Hi guys,

I want to pick up a used 350, and build it up.

My goals:
To come close to 300HP
Use the original pistons (not bore the engine) (keep the shortblock stock!)
Spend as little dough as possible.

I could probably pick up a 350 from the early 80ies at some junkyard near me for cheap.

Do stock chevy 350s vary their compression ratio by head chamber size or dished pistons or a mix of both?

Are the heads from that period good enough? I would port them myself the best I can, maybe get them milled. If they aren't good, then what year heads are, and from which engines? (maybe from a 305 for extra compression?)

I don't know anything about smallblock chevys and their head castings etc.. I want decent compression and flow.

For the intake manifold I'm thinking whatever decent dual-plane I can find.

Carb - whatever I can find. I'll figure out the exhaust part later. and I'll get a cam off summit or ebay or someplace.

Anyone have any info/tips for me? If you know any good websites I'd appreciate it

Also just another question - how important is it to change the timing chain and gears? I'd like to avoid doing that if possible. Hopefully I'll find an engine with less than 100k on it, and it shouldn't be too stretched out.

thanks guys I'm looking forward to replies.

 

Welcome to thridgen.org.

As you can tell, noone really want to touch this

"cheap" and "buildup" usually equals disaster, especially with a "junkyard motor".

 

The stupidly-low CR was because of both the heads AND the pistons. The heads were usually in the 76cc area (too much) and the pistons are usually dished.

I suggest (assuming your 350 has dished pistons) getting a set of mid-80s 305 heads, like the #416 castings. They have much smaller chambers making for about a 9.5:1 CR with dished pistons on the 350, which is about right for pump gas. They are quite common, so you shouldn't have much of a problem finding a decent set.

Any 350 you find will also probably have the #929 cam, which was a pretty anemic cam for performance use. Just replace that with a new aftermarket one, they are cheap enough.

After that, I'd do headers.. they can be as cheap as $80 for a new set of shorties, all the way up to about $400... its your call here.

I'd do the timing chain before it goes into the car. It could be stretched all to hell and that's not good.

Oh yea... if its got a Qjet 4bbl carb on it, leave it there. Its a good carb for street use and can support quite a bit of power.

 

I'm going to risk raising a few eye brows and tell you how i put my motor Together.I found a 350 out of a old 3/4 ton chev truck,the block was a 3970010.This meant it had a forged crank and 4-bolt main caps along with flat-top pistons.I paid 450$(Can.)for it.I tore it down to reveal very little if any wear or ridge at the top of the cylinder, and the main and rod bearings looked like new.I replaced the old oil pump(40$Can.),ordered a Cloyes double roller timing set(less than 20$Amer. on sale) and a Summit #1102 cam kit (80$Amer.)and i used a Felpro gasket set that cost me about 100$Can.
For the heads,i had three sets to choose from,the old 882 castings that came with the motor,a set from a 307,and a set of 350 heads from 94' TBI engine .I know everyone hates the TBI heads,but i decided with a pocket porting job and new valve seals,they'ed have to be better than the old smog heads(love the center bolt valvecovers)They were free.
I bought a Weiand action+ intake(51$amer.),Holley4-barrel(31$Amer.)Edelbrock 3-inch breather(15$Amer.)Holley Powershot Airfilter(10$Amer.)All on E-bay.
I put it all together and added a recurved HEI with an Accel cap and rotor,and Hedman shorties.This motor has been running now for two years,doesn't burn or leak a drop of oil,gets 25mpg.on the highway,and i estimate close to 300 horsepower.

 

3970010 blocks could be 2 or 4 bolt main and I know that mine had dished pistons in it when I took it apart. I don't think the cranks were forged either. Unless you got one of the 1969 camaro 302's, they use the same casting as your 350.

 

I would at least hone anything I'd get from a junkyard and put new bearings in it. I found a used 350 and tore it down. Had it checked for cracks, then bored .030 and honed. The crank was polished. I brought it home and put new bearings in it along with new pistons. I reused the crank/rods. I bolted on a set of L98 aluminum heads I found cheap and slapped in a ZZ4 cam that I found from a buddy. I also added a Cloyes timing set. I came out of the project for less than $1000. Closer to $900 including all the parts and machining. What I've got is basically the ZZ4 Crate motor, but I have the pleasure of saying I built it myself.

 

i 2nd that. i do not touch bone yard motors. and if i did it would get a .030 over bore, hot tanked, decked, get new cam bearings pressed in then check out the crackshaft and make sure its ok. thats the only why i would rebuilt a boneyard motor. then i would also get the heads decked and new vavle seals.

getting a used motor that you have no clue how it was used is a bad thing. you don;t now if it over heated or anything

your best bet is to find a motor that someone is selling in the news paper so you can get all the info on the motor

the 305 i swaped in my car i got from my friend i new what happen to it so i didn't walk into the rebuilt blind.

 

I didn't mean to imply that all 3970010 blocks are 4 bolts.I know that they came in both 2 and 4 bolt versions.I am pretty sure a flat top piston is flat across the top with valve reliefs,right?As for the forged crank,i was pretty sure most truck engines had them,it's to late for me to hit it with a hammer to see if it rings or not.The details aren't the point,i was just trying to illustrate that you can get a junk yard block and with a little detective work you can make a educated guess as to how it was used.Check the plugs in all cylinders to see how it was running,when you pull the heads,inspect the gaskets to see if there was a problem and have the heads checked for cracks ect..If you find a problem along the way,correct it.

 

Find a complete long block vortec engine at the scarp yard, sell the FI off that engine and buy a cam, intake,carb and headers and you will see well over 300 hp....

Just my .02

 

nope, my 010 block came out of a truck and its a cast crank