I just wanted to know how much it would cost to bored a 305 out to a 350. And will I have to change anything on my old 305 setup for the 350 to function properly. Change of heads? will computer work? All i want is a 350 and I was just wondering if its that simple. Thanks for any comments or suggestions.

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1986 Pontiac TA 305 carbuerated.

 

You cannot bore a 305 out to a 350. You'll need a different block.

 

Now i dont want to show my intelligence level here but isnt a 305 and 350 the same block only differnt bore and stroke??


sorry if its a stupid comment

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1983 CHEVROLET CAMARO
305 C.I.D.V8 BORED .30 OVER
HIGH VOLUME OIL PUMP
FLAT-TOP PISTONS
MILD CAM
3" CAT BACK EXHAUST W/ FLOWMASTER MUFFFLER
KEYSTONE CLASSIC WHEELS.
B&M RATCHET SHIFTER
STAGE THREE SHIFT KIT

MUSTANGS SUCK

 

the 305 and 350 blocks are not the same. the stroke is the same, 3.48". the 305 has a bore of 3.7 something" and the 350 with a 4.0" bore, which is what the difference is. i am afraid that you would bore into the water jackets before you reach 4.0" bore .

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87 iroc-z 355 TPI 5 spd. 51006 SLP cam adv. 4* (106.5* centerline)
hypertech stage II chip/ 160* stat./ Airfoil, accel AFPR
19# injectors, ported plenum and runners. 9.8:1 compression
stock heads, pocket ported, 1.94 int., unshrouded.
stock exhaust manifolds and y pipe! hopefully soon to change
3.45 rear (stock)
Flowmaster, K&N w/ hacked airbox/removed MAF screens
14.38@100mph 2.2 60'

 

To clarify slightly, externally the blocks are the same, meaning the engine mounts, transmission mounting, and accessory mounts are all the same.

For the cylinders, though, the casting are different, such that the 305 bore is on a smaller radius than the 350. The centerlines of the bores are the same, however. Since there is only a small range for "ideal" cylinder wall thickness, they made them different so that the wall would be too thin to take the stress of operation if a 305 is bored out to 4" (not sure, but may not even be anything left).

The typical maximum "safe" oversize is between .030" - .040" from stock. Since the 350 stock bore is 4.000" and the 305 is 3.735", you are way over .040 getting a 305 to 4".

I've never even heard of sleeving a 305 block to 4". Probably a good reason for that.

If you really want a 350, find a 350, either new or used. You don't want to use 305 heads on a 350, although it could be done, due to smaller chambers, valves, and ports. But, the computer will work with a 350. For what it's worth, GM makes a complete kit to replace your carburated 305 with a ZZ4 350 (assuming you have an automatic tranny). Costs about $4400 + tax & shipping. Even includes a new computer.

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82 Berlinetta, orig V-6 car, now w/86 LG4/TH700R. 2.93 limited slip. Cat-back from '91 GTA, Accel HEI SuperCoil. AMSOIL syn lubes bumper-to-bumper. Daily driver, work-in-progress (LG4 w/LB9 block, ZZ3 cam and intake, WP 305 heads ported & polished, Hooker headers & y-pipe, hi-flow cat).
57 Bel Air, my 1st car. 0.030 over 396, Weiand Action+, Edelbrock 1901 Q-Jet, Jacobs Omnipack, 1-3/4" headers, TH400 w/TCI Sat Night Special conv & shift kit, 3.08 10-bolt, AMSOIL syn lubes bumper-to-bumper. Best 15.1 @ 5800' Bandimere. Daily driver while Camaro was being put together.

 

I know where this post came from

I think you should probably pick up some magazines, and maybe a book or two on camaros/firebirds and the small block chevy engine. There have been a few magazine articles on getting more power out of carb'd 305's and similar in the past couple years, and Im sure there will be more in the future. This will give you a good basis on your own to decide what to do, and even give you an idea how to go about it. Ive been around this stuff for about 25 years now, so I know a fair amount. Nothing wrong with where you are at, but if I were you I would read as much as possible and then go ahead and figure out what you want to do. It will end up costing you less in the long run too. Or you can go the simple and more expensive route and drop in the zz4 crate engine everyone keeps suggesting.

 

There is nothing wrong with that 305 and no, you can't bore a 305 to a 350. I think the largest a 305 can go is like 335 and that's with a new crank.
You can feed your 305 well with a nice set of trick flow heads, a good mid-range power cam from Crane, Comp, ect. An air-gap intake and a good q-jet will help those mods out. Get a high flow exhaust and a set of TES 1 5/8" headers. Match the engine with the drivetrain next. Get a set of 3.42 or 3.73 gears and some stickeyt tires and your 305 will challenge some LT1s!

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1987 Chevy Camaro IROC-Z
L98 TPI 350 (5.7L)
TH 700R-4 Transmission
Borg Warner 7.75" 9 Bolt Rear End

Current Mods: LT4 Hot Cam, Comp Cams 1.52:1 Roller Rocker Arms, Edelbrock TES 1 5/8" Headers, Hooker 3" Aerochamber Cat-Back System, Performance Resource Chip, Accel Ignition Coil, Cap, Rotor, 8.8mm Wires, K&N Filters, JET TPI Air Foil, All Free Mods, Falken ZIEX Z-Rated Tires.

Best ET (w/o LT4 cam): 14.32 @ 97.7mph
(corrected for elevation)

7.5" 10 Bolt with 3.42s soon to come!

 

Cool thanks for the comments and suggestions. I figured that maybe since they are the same blocks the 305 could be bored to a 350, guess not. So maybe ill keep the 305 and give it some mods and save some money and check out what I can afford. Thanks again.