I've had my 92 Z28 for little over a year now, I love the car. It gets my compliments and attention that I've never really gotten before .

Anyways When I bought the car I didn't know about 305s and 350s much, and I didn't know that 305s were so bad apparently. Now I've never driven anything faster then 4cyls before so to me this car is fast. I never dynod and it does have some mods. Can anyone of yall guess the HP I'm getting out of my sbc.

Mods: Flowmaster Exhaust(3inch), Edelbrock Longtube headers, Accel 24# injectors (prom never tuned, running rich probably), MSD GM Blaster thingy with MSD Supercondutors, and K&N Filters. Now those are all from the naked eye, I'm sure if I looked further I think I would find more parts. It could have a chip but I'm not sure and prolly doesn't. The car could probably use a tune. The car is an Auto .

Anyways why does everyone switch to 350s, are they really that bad of an engine? I heard they are practically the same, but in that case, why are the 305s called "dogs"? And how much should I be spending on Junk Yard 350s? What should I look for when I go to purchase one of these engines? (Used, from salvage yards of couse)

Thanks

 

It's not that 305s are "bad"; it's just that 350s are SO much better, SO cheep, and SO plentiful. It's just economic suicide to mod a 305, if you have to touch the short block. Any money you spend on a 305, gets you less results than if you spent the same money on a 350.

Think of cubic inches as acting like an multiplier for your money. xxx inches x $$$$ = speed. How much faster could you go with more inches and the same money?

 

I've heard many times that modding 305s is stupid...

 

The 350 owners seem to be compensating for something, hmmm what could it be? Just kidding, 350's produce more power from the same mods that you can do with a 305. There's nothing wrong with a 305, they are better for fuel economy and considering what gas goes for now. It just depends on what you want out of the car. If you want power and speed your better of with a 350 even though a 305 can be made fast it will cost more in the long run. If you want a good reliable car with good gas mileage, a 305 will do you fine. I plan on building my own 350 someday even though I've never done it before. Until then I am happy with my 305!

I will say this though, 350 owners love to put us 305 owners down, even though we're suppose to be a 3rg Gen family. Of course the 400 owners probably put the 350 owners down too, lol.

 

Well I do love my 305.

 

Bump for the 305s great on gas and (no offense) not a slug like the 6's (i live in a hilly area...the gas is to the floor 99% of the time, views would be different if i was in a flat area)

Basically i think the break down is (i'm assuming) you can get a 305 or a 350 for just about the same price, probably a bit more for the 350, but the difference is with the 350 your already starting at a higher HP for the same $, and then the mods you make will be the same (cause 305 and 350 are the same block, parts are just about the same) so for the same money you put into a 305, you can put on a 350 and get a lot more HP for the same $$$. But i don't think people that critisize 305s are basing their comments on the person that has the 305, the budget they are on, and if the car is even worth switching motors. I don't know, just my two cents!

 

Nothing wrong with loving your 305.

The problems come when statements are made that you can make a 305 faster than a 350. Well, sure, if you spend more money on the 305 than you do on the 350. But, as sofa said, if you start spending money on the shortblock, the return on your performance $'s will be reduced.

The engine in my first Camaro was a 305. I almost doubled the HP without touching the shortblock. Of course, gas mileage went down. When I put in the 350 shortblock, HP went way up, but gas mileage did not go down again. I now have a 2nd Camaro, with the stock 305 in great shape, and it doesn't get as good of mileage as the Camaro with the 350 - 3.23 gears vs. 2.93, and no overdrive vs OD, restrictive exhaust vs. free flowing exhaust are what make the difference.

 

Only comment I didn't agree with in this thread is that "305's get better gas mileage" If all things were equal the 350 would make more power than the 305 and would get basically the same gas mileage.

 

You can spend your $$$ in places that can be re-used with a 350 later. 305's are not so bad. They are great dependable small blocks and that can give you years of life with good gas mileage for V8's. Especially when you were blessed with 2.73's like me.

 

Stock, it's only 20hp different. No real difference except for the extra displacement. Big whoop.

Mods are a whole different animal...

1. The 350 has a larger bore, allows for larger valves, better flow, and more displacement is always better if all else is equal

2. Machinework costs the same on a 350 block as it does a 305 block. If you're starting from scratch, it's a little silly to NOT use a 350 as your base. This combined with number 1 is why the 305's get so muchy flack.


Since your car is practically stock, it really doesn't matter all that much. Even after you do a bunch of mods to it, you'll still get benefits out of it and you'll still make decent power. The difference is when you are in a situation where you have to either start from scratch or spend so much money to make the 305 fast that you would be better off starting with a 350 which, due to it's bore and displacement, has much more potential.

Unless you're doing a rebuild, dont bother with feeling sorry for yourself over your 305. It's a lot more cost efficient to mod the 305 you already have than to swap a 350 in. The reason people give 305s a hard time is simply because you get less return for your money than you do with a 350, and when starting from scratch, that's a very real difference.

Since you already have the 305, it's really a moot point. It's about efficiency with money. Think about how much money you'd have to spend on that 305 you already have before it would be more cost effective to buy a 350. If it runs good, then it would be equally silly to ditch it for a 350 for no other reason than just to hvae a 350. Because you'd only be getting 20 more hp (Assuming an L98) for all the money you have invested.

This is why when people do 305-350 swaps, they're usually aiming for a lot higher than an L98's power level, because otherwise it's relatively pointless. You can get 20 more hp out of a 305 a lot cheaper than you can build and swap in an L98.

It's not about the 305 being bad, it's about getting the most performance for your money. In some cases that means staying with the 305, in a lot of cases that means going for a 350.

 

To bump his original question as I am interested in this as well. Also is a 350 a 350, or should we be looking for an f body 350 when we go to the junkyard?? Other than if it's FI and we need the computer...should we be pulling anything else in this process?

 

They made millions of different 350s and most of them were terrible. Everything from 150 hp abominations to the pinnacle with the Vortec 350s in the mid 90s.

A 350 block is a 350 block, in order to make it fast you need good heads, cam, and induction. The top end is where the power is and you should do some research on how to mix and match those 3 to get a good combination. Look into 083, 113, and 906/062 heads. For the most part, the rest aren't worth your time.

 

In aggreance with most all thats posted. Id like to add that the 305 is a very durable motor just like most any SBC size. The 305 was more designed for economy but it doesnt mean that a 350 or any other size SBC couldnt make more HP while giving better MPG. The setbacks of a 305 start with a small cylinder size. They arent capable of the volume of air needed to make a ton of HP but they have been known to produce stoudt Tq. Even with alot of well-thought mods, they are gasping for air above 5K RPMs. They just done respond well to the heads and cams like their bigger brother. Streetable they are capable around 330HP from a reliable and decent MPG standpoint. But the 350s are just getting started in that HP area. If you dumped $3000 in both a 305 and 350 (weather you did the exact same mods or tailored them for the specific motor) , you would get more bang for your buck out of the 350. But, the beauty of doing some stuff to youre 305 now like headers, exhaust, and such...is that those componets are compatable to the 350 in the event you decide to up the cubes one day.
To answer 84RedTAs question, Yes and No.
Yes a Chevy-built 350 is the same in 1987 as it was in 1975. But there are some differences in the blocks in respect of componets or strength. The mains are availible in 2-bolt or 4-bolt. The 4-bolt was a strenght measure and mostly found in high HP or Truck applications. But not limited to. GM went to a 1-pc rear main seal around 1986 for a duribility standpoint. There are 2 different cranks for the 1-pc or 2-pc design. But there are adapters too. 1-pc designs were less leak-prone. Around 1987 some apps like the F-body had a extra machined boss in the lifter valley. It was to accomidate the guide-plates needed for the up and coming roller lifter cam engines. Since roller lifters need to be kept from turning, the 'spider' bolted in the valley was needed. Pretty much all else has remained the same from the blocks perspective.
Hope this helps and if I left anything out or mis-interpeted anything, mayne someone will add to it.

 

Is it worth bumping up to an LT1 or LS1 for what time and $$$$ we're going to dump into a 350 swap or are these still too valuable compared to 3rd gen powerhouses?

 

If you do go searching for a 350, here is a site that has casting numbers to determine what you have found.
http://www.mortec.com/castnum.htm
The orig HP numbers dont really mean sh*t. You are just searching for a good seasoned block. Finding one with a 4-bolt main is most builders first area of focus. Getting a seasoned block just means it has miles on it. Most builders swear by a seasoned (used) block rather than a new casting. Reason it that the years of the piston movement in the cylinder has cycled heat and cooling to produce a stronger wall of iron. Therefore strengthening the iron naturally.
A few links to a different page on that site shows locations to find the ID number.
----------
LT1 IMO isnt worth it. Due mainly to the fact its strech of years is narrow. And also some non-favorable design features.
LSx motors are getting cheaper and can be found in many varieties. Tho the swap parts are pricey compared to you already have whats needed in a OEM SBC-equipped 3rd gen.
But the LSx motors are strong, have good updated engineering and go fast goodies are plentiful. Im impressed with their seemless TQ and HP.

 

What about stroking the 305 to a 334, and/or Poweradders. Not spray, but Superchargers. I know they are way expensive, but just wondering what power people are getting with a vortech or something.

 

Stroking the 305 is a waste of time, because in the end it'll make less power and cost you more than an equivalent 350 or 383 would, even after you factor in the cost of the block.

 

No. If you do a search with '305' and 'five7kid' or 'red devil' you'll find a really good hash out that was done, maybe two three years ago about the whole 305 v 350 debate and where you stop. If the thread wasn't purged anyway.

 

I love my 305 (when it runs) as the 350s use way too much fuel. It is a simple design and a complete fit for going and living in socal. Also good for New Jerseys low speed limits. I have nothing against 350 owners, it is just not for me. Raw HP is overrated.

 

I have had them in several vehicles. Same trans and same gearing. The 350 always netted a mpg or two worse, but could have been regeared to match the 305s MPG at the expense of performance. Much the same as regearing a 305 powered vehicle with an economy gear adds performance.

I run a very healthy 383 with a 4L85E behind it and 3.73s with a 30.5" tall tire. Gets good mpg.

I also have a cammed big block 496 in my 99 Tahoe. 4L80E and 3.42s with 32" tall tires. I still see 17-18 mpg highway with it. The only time I even see 2,000 rpm with that 8.1 is if I am tearing down the road.

 

2007 yikes

 

What is good gas mileage? I plan on using mine as a second car when my Forrester is being driven by my hubby. My Camry V-6 XSE is missing that certain something

 

Mileage.... power is overrated.... perfect for slow speed limits.... Forester.... Camry.....

 

Honestly there isn't hardly any difference between 305 and 350 using stock heads and intake. That's why so many F-body owners kind of scoff at the 305 vs. 350 debate. It's not until you abandon the stock induction system that the 350 struts its stuff. Run up against somebody that actually put together a good build and you'll be slack jawed how much more fun the car is at part throttle or full throttle.

 

My Camry V6 XSE has over 300 HP and a top speed of 136 mph. Really for ME it is more than enough. I plan on selling it for an electric car. The best part of cars is people can drive what they like. My cars have the State Farm Drive Safe or a fink. Speed, drive aggressive and my rate goes up.

 

I don't believe this to be true. The fact that i'm arguing with Quick means I have a high chance of being wrong but, you can't even run some decent heads on a 305 because the valves will hit the top of the block as the cylinders are too small to have enough clearance for them and if you do grind enough of the upper cylinder block away, the valves end up shrouded enough that you still have poorer flows . This puts a major near total killer of potential of the 305 and makes the bigger bore of the 350 mandatory for anything but a one off build on the old SBC's.

 

My Firebird will be for fun driving not fast.

 

Nothing spells fun more than State Farm Drive Safe & Save and a cup holder.

 

Nah, we're on the same page, I probably just worded it badly.

And I appreciate the compliment but don't give me too much credit, I don't know much in reality. Guys like Fast355, Orr89Rocz, and Sofakingdom are much smarter. My only talent is copying what other people figured out.

 

Having had both L98 and a LB9 car, same trans and gearing, i will say my 305 was a turd and didnt get any different fuel mileage in stock form. You do hear that some stock tpi 305 cars ran into the 14’s but most seem to be near 15.0. L98 cars were mid lower 14’s.

you are right, 305 bore size limits the valve size you can get in the head, in a conventional 23 deg layout that is. Valve size is air flow, so ultimately potential will be limited.

you can take a 350 L98 and do all the bolt ons with a new intake like a holley stealth ram and go 12’s in 1/4 mile. Stock heads and cam. I havent seen any 305’s come close to that and really havent seen many cammed 305’s anywhere. People just do not build them for good reasons.

i will say they make great turbo motors…stock 305 with 8 psi boost becomes a fun car again

 

Think people misunderstand me, my 87 Pontiac Firebird with the LG4 engine is slow, so so very slow. My Camry will leave me in the dirt as well as my Forrester and thought I saw an elderly women using her walker moving faster. If I get series, what should I put in my Bird?

 

In 2022...

LS3

 

All 305s are not created equal. I think this might be Smitty's old "305" TPI:

 

My friend David Kauffung's 305 did very well in Engine Masters. Went back the 2nd year with a different cam and higher ratio rockers, made alot more power but they had an oil pan rule change and it was disqualified.

I have had several very strong 305s as well.

 

HP is over rated? But...you bought a sports car. (?)

I have to wonder...what kind of gas mileage are you seeing with your "thrifty" 305? :bigears

 

I had both and the 305 wasn’t any different on fuel

 

Same. I was setting up the question.


The other thing is, most people who claim "Gas mileage!" don't even calc or know what they're getting. So.....

 

So, do 383's get worse mileage than 350's? When my 305 gets replaced I'm definitely NOT going 305 again.

 

Lot's of variables there, but I'm going to say, not meaningfully worse.

One of my 3rd gens had three engines in it: 305, 350 and a 400. All three got 24, hand calc'd mpg on the highway/road trips. The 400 was the worst around town....beeeeecause it made the most power, and I used that power.

 

Once well tuned my 383 didnt seem all that bad compared to stock 350 in day to day driving. I never did run the numbers tho but it certainly got around without having to stop for gas. The L98 was around 16 mpg city and 23 highway. My bolt on ls1 car was about the same and had 100 more hp. My turbo 400 sbc got around 10 city lol it all depends. You can get decent highway mileage in bigger motors

 

Yea, a few years back, I put a K&N intake and a flowmaster cat back on a chev pickup and all of a sudden got about 5mpg less for a couple of months. The mileage came back and a little more after I got used to the better sounds it made so I know using the power will have a major influence, perhaps more than the displacement, on mileage.

 

My L03 TBI engine got 25mpg on the hwy even with 3.73 gears. Swapped an L98 over using a bored TBI with bigger injectors and more spring pressure and still get 23mpg hwy.... If..Im not gouging on it.

 

When i bought my car it came with the factory 305, as i drove it i felt "fast" but really only ever seen my 80mph speedometer hit 60ish, the 305 blew and i knew i wanted to do mods and i looked up the difference, i felt i was willing to buy a 350 and start over, at first i wanted a 327 but the 350 was the right choice. you can get a 350 in both 2-bolt and 4-bolt mains, obviously the 4-bolt will be better off for more forced induction power gains, id say do what you want 305s sound great, 350s perform even better

 

Need to change plugs and wires, I do not expect much with all of the emission controls including a smog pump.

 

When I did my V8 swap into my 86 bird from the V6, I was able to find a gently used low mileage 305 for such a low price that I couldn't pass it up. It came with almost all the parts I needed to do the swap*, which factored heavily into my decision. It performs very nicely with my 3" Magnaflow exhaust. That said, had I elected to get a core and rebuild, I would have gone with the 350, primarily because the internals for the 350 are more common and actually cost less than the same parts for the 305. So you get an engine with more potential without spending more. Others have posted elsewhere that the cost of a junkyard 350 core plus the cost of rebuild is actually the same or less cost for rebuilding your 305. If my 305 ever bites the dust in my lifetime, I'll be replacing it with a 350.


*all accessories, brackets, wiring harness, computer, fans, starter and complete TPI assembly. Now that I have those parts, I could swap them over to a 350 if I should ever need a rebuild.

 

A 305 sbc is a great base engine to use for moderate street supercharging.
The lil Weiand 142 and 144 mini blowers do sick things to a hot rodded low compression ratio 305.
Easy to drop the compression ratio on a 305 by swapping on a 350 cylinder head that has 64 cc or larger chambers EG: 76 cc heads.
You are limited to a 1.94" intake valve.
But you can get plenty airflow by fully porting with a 1.94x 1.50" valve set. on any 350 head. (64-76cc chamber)
Add a cam + springs, ,750 cfm carb open up the stock piston ring end gaps and have at it.

Home ported L31 vortec heads are excellent on a 305 for this. Pretty much any all the 350 sbc heads with 1.94" intake valves are suitable.
Avoid the swirl port heads, Avoid the crappy 882 and 462624 350 heads. All the others are better start points.
The Edelbrock/Eaton Enforcer 122HH blower
Is great for this too.
You will more than slay your fair share of 355 and 383 n/a small blocks.

The result of these small street blowers is sick on a budget prepped low cr 305. (7.5-8.5:1 cr)
The lower the CR the harder you can drive the blower to make more boost and more power and torque on pump gas.

 

Here is a good comparison. Both are 1984 5 speed cars. Black has a rebuilt 350 with Flattop pistons and about 10:1 with 062 vortec heads no porting and a summit 1103 camshaft. Also has 3.23 rear gears. White car has a stock block l69 with same cam and vortec 059 heads no porting. Steel shim head gasket about 9:5 compression or so. Heads were surfaced slightly. 305 car has 3.73 rear gears. Both cars have same exhaust, intake, and carb. These cars are almost dead even from a 20-100mph roll. Each car inching ahead depending on gear change and rpm. Believe it or not the 305 pulls a bit after 90....must be the 3.73 gear and maybe better valve springs, as it revs clean to 6500 and the 350 seems to fall off at that rpm.. If gears were the same im sure the 350 would pull ahead, feels like more torque down low,. But the 305 definitely revs up high with the 059 heads...no prob. One time the 350 did pull ahead by one car length was climbing a long hill.. Btw Black car has run a 13.6 at 104mph with major wheel spin at launch...like a 2.2 60 ft time.

 

Not sure how you consider that a good comparison. Do the same things to the 350 that were done to the 305, and the 350 will smoke it every time...

 

Huh? Same cam, intake, Headers, And better flowing heads (062 vs 059) on the 350 not a good comparison? You should read the post completely before you reply.

 

They're not the same heads on both engines, and there is zero reason the 305 would rev higher, or that power would fall off sooner with the 350 since both engines have the same stroke. And you're comparing them in cars with different gear ratios. How about an actual "apples-to-apples" comparison?...