Hi All,

I have a '91 Formula Firebird WS6/G92 with a 305 LB9 that I want to swap out for a 350 L98 block-only. I am going to use EVERYTHING possible from the existing system during the swap -- in other words no other upgrades at this point in time.

My question is does anyone have any list of items that will have to be replaced or altered because of the differences between the 350 and the 305 ? Eg: flywheel, hormonic balancer, etc ?
The 350 donor block will be an 89-95 , either f-body (89-91) or truck (89-95). Have any of you done this swap ? I would really appreciate some advice.

Thx, RP.




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'91 Formula Firebird G92,WS6,5-speed,3.42 a ton of fun to drive.

 

well, last year i swapped a 350 from a tpi 89 iroc automatic, in a 87 tpi 305 iroc. i just sawpped the motor... kept the same flywheele, intake and tranny, and id like to say everything was fine, till my clutch went....

but it worked for a year.

i dont remember needing anything new.

jon

 

I'll attest to that. Jon certainly did swap a 350 in place of a 305. But remember, he swapped the whole TPI unit (injectors, intake, everything) also along with the 305. The only difference between the the TPI units, though, is that when you throw in the 350, you have to throw in 350 injectors, also.

Another Jon from Madison

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89 GTA
Beautiful Gunmetal gray, LB9 305 and T5 tranny. Only 60,000 miles!
Dual cats, 3"flomaster
Accel 300+ Ignition, wires, cap, coil, etc
Airfoil
KN Airfilter
Removed Screens on MAF
SLP 1 3/4 headers
No Smog/AIR system

 

Interesting note. I had not considered the 305 injectors may be under-powered for the 350. I was intending to use the stock TPI setup complete with no changes. I take it the injector swap is not mandatory but I may see less power until I do it ?

RP.

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'91 Formula Firebird G92,WS6,5-speed,3.42 a ton of fun to drive.

 

You will also need to upgade your 305 computer chip to 89 GM 350 Chip. A new AFPR may be needed, when I made that swap the stock regulator made the engine run rich.
Again all the 305 sensors may not work. The
list goes on and on, just small items that
cause problems. When I completed my engine
swap I had no problems, a rare happening.
Good Luck


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1987 Black Camaro IROC-Z (original owner) Replaced LB9 @ 86100 miles.
New 350 Crate engine
Balanced & blueprinted
World Prod SR 67cc Heads 9.6:1 C.R.
Cam: 454lift,216dur@50,110ls
TPI Induction(from 305)
22# Fuel Injectors
AFPR & Gauge
SLP Intake runners
Fastchip stage 2 chip
K&N filters & Air Foil
Hothkis STB
SLP 1 3/4 Headers
CATCO 3" Catalytic conv.
SLP 3" Cat Back Exhaust
700R4 Auto
SLP Torque Converter (2400 stall)
1LE Aluminum Dr Shaft
B-W 9 bolt rear 2:77 Possi. Four wheel disc brakes,245/45/ZR-17 Tires
17x8.5 ATI 5 Razze Wheels
Dyno results: 211 RWHP & 282 RWTQ.
271 HP & 362#/ft at flywheel with all Emission controls installed. New Toy!

 

You will either need a gm chip for an sd 350 and 350 injectors or a custom chip that incorporates the 305 injectors into a 350 calibration. 305 sd chip + 305 calibration = very lean operation

John

Heart of Texas Power and Performance

 

I did the same swap with mine and didnt change a thing. Car ran fine, but a little rich. I did the swap two years ago and just recently replaced the 305 chip with a 350 chip and last fall switched to 24lb injectors, but I'm still running the original fuel regulator. Now it runs darn near perfect and I'm getting 24mpg.

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1992 Camaro Z-28 custom 25th anniversary, 5.7 TPI auto, 2.73 posi, t-tops, arctic white with 92' medium mettalic gray stripes with black border stripe.

1967 Pontiac Catalina 2 door fastback, 400 v-8, auto, cameo white, dark red interior