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  1. highwaydevil

    highwaydevil 1/2 ton status

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    What is the best/value/quiet header I can buy for low-end torque for 350? I also would like something that doesn't hang too low.
     
  2. Rasberry

    Rasberry 1/2 ton status

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    Someone correct me if i'm wrong but I thought headers really aren't designed to increase low end tourqe. I though they where designed for horsepower buy allowing the engine to breath better at higher rpms. If headers did increase low end tourqe, it was nominal.

    I maybe be wrong but that is what I've come to learn.

    Rasberry 71' K/5 Blazer
    http://www.geocities.com/71blazer
     
  3. Neil

    Neil 1/2 ton status

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    The gain wouldn't be noticed at low rpm.Do you have a automatic trans? what stall is your convertor? Best price is probably Thrush,JBA, or Hooker. Get them coated to prevent rust too...NeilH. Alabama K5 4x4
     
  4. kilomanjaro

    kilomanjaro 1/2 ton status

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    i have a new set of dynomax headers for sale, they have never been run on a truck, a little shelf wear. 45 dollars plus shipping email me at kilomanjaro63@hotmail.com if you are interested. i am currently running a set on my truck, i haven't had any problem with them at all.
     
  5. highwaydevil

    highwaydevil 1/2 ton status

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    I thought headers would be my best bet for the money. I am towing trailers, and would like more umpfh up the hills. Any other ideas? Kilimanjaro, I'll probably take you up on that if the verdict is that they may help me out.
     
  6. travis

    travis 1/2 ton status

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    kilomanjaro, check your PM. I may be interested in the headers if you still have them.

    Travis
     
  7. ChrisM72beast

    ChrisM72beast 1/2 ton status

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    You may want to think about an r.v. cam. It will help you towing at low to medium speeds. Also, as far as good headers go, I love my Thorley headers.
     
  8. Steve_Chin

    Steve_Chin 1/2 ton status

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    Header design is a rather complex subject. But, I can say that a properly designed header can increase low end performance over that of the log type exhaust manifolds. What is normally necessary to do so is a header with a long primary tract or with small ID primary tubes (or some combination of those). Longer tubes will "rock" the torque curve about the torque peak, making the curve climb more rapidly at low RPM and flattening the curve just below the peak. The down side of that is the torque curve will fall off more quickly at higher RPM, affecting the HP peak rating and RPM negatively (of course, we don't give too much of a darn about that having trucks anyway). The other down side is that the long primary tract is hard to package and won't fit into most chassis (including out Blazers). Smaller ID tubes will lower the RPM at which peak torque is produced. They also build torque quickly and flatten the torque curve about the peak. If a tube has an ID that is too small for the engine size or camming, it will choke off top end power rather abruptly.
     
  9. highwaydevil

    highwaydevil 1/2 ton status

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    Steve,
    Thanks for the in-depth reply. What i.d. and brand do you recommend assuming I can't fit a long header very well?
     
  10. Triaged

    Triaged 1/2 ton status

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    Towing is not necessarily a low end torque thing. Going up a hil you should be spinning around 3000 RPM. That is in the range where headers start to work. Also headers would help a RV cam make more power. IMO a free flowing exhaust should be the first thing done to an enging in the quest for more power.

    '71 Blazer CST with alot of rust
     
  11. MikeS

    MikeS Registered Member

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    Correct me if I'm wrong here, but a properly placed crossover tube is also critical for good low end torque. I think it's supposed to be placed about a foot or two from the collectors (at least that's where it is on mine).

    Mike
     
  12. highwaydevil

    highwaydevil 1/2 ton status

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    I agree with the 3000 rpm guess. I don't have any problem starting out, just keeping it moving at a decent speed up steep hills. I already have dual exhaust with dynomax mufflers, and an "H" (cross-over) pipe. I had not done headers yet because I was trying to avoid the extra noise, and gasket blow-out/ sparkplug access issues. I also have the factory air system, and it won't bolt to the headers. (It isn't hooked up yet, but was planning on doing so). At this point, I would rather have the power, and worry about the a/c later. Has anyone rigged up an adaptor? Seems like a piece of pipe with a longer stud would work for the bracket. Thanks for all the advice.
     
  13. Steve_Chin

    Steve_Chin 1/2 ton status

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    You're not wrong, Mike. A correctly placed and sized crossover can help boost signal in the lower midrange and quiet the exhaust noise a little. H-type crossovers are the most common since they're pretty much no-brainers to install. X-type crossovers are more effective at the lower midrange but give a wierd sound quality that some people don't like (beauty is as function does in my book). An X-type crossover isn't something that will fit well on our 4x4s with that transfer case in the way. We're also pretty limited in where we can place an H-type crossover because of the placement of the transmission and transfer case. Determining the best placement of the crossover is dependent on the exhaust valve timing and stroke length of the engine. We usually can't place it where we want it because of packaging constraints (placement of the tranny and transfer case). Crossovers get more effective with a reduction in their length. The cross-sectional area of the crossover should be between 85% and 100% of the cross-sectional area of the exhaust pipes (100% is not better than 85%, but it's sometimes necessary to run the larger pipe).

    Highwaydevil, without knowing your camming, I'd just suggest a header with a 1.625" OD primary pipe. They seem to work well on street and off-road 350 engines. Hooker makes a nice header in its Super Competition series for our Blazers. If you have an automatic tranny, Hedman makes a nice model as well.
     
  14. highwaydevil

    highwaydevil 1/2 ton status

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    Steve,
    I have my h pipe behind my transfer case, and I have no performance mods of any significance (unfortunately!)
     
  15. 2quicK5

    2quicK5 Registered Member

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    Dynomax headers work great. Mine have no clearance issues. You can buy the Summit brand headers from Summit racing, they are made by Dynomax and can be had for $75. They have 1-5/8" primary tube diameter and 3" collectors. The primary tubes are decently long at 26-30". As Steve pointed out, you will want long tube headers for low rpm torque production, the longer the better. A crossover pipe is very nice, but you will want it in front of the transfer case as close to the collectors and you can get it. You will want to use 2-1/4" to 2-1/2" exhaust pipe with a good set of free flowing turbo mufflers. The Dynomax Ultra Flow race welded muffler is very nice, flows about 900 cfm and is still pretty quiet. As for me, I have a set of chrome sidepipes with integral mufflers on my rig as I like the look and sound.

    John

    1972 K5 Blazer: 400 ci, 4 sp, 4" springs, 35" Tires

    2000 Trans Am, A4
    11.97@114 mph
     
  16. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    I also tow with my K5. Adding a set of 1 5/8 primary long tube headers increased the low end noticeably. Shortly after the headers and dual flowmasters were installed I did a cam swap. I used the Comp Cams 260 HE for my 350, this combined with a new 600 CFM Edelbrock carb and the exhaust system really made towing much easier, especially on the long steep grades.

    Headers are a bit more maintenance though, I try and at least check the header bolts regularly...most times I find a couple that are getting loose. I use the 'dead soft' collector gaskets, they're aluminum and conform very nicely and I haven't had any collector leaks yet. They are also re-usable.

    Rene

    <font color=green>Dyslexics of the world...UNTIE!</font color=green>
     
  17. Steve_Chin

    Steve_Chin 1/2 ton status

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    tRustyK5: If you never want to have to tighten the header flange bolts again, use the Earl's Pressure Master header seals instead of gaskets. I use them with the ARP stainless steel 6-point header bolts and I don't need to re-tighten them. I've also re-used them a couple of times without incurring a leak.
     
  18. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    Thanks for the tip Steve. I'll look into it when I swap my drivetrain later in the month.

    Rene

    <font color=green>Dyslexics of the world...UNTIE!</font color=green>
     
  19. highwaydevil

    highwaydevil 1/2 ton status

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    Steve,
    Where do you buy those at?
     
  20. Steve_Chin

    Steve_Chin 1/2 ton status

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    Summit Racing carries them. Earl's makes a variety of port sizes, but Summit should be able to set you up with the right size for your ports if you talk to their techs.
     

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