Hey I'm a new member I've done a lot of reading on here and found a lot of help but just need to be certain. I want to switch the 305 in my 1984 Z28 to a 350 out of a 79 truck. My plan is to take the heads off the 305 and put them on the 350 for the higher compression. The 305 has the 4 barrel Rochester carb so I may as well reuse it and the manifold as well. My carb right now is not computer controlled nor do I want it to be computer controlled with the 350. Would I have any difficulties putting those parts from the 305 on the 350? Does this sound like a good plan? And would I have any trouble putting the 350 block in? Im concerned about having to move motor mounts. I'm just looking at the block itself so I would have to buy a new bottom end. Might there be harm in using the new bottom end with the old top end?

 

305 and 350 (and 262.5, 265, 267, 283, 302, 307, 327, & 400) are all Chevy small blokcs. Motor mounts are all the same.

Yes putting in a 350 would be a good plan; from there, the quality of the plan, depends on the quality of the 350.

 

 

Okay that's what I wanted to hear, the top of end my current 305 isnt in the best shape, but considering a new top end after shipping and taxes would be about $2000 reusing the parts its certainly the cheaper option. But how about the power difference? The 305 now is only 150 horse, any idea just how much improvement there would be with the extra quarter inch bore of the 350 and higher compression? I feel it would make sense to just get a new top end before putting it in the car the first time.

 

double post

 

What?

 

I wouldn't really consider a 1979 Chevy 350 with a 2 piece oil seal a new bottom end. I think the 84 was also a 2 piece main. I am not sure if the 350 was a 4 bolt main or not.

Depending on the condition and wear on the 350 truck, depending on if it was ever freshened up, will depend on it's power. You have the right idea but we really don't have enough info to base an approx decision on how much power you will be making on a 34 year old motor or something that was built 11 years before you were born..

 

350 is a 4 bolt main. Its been, washed well say. If I get it I would plan on boring it maybe .040 over. The reason I said "new bottom end" is because all of the parts inside the bare block will be new. I'd like to get around 350hp. Maybe more down the line if I decide to stroke it and get new heads.

 

OK; doesn't too much matter one way or the other though.

Bore it as little as possible, and still clean up the wear. Every .001" you bore it, brings it that much closer to the grave. Doesn't matter how much you stroke it; The Rule of boring as little as possible, remains The Rule.

 

350 HP with little 305 valves? I have done the 305 head 350 a few times and it has a ton of grunt down low even with a 510 lift cam but chokes out fast because of the small valves. your better off spending a little money and get vortec heads. you can get them drilled from suppliers for your older intake. Check ebay.. there all over. Dont take the time to pull a engine and build a turd. spend the little bit of cash and do it right. you will hate your self for building a pile of sh*t and hacking it together.

 

Might be able to bolt the intake on but the intake ports won't match up.
Need a Vortec only intake

Observe the gap at top of a reg SBC intake on Vortec heads

 

if you havent rebuilt the engine yet mabee you should check out new crate motors there reasonable priced from summit then add on to that..... i wouldnt run 305 heads but then again thats my opinion ... i have a 85 and i replaced the tranny with a built turbo 350....best move i made for the car i hate lock up converters and o.d. in a good street toy...lol................ when u can break the tires lose shifting into drive u know yr having a good time

 

I have not rebuilt the engine yet I dont even have the block yet I just want to get all my research done first. I have no idea what tranny is in my car. It is a 5spd manual. I had read that the 305 heads would be better than using vortec heads. If I stroke it is there a particular length I should aim for? What all needs to be changed to allow the lengthened stroke? I'm basically just looking for the best power : dollar ratio for this car.

 

5-spd manual = T-5

Wherever you read that 305 heads are "better" than Vortecs, you need to quite reading there. That's about as wrong as it gets as far as power output potential.

Usual stroker combo for the 350 block, is the 383. 3.75" stroke compared to the 350's 3.48". Requires pistons specific to that stroke as well as the crank. Best rods to use are 5.7", but generally NOT the stock 350 rods; their bolt heads stick WAY up into everything and often cause interference with the cam, and necessitate extra grinding around the bottom of the cyls and the oil pan rail. Instead, the best way to go, is aftermarket rods w capscrews instead of the bolt-&-nut setup.

Stock 305/350 rods vs aftermarket w capscrews...



Not hard to figure out which will require less work to make fit.

 

Maybe it wasnt so much more power it said rather than higher compression over vortecs. I dont know. None the less for the amount it will cost to rebuild a block a crate engine may not be a bad way to go. I'm looking at the Chevy economy performance 290hp 350. My issue is I live in Canada and shipping on that engine is almost $1000

 

That's not a good choice...

Same motor as the 260 HP one, which is IDENTICAL IN EVERY WAY, PART NUMBER FOR PART NUMBER, to the 160 HP wonders of the 70s. Same cam, same 8:1ish compression, same crap smogger heads. The 290 HP version is IDENTICAL to that except with a different cam.

Best cheapest way to go these days is, go to the junkyard and pick up a motor out of a 96-2000 Chevy or GMC full-size truck or van; might not even have to rebuild it. Then put the cam, intake, & carb of your choice on it.

 

Are the mounts the same on the 96-2000 blocks? I just really dont want to have to relocate them

 

That was my concern with the crate engine too. Being a new block

 

Yup, mounts are all the same, from 57 to 2000.