Author Topic: 86 GMC k1500 w/350 crate swap, horrible rev response and no power in gear.  (Read 1873 times)

Offline Hypageck

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Warning, long post because I want to give as much info as possible.
Hoping to get some help.
To start off, I've searched the forums endlessly and haven't found anyone with my exact issues.
Specs -
86 k1500, originally had 305 & 700r4. Quadrajet M4MED.
Work done - essentially everything below the doors is new, short of the tranny which was *supposedly* rebuilt about 5k miles ago. Transfer case, brake system from the pedal to all 4 corners, radiator, all suspension, every bearing and seal that exists on the vehicle, body mounts, etc etc etc

Recent work leading to problems -
Spun a rod bearing on 305 so I dropped in a new GM Performance 350 crate. 195hp version. Had my original intake manifold hot tanked, replaced the oem exhaust manifolds, new distributor, new spark plugs, reused plug wires (only 500 miles on them), new water pump, new alternator, new fuel pump and pushrod, new battery, new reman Quadrajet, reused flexplate (looked good with no cracks/wear), new visible fuel filter(removed the one in the carb), new motor mounts, new TV cable for 700r4(mounting clip broke during removal), all new gaskets, new 8" harmonic balancer (I'm probably forgetting a few things)

Put on harmonic balancer per every instruction I could find and common sense (it really only goes on one way because of the key) and checked initial timing by looking down the oil  holes in the valley to ensure balancer wasn't off at all. Painted marks on balancer to check for outer/inner movement. Installed intake and set intial timing to 12° btdc, primed oil system and installed new HEI dizzy and made sure it was visually close to firing on #1. Installed new carb with new mounting gasket. all Electronic Spark Control components unhooked, all emissions crapola removed, ran new vacuum lines for everything (brake booster in rear, TCC switch to manifold vac, dizzy to manifold vac). Reinstalled all pulleys and belts, etc

Fired engine up, set initial timing (with vac advance unhooked/plugged) to 12° BTDC, ran engine for 30 minutes @2k rpm with zinc break in additive. Engine ran fine the entire time and never had a problem. Drained it down, new oil/filter. Start truck up, want to go for a spin and this is where the problems happen -

Truck has NO power when in gear, feels as if the transmission won't let it move. Pull it out of gear, and it's delayed to respond, but will rev up. In higher revs, it's a lot more responsive. Back in gear, same problem. As if the engine won't spin up. My old 305 was very responsive at lower rpm and would occasionally break the tires loose on gravel, the new 350 won't even get out of its own way, feels like the brakes are locked up (verified they aren't) or as if the tranny is turning against itself. It's also VERY hard to push in neutral.

I've adjusted the timing 876 different ways - 10°, 12°, 4°, 8°, tried ported and manifold vacuum. Best running is 12°BTDC and manifold vac on VA can.
Set the TV cable per the GM service manual(press the release button, push adjuster toward firewall till flush, open carb throttle by hand to full and listen for clicks from the adjuster).
I've checked for vac leaks with ether on the base of the carb, all vac ports, intake manifold sides and front/rear

I originally tried to reuse my old dizzy as it has brand new rotor/cap/coil. I cleaned the insides of it and checked the VA can for proper movement. With this installed, the truck would eventually jump timing by 12-17 degrees and I'd have to pull it and start the timing process all over again. Before install I shimmed it for endplay and measured the gear against a new dizzy (1.225OD on both). Dizzy kept jumping timing during anything other than idle. Replaced dizzy and now it will keep timing.

Although it keeps timing, it just doesn't seem to have the power a new 350 would. My worn out 305 had more.

During a test drive, the vehicle had NO acceleration ability until higher rpms(3k or so).

TL,DR -new 350 has horrible power, won't rev up and vehicle hardly moves while in gear. >:( :'(

Any suggestions and questions/comments are welcome.

Offline VileZambonie

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The balancer you installed is most likely indexed for a different timing indicator. Advance the timing by turning the DISTRIBUTOR counterclockwise.
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              ⌠ŻŻŻŻŻ'   [☼===☼]
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74 GMC, 75 K5, 84 GMC, 85 K20, 86 k20, 79 K10

Offline Hypageck

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The balancer you installed is most likely indexed for a different timing indicator. Advance the timing by turning the DISTRIBUTOR counterclockwise.

You nailed it. I was recommended by someone on FB that I had the incorrect balancer. I bought one for an 86, which should be read @ 1200. The timing tab I installed should be read @ 0200. Bought a new balancer that should be read @ 0200, and everything is good now.

Any recommendations on the best initial timing for this engine? I've got it set to 12 BTDC (with the V.A. unplugged). Would a higher initial be better? 16 maybe?

Offline VileZambonie

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Play with it and find out. If it starts to ping, retard it.
,                           ___ 
                         /  _ _ _\_
              ⌠ŻŻŻŻŻ'   [☼===☼]
              `()_);-;()_)--o--)_)

74 GMC, 75 K5, 84 GMC, 85 K20, 86 k20, 79 K10