1994 GMC Pickup engine swap - advice please - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Psycho Billy · 05-09-2006, 03:43 PM

I am planning on swapping out the 350 in my 1994 GMC pickup with another 350 I'm farming out of a 1989 Suburban. I was going to build the engine on the side and swap them out one-for-one to save downtime on my pickup (it's my daily driver). I haven't pulled the suburban engine yet, I want to do a compression test first. What kind of PSI values should I be looking for? Also, are both these engines 4-bolt mains or 2-bolt? The direct crate replacement engines are 2-bolt.

One last question; I was considering running it carbureted, is there anything special I have to do to accommodate the emmissions system or the computer? I've heard I also need a "return-style" fuel regulator, is this also true?

I appreciate any advice you can give me.

Thanks!

Kevin45 · 05-09-2006, 03:54 PM

Carburated does not require the fuel pressure that a throttle body does. First question...why would you want to go with a carburator over throttle body. Performance and gas mileage will be way better with a throttle body. Also to run a carb you will need to do away with the computer and in doing so you will need to get an aftermarket computer to run your transmission as it is all electronic. You would be way better ahead to just build the engine the way you want and run a throttle body on it. It can be done. Mine is a .060 over 350 with Edelbrock header, RV cam, and 2.02 / 1.60 heads and running a 2 barrel stock TB and intake. And it will run like a scalded dog.

Kevin

Psycho Billy · 05-09-2006, 04:07 PM

Thank you for the advice. I have the 3-speed manual transmission with OD & grannys, that's how I know I could get away with a carburetor. I know Hollys inside and out; however I don't know much about the TBI's. I have two of them, one with 125k & the other with 138k miles on them. Do they sell rebuild kits? What is the best way to approach it?

82c10 · 05-09-2006, 04:08 PM

Quote:

Originally Posted by Psycho Billy

Thank you for the advice. I have the 3-speed manual transmission with OD & grannys, that's how I know I could get away with a carburetor. I know Hollys inside and out; however I don't know much about the TBI's. I have two of them, one with 125k & the other with 138k miles on them. Do they sell rebuild kits? What is the best way to approach it?

yes, they sell rebuild kits, just call napa, i believe should have them

cantburn · 05-09-2006, 08:24 PM

Rebuild for a TBI is not only faster but easy compared to a rochester or even Holly. I've had much better luck running a TBI then I ever did with a Rochester 4bbl. For than matter Performance Truck sells a complete TBI unit for $342.00, plus the fact that if you switch to carb, you have to disconnect the fuel pump in the fuel tank and seal the line and have a different one placed in line somewhere for the carb. I've seen a couple of high perf. swaps and there was a boat load of money and time put in them before all the bugs were worked out and since this is your daily driver, you may be thinking about biting off more than you want at this juncture. I have done several direct swaps and they go smoothly if you stick to the basic block configuration and stay within the designed bounderies. Change your cam, screw with new components but stay with the computer and what came with the truck and you will have great time with it. As for the block, It won't matter what the bottom end is going to be with the bild yu are thinking of doing. If you pull the engine from the Suburban, I would thing that you would strip it down and redo the heads and all the gaskets just so you don't have any issues in the future. I always had a rule when performing an engine swap. If it bolts on...take it off and clean, replace, inspect, place in a new gasket on and have the reassurance that it is done right. Good luck with it....Chip

Psycho Billy · 05-10-2006, 10:14 AM

Thanks for the great responses. I've been convinced to stay with the TBI. I checked around at a couple local carb. shops and they can completely rebuild/clean/flow bench mine for about $300. At a minimum I was going to have the heads rebuilt, the block decked & honed, install new bearings on the crank, and a new rear main seal.

Does anyone know the acceptable PSI values I should get from the '89 350 if I did a compression test?

Thank you.

piecesparts · 05-10-2006, 03:51 PM

Are you doing the motor in the truck or the one that you are going to put into the truck. If the motor is sitting on the shop floor, I would consider a "Leakdown test" over the compression test. It will tell you whether or not you have a weak cylinder and possibly where the problem is. The motor would not have to be cranked over to get this done. If you do this then look for a good percentage number on the cylinders below the number of 25%. A real good moter would be at 5% or less on the cylinders.

If you do a compression test, I would be concerned if any one cylinder was a lot less than the others and if the compression on any cylinder was below 110#. This shows some wear and tear. In the old days most cylinders on vehicles tested out at about 125# and that was considered really good. Life really doesn't change much in this area.

05-09-2006, 03:43 PM	#1
Psycho Billy Registered User Join Date: Feb 2005 Posts: 5	1994 GMC Pickup engine swap - advice please I am planning on swapping out the 350 in my 1994 GMC pickup with another 350 I'm farming out of a 1989 Suburban. I was going to build the engine on the side and swap them out one-for-one to save downtime on my pickup (it's my daily driver). I haven't pulled the suburban engine yet, I want to do a compression test first. What kind of PSI values should I be looking for? Also, are both these engines 4-bolt mains or 2-bolt? The direct crate replacement engines are 2-bolt. One last question; I was considering running it carbureted, is there anything special I have to do to accommodate the emmissions system or the computer? I've heard I also need a "return-style" fuel regulator, is this also true? I appreciate any advice you can give me. Thanks!

05-09-2006, 03:54 PM	#2
Kevin45 Registered User Join Date: Oct 2004 Location: Urbana, Ohio Posts: 591	Re: 1994 GMC Pickup engine swap - advice please Carburated does not require the fuel pressure that a throttle body does. First question...why would you want to go with a carburator over throttle body. Performance and gas mileage will be way better with a throttle body. Also to run a carb you will need to do away with the computer and in doing so you will need to get an aftermarket computer to run your transmission as it is all electronic. You would be way better ahead to just build the engine the way you want and run a throttle body on it. It can be done. Mine is a .060 over 350 with Edelbrock header, RV cam, and 2.02 / 1.60 heads and running a 2 barrel stock TB and intake. And it will run like a scalded dog. Kevin __________________ '93 Silverado Reg. Cab Shortbox .060 over 350 Quick and fun!!!

05-09-2006, 04:07 PM	#3
Psycho Billy Registered User Join Date: Feb 2005 Posts: 5	Re: 1994 GMC Pickup engine swap - advice please Thank you for the advice. I have the 3-speed manual transmission with OD & grannys, that's how I know I could get away with a carburetor. I know Hollys inside and out; however I don't know much about the TBI's. I have two of them, one with 125k & the other with 138k miles on them. Do they sell rebuild kits? What is the best way to approach it?

05-09-2006, 08:24 PM	#5
cantburn ParrotHead Parts Join Date: Mar 2005 Location: Port St Lucie, Florida Posts: 218	Re: 1994 GMC Pickup engine swap - advice please Rebuild for a TBI is not only faster but easy compared to a rochester or even Holly. I've had much better luck running a TBI then I ever did with a Rochester 4bbl. For than matter Performance Truck sells a complete TBI unit for $342.00, plus the fact that if you switch to carb, you have to disconnect the fuel pump in the fuel tank and seal the line and have a different one placed in line somewhere for the carb. I've seen a couple of high perf. swaps and there was a boat load of money and time put in them before all the bugs were worked out and since this is your daily driver, you may be thinking about biting off more than you want at this juncture. I have done several direct swaps and they go smoothly if you stick to the basic block configuration and stay within the designed bounderies. Change your cam, screw with new components but stay with the computer and what came with the truck and you will have great time with it. As for the block, It won't matter what the bottom end is going to be with the bild yu are thinking of doing. If you pull the engine from the Suburban, I would thing that you would strip it down and redo the heads and all the gaskets just so you don't have any issues in the future. I always had a rule when performing an engine swap. If it bolts on...take it off and clean, replace, inspect, place in a new gasket on and have the reassurance that it is done right. Good luck with it....Chip __________________ "I Love the Smell of a Salvage Yard in the Morning" 1992 GMC K1500; The best projects are those still in progress. (Paypal verified 100% positive feedback);

05-10-2006, 10:14 AM	#6
Psycho Billy Registered User Join Date: Feb 2005 Posts: 5	Re: 1994 GMC Pickup engine swap - advice please Thanks for the great responses. I've been convinced to stay with the TBI. I checked around at a couple local carb. shops and they can completely rebuild/clean/flow bench mine for about $300. At a minimum I was going to have the heads rebuilt, the block decked & honed, install new bearings on the crank, and a new rear main seal. Does anyone know the acceptable PSI values I should get from the '89 350 if I did a compression test? Thank you.

05-10-2006, 03:51 PM	#7
piecesparts Parts and more parts Join Date: Nov 2003 Location: Lebo, Kansas (middle of nowhere Posts: 6,821	Re: 1994 GMC Pickup engine swap - advice please Are you doing the motor in the truck or the one that you are going to put into the truck. If the motor is sitting on the shop floor, I would consider a "Leakdown test" over the compression test. It will tell you whether or not you have a weak cylinder and possibly where the problem is. The motor would not have to be cranked over to get this done. If you do this then look for a good percentage number on the cylinders below the number of 25%. A real good moter would be at 5% or less on the cylinders. If you do a compression test, I would be concerned if any one cylinder was a lot less than the others and if the compression on any cylinder was below 110#. This shows some wear and tear. In the old days most cylinders on vehicles tested out at about 125# and that was considered really good. Life really doesn't change much in this area.



Register or Log In To remove these advertisements.

Register or Log In To remove these advertisements.