Are all 305 throttle bodies basically the same?
05-25-2006, 08:30 PM
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Are all 305 throttle bodies basically the same?
I just picked up and rebuilt a 305 (TBI) 1989 IROC roller block engine and installed it in my 88 Chevy C1500 2wd pickup. I am using the trucks ECM, the Camaros, ignition, distributor, coil, EGR and Throttle Body, basically everythin except for the ECM. The truck runs really great but has no power, it feels like it is starving for fuel.
Again , it runs great, has "very unrestricted exhaust"
, good fuel pressure, compression and using my Actron scanner...all sensors are right on. The truck drives great without a load, but hook-up even an empty open car trailer and I can't get it over 65 MPH without a battle!
The truck has a 3.08 rear end and manual 5sp. I picked the Camaro engine because it is a roller block...the 305 truck engines aren't. I'm really disappointed with the lack of power and was wondering if the throttle bodies from the 88 305 truck and the 89 IROC 305 are the same relating to injectors? Could I install a 350 throttle body to get more fuel output?
I may also try blocking the EGR just for test purposes. Any ideas?
Again , it runs great, has "very unrestricted exhaust"
, good fuel pressure, compression and using my Actron scanner...all sensors are right on. The truck drives great without a load, but hook-up even an empty open car trailer and I can't get it over 65 MPH without a battle!The truck has a 3.08 rear end and manual 5sp. I picked the Camaro engine because it is a roller block...the 305 truck engines aren't. I'm really disappointed with the lack of power and was wondering if the throttle bodies from the 88 305 truck and the 89 IROC 305 are the same relating to injectors? Could I install a 350 throttle body to get more fuel output?
I may also try blocking the EGR just for test purposes. Any ideas?
05-25-2006, 08:38 PM
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Car: 1983 G20 Chevy
Engine: 305 TPI
Transmission: 4L60
Axle/Gears: 14 bolt with 3.07 gears
Timing? (set it at 0-4* BTDC with the EST bypass wire disconnected) Fuel pressure? (12 PSI is a good starting point). When was the last time the fuel filter was changed? You should have no problem pulling with the 305/5spd/3.08 gear combo. I used a G20 with a 305/700r4/3.08 combo and it didn't have too much difficulty handling my 4,000 lbs boat, 65+ with pedal to spare.
The injectors should be the same at 55 lb/hr, but the ECMs have different calibrations in them.
IIRC, the roller cam is not as hot as the trucks cam. A LT1 or Vortec cam works well with a truck 305 ecm, in my experience. The typical truck L03 uses a cam that specs 193/202 @ .050, .390/.410" lift, 112 LSA on a 107* intake centerline. The early HD 350 TBI used the same cam.
The injectors should be the same at 55 lb/hr, but the ECMs have different calibrations in them.
IIRC, the roller cam is not as hot as the trucks cam. A LT1 or Vortec cam works well with a truck 305 ecm, in my experience. The typical truck L03 uses a cam that specs 193/202 @ .050, .390/.410" lift, 112 LSA on a 107* intake centerline. The early HD 350 TBI used the same cam.
Last edited by Fast355; 05-25-2006 at 08:45 PM.
05-25-2006, 09:47 PM
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I have straight exhaust to a cherry bomb...no restriction at all. Fuel pressure is right on, timing at "0" unplugged, new fuel filter. I'm going to install the original truck TB, block off the EGR and try an extra ECM I have. The info on the TB injectors helps..thanks.
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