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Probably a stupid question here, but I can't remember if there were any big block G-bodies from the factory. Can a BBC even fit into a G-body or would you have to stick with a Caddy engine to get monster cubes? (I know you can transplant 500Cads into G-bodies, but they're smaller than a BBC in actual physical size). Either way, money spent per horsepower gained, you'd be better off with a 350 or a stroker. Much better power builders.
 

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Here's one to bend your noodle...

Try a 307! There should be lots of them hanging around from all the Chevelle Big Block swap projects people have been doing.

I had one built up and bored 60 over that I put in a 79 Z28.
The bottom end was beefed up and ran 882 heads with some major port
work.

I didn't choose this motor it just kind of worked out that way when the 305 in the Z28 (a replacement motor as well) finally died.

That 307 was one torquey monster though..
I was able to put down 20 foot long stripes with ease.
I used to have great fun enveloping UPS trucks in tire smoke when the creeped up to close to my rear end.

Of course having the same long stroke of a 400 It was horrible on gas mileage. I got around 7MPG but then Gas was only 1.25 back then so it wasn't a big deal.

Was a great motor and aside from the gas mileage the only other problem I had with it was that it ran hot. Like never below 200 degrees hot. Of course I lived in an area with lots of hills and 110 degree temps so I can't really complain...

Still, it was fun.
 

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66trar said:
Probably a stupid question here, but I can't remember if there were any big block G-bodies from the factory. Can a BBC even fit into a G-body or would you have to stick with a Caddy engine to get monster cubes? (I know you can transplant 500Cads into G-bodies, but they're smaller than a BBC in actual physical size). Either way, money spent per horsepower gained, you'd be better off with a 350 or a stroker. Much better power builders.
no BBC from the factory. I know a guy that has a 454 in his 84. He swapped it in. I think he had to modify the air box, and he used Eibach front springs. not sure what else was involved...
 

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TRIK-56 I can assure you that there is such a thing as volumetric efficiency that a 350 is much better at than a 305 can ever achieve---you can make a 350 get worse fuel economy than an optimised 305 if you completely screw up the combination but when comparing apples to apples the 350 comes out on top in all areas---and if you buy parts that are optimised for a 305 they will be woefully undersized for a 383 or bigger small block----I had a Monte Carlo SS that I put a 383 in that ran consistant 12.80s in the quarter on real street radials with closed exhaust and when I drove it like a sane person it got better than 20 mpg---I defie anyone to get near that level of performance and economy from a 305---you might do one but not both from a 305 and I am not going to hold my breath until someone gets a 12 second quarter out of one normally aspirated in a full bodied car --even a monza or vega.................Dan
 

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Old Coot,

I'm certainly not arguing that a 305 can outperform or even match a 350 in speed or quikness.

I am only going by the experience I have had with the several 350's I've had in the past and the 305 I currently have in my El Camino now.

Of all the past 350's I've owned none have been able to give me the gas mileage this 305 has and is.

Maybe if you know a lot about super tuning for "volumetric efficiency" you can make a 350 sqeeze a lot of miles per gallon.

However. I'm not skilled at that as I'm sure MOST guys are not either.
Soooo, comparing apples to apples as you say, I don't think you can make a broad statement and say a stock 350 is going to get better mileage than a stock 305. At least none of mine both stock and modified have ever done it!

If you know how to tweek them to run 12's in the quarter AND get 20 mpg too, then I'd be willing to bet you are one of the few who can.
 

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TRIK-56
Please don't misunderstand me, I am not saying you are wrong or putting down what you are saying at all---its just that we seem to have had very different experiences with these engines and I don't know any "secrets". You can go to any car lot and pick up a Camero with TPI and a 350 that will get into the 20s even with an automatic and loaded to the hilt that will run 14's showroom stock and the newer ones do even better
My point was and is that the 305 was a solution to an emissions problem that had to be dealt with and was for the day passable, things have gotten better and so have engines, so if you are building one today why not take advantage of what has been learned instead of copying something that was not as good......................Dan
 

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Old Coot,

I think I have finally figured out why we have such differing opinions about mileage from these two engines.

It seems from what you stated in your last post that you are really referring to later model, fuel injected, computerized 350 engines and all along I was referring to the older carburated (1960's and 70's) versions.

I will absolutely agree the newer injected 350's do better in every catagory than the old carburated 305's but thats almost like comparing apples to oranges.

It seems that when someone mentions rebuilding a 305 he gets berated for not going with a 350 instead.

Its one thing to rebuild a 305 or a 350 (carburated) but when you are talking about changing over to a late model version with fuel injection, computer, different gas tank, wiring, etc. it can get REAL expensive and REAL technical pretty quickly!

Thats why when some guys just need a rebuilt engine as economically and uncomplicated as possible with good mileage in mind I think a 305 is a good way to go.
No, it won't pull tree stumps out of the ground but decent milage can be expected if done correctly.

If you have the financial capability to go with the later model stuff then I will agree thats what you should do.

Kinda makes me wonder though, if the 305 had got the development put into it the 350 has over the years, how much better engine would it be?

Anyhow, thats my story and I'm sticken to it! :-D
 

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Noob here but I am enjoying this thread, thank you for the conversation. I have a completely stock '87 with 305 and two young sons who need to get greasy on it, and also need to see how their hard work pays off. Would someone please recommend a few simple mods to exhaust or headers or carb to get a little more power and better sound? I saw in more than one place that shorty headers and dual exhaust were basically bolt-on and could work with/around all the emission stuff (which we dont really care about but under the impression that its the least headache to leave in place, please tell me if im wrong), I appreciate any advice you may have.
Curt
 

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A good tune up and general maintenance lookover are good places to start. Check the condition of cap, rotor, wires and plugs and replace with AC Delco if needed. Check the belts and hoses, air, fuel and breather filter. Check the center link, ball joints, shocks snd bushings. Carburetor? The original Quadrajet is the best thing for it. If it works right, leave it alone. If it doesn’t, pull it and have it rebuilt by a pro like Moutain Man. Don’t buy a parts store reman, don’t buy a Holley or Edelbrock. Exhaust? The 305 doesn’t need much, but you could buy a transverse muffler with two outlets for better sound and dual tips. Or, you could adapt a cat back system with twin mufflers and tailpipes. Either way though you’re just gaining sound. A rear gear swap will make it feel more powerful. Otherwise enjoy the thrifty reliability the 305 brings (I’m at 185k on mine and it still gets over 20mpg onthe highway). Save the headers and true dual exhaust for the future-an emissions exempt 350 or 383 swap maybe.
Patrick
 

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Noob here but I am enjoying this thread, thank you for the conversation. I have a completely stock '87 with 305 and two young sons who need to get greasy on it, and also need to see how their hard work pays off. Would someone please recommend a few simple mods to exhaust or headers or carb to get a little more power and better sound? I saw in more than one place that shorty headers and dual exhaust were basically bolt-on and could work with/around all the emission stuff (which we dont really care about but under the impression that its the least headache to leave in place, please tell me if im wrong), I appreciate any advice you may have.
Curt
I was in the same boat at one time! Patrick has some good suggestions. Everything he said will add to your cruck feeling and sounding better. I will hit on the point that is mentioned all over this 12 year+ old thread. The 305 is extremely reliable but also a problem if you really want to have any real fun! My ElCo had the original 305 with the computer controlled carb needing a re-build. I could drop a brick on the gas pedal and jump out and pass it on foot! Drop a 350 horse 350 in and loose the emmission stuff and double the fun. Me, I went a totally opposite direction, you might get it from my user name. Hope you have fun and those boys do too. Welcome to the group, best wishes! And there's a bunch of guys wiling to help whatever way you decide to go!

Joe
 

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After reading this 12 year-old thread... A few points:

1. Maybe I don't want to pull my 305 out
2. I may just want to have fun making a boat anchor float
3. I don't want to leap tall building in a single bound
4. My 305 is super reliable
5. It is a general cruising engine.

I could go on and on.

So, you want a little more punch for your right foot? And don't have a money tree in your back yard?
Well, do I have a nice bridge in the Sahara for you to buy.

Try this out for laughs:

A. Remember the early Mote Carlo SSs? They had High Output 305s in them. They also had hugely improved heads on them - Find a set. Probably around $200
B. Remember the factory aluminum spread bore intake manifold? Very inexpensive. $25 to $100
C. I ran a Carter Thermoquad - remember those? $25
D. Cam kit: Good mid range power cam with lifters..480 lift, 280* advertised duration and 112* lobe split. Slightly lumpish idle. $150
E. True roller timing chain. $50
F. A set of headers $150. Don't have to be Super Comps
G. Twice pipes - You can buy a kit for around $200 with muffs
H. An advance kit for your HEI distributor - heavier weights and lighter springs - $10

I ran this in a '72 C10. It was already in the truck when I bought it, and had a bombed cam. 3 lobes almost perfectly round!
It had enough bag to grenade a cheesy Saginaw 4 speed. And I mean GRENADE.
Scared the crap out of the guy who was in the passenger seat....
I went to a Muncie M21 after that incident.
The truck had a 3.73 rear gear single track, and even so, I bet it would have run a 14 second 1320...

Ok, sorry for the novel.
The moral of the story?
I didn't want to source another engine, rebuild it and install it.
I did all of this in a weekend and the cost was under a stack.
Even a measly 305 can have fun.. :p
 

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Oh, and in addition to this^^^
350 heads do not work on a 305
The 305 uses a tiny 3.736-inch bore and the same 3.48-inch stroke as the 350ci but, the 350 heads bolt on, but the valves will be shrouded by the cylinder.
The 350 has a 4.00" bore
 

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Oh, and in addition to this^^^
350 heads do not work on a 305
The 305 uses a tiny 3.736-inch bore and the same 3.48-inch stroke as the 350ci but, the 350 heads bolt on, but the valves will be shrouded by the cylinder.
The 350 has a 4.00" bore
you totally forgot to mention the cc-size of the chamber. much larger, making for much less compression.
 

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I have seen that most of the answers to the questions regarding performance modifications on a 305 is "build a 350 instead". Granted, I will agree that using comparable parts a 350 will always make more power.
All of the modifications that work on any other engine will work on the 305 as it is nothing more than a typical internal combustion engine. It might not make as much power as some other combination, and all engines have some sort of limitation as to what you can achieve. Vortec heads will work on a 305, but in order to get the compression back up, you have to mill them a whole bunch making them essentially useless on anything other than a 305. Not to mention that the chamber "width" is larger than the bore of the 305 creating a "step" in the airflow into the cylinder potentially hurting performance further. Pistons and rings might cost a bit more than a 350, but they are still not anything "Oh my god."
307's may have made more advertised hp, but they were also "gross rated" an not "net" rated like the 305. They (305) typically are not any more or less durable than any other small block Chevy if assembled correctly. Everybody has a "magical combination" for the 350 and claim that it will "beat anything on the road" in some form or another. If it was pure performance that everyone was after, then build a bigger engine. For reasonable street performance, the 305 is not as bad as some may claim. The first engine I ever built was a 305 in a '78 Nova with a four speed. It ran high 13's at just under 100 mph and that was with a peg leg 3.08, and 225/60-14 radials. Trust me the 60' foot time was nothing to be proud of due to a serious lack of traction. (Probably helped that Saginaw live another day)
I'm not trying to say that its the greatest thing since sliced bread, but they're not as bad as poeple think. Especially for street performance.
There are a lot of engines that people still build these days that are not the greatest for peformance yet they are still getting screwed together everyday. (aka 326, 350 Pontiac; 350, 403 Olds; nailhead Buick; flathead and "Y" block Fords, etc)

The biggest thing to remember is that no matter how fast you make it, someone will always be faster. Also, be realistic with your goals. As I mentioned earlier, all engines have limitations, especially when you are on a budget. I'm not trying to bash anyone's ride in any way but for some of the folks that are learning, there are MANY other areas to learn about other than what engine should I build for a bit more power? If a 305 is what you already have, go ahead and tinker, it could be the money that wasn't spent on hunting a 350 core that helped pay for your _. (fill in the blank) Another engine can always be built at a later date as true "gearheads" are never really finished with a project. This is all just my opinion of course, I am sure many other may think differently.
The 305 is a great engine! I'm running a 350 but aint nothing wrong with a 305.
 

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Dredging an older thread...
Think about this... Ford builds some pretty crazy 5.0 liter engines. Sorry, but it's true.
305 = 5.0 liters.(or close to it)
You can bolt on a lot of performance parts that will wake these lumps right up.
I did...
 

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ON THE 305, WELL I HAVE ONE IN ANOTHER ELCO BESIDES "HELL CAMINO".IT HAS A FEW MODS,SUPER CLEAN AND IS THE MOST RELIABLE WORRY FREE CAR, IT STARTS RIGHT UP,CAN RUN A TRIP AT 80MPH SMOOTH AS SILK,AND NOT WORRY ABOUT OVERHEATING OR BREAKING DOWN. IT HAS A 305, SURE YOU CAN BUILD A 350 AND SOON YOU WILL HAVE THE HOOD OPEN EVERYTIME LOL.
1,EXHAUST LEAK FROM CRAPPY HEADERS
2.HEATING ISSUES
3.TRANS SLIP OR OVERHEATING, WORN OUT U JOINTS
4..CONSTANT CARB SWAPING TUNING ETC
5.EXCESSIVE REAR TIRE WEAR FROM DOING A POWER BRAKE BURNOUT FROM EVERY LIGHT YOU CAN WHEN SOMEONES WATCHING
6.EXCESSIVE FRONT BRAKE WEAR.
7. A GREASY HANDPRINT PAINTJOB UP FRONT FROM ALL THE CONSTANT WORK TO MOTOR
8.CASHLESS FROM ALL EXPENCES ABOVE.
LOLOLOL ITS A VERSION OF WHAT YOULL BE EXPERIENCING TOO FUNNY. OR, YOU CAN JUST RUN THE 305,.HAVE A GREAT ELCO THAT CAN DRIVE ANYWHERE BESIDES THE CAR SHOW AND STORE. EVERYONE WILL SEE HOW COOL YOU AND THE CAR ARE AND HAVE THE BEST TIME OF YOUR LIFE..
YOU DONT NEED A 9 SEC ELCO ,AND THERES NO CHICKS AT THE STREET DRAGS ANYWAY IVE SEEN LOTS OF BUILDS , SOME KNOW WTF THEIR DOING. AND THE OTHERS WELL

SO 305 AND HAVE A COOL LIFE,,
OR PUT 18K INTO A 10K CAR...
THIS IS A FUNNY THOUGHT AND HOPE YOU ALL PULL OUT YOUR RECIEPTS AND HAVE A LAUGH TOO...
CHEERS
 

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Dredging an older thread...
Think about this... Ford builds some pretty crazy 5.0 liter engines. Sorry, but it's true.
305 = 5.0 liters.(or close to it)
You can bolt on a lot of performance parts that will wake these lumps right up.
I did...
(v8) 305 = 3.736" bore x 3.48" stroke
(v8) 302 = 4.000" bore x 3.00" stroke
(i6) 300 = 4.000" bore x 3.98" stroke

different bore and stroke configurations
 

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^^^ Aware of the differences with bore and stroke.
The point I was making is: for a small displacement engine you can still have some fun [cheaply]

And the last point I'd like to make - most elkys came with cheesy rear end gears - like 2.73 and (maybe) 3.23.
Since the 305 is not a torque monster, a set of higher (numerically) ratio gears would really help acceleration.
One of the reasons the Monte Carlos SS was quicker than a stocker - most had 3.73 rear gears.
The only issue is this - if you have the lower ratios - like 3.23 or lower, you will need a new carrier or thicker gear set to upgrade to bigger ratios.
Anyway, just some suggestions for those who still want to keep their "Boat Anchor"

And...to those who want to replace your 305 with a 350? Go for the max. Remember that Chevrolet made a 400 CID engine? Torque baby
 
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