...."it will work" Yea and one size fits all! Maybe the flatheads went through this faze once until they became popular again. SBC may have to wait awhile. Not everyone wants an LS motor.
     
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  15. Damm, now i have to find some sets and stock pile them. I only have one left.
     
  16. The GM steel shim gasket P/N 3830711 has a 4" bore size, I remember from my GM parts days that was in the catalogs as fitting everything from 265 to 350 engines despite the bore size difference. There was an earlier number, it escapes me at present but it started with a 37 prefix but that was long gone by the early 1970's era at least from GM.
     
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  17. Roothawg
    Joined: Mar 14, 2001
    Posts: 21,410

    Roothawg
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  18. Budget36
    Joined: Nov 29, 2014
    Posts: 6,421

    Budget36
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    I’m curious. Has anyone seen a performance loss running a 4in bore gasket on a smaller bore engine like the 283?
     
  19. Roothawg
    Joined: Mar 14, 2001
    Posts: 21,410

    Roothawg
    Member

    I did a quick calculation last night and the difference I came up with was enough to worry about. It went from 9.16:1 to 8.5:1. I always worry about it on my 265's, 283's and 301's. It's like raising the deck height by .015". You probably wouldn't feel it in the "seat f your pants" gauge, but when you are talking about 5-10 hp, when you are only making 220. It's enough to try and avoid. Just my humble opinion.
     
  20. Budget36
    Joined: Nov 29, 2014
    Posts: 6,421

    Budget36
    Member

    Good info. Is that from the volume lost between the block and the head form the bore difference?
     
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  21. Good info for me before I put the 283 back together for my kids pu.
     
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  22. Roothawg
    Joined: Mar 14, 2001
    Posts: 21,410

    Roothawg
    Member

    Visualize a cylinder filled with fluid. If you fill every nook and cranny with fluid, the volume increases dramatically. So you have raised the cylinder by adding .015" to the height, and then you have to think about the difference in the bore as well. The fire sealing ring is way out away from the edge of the bore. The 283 is a 3.8750" bore stock, so for giggles lets say .030 over on bore so 3.905". If you order a gasket that is 4.100" That's just short of .200". All of that extra space gets filled along with the .015" of increased height.

    On a 440 Dodge or a BBC it's a nothing deal, but on a wee block, it counts.

    Did that make any sense? In my head it did....
     
    Last edited: Dec 1, 2020
  23. Budget36
    Joined: Nov 29, 2014
    Posts: 6,421

    Budget36
    Member

    Oh yes, I understand completely. When I get to work tonight I’ll look at it as well. I’ve never been concerned with a small change in CR, I was wondering what was happening if say the quench was good (assuming compressed gasket is the same) and how flame travel would/could be affected by the extra area under the head/block.
    Not to bring OT into this, but GM used the same .022 (to my knowledge) compressed gaskets on 305’s and 350’s during the 80’s and early 90’s in the TPI engines.
    I’d always wondered about what if a proper sized head gasket was used for the 305, would it have helped?
    Just being an inquiring mind:)
     
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  24. Roothawg
    Joined: Mar 14, 2001
    Posts: 21,410

    Roothawg
    Member

    Actually, the quench would have been right with the steel shim. Figure deck height at .025" plus the .016" gasket gets you close to the .038-.040". For production purposes GM would have said "close enough".

    The 305's did also have a similar gasket, but it was composite. I think it was thinner than the 350 standard gaskets as you stated. It seems like it had a cardboard feel, rather than a composite laminate. It's been a minute, though.

    I used to be able to buy the Fel Pro version of the 305 gasket, but I am guessing that went away a long time ago.

    Glenn (@AHotRod )would know. He used to be a rep for them, many moons ago.

    I did find this one. The bore is smaller, but the compressed thickness is still too thick. https://www.summitracing.com/parts/fel-8510pt/make/chevrolet
     
    Last edited: Dec 1, 2020
  25. Great info @Roothawg
     
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  26. Budget36
    Joined: Nov 29, 2014
    Posts: 6,421

    Budget36
    Member

    I asked when I was doing the OT 350 on another board about the head gaskets. Now I did not research it much, but the closest I could find for “factory replacement” was. Mahle. Comp with a steel shim at .022 compressed. Stated on the infor was 305/350 for my year I needed.
    Now these were masses produce vehicles, so probably fit the “one size” thing


    Regardless, just to be clear, I’m not discounting a thing/ word you have said. :). It was just a brain tickler for me
     
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  27. Roothawg
    Joined: Mar 14, 2001
    Posts: 21,410

    Roothawg
    Member

    Oh, I didn't take it that way. I'm too dumb to get offended easily.
     
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  28. Ericnova72
    Joined: May 1, 2007
    Posts: 455

    Ericnova72
    Member

    Way too much emphasis in nothing...do the math.

    Difference in compression ratio on a 283 between two .015" gaskets, one with a 3.960" bore and one with a 4.100" bore....is 0.03:1 difference in compression ratio.

    3.905" bore, 3" stroke, 58cc head, 4cc valve relief(Flat top piston), a .025" piston-to-deck, and .015" x 3.960" bore gasket = 9.42:1 compression.
    3.905" bore, 3" stroke, 58cc head, 4cc valve relief, a .025" piston-to-deck, and .015" x 4.100" gasket = 9.39:1 compression.

    Just use the 4.100" bore version, it won't make enough difference to notice.

    You'll have a bigger difference in compression ratio if your block isn't decked square than you will worrying about a little bit excess gasket bore diameter.

    Gasket thickness, on the other hand, I will agree is critical, because of the area of opening involved the volume is a lot bigger gain/loss.
     
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  29. Roothawg
    Joined: Mar 14, 2001
    Posts: 21,410

    Roothawg
    Member

    Eric, I think the compressed gasket makes a bigger difference, rather than the larger bore size.

    I'm not sure that the steel shim is even available in the larger bore.... I've gotten lost since we started. I'll have to read the whole post again.
     
  30. Budget36
    Joined: Nov 29, 2014
    Posts: 6,421

    Budget36
    Member

    I see what @ericnova is saying, I’ll clock in soon and post a link to the mahles’s i used
     

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