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1983 K20 350 SBC Upgrade Opinions

Discussion in 'Engine & Performance' started by Old60Driver, May 19, 2020.

  1. Old60Driver

    Old60Driver Junior Member

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    Location:
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    First Name:
    Michael
    Truck Year:
    1983
    Truck Model:
    C20
    Engine Size:
    350
    Good afternoon! I'm sure this will just be the first in a long like of requests looking for advice. :)

    For a bit of background, here's my introduction thread:

    https://www.gmsquarebody.com/threads/hello-from-houston.29459/#post-573685

    So, as my introduction mentions, she's in REALLY great shape, but she's lacking a bit of pep in her step. Leaning toward the following modifications:

    Vortec Heads
    Edelbrock Intake
    Edelbrock Carb
    Comp Cam XE256H
    Long tube headers

    There will definitely be other mods as well (ignition, fuel pump, fuel pressure regulator, etc) but this is really the heart of it. What I'm looking for is a truck that the wife and I can cruise around in on a Saturday night. Maybe cruise the beach for a bit of good surf fishing and playing. I just don't see myself wanting to create crazy horsepower (that may change with time lol). Just some nice low end grunt, a bit of of lope, and a nice set of headers and exhaust.

    So, square body gurus, what say you? :)

    Does this set up look like it might serve my needs?

    Going to try to post a few pictures. These were taken last summer. We don't have many, but when I get up there at the end of June, I'll grab some more.

    Thanks in advance y'all, and stay safe!

    20190914_190051.jpg 20190914_190104.jpg
    20190914_190059.jpg


    InkedIMG_0563_LI.jpg IMG_0567.jpg
     
  2. 82sbshortbed

    82sbshortbed Get outta there! Supporting Member

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    Truck Year:
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    Truck Model:
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    Engine Size:
    454
    Nice dog too. I think you'll be happy with those upgrades. You should gain a good bit of horsees for the money. I did that or in the process of putting them on on my sbc. I got the new Edelbrock performer eps intake and new Quadrajet on and seen a great improvement in the motor. Then I was going to put t he cam and hedders on but, found a BBC 454 that had all that already done to it so I went that route.

    Anyways I like the plan you got going forward. I'm sure y'all will enjoy it.
     
  3. Old60Driver

    Old60Driver Junior Member

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    Engine Size:
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    Thanks for the reply. I don't actually get to bring her home until the end of June (work), but I think I'm going to start stockpiling some parts in preparation. Even with the relatively low miles, I think a compression check is in order. Additionally, I would like to desmog it. Given that I live in Texas, and it's almost 40 years old, I think that's legal? Thoughts?

    Also, thanks for the comment on my bud. His name is Bourre. Amazing dog!
    20181009_115318.jpg
     
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  4. 1987 GMC Jimmy

    1987 GMC Jimmy Automobile Hoarder

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    Engine Size:
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    The cam seems like a solid choice, although you’d need to add valve springs to the list for that model. Those lift specs are right on the edge of the ceiling for Vortec Springs so I’d rather knock that out rather than playing chicken with the ones you have. Plus, Comp recommends it with that cam anyway. The Vortec heads are another good upgrade if the ones you find don’t have cracks. I’d also see what aftermarket cast iron options are out there because there are some good ones. Headers are good to go in my book. The aluminum intake’s value to performance is overrated IMO, but there is definitely a value to aesthetics and reassembly at a meager cost.

    The only one I’d say is a downgrade is the carb option. If you just hate the Quadrajet, assuming it still has it, go Holley. That being said, the Quadrajet can handle the raunchiest 454 out there, much less a mild 350.

    If it’s still got air injection, I’d say ditch that, and don’t overlook the little things like a tuned up ignition system, which you already mentioned. Unless the pump is weeping, they either work or don’t, so I wouldn’t concern myself too much there. And a regulator should be totally unnecessary for a mechanical pump/carb fuel system. It wouldn’t be a bad idea to check your fuel pressure to ascertain how it’s doing, and some pumps do go above the nominal pressure, but I wouldn’t fret, especially if it’s already working fine.
     
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  5. SquareRoot

    SquareRoot Full Access Member

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    Engine Size:
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    I just went through this. You know that saying "hindsight is 20-20"?

    Think about this. By the time you buy the carb, intake and gasket set your halfway to the Awesome Edelbrock Pro-Flo 4 efi system. The efi comes with the intake, all hardware and a new distributor, gaskets, the works.

    I guarantee you the drivability and new truck reliability will put a smile on your face.

    I converted my new Goodwrench 350 to Vortec heads, a similar comp cam, Pro-flo and headers and I'm extremely satisfied. Of course, if I had to do it over again, I'd just drop an LS in it. Hindsight....lol.
     
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  6. 82sbshortbed

    82sbshortbed Get outta there! Supporting Member

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    I live in Texas too and have true duals with flowmasters on BBC 454 and it's legal. So I'd pull it off. Some people on here might leave it on but, not me.
     
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  7. Catbox

    Catbox Full Access Member

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    I agree with all of this, except the LS part.
    Hahahhahahaaa.
    I just don't care for the way they look in an old car or truck.
     
  8. SquareRoot

    SquareRoot Full Access Member

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    I don't disagree with you. On the other hand, after spending hundreds of hours putting all this together, I'm burnt out on it.

    I only want to open the hood and see the engine every 5000 miles when I change the oil. There could be a box of dirty diapers in there as long as it runs like an LS.
     
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  9. Old60Driver

    Old60Driver Junior Member

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    Thank you all for your replies!!! I apologize for the late replies. Due to COVID, I'd been requested to work onsite for the foreseeable future. Working 13 hour days. At night. Seven days a week. :eek: Heck, I haven't stayed away past 2 in the morning in forever, so the switch to nights has been...challenging. lol Still, I plan on moving forward with the project, and really appreciate you folks taking the time to reply!!

    A few questions:

    If I buy the Vortec heads in my original post, I'll still need to upgrade the springs, correct? You're right, the clearance is pretty tight...

    I hear ya! And I originally looked into just that. But I kind of miss tinkering with a carb, and my boys (who will be assisting with the build) have never tuned one. Still toying with the idea though!

    Thanks! And good to know! I think the first thing I'll do is de smog her while she's still stock. Been looking into all the emissions junk. What a pain. LOL

    I'm sure I'll have MANY more questions as this moves along, thanks again for the insight y'all!!
     
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  10. 1987 GMC Jimmy

    1987 GMC Jimmy Automobile Hoarder

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    To answer your question to me, you’ll need to upgrade valve springs if you go with that cam. If you go with one that’s below the Vortec stock spring .450 lift threshold, you can keep what’s on there. The cam you posted was like .447/.452 so even though it’s flirting with that ceiling, I’d still err on the side of caution.

    Also, I saw a video of that cam in a car idling at 12” of vacuum. That’s somewhere between better than mediocre but not quite ideal with respect to vacuum accessories’ functionality. I would assume HVAC mode control would still work, albeit a little slower, and I would assume the brake booster will still do it’s job, although you’ll feel a slightly more rigid brake pedal. The only one I’m not sure how it would react is the cruise servo. That may still be within its normal operating range, or it may have trouble keeping the preset speed fixed on a hill, but I don’t know. If everything worked perfectly, that’d be great. It’d be nice to have a somewhat lopey cam like that and still have access to the few luxuries we were afforded in the 70s/80s automobiles.
     
  11. 75gmck25

    75gmck25 Full Access Member

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    I am surprised the video you saw shows only 12” of vacuum with the xe256h 212/218 @ .050 cam. I have a Howard’s cam with 213/217 @ .050 and 112 LSA, and I show about 19” of vacuum at idle. I use 15 degrees BTDC initial timing and 20 degrees mechanical, and it idles and accelerates very smoothly.

    I used Blueprint aluminum heads instead of Vortecs. By the time I would have purchased Vortecs and then swapped to a new Vortec intake, the total cost was very close to the $899 for the Blueprint heads.

    Bruce
     
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  12. Old60Driver

    Old60Driver Junior Member

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    Engine Size:
    350
    1987 GMC Jimmy - Thanks for the reply! I do, however, have a question regarding the following statement:

    You mention the stock spring .450 lift threshold. In the heads I'm looking at from Summit, the maximum valve lift is 0.520 in. Is 'lift threshold' and 'maximum valve lift' the same?

    Again, thanks for the feedback; it's much appreciated!
     
  13. Old60Driver

    Old60Driver Junior Member

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    75gmck25 - Thanks for the reply!

    Did you use the stock intake when you went with the Blueprint heads? Or did you already have a 'performance' intake installed when you made the head change?

    Thanks again!
     
  14. Catbox

    Catbox Full Access Member

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    Those would be the already upgraded heads.
    I would check to be 100% sure, a quick call to Summit should find out what you want to know.
     
  15. cptsnoopy

    cptsnoopy Junior Member

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    First Name:
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    Truck Year:
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    Truck Model:
    K-20 Silverado
    Engine Size:
    454
    My 81 K20 350sb/th400/np208 with 4” lift & 33”x12” tires slowed down if it even saw a hill coming. And, 7.5 mpg.

    I swapped in a 1973 454 with 9:1 compression and an rv cam and that made it drive and feel like I thought it was meant to. Plus, new mpg was 10 with a camper. Huge improvement. Torque is king, not so much the hp.

    25 years later, I’ve got it apart again to swap in a 4L80 in place of the th400. Good luck with your project and I hope it works out the way you want.
     
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