86 Silverado Engine Swap

[davidguy]

I have an 86 Silverado SWB 2WD with a dead 305 in it. I would like to put a crate 350 in it. What will need to be changed, added or discarded to make this happen? If at all possible I would like to get back to a basic engine setup (Carb, A/C, Alternator....no smog or ECM stuff). If I discard all the smog stuff and put a new HEI Ingition on it, will anything on the dash go crazy? I have all guages, except for one or two idiot lights?

Thanks.

[trickedout420]

no it will work just fine. i beleive intakes will swap along with exhaust get rid of your smog stuff and your gas mileage will go down some but its pretty much all swapable i beleive

[Redbird]

Everything should swap out/over provided that the 305 isn't TBI. The only dash "issue" you might have is if you have a Check Engine light. It'll stay on. But all you need to do is unplug the bulb.

[spr85gmc]

judt did this a couple months back it should run just fine but my recommendation is get as much new stuff as possible or atleast make sure everything is in proper working order. and word on mph dropping without extra stuff

[davidguy]

Thanks for the info Trickedout420, Redbird and Spr85gmc. What kind of mpg drop are you discribing, 1-2 mpg or 4-5mpg?

Thanks

Dave

[FordeatinZ71]

you will most likely have to change the starter. most 350's use a different starter than the 305s. your gas mileage should stay about the same or even improve when you change motors...the 305 is a really inefficient engine. if it DOES drop, it shouldn't be over 1-2 mpg, but i'm pretty sure it won't.

being that your's is an '86 you shouldn't have TBI (you didn't factory) and i don't think you have a check engine light until the TBI came into the pic. if you do, and you put in all the same stock stuff, your check engine light will function as normal. this is one of the easiest swaps known to man, i'm about to do it in my '83 Sierra in Feb...

[davidguy]

Thanks for the confidence. It is a carb motor, and the only like that I can think if is a CHOKE light. The reason I know this is that this is the light that was on when my son let the engine run out of oil. So I assumed this is the one light I have to worry about. All the replacement engines that I can find is up to an ’85 and ’87 or newer. What happen to the ‘86’s? Do I need to get a standard two piece rear seal or a newer Vortec type engine?

Thanks.

[bored&stroked]

86 was the change over years for 1pc rear mains. Im not sure what you have. Dosen't really matter though, the only difference is the flexplate/flywheel used and you can swap that easy when doing the motor.

[davidguy]

It's a one peice, but it doesn't matter to me one way or the other. If I need to use existing equipment (A/C, Alt., Pwr Steering...) do I need to stay with one for up to '85 or for '87 or older?

[FordeatinZ71]

Thanks for the confidence. It is a carb motor, and the only like that I can think if is a CHOKE light. The reason I know this is that this is the light that was on when my son let the engine run out of oil. So I assumed this is the one light I have to worry about. All the replacement engines that I can find is up to an ’85 and ’87 or newer. What happen to the ‘86’s? Do I need to get a standard two piece rear seal or a newer Vortec type engine?

Thanks.

the choke is easy. i have that light as well. it can or cannot be hooked up, doesn't really matter. it just hooks up to your choke element and determines if it's on or not. it doesn't usually work right but mine does sometimes. i didn't think you had a SES light, but i wasn't sure. as for the rear seal, it doesn't matter, just make sure you get the right seal for the motor. most motors you buy will already have a flexplate on them, so that shouldn't be an issue, just make sure the flexplate/starter match up...

the big change in the '87-up motors is they changed heads and the heads require a different angled intake. you can tell the difference by the way the valve covers mount, the 87-up will have centerbolt valve covers, the 86-down will have outer bolt valve covers. you will have to have either older heads or a special intake to run a carb on an '87 up engine. when i say special carb, don't get scared, these intakes have been around for years and are stupidly easy to get, just make sure you specify you have an '87-up engine when you are ordering them.

so as to what motor you get, it doesn't really matter. good luck and keep us posted. if you have anymore questions feel free to post 'em and we'll help as much as we can

[Redbird]

I don't know about "head angles", but I bolted an Edelbrock intake from a perimeter bolt, steel head 305 onto a centerbolt, aluminum head L98 out of a '89 Corvette. Matched right up, ran like a champ. What you have to watch out for is some of the '87 and up heads/intakes have an odd bolt pattern set-up.
You'll notice on the perimeter bolt heads that the intake bolts all screw in at the same angle (basically 90* to the mounting surface), while on some of the centerbolt heads the four bolts (two each side) nearest the carb will screw in at a different angle (basically at a 45* angle to the mounting surface). If you're looking at the engine, these four bolts will appear like they screw straight down (vertically) into the head, while the rest appear to go in at an angle (in relation to the horizon).

[FordeatinZ71]

well, i've always been told/seen that they are different. maybe the manifold was designed to work on both?

[spr85gmc]

for the intake yo ine up rigth with the heads you may need to get thw bolt addapter which intern will line up the bolts correctly . dont quote me but i think these are some of the easyest engines to put together only thing is its going to to be hell making sure it doesnt leak oil so have extr cskets on hand after the break in