305 swap

[truckertom21]

Hi I have a 1985 Chevy C-10 2X4 with a 305 and a 700R4 in it. I?m looking at swapping the motor because the old one has a couple of problems with it. I want to keep it a 305 because I?ve been hearing that the 305 and the other sbc's are completely different. But if I were to find a vortech 305 and put a carb intake on it then would that be like be putting the same motor I have into my truck? Or would it be another big pain in my butt? I am a heavy equipment mechanic so I have the skill to do the swap but I don?t know too much about this gas stuff.

Also would the stock 10 bolt rear end stand up to the newer motor? I?m hoping to push out about 350HP to the wheels after a cam, intake, carb, and a slight porting job

[squirrel]

Re: 305 swap

A 305 and a 350 from the same year look almost identical, and can be swapped very easily. The only substantial differences are the bore size and pistons, and the heads use smaller chambers and slightly smaller valves. The 10 bolt from the 80s is the 8.5" ring gear and should hold up fine with a 350 engine (assuming it's in good condition). Good luck getting that much power out of a 305 without spending a bunch of money (or using nitrous)....a 350 or a 400 or a stroked 350 (383) would be more cost effective.

[truckertom21]

Re: 305 swap

okay i did go to the junk yard and i found a 305 in a camaro (3rd gen) its a TBI motor but i believe my intake and carb will work on it. i don't think it's a vortech motor but it will work and the 350 is just a dream i don't plan on building the poop out of the truck. it's just my daily driver.

[squirrel]

Re: 305 swap

You still ought to spend some more time and a bit more money trying to find a 350 to start with, you'll be glad you did.

[truckertom21]

Re: 305 swap

okay...what year 350's should i be looking for?

[yellomalibu]

Re: 305 swap

okay...what year 350's should i be looking for?

Pretty much any year. I doubt you'd find an intact motor from the 60's, but 68 and older used the short water pump and didn't have accesory bolt holes in the heads... your alternator, power steering, and a/c brackets wouldn't bolt up to them.

Aside from that, pretty much any* carbureted, TBI, TPI, vortec 350 would work with an intake change. Just be sure to buy the appropriate intake for the engine you get.

You'll really like the extra torque from the extra cubic inches. That said, if you happen across a 400 small block, you'll really like the torque it makes; and it, too, will bolt right in place of the 305. It would probably need a rebuild, though.

*The LT1's use reverse cooling. I guess you could use one of them if you got the belt/pulley stuff from the donor car... but it may be a can of worms to avoid.

-anyone, feel free to correct me if I am wrong.

[truckertom21]

Re: 305 swap

ya i thought about the 400 is their a big aftermarket for them? i know that the support for the 350 is huge is it the same for the 400?

[yellomalibu]

Re: 305 swap

ya i thought about the 400 is their a big aftermarket for them? i know that the support for the 350 is huge is it the same for the 400?

Pretty much. You won't have quite the selection of "on the shelf" items for the 400, but for a basic or mild rebuild, absolutely no problem. Tons of parts available.

[truckertom21]

Re: 305 swap

and will my stock 10 bold and 700R4 handle the extra power? thats not really the thing i want to find out about when i'm hauling/pulling something

[383S-10]

Re: 305 swap

Two more things about the 400........heads are specific to them they will need steam holes drilled in them & use a specific head gasket & 400s are externally balanced for the most part even though you can order internally balanced parts for them....still no big deal but something you will need to remember

yes they should handle up to 400hp a little over mild....or you can get

http://cgi.ebay.com/ebaymotors/GM-70...mZ300283693866

[truckertom21]

Re: 305 swap

okay cool i didnt want to be pulling my buddys trail jeep and hit the gas a bit too hard then blow out a rear end

[Schtauffer]

Re: 305 swap

Best option for what you want-- find a take-out 350 engine from a 96-99 Chevy or GMC pickup. These are the Vortec engines. It will bolt right in, with the exception of the intake. Buy an Edelbrock Performer Vortec intake, and it will run great for you. With fuel injection these are rated at 255 hp. These motors really run for a 255 hp rating. Also, they have a roller cam. You might be able to find one of these in good condition for less than $1000.

Another very good option is a new 350 from GM. You can get them with a 260 or 290 hp rating. These have standard heads; your current intake and carb would bolt right on. These motors also run strong, but the heads are not as good and they have hydraulic flat-tappet cams. Brand-new with a warranty these engines are something like $1500 - 1800.

Your trans and rear will live a long, happy life with either of these engines (provided that they are in good shape now). Also, you'll like either of these options a whole lot better than the weak-kneed 305. Both will provide better power and fuel milage. The 305's are known for being inefficient; popular thought is because the bores are so small, the valves are not free to breath. The 305 and the 350 have the same stroke, but the 350 has a bigger bore, which unshrouds the valves.

Any Chevy small block from 1955-99 will bolt right in physically. Like yellowmalibu said, avoid the LT1 (Corvette 1992-96 and Camaro 93-97). They are different. Other than that, all small blocks are externally the same as far as bolting into place, except for the accessories. GM did not put bolt holes in the heads for accessories until somewhere around 1970.

Happy motoring.

Gene

[FoFittyFoSS]

Re: 305 swap

Did the same swap on my 86 C10 last year. I used a newer block that was not machined for a mechanical pump and had to switch to an electric fuel pump. The hole was there and probably could have been machined for the pushrod while it was getting bored but I didn't notice till I got it back and had already built it.

[yellomalibu]

Re: 305 swap

Did the same swap on my 86 C10 last year. I used a newer block that was not machined for a mechanical pump and had to switch to an electric fuel pump. The hole was there and probably could have been machined for the pushrod while it was getting bored but I didn't notice till I got it back and had already built it.

Good point.
Last August I put a 93 TBI 350 in my Blazer to get rid of the tired 305. The 93 truck didn't come with a mechanical fuel pump, but luckily the block was machined and bored for it. After cleaning the gunk out of the pushrod hole with a rag, a screwdriver, and some brake clean, the pushrod from the 305 worked nice and smooth. Re-used the fuel pump from the 305, too.

[squirrel]

Re: 305 swap

Also note that the crankshaft design changed in 1987 to a one piece rear seal, along with a different bolt pattern flywheel. And that 700 might handle more HP ok, or it might burn up, there's no way for us to know what condition it's in....so you do need to be concerned about it. 1985 is a kind of early version of the trans, they got better in later years, GM made a lot of design changes as time went by. You definitley need to be careful with the throttle valve cable adjustment when you do any work on the engine/carburetor, if the cable is not adjusted right it can burn up the transmission quickly.