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HT502 Crate motor.....

Discussion in 'Tow & Trailer' started by Greg72, Sep 14, 2005.

  1. Greg72

    Greg72 "Might As Well..." Staff Member Super Moderator

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    Has anyone used one of the GM "Tow Truck Retrofit" version 502s in a rig yet?

    It's basically a lower-cost version of the standard 502 crate motor, setup for a LOT less horsepower (peak is something like 330HP), but the torque is massive and starts aroud 1500RPM.

    Of course, it is described as a towing motor so you'd expect it to perform well in that application....just curious about driveability, impressions and maybe what it's like when there ISN'T a 7500Lb load being pulled behind...????

    This is under consideration for the '72 Burb. I can't complain about the 350SBC that has been faithfully pulling my trailer over the Rockies & Sierras so far....but I think it's foolish to expect that it's a "smart" thing to keep doing.
     
  2. Burt4x4

    Burt4x4 3/4 ton status

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    Go For It
    RamJet HT502 would be SWEEEEET! :bow:
     
  3. Greg72

    Greg72 "Might As Well..." Staff Member Super Moderator

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    Great enthusiasm Burt.....but you're kind of missing the point.

    RamJet 502 = $8999. :eek1:
    HT502 = $5918. :wink1:


    I think the RJ502 is more of a high-revving motor, and I don't think it has the BIG TQ numbers down low like the HT502 does. When you're trying to get about 15,000 Lbs moving from a dead stop.....lots of TQ off-idle is going to be the key.

    I'm not putting a diesel into the Burb, so I think a big-cube, TQ down low engine is going to be the next best thing.


    :thumb:
     
  4. SUBFAN

    SUBFAN 1/2 ton status

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  5. Greg72

    Greg72 "Might As Well..." Staff Member Super Moderator

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    Point taken.....last night I went to the GM Goodwrench site directly and downloaded .pdfs for each 502 motor, to compare the dyno sheets. [slight rant] Hey GM, how about a little discipline about how you create a dyno graph? Every engine has a different set of RPM values and the scales for HP/TQ are never the same twice [/slight rant]

    What I'm finding (to your point) is that all of the 502s appear to make at least 500 Lb/Ft down at low RPMs. There may not be anything that remarkable about the HT502 after all. It is one of the cheaper ways to get that kind of power though....and the retrofit kit (for the later trucks) is designed to replace a factory 454 but re-use the TBI setup, etc. It's more about the convenience of being able to swap in a 502 for a 454 using stock accessories.... at this point the 502HO looks to be a decent value (with better overall torque)...the ZZ502 is a little sexier, but costs about $2000 more than the 502HO...aluminum heads may look a little strange in my classic Chebby anyhow. :wink1:

    As for you other question (big inch envy?:D)...if you read carefully you will see this is for the Suburban, not the K5.

    The Burb has towed the K5 & trailer combo (probably 7500Lbs) over the Sierras (9000+ feet) and also the Rockies (11,000+ feet) using a 350SBC and a TH350 trans..... just because I got away with it on my Moab trip and my cross country trip doesn't mean it's a smart thing to keep doing.....my foot was DEEP into the throttle to keep that combo moving along and that's a lot of mechanical stress for 8 - 9 straight hours a day for 6 continuous days!!!!!

    Don't worry, the 632BBC is still in the plans for the K5 (the 1969 K5, BTW)...this query is just to start preparing my tow rig for BlazerBash 2006.


    :thumb:
     
  6. K1Orion

    K1Orion 1/2 ton status

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    You may want to consider a 502 short block and adding the top end of your choice. You might get more for your money with a "bolt-on build"( I use the term loosely). Unless, of course, you really want a warranty.
     
  7. Burt4x4

    Burt4x4 3/4 ton status

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    Ahhh I said RJHT502 silly goose... simply meaning take a HT502 and use ramjet FI....I guess Edlebrocks MPFI would be fine too :p:

    hell just build a stump pulling 454 and be done, with FI ofcourse :bow:
     
  8. Greg72

    Greg72 "Might As Well..." Staff Member Super Moderator

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    What's interesting on the HT502, is that they make 2 part numbers. One is for existing FI trucks and one isn't.

    The one that ISN'T has a warning that you shouldn't try to adapt it to a stock FI system....something about it running too lean under certain conditions?? I dunno, it was weird.

    Anyway, I've go SO many projects to work on I think I really need to be realistic. A turnkey crate motor (or close to it) for the Burb is probably the way to go. I really should be thinking about a different tranny too...maybe a built 700R4 or use the freshly built TH400 that's just sitting in my garage (though it's a 4WD version)....I'd hate to install a fresh thumper BBC and then puke out the tranny a month later.
     
  9. SUBFAN

    SUBFAN 1/2 ton status

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    Where are those dyno graphs?

    Yeah, it seems as if the General changes its mind on what each motor puts out.
     
  10. rjfguitar

    rjfguitar 3/4 ton status GMOTM Winner

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    A 502 sounds like it would pull great, but not economical with today's fuel prices. $6K is a lot of money. If it was me I would be thinking about a turn key 383ci before an expensive big block, heck you could do a Cummins conversion for half the cost of that 502...
     
  11. Greg72

    Greg72 "Might As Well..." Staff Member Super Moderator

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    You don't know me at ALL, do you? :D




    A 383 won't get me where I want to be TQ-wise. True, it's a better choice than a 350, but it's no match for the cubes of a 502. A rappy small-block just doesn't "do it" for me.....I fell in love with the deep burble, and rumble of a BBC long ago...and a big-block for a tow rig is kind of a no-brainer.

    A diesel conversion? Eeeewwww. Where's that vomit emoticon when I need it?? :p:

    There's a lot more to this than economics... I place a huge amount of imporance on the aesthetics and "rightness" also. Maybe it's a "1st Gen Thing"?? If I end up putting in a BBC, I am going have to paint the engine block Chevy orange instead of black......because that's what would be RIGHT for the Burb. And if it uses a plastic timing cover, I will swap it for a metal one....plastic doesn't belong on the engine of an early truck. Same goes for the valve covers....It's going to need something more "classic" looking than those modern "502" machined covers.

    .....that's just me I suppose. :dunno:
     
  12. Greg72

    Greg72 "Might As Well..." Staff Member Super Moderator

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    [​IMG]

    [​IMG]
    [​IMG]
    [​IMG]
     
    Last edited: Sep 16, 2005
  13. SUBFAN

    SUBFAN 1/2 ton status

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    Interesting....I thought the RJ was supposed to put out 565 HP? That is a nice flat torque curve though.... :D
     
  14. Greg72

    Greg72 "Might As Well..." Staff Member Super Moderator

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    See what I mean about the power "scales"???

    Torque and HP are supposed to ALWAYS be identical at 5252RPM (that's where the two lines typically cross each other). On these graphs the crossover point is all screwy...it gives a VERY distorted view of things. Especially on the HT502.

    I may go to the trouble of normalizing all these dyno charts onto a single graph just to compare them more effectively.

    It's Friday, why not??!!! :D


    !NEW!

    [​IMG]
     
    Last edited: Sep 16, 2005
  15. bigjbear

    bigjbear 1 ton status Staff Member Moderator

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    Torque and HP should always be the same at 5252 RPM by deffinition.

    HP = torque x RPM/5252. Just think about it, if RPM = 5252, than HP will equal torque times one.

    The guy who cooked up that chart must have designed the Aztec too.
     
  16. Greg72

    Greg72 "Might As Well..." Staff Member Super Moderator

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    Yeah, well the problem is that they use a second scale on the right for horsepower, and they simply adjust the scale and division marks to make the HP
    "look" more impressive....

    I mean c'mon, the HT502 only has 330HP, but when you look at the graph the HP peak is taller than the peak torque of 518 Lb/Ft!!!! Since when is 330 larger than 518??? Product marketing at it's finest.... :D

    Anyway, MY chart (which only shows torque) is at least a more fair assessment...all 4 engines are plotted against the same scale, so the highest curve IS the most powerful engine.... BTW -> The HT502 sure looks a lot less impressive now doesn't it?? :eek:
     
  17. SUBFAN

    SUBFAN 1/2 ton status

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    I thought the HT 502's torque was low....It should be fairly easy to get 550 ft lbs down low with a 502....
     
  18. rjfguitar

    rjfguitar 3/4 ton status GMOTM Winner

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    I would agree that having a 502 under the hood of a 1st gen would be cool stuff..... I've gathered from your last few threads that you have some deep pockets.....good for you, it's nice having the money to do what you want, not just what you can afford, from what I hear :doah:

    Ha..... I guess you haven't been slapped in the face with the diesel bug yet. Bring on your flashy orange 502, all I'd need is an Edge EZ and you'd never hang with me on a 10% grade with 15K hooked up.... and I'd use 1/3 the fuel you would.... :p:

    A P series 12v in that burb would be awesome! Almost as cool as having a modern rig hooked to the trailer.... :whistle: :laugh:
     
  19. mini_mull

    mini_mull 1/2 ton status

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    I know it's impossible to beat a 502, but you might want to check out this article before you dump the extra 4K for the ZZ502 instead of the HT383. 500 Lb-Ft in Six Easy Steps Of course, the 502 wins no comp, but dollar for dollar the HT383 is the more practical choice, but then again, not all of us care about being practical, so put in the 502 and keep up with those newer diesels well almost :D
     
  20. Greg72

    Greg72 "Might As Well..." Staff Member Super Moderator

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    RJF,

    It's not really about "deep pockets".....(though I seem to always find a way when it's something I really want) Please understand that this is my hobby; I can demonstrate a lot of patience if the parts I want will cost more and will take longer to get. "Instant Gratification" doesn't really apply to me any more....I've suffered from too much "buyers remorse" in the past after buying something that wasn't what I wanted just to have it SOONER, and I've learned that I'd rather just wait and save, and get what I really want.

    No arguements about the diesel thing either really (I see enough about them on EVERY television show these days to know the power is real!)....if I were buying a dually, or something newer I'd probably take a more serious look. I can tell that you already understand the "early truck" disease I've got...and with that comes some rather "odd" side effects. I don't really want to use fuel injection either......just pushrod V8s and carbs on top. (OK, maybe a TBI setup if I can hide it with a drop base air cleaner!:D)


    MM,

    I hear what you're saying on the 383, and I quickly read the article you linked to. The problem is still two-fold......

    1. The modded 383 still only produced 425 Lb/Ft of torque at 2500RPM, that's quite a bit off the mark of the BBC (even the HT502)....I'd say it gives up about 50 LBs of torque in that critical area.

    2. The 383 is working pretty hard at making 500HP with only 383 cubes. Most people understand that conventional gas engines can make 1HP per cubic inch pretty easily (and have since about the 1960's!)... not only is it pretty easy to do, but it's a low-stress setup so the engine will last a good long time. Durability is a big consideration too.

    I think instead of fighting for the TQ in a smaller package, it just makes sense to add the extra cubes and get it more effortlessly. Either way though.....it costs $$$$, there's no getting around that.



    Something else to consider (because it goes along the same lines as the aesthetics and 1st Gen disease)..... I just LOVE towing the 1st Gen with the old Burb! It is already a capable setup and could be made REALLY comfortable with a few select upgrades. AND you can't believe all the smiles and waves and "Thumbs Ups" I get when I'm on the road! :thumb: I think for me, that's as much fun as anything else. It's like being in a parade....SO many people enjoy seeing the old iron on the roads, especially as a tow vehicle...and I do enjoy putting a smile on people's faces.

    :usaflag: :usaflag: :usaflag: :usaflag: :usaflag: :usaflag: :usaflag: :usaflag: :usaflag:
     

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