Hey guys. I am slowly building my 82 K5. Its got a 6" R.C. Lift with MT baja claw 35's so far. The tires really take the power away, plus the truck bogs for a few seconds when I put it down from a cruise. I asked a local mechanic what would be a good carb to swap the Q-Jet out for. He said a 750cfm would be good, since thats what the Q-jet was to begin with... I'm thinking I shouldn't have taken his word. I ordered an Edelbrock 1411 today and was pretty excited to see the performance difference, but when I got home and looked this carb up, Lots of people say an edelbrock 750cfm is way to much for a stock 350(well..headers but thats it)... and as I do plan on getting a cam, ignition and intake manifold( which I read was about the bare minimum you need to run a 750cfm), I can only do one thing at a time with my budget. The carb is only comming in in a few days so I can still exchange for a different one if needed. What do you guys think... I really just want this bogging gone so these little rice burners dont keep killin me off the line so bad.. Perhaps a 650 would be more suitable? or can the 750 be tuned down for now untill I can get other mods? Thanks for any input you guys can give... It is much appreciated

 

I would say somewhere between 450cfm and 500cfm would be about right. IIRC, my old '70 RoadRunner with its 383 came with a Holley 460cfm on it.

 

Dont forget to use a spacer for between your carb and manifold. You can buy this at Kragen.

 

oh ok. So it'll work fine? i just need a spacer?.. I just heard the 750cfm with an un-modified 350 would bog off the line and also when you put the pedal down from a cruise. The only reason I am buying the new carb is that I really want that bogging gone. Has anyone had expeireance with this carb? If the 600cfm would be better, I would rather switch them out. But if the 750 with a spacer would work just the same, thats what i will do.

 

I used some application calculators from Google, plus this article and they all came up ~600cfm for your 350.

 

Check and replace your all your vacuum hoses for direct intake manifold vacuum leak, including one that goes to a vacuum switch which also feeds the PCV valve. You probably want to replace your fuel pump and fuel filter and get the same edelbrock brand too. This should take care of your problem guaranteed. Let me know the outcome.

K5LOVER.

4-BARRELL CARBURETOR SPACERS
Use open spacers where more plenum volume or more carb-to-plenum floor distance is required. 4-hole spacers enhance low-rpm torque and throttle response and dampen reversion effects on the carb. The superior heat insulating properties of wood fiber laminate are ideal for reducing heat transfer to the carb.

 

The carb is not your problem, and never will be until you are making upwards of 400 horsepower and turning high rpm. The Q-Jet is awesome, albeit a little hard to tune for the average user.

Those 35" tires reduced your effective overall gear ratio by a LOT. You need to swap the gears out in your truck for something steeper. It probably came with 3.42's or maybe 3.73's. Gears will improve your low end performance all around and make your truck accelerate much faster.

I can help with some examples to help your decision because me and 2 good friends all have full size K5's like yours.

My truck (76 K5 Jimmy) currently has 4.10's with 35" M/T's through a non-lockup TH350 and I turn a solid 3000 rpm at 65 mph on the freeway, which is borderline. You won't catch me speeding on the freeway without suffering in the gas department, lol. But it gets up off the line FAST and crawls around slowly offroad VERY well. It has a carb'ed 400, completely STOCK except exhaust (low HP numbers in stock form, but great torque) which goes to show what proper gearing does. Your 350 after exhaust, headers, and a cam will put out plenty more power than my engine.

A good buddy of mine has a 700r4 in his truck (88 K5 Blazer), so he got away with 4.88 gears. He is a little quicker off the line and crawls around offroad even better than mine. He turns about 2800 rpm at 65 mph, which is a littler nicer than my truck for long drives too. He also has 35" M/T's.

GEARS.

Be wary of what this may affect and keep in mind future mods. You may want to live with it for awhile until you can swap in 1-ton axles... Then properly gear the axles you WANT. In the meantime, keep your foot out of it. You're killing your gears, your driveline, and your transmission. Not to mention working the hell out of your motor.

 

Wow, this thread had a little age on it.