Throttle body on an 85 or keep the 90?

[buffblazer]

Hey all, it’s been a long time since I have posted here, sold my K5, bought a corvette, now I’m back into the square body’s.

I picked up an 85 K20 350,sm465,208 the other day that is pretty much original. Still has the factory carb on it.

motor has about 146,000 based on the odometer rolling over but the age of the truck not looking like it’s over 200,000

I have access to a 90 K2500 with a TBI 350 that ran when parked. Mileage unknown.

Would I be better off taking the TBI off and putting it on the 85 small block, or taking the 90 out and cleaning it up and install.

emissions are not an issue. But also not looking to dump a ton of money into a build since it’s a budget cruiser.
Thanks

 

[82355]

Post pics.

How clean is the '85?

Martin

 

[buffblazer]

Its pretty clean on the inside, needs paint and rust repair on the outside.

will post pics as soon as my membership goes through. I upgraded on Sunday but even though my payment has left my account, PayPal says it’s still pending.

 

[anwat]

There's a lot of wiring to be routed and work involved in swapping the 90 ino thte 85. You may have some fuel pressure issues, also. I'd say stay simple, and just clean up the 85, leave it carbed: You'll be on the road sooner and I would guess for less money. Easier to tune and troubleshoot with the carb, also. I'd also want to know how well the 90 was running when it was parked...

 

[buffblazer]

There's a lot of wiring to be routed and work involved in swapping the 90 ino thte 85. You may have some fuel pressure issues, also. I'd say stay simple, and just clean up the 85, leave it carbed: You'll be on the road sooner and I would guess for less money. Easier to tune and troubleshoot with the carb, also. I'd also want to know how well the 90 was running when it was parked...

Good points. Should clarify, the 85 is running right now. Been driving it back and forth to work for fun the last 3 weeks. Other than running a little rich it does really well.

the 90 was a farm truck. So it could be very possible the motor wasn’t taken care of well (on a dairy farm with many different people driving it.
The TBI swap is more just of a fun thing. Always have wanted it since all my square body’s have been carved. The 90 is free to me to pick parts. I guess I didn’t know if the 90 motor would have any advantages over the 85. I know everyone goes crazy for vortec heads and the 90 is too old for that, so I wasn’t sure if there was anything worth to swapping motors or just rob the TBI off of it.

 

[82355]

It should be a roller block.

Martin

 

[anwat]

I'm way out of my expertise area, but I think the block in the 90 came with the provisions for a roller cam, but didn't actually have one installed. If that's true of yours, it's a better block if you ever intend to rebuild it, but I don't think there are any substantial differences in the two....I'd stick with the one that runs better right now...it will be cheaper in the end to do that. One thing you may want to verify is that they are both 4-bolt mains. For what it's worth, you could always just slap an FI tech injection on the 85 and be done with it...way more simple than trying to pull out the TBI from one and add it to the other. Also more expensive. Check that GM throttle body, it may be cracked, the bearings get worn, in the end it may not be that cheap even though you have the parts.

 

[buffblazer]

Post pics.

How clean is the '85?

Martin

 

[buffblazer]

I'm way out of my expertise area, but I think the block in the 90 came with the provisions for a roller cam, but didn't actually have one installed. If that's true of yours, it's a better block if you ever intend to rebuild it, but I don't think there are any substantial differences in the two....I'd stick with the one that runs better right now...it will be cheaper in the end to do that. One thing you may want to verify is that they are both 4-bolt mains. For what it's worth, you could always just slap an FI tech injection on the 85 and be done with it...way more simple than trying to pull out the TBI from one and add it to the other. Also more expensive. Check that GM throttle body, it may be cracked, the bearings get worn, in the end it may not be that cheap even though you have the parts.

Good ideas. Didn’t know that about being a roller block or thought about the TBI maybe needing rebuilt. Gonna have to see how many miles its got to see if it’s work it

 

[82355]

Swap it!

Martin

 

[anwat]

If the throttle body is in good condition, and you've got some time for the truck to be down while you swap, I'd say it would be worth the time and effort. You'll get better mileage, your cold starts will be easier, and troubleshooting/tuning will be easier. That's assuming you can just pull off the TBI unit, Intake and associated wires and sensors and put them on the new truck. You may need a new distributor, I'm not sure if the 85 has the ESC system controlling the spark. If all the computer controlled options are the same, the 90 chip in the ECM should be fine. You will want to change the t-stat to a 195*. Fuel delivery upgrades and you should be on the road. I take it you don't have to worry about emissions where you're at? Never mind, I see you don't. My two cents is if you really feel it would be an advantage, swap the TBI intake on the existing block. While the 90 may have the provisions for a roller, you're not planning on going that route now. If you're not going to have that block checked, I'd stick with what I know works...If you swap blocks only to discover a valve issue, or a cracked block or who knows what issue the whole saving time and money thing is gone. Not enough difference to me to swap in an untested block over one I know works. What I would do is pull that '90 out, put it on a stand, and start a rebuild on it. Use your money towards the rebuild, and drive that carbed motor into the ground. Hopefully by the time the '85 dies, you will have a rebuilt TBI completed to drop in. I've been known to make bad car decisions in the past, though, so maybe you shouldn't listen to me...