Engine Swap; 1985 305 to 1987 350TBI

[usar17]

Ok so I scored big on this find. Was routing around my buddies salvage yard when I came across a 1987 C20. Was a local shop truck for years. Asked him what the deal was on it. Said he bought it strictly for the BED lol. Explained to me that the 350 in it was a GM Rebuild with only around 1k Miles on her. He said he'll get it running for me so i can take a look.

I currently have a 305 that needs rebuilt, but why go through that hassle when i planned an upgrade to a 350 anyways. Im retaining my 700r4 that was recently rebuilt.

Questions I have:
What Issues will i have swapping this TBI over to Carb? Im thinking an Edelbrock Intake with a Newly rebuilt Quad Carb. Will i have any issues with bolting this one? I saw on another forum that the heads for a TBI are slightly different. im hoping thats a myth

Any issues bolting this to my 700r4? I would doubt there would be any problems there.

Is it worth trying to find some Vortec Heads now when i swap? If so what vehicles should I be searching for to rip the heads off (I know I would need a vortec to Carb Intake)

Any other issues you can forsee?

 

[whiplash889]

ive done the swap with a demolition derby car motor and a k10 i had a while back, all i did is get a 4bbl carb and intake from summit racing, there is four bolts on either side of the carb to bolt the intake to the motor you will need to cut the bolt holes out, by a hack saw for something. then you will just need 4 washers for those four bolts. like i said ive done it before took me about a hour to do its real easy. and those two motor are still runnig strong today. i would give it a shot and see what happends. sorry no pics due to being in the military and my derby car motor is 500 miles away and the 700r4 will bolt right up to it with no problems. i woundnt go with differnt heads due to having to adjust the valves and head gaskets and torques you will have to do, just saving ya a little work.

 

[Jims86]

If you have a qjet manifold right now, just save your money, and re drill the 4 mid intake bolts to the shallower angle, and it will bolt right up, Ther is a wedge washer kit available...i will have to do a search.
Unless you were going to change te manifold anyway...just make sure you get a manifold with EGR....I think you need that in PA?
For Vortec heads, yes you will need the special manifold, but as far as heads, look for a 96+ 1/2 ton truck or SUV , and you want the p/n 10239906 heads.
I am not sure about what you want to do with the truck, but if you want a good Daily driver/work truck with good low end torque and fuel economy, I would recommend sticking with the TBI heads(20+ MPG with a properly tuned q-jet has been achieved)
If you want to end up with a go fast SS type rig, go with the Vortec heads, but you may want to bump your axle gear ratio's to the next lower gear, to try to make up for the little bit of low end you would loose with the Vortec heads, and depending on the rpm range of the cam you choose.
You will want to see if the 87 engine has a fuel pump block off plate, or if the fuel pump casting was left closed up., in which case, you can run an electric pump, which would likely be in stock at the local parts store.

 

[usar17]

Ya i had looked at the fuel pump area, it appears blanked off after a quick glance.

Ill stick with the TBI heads then. This is for a daily driver/lil fun in the mud truck.

Whats the difference with the bolt patterns between my current 85 Carb and an 87 TBI? I thought they would be the same. I was looking at Edelbrock #3701 or #3706 Performers. ones for Cast iron one is for Aluminum...how can i tell which heads this motor has?

 

[Jims86]

Ya i had looked at the fuel pump area, it appears blanked off after a quick glance.

Ill stick with the TBI heads then. This is for a daily driver/lil fun in the mud truck.

Whats the difference with the bolt patterns between my current 85 Carb and an 87 TBI? I thought they would be the same. I was looking at Edelbrock #3701 or #3706 Performers. ones for Cast iron one is for Aluminum...how can i tell which heads this motor has?

Edelbrck p/n 3706 is what you want, if you want a new manifold.

The valve covers have 4 bolts in the center of the valve cover, as opposed to the parimeter valve cover bolts on the 85.
You would be looking for a manifold that will bolt up to 87 to 95 heads. The Corner 8 manifold bolts are the same angle into the heads as your 85, but the 4 mid manifold bolts, 2 on each side of your carb, are more virtical, and the pre 86 manifold bolt holes nees to be hogged out to work with the 87 heads.

 

[matt21191]

engine swaps

hey guys im new to the forum. im wanting to know something. i have a 1997 chevy pickup witha 5.7 vortec in it. the motor is blown. i found a 1984 5.7 out of a van. will my vortec heads bolt up to the older small block? thanks guys

 

[Jims86]

hey guys im new to the forum. im wanting to know something. i have a 1997 chevy pickup witha 5.7 vortec in it. the motor is blown. i found a 1984 5.7 out of a van. will my vortec heads bolt up to the older small block? thanks guys

Yes,, everything will physically boltmto the block, but you may have to do some fenagling to set up the crank for the crankshaft position sensor, and unless you drill the three castings in the lifter valley, you wont be able to use your roller cam from the 97.
Younwill also neednto use the 84 flywheel and starter, because the 84 has a 2 piece rear seal, and 87 and up had a one piece.

do you know exactly whats "blown" on the 97?