Um, not really, they have an efficiency range which mostly has to do with the total airflow more than anything else. It might be that you’re moving out of the effienency range of that turbo at that point, but it’s not that it’s got a “max boost” at that point. Most of these things are quite happy moving >3bars as long as you stay in it’s efficiency range.

As far as the rest of this discussion… there’s a lot of “this engine is best” BS going on… best for what??? Similarly setup most 305’s will hand a 350 it’s *** when it comes to mpg, and there isn’t as much difference as you make it out to be. My current project car, an 87 LB9 car came from the factory with only 10hp less than the same year’s L98 car, and I bet that swapped between the same car 99% of people couldn’t tell the 2 apart (I have an ’87 formula 350 also for comparison). For that matter, in a properly equipped car, I’d be surprised if it would be difficult to get the LB9 to outrun most L98’s.

Past that it would be a lot more interesting to see what people can get done with whatever they’re tinkering with rather than cloud that with this bitching and whining about why are you messing with ____.

 

It all comes down to attention to detail. Getting the correct port shapes. Getting the right intake. Get the right chamber shape. Getting the right exhaust. Getting the right.....
That is what matters.

I am big on using what you have and making it work. A 305ci can work well. If I had a 350ci and a 305ci in the same shape sitting next to each other I would choose the 350ci. If all I had was a 305ci then I would use it. Tuning with a WBO2 can give similiar gas MPG. The most important thing is not to worry about how big the cubic inches is and to pay attention to how effiecient you can make it in terms of HP and MPG.

 

That is what I was talking about. But thanks for going into detail for others.

 

Do most of you not have a large abundunce of 350 SBC's in your area? They are honestly a dime a dozen by me and you can pick up a bare block for 100-200 bucks.

 

Well that’s the thing, I wouldn’t always choose the 350 over the 305. I’ve seriously considered building a boosted 305 to replace the 350 in my truck, the thinking being that WRT to combustion efficiency there are a lot of advantages to the smaller bore size (better gas mileage when I don’t need the power), and make up for the smaller bore’s breathing deficiencies when needing power with boost…

 

Is that really going to matter much between a 350 on boost and a 305 on boost? Or are you just boosting the 305?

 

I’ve eeked out 37mpg highway out of a 305 in a 3rd gen (that still ran mid 13’s in the ¼), with an auto and 3.23 rear gears. The best that I’ve managed with a similar combination on a 350 (though I didn’t spend as much time optimizing things) was around 24, the best I’ve seen was 28 with a t56 and some tall rear gears. Not even my ’97, 10-15y more advanced, does any better than that.

 

I don't see how fuel consumption would differ between a 305 and a 350 to be that large of a gap.

 

I agree with the choice of the 305ci for the truck. Heavy vehicles are at a disadvantage for MPG so the 305ci makes sense. For the most part you only need the extra power when towing. That was the thought when I put turbos on my 4x4 truck 305ci TPI engine. The thing I learned is that I am in high KPA and low boost a lot more than I expected in everyday driving. The MPG isn't that great because of this. I guess it is more of power thing where if you have extra power (boost) then you use it more than you expected to. The small turbos come in so fast that you have to go very light on the throttle to keep it out of boost. I have the choice between a 1985 305ci engine and a 1989 350ci w/ 193 TBI heads (good swirl/efficiency) and TPI intake if the current engine fails. For the truck I favor the 305ci.

The other thing I noticed recently is the affect of having a big aftercooler with cold weather. The MPG decreases due to the constant supply of very cold air. I have been thinking about bypassing the aftercooler for the Winter months. I will probably leave it as is because of the time to fab the new pipes and cost would be about the same as the amount of fuel used. It may just be a matter of refining the tune for the cold weather.

For a thirdgen I would go with the 350ci because most people are after peak horsepower. A proper tuned turbo TPI will get the MPG you stated which is better than a stock thirdgen and it will also get 2-3 times the stock HP with boost.

 

The 97 SEFI should be able to do better at low RPM under around 2500 RPM. A well tuned SEFI will have better MPG under that RPM because of valve timing and the spray time. The thing is that the SEFI tuning software seems to have lots of stuff missing so they can't be tuned as well as batch fire. I have not switched to SEFI becuase of the lack of good tuning software and cost. A TPI also has the MPG advantage over most SEFI setups because of the range of RPM is was designed for.

 

350s are around. Most of the time they need machine work and people still want decent money for them. I add up the cost for machine work, bearings, piston & rings, etc and then I pass them up because everyone I know says 305s are junk and sell them for $000 to $200 with 100K miles or less. If I come across 350s that don't need machine work for cheap I will buy them. I usually stay away from the roller cam blocks becuase I am too cheap to pay for an aftermarket roller cam especially because I like smaller grinds.

 

wow, you are really cheap.

 

Are you serious? You can get small grinds for 150$ here and there. I can get away with most 350s with a hone job too. You are finding some horrid and abused motors if they all need rebuilding. The roller blocks are the better ones to most, atleast try to sell them if you get them for next to nothing. Make some money if you can.

 

I decided to go cheap on the car stuff years ago. I learned by having a 327ci built that was engine dynoed at 390HP and revs to 7000 RPM. 244* @.050 cam that idles poorly but revs high. I put over $3000 into that engine. Stack on the headers, carb, etc and it is up around $3500-4000.

The stock 305ci turbo setup is putting out around 350HP at 4800 RPM. The complete engine with all accessories and harness was $500. The turbo setup on a 4-bolt 350ci with stock crank, rods, KB hyper pistons is putting out over 400HP with a small 216* @ .050 cam. It idles excellent and drives excellent. I have about $500 into that engine.

The turbo setups make better HP and are cheaper HP per $. The MPG of the turbo setups are 2-3 times better than the non-turbo engine. It is cheaper to push air into an engine than rev it high for HP. Yeah, the HP numbers aren't high for these engines, but decent.

 

Turbo means allot of fabrication, i dont have the tools to do all that. I have 450+ HP in my 383 and i have 1000$ in it.

 

You spent 4K on a motor to make 390hp on the engine dyno? Yikes.

So you bought a turbo kit, headers, motor, hyper pistons, downpipe, cam, for only 500 bucks? Please point me in the direction of your parts dealer.

The only reason you're getting better mpg is because you stay out of the boost. Get into the boost all the time and watch those numbers change. The same happened with me during break in. Got great (well not great but good for a performance car) mpg but as soon as break in was over and I started getting into the boost a lot more, I noticed a big change.

 

Yes and no. It made more on the dyno. With a real air cleaner and exhaust it made 390HP. It lost about 30HP in a real world application without cold free-flowing air and somewhat quiet mufflers. I post real numbers not "perfect world dyno" numbers.

The engine setup was $500. The turbo kit was about $1200-$1500 depending on what one considers as the "kit".

Nah, the point is the small cam and head boost engine will give a much better MPG than a non-turbo setup will give for a given peak HP. If you stay out of boost the turbo setup will give much better MPG than a non-boost engine. Under boost the MPG will be the same as the non-turbo engine and they will make the same HP. The turbo engine will make much more torque at low RPM due to boost. A non-turbo setup needs a big cam and heads that has poor MPG at low cruise RPM and wastes fuel at idle. Been there, done that.

The 350ci turbo setup makes over 400HP at 5200 RPM with a 216* cam. The 327ci makes 390HP at 6300 RPM with a 244* cam. Once you go boost you never look back.

 

most any reputable shop should be able to do the work needed. i think labor would run you around 4-5 hrs normally. If you don't have posi now would also be the time. Check out s-10s at your local junkyard. They were often given 3.73s and an eaton posi on newer stuff, yank it and use it.

btw the heater core realy does take that long to do (for a first timer like me on my last camaro it took over 8), don't underestimate how hard camaro's are to work on lol.

 

I don't know where the orginal quote came from, but good info just the same. To do a set of gears requires a dial indicator. A setup from a cam degree kit works fine. Depending on the skill level and choice of perfection it can take from 4 hours to 15 hours. The last set I did installing a posi with 300K mile gears took about 15 hours including all new bearings. The gears were silent the first time out. I think I adjusted them about 10-15 times before assembling everything. I spent a lot of time getting the pinion as deep as possible becuase of high engine torque.

Anyone can install gears. You just need to pay close attention to the gear pattern and backlash setting.

 

The whole 350-305 controversy, well I can tell you that I have had both and I prefer the 350. If the 305 is as good as people claim why don't they make it anymore, the fact is that it isn't a very good building block, the 350 is what the Ls1 is based on. I think that people who own 305's are very defensive because well they own it. Nobody likes to admit that they have junk..... and I am sure that someone will post some comment after me trying to say how good the 305 is but its going to do nothing but make themselves feel better.

 

They dont make the 350 anymore, either. In fact the LS1 is old news if you want to go that way, the LS2, 3, 7, 9...

The LS1 shares about as much in common with a 350 SBC as... well pick your phrase. They have the same bore spacing, and thats it. Zero sense comparing the two.

 

this is really getting stupid. duh yes a 350 is better and a bit faster(10hp) out of the box. but no a 305 dosent suck! there both great motors.

 

I think I'm splitting hairs when I spit this out there but the LSx series is closer based to old school pontiac motors.

 

It isn't about which engine is "the best". It is about which engine fits the application the best. The LSx series are great with the extra external technology and internal engineering. The 305 and 350 can work well in the right application also. Boost and N2O are the equalizers.

 

How did you pull that? I'm curious, what's the setup on that, I just might have to try it! I'm planning a 305 build anyway

 

I’m actually very surprised at how hard it is to find that kind of efficiency out of the ’97 LT1 car… I mean common, lots of stuff is already optimized there, right down to the borderline streetable, sky high compression right from the factory. I’ll admit that as much as things are “right” drivetrain wise, the rest isn’t there. 4th gens have worse aerodynamics, are much heavier, I’m sure the 17” rims and fat low profile tires don’t help from both a weight and drag/friction perspective…

And then when you get down to it, the fact is that SEFI is a great thing for emissions, but does little for power and less for mpg.

As far as TPI having some advantage, I don’t see how, it ONLY works really well around the only tuning point that it hits in the engine’s operating rang, about 3500rpm. It pretty much sucks above and below that. I have an extra TPI setup sitting around, and although it would look cool sitting under the hood of my truck, that is not what I’m swapping in there since I’m not interested in a power band that high up in it. It’s a truck, I need it to have all of it’s usable power in the 1000-2500rpm range, I don’t care if it’s all done by 3500-4000rpm. I’ll never take advantage of a TPI setup

 

Um, yea, sure… you do realize that they made 305’s right up to the very absolute end of the original small block.

Second, the LS engines were pretty much a clean slate redesign, they don’t have much more to do with a 305 then a 350 or any other SBC. I could make some arguments bout bore proportions and the basic proportions of the smaller 4.8 and 5.3L truck engines, but Is suspect that I’d be wasting my time.

As far as defending/owning junk… I currently own 3, 350’s and 2 305’s, and I’ve even stated that I’m quite likely to purposely replace one of he 350’s with a 305. I’ve also decided to leave the 305 in my project car despite having a 350 and stack of parts for it from a previous car, just for the sake of this argument. On the street, for spirited driving, even with much better gearing and a 6 speed in my LT1 car, I would argue that my LB9 305 car is every bit as fun if not more so.

 

It seems like people just don’t want to hear the truth about that one. It was a mostly stockish crossfire car.

A small, well tuned long runner intake, TBI injection, high compression, iron heads well matched headers/exhaust, everything tweaked, optimized and matched for the task. When I blew up the 3.23 gears in it, I put in a set of 3.42’s that I had sitting around and not only did I loose mpg, but the car ran slower also.

I’m currently working on a similar setup in my truck, we’ll see how much of a change it will be over the stock 12.5mpg stock setup…

 

this has been the funniest and most interesting forums i have ever read. good stuff..

but i do have a question and would appreciat as much help as possible.

i am installing a rebuilt 700r4 with corvette servo. that will be in tomorrow. but im the very near future i want to put in new gears. 3.73's or 4.11's.

I have a stock 1988 305 V8

1) what are pros and cons of 3.73's and 4.11's
2) what are average price to get gears installed by a good shop
3) do i need to change ANYTHING when gears are replaced.
4) and anything else that can help me with my 305 any ideas or anything would be great.

thanks

 

1) Go with the 3.73's. Once you start doing the 4.11's, it doesn't become very highway friendly. I personally would go with 3.42's.

2) Around 250-350 but I have heard some shops quote 500.

3) Yes but the shop will cover all that.

4) Replace it with a different motor and don't waste money on it.

No problem

 

ok. but i can't get a new motor. at least not now. not enough money for that. i really just want new gears and then headers to complete my exhaust then paint my car flat black for now. motor is future.
----------
and why 3.42's?. i have a rebuilt 700r4 that im putting in tomorrow. i hear that that tranny complements higher gear ratios like 3.73's and 4.11's

 

Then I wouldn't touch the motor right now and just do the rest of the stuff you listed.

 

thanks for your help.

what brand of street 3.73's would be the best brand

 

some say richmond, some say gm.
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for the stock unit that is.

 

Richmonds whine (at least mine did). And when I called them about it they basically told me "Our gears whine". I went with GM Motives and the whine went away. I guess it doesn't matter. All depends if you like the idea of a small whine every once in awhile or not.

 

Lol these will always be on this board. And to correct someone on hear who thinks that mustang guys don't have the 302 351 debate have appearantly never been on the turbo forums where once a month the debate comes up and some guys are always defending thier 302's because they already spent the money on a car that needs to be revved higher and needs more boost which means more fuel.

The difference in our deabate is that the blocks essential have the same dimensions unlike the ford's where the deck height is much higher on the 351 which does require a lot more fabricating.

Build what you have. I find it pointless to argue benifits of the 305 because I can't really find any. Not a bad motor depending on the setup. To argue though that you would actually take the 305 over a 350 just shows you are simlar to a salmon who likes to swim against the current to get to it's birth place. If the two options are in front of you for the money i don't see a benifit with the 305 unless you talk about the possibilty in 1 mpg difference. If you really want better mpg's and power you need an aftermarket ecm w/o having to burn more chips.

Use what you have and be happy. A power adder is always a good equalizer to make up for the lack of cubes. My simple bolt on fwd buick regal gs will out run almost all stock third gens and plenty with bolt-ons so that is a good exapmle. (3.8l sc)

Let's face it our cars were meant to be driven so take whatt you got and drive it.

 

yaaa. ok? were talkin about gears here. good imput though. anyone have any imput in richmond gears vs. GM or any other brand? 3.73's.

 

Richmond cuts their gears using a 2 pass method, GM motive and a few others cut them using a 3 pass method. I don’t know for sure what some of the newer guys like Yukon do. Richmond’s style of gear tends to be noisy, even if setup perfectly but are supposed to be stronger, the GM motive gears tend to be quieter.

If you have enough power/heavy enough car with enough traction, you can make either whine after a few hard launches, and you can break any of them after enough regular abuse. You have to remember, we’re talking about a 7.5” gear in a fairly heavy car, in the last 10 years I’ve broken 3 sets of factory GM gears, one set of richmonds, one set of white box richmonds, a set of precision gears and a set of GM motives (well, and I’ve broken the 3.42 factory 8.5” 10 bolt gears in my full size truck also). At some point you start using whatever you find the best deal on, well and then I bought a moser 9” for the project car.

If it’s a street car that’s going to see relatively light abuse I’d go with GM/motive or Precision (Precision would be my first choice), if it’s going to see a lot of dragstrip time I’d literally go with whatever I found the best deal on.