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Acceleration issue

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Jrgunn5150, Apr 27, 2006.

  1. Jrgunn5150

    Jrgunn5150 1/2 ton status

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    I have a 87 K 10 with a 350 (history unknown, but clean inside) it wears a Edelbrock EPS intake, topped with a Holley Truck Avenger 670 cfm carb. It is backed by a TCI truckmaster trans and NP208, along with whatever stock gears are in the 10 bolts. It also has 33" Goodyear MTR's.

    The issue is, that whenever I get out on the freeway and accelerate into overdrive, it starts to bog or something. It's not really a bog per se, more like the truck can't pull the overdrive gear. I can hold my foot the floor and it will slow down. If I let my foot off, there's a certain "sweet spot" that will let me accelerate somewhat. But without doing that it's done accelerating at around 60 mph. Which really sucks because that's right around the 3-4 shift point, so I spend alot of time hunting up and down through the gears, and use way more fuel than I need to.

    I'm really stumped, I suppose it could be fuel related, it still has the stock electric fuel pumps in the tanks, except it pulls fine through the rpm range when not in overdrive. I have a new MSD distributor, wires, and a fresh set of plugs to put on it also, but I'm not entirely sure it's spark related either, unless my vacuum advance isn't working properly?
     
  2. Goose

    Goose 1/2 ton status

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    I have a similar problem with my '85 K30 with carb. I thought it was a carb issue, but I may have to look more into timing now. I know I plenty of fuel so that's not the problem.
     
  3. HarryH3

    HarryH3 1 ton status Author

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    What gear ratio is in the axles? 3.08's and 33's will drive your trans nutz...
     
  4. Jrgunn5150

    Jrgunn5150 1/2 ton status

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    I actually gave it some more thought and some experimentation today. Part of it was timing, my moronic brother had it set to about 2 degrees initial. It's alot snappy in the low end with 14 degrees now.

    The other thing is that I cheaped out and bought a Spectre fuel pressure regulator, that tops out at 5psi. Considering it cost 15 dollars, I'd be surprised if I'm even getting that out of it. So I figure that may be part of it also. I'm gonna throw the new ignition stuff on it this weekend, then we'll see.

    Also, I really don't know what gears it has, and I'm too lazy to jack it up and find out:rolleyes: . But I suppose I will do that also.

    I'm also start to suspect my E-brake is dragging a bit. It never ends...
     
  5. txfiremank5

    txfiremank5 1/2 ton status

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    I had an issue with something like that on my old K5. It got where it seemed to be bogged down out on the highway etc. It was like the power was there, but wasn't getting to the ground.

    My dad told me to replace the cat converter, and sure enough, it must have been clogged or something cause it ran a whole lot better after that. It didn't have that restricted feel to it. Yours does sound a little different though, so it's hard to say. Sometimes it's where you least expect it.
     
  6. Jonny-K5

    Jonny-K5 1/2 ton status

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    i would guess timing. maybe something wrong with vacuum advance.
     
  7. G-Force8

    G-Force8 1/2 ton status

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    actually, it sounds like the point has been adressed. Stock 3.08s and 33" tires are not Overdrive happy together. 3.73's are better,but 4.10's are ideal for overdrive to work properly with 33" tires.

    That would cause your freeway cruising prob,but as for the boggin' down........I would definetly ditch that 5psi Spectre crap regulator. Get something around 10-14 psi, and a quality unit. If you want to save a little, Summit Racing www.summitracing.com has their own brand of equipment that is decent quality and inexpensive when compared to the Holley and Edelbrock units.
     
  8. Jrgunn5150

    Jrgunn5150 1/2 ton status

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    Summit is actually very close to me (30 minutes), so if when I swap out the ignition tomarrow that doesn't fix it I will address the fuel pressure issue and update.

    I'm trying to decide what to do about the axles. It's not a very hard core wheeler, I have a Rubicon Unlimited for that, just my winter driver/occasional hauler. So I don't know if I want to go 3/4 ton axles or re-gear the ten bolts. I also don't know what gears I have now either. Since my Mustang is getting 4.10's right now, I'm kinda cash strapped for gear swaps for awhile anyways.

    I'll let everyone know tomarrow how the ignition works out, and thanks for the suggestions.

    BTW, it's not the cat, because I don't have one. In Ohio with collectors plates, you don't have to comply with emisions since I drive it less than 5k a year.
     
  9. G-Force8

    G-Force8 1/2 ton status

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    on the axles, i'd recommned tried and true GM 3/4 tons with factory 4.10's. You can usually get a pair for a few hundred bucks. Less than the cost for the re-gearing of one 10-bolt axle. You will have to get new rims and tires tho. But selling the ones you have and 10-bolt axles will help with much of the cost.

    hope it all works out soon
     
  10. ivie29

    ivie29 1/2 ton status

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    fuel pressure

    a good setting for fuel pressure on a carb set up is around 7 psi any more and the float cant hold back the pressure and it overfills the fuel bowls. Also Im not sure but i think in 87 everthing was fuel injected so if your running a carb with the original fuel pump and dont have a good regulater that could be your problem.
     
  11. G-Force8

    G-Force8 1/2 ton status

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    my bad, I was thinking fuel injection. He is right, 10-14 psi is to much. But 5 is to low for any kind of performance with a carb. I have the electric pump feeding my Jeep 360 set @ 8psi and it works well for a fairly stock motor.

    Yes, in 1987 GM introduced TBI fuel injection on the fullsize trucks. If your truck is an 87 then someone at some point removed the computer and fuel injection in favor of a carb.
     
  12. Jrgunn5150

    Jrgunn5150 1/2 ton status

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    Yeah that was my dad, he actually removed the whole motor, then I did it again.

    It turns out the problem was two fold. First, the regulator was causing it to starve and cut out, and second the number four plug wire had falllen off:eek1: .

    It's running well now, thanks guys.
     
  13. G-Force8

    G-Force8 1/2 ton status

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    awesome
     

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