HELP 85 Blazer!!!

I have a 85 K5 Blazer ,Runs great until I get on the highway, No top end power slows down going up hills,(tractor trailers pass me) Hard starting in
the morning choke problem? After it gets warm runs good till hills. Does this sound like the carb?? Motor is a 305ci, Thanks for any help!!
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Check the choke first then the carb

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That sounds a lot like my situation. My K5 came with the 305 and 3.08 gears in the axles. I couldn't maintain 80mph on the interstate without shifting from OD down to Drive.
I replaced the 305 with a 350 when I blew a head gasket, but it never has run right because of carb/vacuum issues which I'm currently in the process of resolving. I thought the 350 would have more pull on the interstate, and if properly would have been a solution to my problem. But the rear axle gave up the ghost a few months back and I had it rebuilt using 3.73 gears. This put the engine in a higher RPM range that, while offering better power and acceleration on the interstate, made the tuning problems much more obvious.
Definitely start checking everything in that carb. Is it a Quadrajet? My K5 is an '86, and while it had been properly maintained, it has natural wear and tear from being a 19 year old truck.
How long have you owned the truck and how long has this been a problem? I think that 305 was only a 185hp engine when it was new 20 years ago!
~jp
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The manifold should work. My stock manifolds (intake and exhaust) from the 305 are now on the 350.
The Quadrajet can be a great carb when it's not worn out and is adjusted properly. A lot of people like them for their "off-roadability" when climbing steep hills or being at odd angles. They apparently work better than most carbs in that aspect. Knowing what I know now, I should've rebuilt (or had someone rebuild) my Quadrajet rather than go aftermarket. I wasn't trying to build a high-performance engine, just a good solid street engine that would get me there and be able to tow when required.
If you're thinking of installing that 350, I'd make sure to test all the usual stuff like compression. Check the oil in the 350 for any weirdness, like particles of metal that would indicate heavy wear of parts, etc... Basically inspect everything you can before removing it.
I'd replace all the gaskets while it was out of the truck. Gaskets aren't terribly expensive but can be a real pain later if they decide to go out on you. And if it doesn't compress well I'd go ahead and do a ring job while it was out and apart. Again, not a huge expense if you can DIY. Make sure you've got a good torque wrench.
Reconnecting all the factory emissions control equipment would help ensure that it still passes inspection.
If you have the space and a little help from a friend (to pull the engine and get it on a stand) you could probably have the engine inspected, removed, torn down, gaskets replaced and back together in a few evenings. Then I'd allot a weekend to get the 305 out and the 350 into the Blazer.
Unfortunately for me, I live in an apartment (gated community) in Midtown Atlanta, GA. So I'm unable to do any real work here at home. Because of that I've lately been wondering if there's any local Chevy truck clubs where people can get together and work on each others vehicles and "talk shop".
Good luck to you... This is a pretty good forum for picking up tips. I've learned a lot by just reading posts and not necessarily asking questions.
~jp
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Jon Pickens wrote:

    There is a Huge differance between a Carter ABF/Elderbrock Carb and a Holley, Demon or Barry Grant Carb. I Personally perfer a Holley over a Q-jet on any non stock application. Charles
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Actually, although I hope to have my carburetor woes solved this week, it won't matter much once I begin actually building the truck up to be more capable off road. I'll probably switch to a TBI setup at that time.
I just wish a new multi-point EFI unit was more affordable, although I've seen some nice used TPI setups for not too much money.
~jp
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Jon Pickens wrote:

    Why use TPI? You can get compleate 87/88 to 90/91 TBI engine harness for your truck, from a salvage yard for not much money. TBI parts cost less, and work just as well. Besides I doubt you will want to rev over 4,500 RPM where TPI really makes power. Charles
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True... I didn't consider the RPM range I'd be operating in. I'm not drag racing :-)
3000rpm and down would obviously be where I'd need to concentrate.
But to be realistic, I've always kinda considered TBI the more viable option. Simpler and cheaper for sure.
~jp
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Had the same problem in a Chevy van with the same engine. My problem was in the tranny.
Good luck with it,
Blair

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