1991 Caprice swap 305 to 350 problems
12-15-2016, 12:13 PM
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1991 Caprice swap 305 to 350 problems
Hi guys, my name is Mario, Iīm from germany and Iīm a newbie.
I have a 1991 Caprice Station Wagon, originally with a 305 engine. Back in april, I swapped to a 350. I didntīt do it myself. An US-Car dealer with a small garage took my car and did the work. He told me, the engine is from a 1992 Chevy G10. So far, so good.
When i start the engine, it runs normal. Also when I accelerate while iīm driving.
But when itīs running normal speed, 35,40 or 50 mph, no matter if i use cruise control or not, the problems begin.
The engine has some certain kind of dropouts or ignition failures. And when it comes to very slow driving, in traffic or on small parking lots, the engine stall sometimes.
I hope you guys understand what I mean, cause I donīt know all the specific expressions in english, sorry.
I guess, I have to switch the ECM, but is there anything else? I would highly appreciate if someone could give me some tipps or maybe can tell me, what exactly parts I need, cause I love my Wagon.
Thanks in advance,
Mario
I have a 1991 Caprice Station Wagon, originally with a 305 engine. Back in april, I swapped to a 350. I didntīt do it myself. An US-Car dealer with a small garage took my car and did the work. He told me, the engine is from a 1992 Chevy G10. So far, so good.
When i start the engine, it runs normal. Also when I accelerate while iīm driving.
But when itīs running normal speed, 35,40 or 50 mph, no matter if i use cruise control or not, the problems begin.
The engine has some certain kind of dropouts or ignition failures. And when it comes to very slow driving, in traffic or on small parking lots, the engine stall sometimes.
I hope you guys understand what I mean, cause I donīt know all the specific expressions in english, sorry.
I guess, I have to switch the ECM, but is there anything else? I would highly appreciate if someone could give me some tipps or maybe can tell me, what exactly parts I need, cause I love my Wagon.
Thanks in advance,
Mario
12-21-2016, 12:08 PM
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Re: 1991 Caprice swap 305 to 350 problems
Welcome aboard thirdgen.org.
This Board is dedicated to 3rd generation, 1982-1992 GM f-body cars (Firebird and Camaro), but what you are dealing with is a 305 TBI system trying to run a 350 engine. The same issue pertains to the 1988-1992 f-body 305 TBI cars.
So, with the TBI forum moderators' indulgence, perhaps the people here can help you out.
This Board is dedicated to 3rd generation, 1982-1992 GM f-body cars (Firebird and Camaro), but what you are dealing with is a 305 TBI system trying to run a 350 engine. The same issue pertains to the 1988-1992 f-body 305 TBI cars.
So, with the TBI forum moderators' indulgence, perhaps the people here can help you out.
12-21-2016, 04:28 PM
#4
Re: 1991 Caprice swap 305 to 350 problems
Aside from all the 305-to-350 conversion headaches--different injectors, different programming in the computer, etc., you might have what I had on my TBI 350 in a 4wd pickup truck.
The magnets on the distributor shaft crack and get weak. The result is engine misfire. The cracked magnet issue is very common. I had mine fixed at a Chevy dealership, they installed a new main shaft in the distributor. A (new) replacement distributor would have worked, too, although you need to beware low-quality Chinese distributors. Wasn't as much of a problem years ago when mine failed.
Mine started out as a high-speed (80 mph) misfire at steady throttle, got worse (progressively lower speed misfire) then became low-speed (15 mph) stalling, and eventually a no-start condition where the engine would crank but not run.
For the record, the Caprice in '91 would have had a roller cam and flat-top pistons, which I don't think the G-van would have gotten. I could be wrong. The pickup trucks had dish pistons and flat-tappet cams. My '88 K1500 got a '91 Caprice engine when the original engine failed at 235,000 miles.
The magnets on the distributor shaft crack and get weak. The result is engine misfire. The cracked magnet issue is very common. I had mine fixed at a Chevy dealership, they installed a new main shaft in the distributor. A (new) replacement distributor would have worked, too, although you need to beware low-quality Chinese distributors. Wasn't as much of a problem years ago when mine failed.
Mine started out as a high-speed (80 mph) misfire at steady throttle, got worse (progressively lower speed misfire) then became low-speed (15 mph) stalling, and eventually a no-start condition where the engine would crank but not run.
For the record, the Caprice in '91 would have had a roller cam and flat-top pistons, which I don't think the G-van would have gotten. I could be wrong. The pickup trucks had dish pistons and flat-tappet cams. My '88 K1500 got a '91 Caprice engine when the original engine failed at 235,000 miles.
