Aaron R.

I am debating rebuilding my 305 or just buying a GM crate long block from Summit. I figure cost will be about the same (about $1,800) either way.
I know I can get more power out of the 350, but I am wanting a balance of power and fuel economy. Also, my T5 won't handle a lot more than stock and I don't want to upgrade it, so more potential power isn't something I'm interested in. Once I drop it in, it stays there exactly how I built it, no more power add-ons.
My biggest concern about going with the 350 is seeing a decrease of 2 or 3 mpg or more. I am thinking by having my machinist rebuild the 305 we can maybe do a better job of it and end up with a very efficient, above stock hp engine.
I really don't feel like shopping around for a 350 block and doing a buildup of that either.

Any ideas on this, guys?
What kind of gas mileage are you guys seeing with your crate 350s?

Rolling Thunder

Well honestly since the cost is the same roughly its really a matter of preference. Its a matter of new vs rebuilt personally id want new motor which would also be of better quality than the original. A lot depends on what crate motor you get. As far as gas mileage is concerned although yes your going up a few cubic inches but the stock 305 could have done much better in terms of MPGs with the appropriate mods. What im getting at is a 350 built properly could get better gas mileage and perform better than the factory LG4. Granted that also means with appropriate mods the 305 could out MPG the 350. Alot really depends on what your specific requirements are really. Though i think the real deciding factor is the t-5 if you dont want to upgrade it or change it i believe the max rating was somewhere around 250 foot pounds of torque and even a tame 350 that got 20+miles to the gallon will produce enough power to break that. As a matter of fact even the stock LG4s were pushing close to the edge of their limitations theoretically so even a lightly modded lg4 could exceed the ratings of the standard t-5. I think even just headers + exhaust would push the LG4 over its rated max. Before the word class t-5 you couldn't even get a stick shift 5.0 TPI car and they only produced 270 foot pounds of torque. Granted alot of it is how you drive it but on paper anyways 350 + t-5 = doomed to failure and modded 305 + T-5 = doomed to failure. Yea the early non world class T-5s are really that crappy. If you were willing to accept the fact that it may break somewhere down the road and were willing to replace it with a world class T-5 (which is a bolt in replacement same trans just better version) a little more could be done but they weren't all that much stronger.

Aaron R.

I'm not entirely opposed to putting in a WC T5 later, but for now I really don't want to get into that. Recently had a lot of work done on the T5, and I'm not in a rush to replace. I do drive pretty gently, not many hard, high revving, sudden shifts so I expect this T5 to last for a while.

What kind of mpg mods are you talking about with the 305?
I have the engine out now and am ready to start rebuilding or going crate, I just need to get better educated on my options.

Saabster

iTrader: (2)

What about a crate vortec 305? I've seen them on summit for $2200. Stock numbers for one of those is 255 hp and 290 lb-ft.

Rolling Thunder

Well many people think performance mods = bad gas mileage but in truth the way power is built is by increasing the dissplacement or increasing the efficiency. To build better MPG well toy on the latter part of that equation. Theres simple things like a better cold air intake which pretty much universally applies to these cars. The addition headers and exhaust alone people have notices rediculose gains ive heard 2-3 MPG improvements some claim even more. The LG4 has pretty low compression bumping it up a bit would improve power and fuel economy due to greater efficiency. The cam shaft in the LG4 is pretty bad all around and a new cam selected properly using new technology can again not only out perform the factory cam but bump up your MPGs too. Heads the vortecs flow great due to the new angle there designed at vs the standard 23 degree chevy head. Because there more efficient they can use smaller runners (which improves velocity very important for fuel atomization) while still out flowing the originals by a large margin. A big mod that your probably not interested in is going to TPI when they first were tested by swapping the TPI intake onto already existing carbed motors in chevys line up and gains of 20-30% were realized in HP, tourque, and fuel economy! Thats pretty huge. As you can see ive touched on pretty close to the entire motor lol. If you look at the cost to build your motor to correct these issues youll see it might have been cheaper to buy a short block or a long block that already had high compression or vortec heads. Not to mention there are other things that can be corrected for reliability. Newer block have roller valve trains to avoid the dreaded cam failure which is all too common these days. Also the one piece rear seal is nice addition. Then lets talk about quality these old motors came with cast pistons, cast iron cranks, not sure on the connecting rods but there nothing special. Many of the new crate motors come with hypertunic pistons which arnt much better than your pistions in terms of function but weigh about half as much and a lighter rotating assembly is the best. Many come with cast steel cranks vs cast iron. Many come with powdered mettle rods a nice improvement over stock.