Comparing SBO to SBC in general. The SBC was a decent motor by the 80's, you could get 300,000+ km out of them. The 70's SBC was a blue smoke puffing, cam burning turd.
SBC v. SBO
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If you just want a reliable driver it is easiest to do it with the Olds 350. IIRC, Olds used high nickel blocks which GM did not use in Chevy engines. For a transmission, use a TH 200 4R. It fits anything GM, and can be made reliable. Plus the gear ratios are far better than the Th 700 R4. Run a modest gear like (my favorite right now) a 3.23, a Quadrajet and an HEI and you will have plenty of trouble free motoring. The Chevy has advantages when it comes to price, parts availability and workable native EFI setups. It also has a very good oiling system and may be available with a high nickel block too (research is needed to find an application). The cam that comes stock is irrelevant as it will be changed (and only 305's had that issue). However, it is more work to properly swap in the Chevy than the bigger Olds family swap. At the mild level you seem to be wanting to go with, there is no real advantage to the Chevy.
Now if you want to start from scratch, go with an LSX. I would try to use a smaller engine like the 4.9 or 5.3 out of a truck instead of the larger ones for your application. Why? Iron block, and better fuel economy on the highway due to a smaller displacement. Run the ignition off an MSD box (special one just for an LS), and run the injection off a Megasquirt. This will let you bypass a lot of tricky things like CAN, OBD II, and Passkey. It will also bolt to a standard SBC bell housing, so I would again go with a TH 200 4R if you want an automatic.
All this supposes that an emissions inspection is not in your future. If you do have to pass smog, go with the Olds 350 and run it off the CCC computer that is native to your car. Paint it black, use the 307 valve covers and use an intake with an EGR valve provision from an aftermarket company but grind off the brand name of the maker before sand blasting the intake. Richen the secondary metering rods, and consider a custom made PROM chip burned in an emulator to set a better timing curve. I would also cut off the thick stop on the secondary air valve to make the carb a computer Quadrajet 750 instead of the 600 it is. For exhaust, run a single 3 or 3.5 in cat with a Hooker cat back system and the stock 350 exhaust AIR manifolds extrude honed internally and run with a good free flowing Y pipe. Get a 80's 442 air cleaner base too, while you are at it. Get a cam with a wide LSA, and run around 9.5:1 compression for good idle quality and decreased Hydrocarbon emissions. Will this ensure a pass come smog time? No, but it makes it more likely.
As far as practical goes, that is exactly how my car was planned. It was initially supposed to be a pizza delivery car ( and was for a year, or 40k miles) and as such fuel economy was a big concern. Mine is Chevy powered, but it was originally a Buick V6 car and I had lots of Chevy stuff and knowledge, so I went with it. It was also built in the 90's when information about stuff other than Chevy was hard to come by and the internet was in it's infancy (and not in my home). So, how did it do on gas? initially, not well. I was getting 12 mpg city and it ran so rich that it belched black smoke. It was an issue I only solved after taking the car out of service and traced back to an AIR system leak that tricked the O2 sensor into seeing dead lean instead of the right mixture. As it sits now, it gets better city fuel economy than the V6 did by about 1-3 MPG (The V6 got 14 mpg city, 29 highway). It is worse on the highway though by 5-8 MPG. That is normal though as a larger engine needs a larger minimum amount of fuel to run at a steady state speed than a smaller one of equivalent design efficiency. Surprisingly, the switch from 2.41 gears to 3.23 netted a huge gain in fuel economy because it keep this engine in the power band. Even still, I have a compound 4th of 2.14:1, which is lower than the V6's 2.41 compound 3rd, so the engine RPM for equivalent speed is lower with the v8 than the V6 at a steady state speed. I could write a book on theory here, but I will stop. Let me know if you want to know my whole combination and I will post it here.
Now if you want to start from scratch, go with an LSX. I would try to use a smaller engine like the 4.9 or 5.3 out of a truck instead of the larger ones for your application. Why? Iron block, and better fuel economy on the highway due to a smaller displacement. Run the ignition off an MSD box (special one just for an LS), and run the injection off a Megasquirt. This will let you bypass a lot of tricky things like CAN, OBD II, and Passkey. It will also bolt to a standard SBC bell housing, so I would again go with a TH 200 4R if you want an automatic.
All this supposes that an emissions inspection is not in your future. If you do have to pass smog, go with the Olds 350 and run it off the CCC computer that is native to your car. Paint it black, use the 307 valve covers and use an intake with an EGR valve provision from an aftermarket company but grind off the brand name of the maker before sand blasting the intake. Richen the secondary metering rods, and consider a custom made PROM chip burned in an emulator to set a better timing curve. I would also cut off the thick stop on the secondary air valve to make the carb a computer Quadrajet 750 instead of the 600 it is. For exhaust, run a single 3 or 3.5 in cat with a Hooker cat back system and the stock 350 exhaust AIR manifolds extrude honed internally and run with a good free flowing Y pipe. Get a 80's 442 air cleaner base too, while you are at it. Get a cam with a wide LSA, and run around 9.5:1 compression for good idle quality and decreased Hydrocarbon emissions. Will this ensure a pass come smog time? No, but it makes it more likely.
As far as practical goes, that is exactly how my car was planned. It was initially supposed to be a pizza delivery car ( and was for a year, or 40k miles) and as such fuel economy was a big concern. Mine is Chevy powered, but it was originally a Buick V6 car and I had lots of Chevy stuff and knowledge, so I went with it. It was also built in the 90's when information about stuff other than Chevy was hard to come by and the internet was in it's infancy (and not in my home). So, how did it do on gas? initially, not well. I was getting 12 mpg city and it ran so rich that it belched black smoke. It was an issue I only solved after taking the car out of service and traced back to an AIR system leak that tricked the O2 sensor into seeing dead lean instead of the right mixture. As it sits now, it gets better city fuel economy than the V6 did by about 1-3 MPG (The V6 got 14 mpg city, 29 highway). It is worse on the highway though by 5-8 MPG. That is normal though as a larger engine needs a larger minimum amount of fuel to run at a steady state speed than a smaller one of equivalent design efficiency. Surprisingly, the switch from 2.41 gears to 3.23 netted a huge gain in fuel economy because it keep this engine in the power band. Even still, I have a compound 4th of 2.14:1, which is lower than the V6's 2.41 compound 3rd, so the engine RPM for equivalent speed is lower with the v8 than the V6 at a steady state speed. I could write a book on theory here, but I will stop. Let me know if you want to know my whole combination and I will post it here.
(I used to drive a 2000 Cadillac SLS with 17-25mpg city/hwy Im pretty sure and that car could make the roughly 300mi. trip on about 3/4 tank
I just went on a 325 mile drive this weekend and averaged 24.5mpg on the highway in my 2000 SLS. !NICE! Sorry for hijacking the thread but fuel injection is going to be a upgrade soon on my GP with a Chevy 350.
I just went on a 325 mile drive this weekend and averaged 24.5mpg on the highway in my 2000 SLS. !NICE! Sorry for hijacking the thread but fuel injection is going to be a upgrade soon on my GP with a Chevy 350.
Remember too that the SLS has a smaller engine and is far more aerodynamic than the barn door G body.
85GPLef41 said:
I am trying to find that out myself, actually (but with a 3.23 gear). I am hoping for 25 mpg highway, but doubt I will see it. I don't have cruise control (helps A LOT!) yet, my TCC is not hooked up, and my speedo is not accurate either. My guess is I will see 23 MPG at best when all is said and done. This is in a car that was built with fuel economy in mind as being equal in importance to acceleration. I think the MCSS with the 3.73 gear was rated at 23 MPG, so it should be less than that with a 350. Then again, it all depends on the combination of parts as there are so many things that affect fuel economy. I have even seen a 1-2 MPG difference due to going from a 215 to a 235 tire. It made me go back to 215's in my truck. Rolling resistance and aerodynamic drag are huge factors in determining how far the accelerator pedal needs to be pushed down to maintain a speed.
Remember too that not all engines need the torque multiplication offered by a 3.73 gear. The tires can only take so much torque and exceeding it will not make the car any quicker. So while a 235 ft/lb 305 may need a 3.73 to get it moving, a 425 ft/lb 350 would not. In a drag car the numbers are different, but since we are talking practical street car here, it is important to consider all parameters when choosing a combination of parts. Also, a high winding engine like a Chevy 302 or a Honda B16 would need more gear to get it off the line because it lacks torque in the low end. Horsepower is after all a mechanical function of torque and RPM. It is used to describe the way in which work is performed by using multiple smaller events rather than lesser large events. Even if each event has less power, the sheer number catches up after a point and makes the car faster.
I had a 260 hp SBC crate 350 in my 442 with the stock 200-4R and 3.73's after I blew up the original 307.
The motor only had 25,*** miles on it and I got it out of a rusty K-5 ex-plow truck I got for free.
I ran a junkyard computer controlled distributor as well as the original computer controlled quadrajet.
It got a pretty consistant 15-17 mpg if I kept my foot out of it in mostly city driving, and got a best of 19 mpg on the highway.
I miss driving it everyday in the summer like I used to back then, there's no way I could do that now. ****in 8 mpg...
:lol:
I run the 350 olds in my malibu, th350, and 2.41 gears 
,however with that setup on highway trips my car sees close to 24 mpg consistantly. The engine is mild, 77 block mostly stock rebuild, towing cam, 1970 heads, headers, rpm intake, Carter carb, nothing fancy, I plugged this combo into an engine building program a while back (don't know how accurate the program was) but it said the engine should make a tick over 300hp. I been torturing this engine since 2002, and have racked up about 55,000 miles on it so far, but as long as you keep the revs below 5000 they hold up fine. Like was mentioned earlier the olds makes all sorts of torque on the bottom so a 3.73 gear is a little steep, even with the O.D. A 2004r trans with a 3.23/3.42 gear would probably be about perfect for an olds engine, could probably produce about the same results. If your car is already setup for the olds small block it would be easier to repalce it with an olds small block. SBC would require entirely different mounts (frame and engine) your harness would have to be lengthened all oldsmobile electronics are on the LH side of the car, where as chevy is on the RH. The chev is cheaper by far to build however (olds is almost double the cost), but a compareably built olds vs chev, the olds will see better milage, it has something to do with the way the engine was engineered, allowed it to be more efficient without sacrificing too much power. So really it's up to you, spend more now and pay a little less at the pump, or spend a little now and make up the difference at the pump.
,however with that setup on highway trips my car sees close to 24 mpg consistantly. The engine is mild, 77 block mostly stock rebuild, towing cam, 1970 heads, headers, rpm intake, Carter carb, nothing fancy, I plugged this combo into an engine building program a while back (don't know how accurate the program was) but it said the engine should make a tick over 300hp. I been torturing this engine since 2002, and have racked up about 55,000 miles on it so far, but as long as you keep the revs below 5000 they hold up fine. Like was mentioned earlier the olds makes all sorts of torque on the bottom so a 3.73 gear is a little steep, even with the O.D. A 2004r trans with a 3.23/3.42 gear would probably be about perfect for an olds engine, could probably produce about the same results. If your car is already setup for the olds small block it would be easier to repalce it with an olds small block. SBC would require entirely different mounts (frame and engine) your harness would have to be lengthened all oldsmobile electronics are on the LH side of the car, where as chevy is on the RH. The chev is cheaper by far to build however (olds is almost double the cost), but a compareably built olds vs chev, the olds will see better milage, it has something to do with the way the engine was engineered, allowed it to be more efficient without sacrificing too much power. So really it's up to you, spend more now and pay a little less at the pump, or spend a little now and make up the difference at the pump.
my 305 powered 7000lb C20 gets 18mpg highway running 4.11 or 4.56:1 (research lead me to these 2) on a th400 and It can still haul a 27' tag along trailer when it needs too. (yeah I wouldn't take it across mountains or anything but it gets me there at the speed limit. Thats of course when your driving pattern includes staying at a constant speed not swerving in and out of the passing lane and walking it up hills.
When I bought it it got 13mpg and basically I couldn't afford to drive it anywhere, also the big block was starting to burn oil faster than it did gas
I like the 305, not alot of huge power,but it spools up the 4;11 decently fast enough and with the crappy true duals all the way back with the leaks here and there make it sound and respond like a 350(yes I said respond with my tractor geared rear end) (anything under 65mph)
Also I got my 305 dressed up purtty as it take pretty much anything the 350 will for bolt ons... The Aluminum intake, valve covers, timing cover, headers, shiny new wires and chromy air filter all bolted onto a 305 off my 350 and when I'm done it'll all go back in the camino one day.
I know alot of people would say 305's are a waste of time and money but IMO you run what you got or can get. Not everyone can get their hands on a donor LS1. Not everyone can afford to gas a v8. If I was do do something out of the ordinary it would be to try and shove a newer 3800 Buick motor where a v8 goes. thats right. take out the v8. put in a v6. I'm for different, and when I see everyone shoving chevy 350's in everything it makes me want to take the other road.
If you've come to a fork in the road your not making your own path
When I bought it it got 13mpg and basically I couldn't afford to drive it anywhere, also the big block was starting to burn oil faster than it did gas
I like the 305, not alot of huge power,but it spools up the 4;11 decently fast enough and with the crappy true duals all the way back with the leaks here and there make it sound and respond like a 350(yes I said respond with my tractor geared rear end) (anything under 65mph)
Also I got my 305 dressed up purtty as it take pretty much anything the 350 will for bolt ons... The Aluminum intake, valve covers, timing cover, headers, shiny new wires and chromy air filter all bolted onto a 305 off my 350 and when I'm done it'll all go back in the camino one day.
I know alot of people would say 305's are a waste of time and money but IMO you run what you got or can get. Not everyone can get their hands on a donor LS1. Not everyone can afford to gas a v8. If I was do do something out of the ordinary it would be to try and shove a newer 3800 Buick motor where a v8 goes. thats right. take out the v8. put in a v6. I'm for different, and when I see everyone shoving chevy 350's in everything it makes me want to take the other road.
If you've come to a fork in the road your not making your own path
Well... if you really wanted to be different, you'd use a Japanese or German L6, V8 or V12. Reliable engines that have good power and fuel economy and can be bought relatively cheaply. I'd love to see a 2JZ-GTTE out of a Supra (or a 1JZ-GTE out of a Soarer) dropped in a G body. Heck, even the V12 out of a BMW 7 Series would still be pretty fun.
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