Thread: TBI swap 1990 pickup

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Hello there I have a 350 motor in my pickup that is almost dead. I have a 355 that i overhauled about 2 years ago that I had in my mud drag pickup for two races then went to a big block. The 355 has stock heads with flat top pistons I don't know the cr of it. The cam only pulls about 15 inches of vaccum. Don't know the specs of it. But anyways can I put this older 355 in this newer pickup with a tbi adapter for the spreadbore intake. I have to buy a different tbi anyways for this pickup the linkage is wore out in the tbi unit. Or should I just put a carb on it. what do you guys think.

Originally Posted by sawking

Hello there I have a 350 motor in my pickup that is almost dead. I have a 355 that i overhauled about 2 years ago that I had in my mud drag pickup for two races then went to a big block. The 355 has stock heads with flat top pistons I don't know the cr of it. The cam only pulls about 15 inches of vaccum. Don't know the specs of it. But anyways can I put this older 355 in this newer pickup with a tbi adapter for the spreadbore intake. I have to buy a different tbi anyways for this pickup the linkage is wore out in the tbi unit. Or should I just put a carb on it. what do you guys think.

Doing the TBI would be easier, as you already have that on your 1990. Putting the older motor in the newer chevy will not be a problem. You should be able to use the intake that is currently on your 1990, and install it onto the 355 your putting into the truck. That way, all your EGR, wiring harnesses, throttlebody, and your throttle linkage will bolt right up no problem.
I have a 1988 chevy silverado, that I put a rebuilt 355 into, and thats exactly what I did, to keep the fuel injection. Its really simple and straight forward. Everything else should bolt up fine and all line up.

And if you wanted to run a carb, its possible and fairly simple. Doing TBI, since you already have it would be easier. But for the carb, you would need to have new throttle linkage, as your stock linkage is not long enough, and the mounting plate it currently has, will not match up with your current intake on the 355. You will have to extend your fuel lines about 5 inches to accomodate for the different location for fuel inlets and outlets on a carb. On your throttlebodie, they are right in the back side, but the carb they are on the passenger side. You will pretty much have to eliminate a lot of the computer wires, etc, as you will want to run a hot lead directly to the distributor. There is also a plugin for the timing advance, when with a TBI engine with the computer, you can just unplug it, set it at 34 degrees, and then plug it back in, and the computer will adjust vacuum.

IMO I would go TBI, as you already have it, carb you can make some good power, I think you would be less fuel efficient too, depending on how well its tuned, etc.

-cory

15" of vacuum? Carb it. It's not too low, but the MAP sensor or which system you rely on is going to fatten it up. If you're lucky to be able to run a Mass Air Flow Sensor within the intake sytem It can be "tricked" into seeing the right flow. This job is for somebody that has some time to figure out. Run a carb and be patient to learn to tune the system. If you would, please fill us in on more of what you wanna do. Too many ways to do this.

Absolutely nothing wrong with a properly set up TBI... Heck, a lot of the aftermarket EFI kits (Holley and others) are TBI's and work quite well...

Face, throw us a bone. I'm sure Sawking can use a bunch of tunabilty. Thanks Dude.

Dave, Jump in, the water's fine. I think he can do it. Just needs more info.

Originally Posted by nitrowarrior

Face, throw us a bone. I'm sure Sawking can use a bunch of tunabilty. Thanks Dude.

Im offering my advice, as I did the same exact thing to my truck lol. I had all the same questions too.
IMO I would do the TBI, hes not looking for a ton of power he just has a worn out engine and looking to replace. It would be cheaper as well, considering he already has the whole setup. Youd have to buy the carb, if you dont have one. linkage, longer fuel lines, and other miscellaneous stuff which can all add up fast. TBI swap would be the easiest and cheapest way to go since you already have the whole setup to do so.
-cory

Wish I knew more about fuel injection!!! Got a couple good books off Amazon and started doing some studying. I know the stand alone systems and multi-port systems work great and understand the basics, just trying to learn how to make them better!!!!!

The dynot results on some of the new engines are phenomenal!!!! 4.6 litre engines making 600 RWHP!!! Gotta get me some of that !!!!!!

Thanks Cory...Thanks Dave....Antyhing can be accomplished. It's great we all can help and everyone that asks questions can be helped.

The biggie on TBI is cam duration; no more than 212 degrees.

Thanks guys for all the feed back. I think I'm going to stay with the tbi. But I've had people tell the tbi intake won't bolt on the older 350 heads any truth to this. or maybe it was the exhaust side was different. It sounds like I might have to put a diffent cam in it to work with the tbi sensors. Any body on this form have a used tbi to sell me. I can hardly push the throttle in on mine. What cam should I put in it. I mostly use the pickup for hunting. I looking for something with a lot of torque and good mileage.

heres the one i used in my truck. yes you will need a computer controled one.
I used the XFI Extreme FUel injection cam from comp cams, and it gave me great low end torque. and good midrange.

www.jegs.com
heres the description below

"XFI" 252 Hydraulic Flat Tappet Camshaft
Chevy 262-400ci 1955-98
Lift: .477"/.472" w/1.6 Rockers
Duration: 252°/266°
RPM Range: 1300-5300
249-12-364-4

Excellent throttle body cam. Lots of torque.
Operating Range: 1300-5300 RPM
Duration Advertised: 252° Intake / 266° Exhaust
Duration @ .050'' Lift: 208° Intake / 217° Exhaust
Valve Lift w/1.6 Rockers: .477'' Intake / .472'' Exhaust
Lobe Separation Angle: 113°

hope this helps

Yes that does help.I'll probly get that cam for it. Does my older 350 have 1.5 rockers on it and Does the 1990 350 have 1.6 rockers on it. Which ones should I use. Also will the tbi intake fit on the older 350. Or should I get a adapter for the four-barrel intake to tbi

Thats the same problem I ran into, no the intake will not fit on earlier style heads. What I did was to use my stock heads from my 88 chevy, I ported them out, rebuilt them, etc, and put them on my new 355.
What you could do if you wanna, it would be a long shot but you could get a nice set of vortecs, and a vortec TBI intake, since they have a different bolt pattern. You'd get a lot more power out of your 355 since the heads currently on your 1990 are pretty restrictive.

-cory

Originally Posted by sawking

Yes that does help.I'll probly get that cam for it. Does my older 350 have 1.5 rockers on it and Does the 1990 350 have 1.6 rockers on it. Which ones should I use. Also will the tbi intake fit on the older 350. Or should I get a adapter for the four-barrel intake to tbi

I just did this conversion on a 91 PU. We replaced the 350 with a 383 and a mild cam. The heads were ported and we installed headers and dual exhaust. Between the computer and the TBI, we had nothing but problems. It was too lean and it would fall flat on it’s nose. So we got a TBI off of a 454 which helped a little and we added a one inch spacer but the fuel economy was not good.

Finally we installed a Holley carb and an HEI distributor, what a difference. We can fry the tires without any problem and the fuel economy went up. So now we have all this TBI junk laying around collecting dust.

As for mounting the TBI and intake on the 355, you can make it work if you message the center 4 bolt holes of the intake. The newer heads have a different angel to the four center bolt holes. Obviously you don’t mess with the threaded bolt holes in the heads.