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How to get 305 TBI working on 350 block.

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Old 08-09-2017, 10:55 PM   #1
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Join Date: Apr 2007
Posts: 11
Car: 1989 Camaro RS Vert
Engine: 350 Block, 305 head TBI

How to get 305 TBI working on 350 block.

Purchased an 89 RS convertible vin E almost a year ago as a learning project. It started and ran but not good so I figured it wouldn't take too long to get it running smooth.
So after a l a lot of time tinkering and fixing several things, I discovered that the big issue could be that there is a 350 block with 305 head.

Sorry for the long post, just trying to be informative. Cut to the bottom if you want the short version of my post.

Current issues are:
Surging idle at cold start 1200-300rpm.

Cold or warm (warms idle to 180-190), when first driving, engine surges and occasionally stalls under load. Then an intake backfire or two and then it runs strong. It won't backfire again even at WOT. If I let it sit for over 4 hours, it will repeat.

High idle, after engine calms down from surging, it will idle 1100-1000RPM.

High idle in D or R. Climbs to 1400. Tires will start to spin if I'm stopped in gravel.

Things I have tried or know:
Plugs and wires
Entire distributor assembly and coil
Timing currently at 0 but I've been trying all over the place.
Consistent 11PSI fuel pressure.
Fuel filter replaced
TBI has been rebuilt (twice)
All vacuum lines and check valves have been replaced. (Or capped off)
MAP replaced
Intake manifold gasket replaced.
ECT replaced
TPS replaced (.54v at idle)
Coolant sender replaced
IAC replaced (twice)
EGR replaced
EGR solenoid replaced
Injectors spray nice cones
Idle speed screw set to 475rpm with IAC fully extended (with and without EST connected)
IAC runs at about 35 counts after engine warmed up at idle.
Pressure tests put all about 135-140psi
Over all, sensors all seem to run within expectations but I contantly get a "rich flag" on the winaldl.

Since I now know I have a 350 block, I think I have a computer problem.
I have the 8746 ECM and there is a ANTT chip in it.
I have the 5.0 injectors
My ESC has "HKM" and 882391 on it.

What do I need to do to get this car running good?
Buy hardware and figure out how to burn my chip for a 5.7 TBI and get 5.7 injectors?

Thanks for you help!
jared1264 is offline   Reply With Quote
Old 08-12-2017, 02:09 AM   #2
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Join Date: Jan 2005
Location: Hurst, Texas
Posts: 7,961
Car: 1983 G20 Chevy
Engine: 305 TPI
Transmission: 4L60
Axle/Gears: 14 bolt with 3.07 gears

Re: How to get 305 TBI working on 350 block.

I would start by reading the 305 to 350 swap sticky above your post.
Fast355 is offline   Reply With Quote

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