I'm getting to pull out my 305 and rebuild it. (84 Camero Z28 ) Would you get as much power from a motor that was bored 30 than 60 over? Any advice would help greatly.

 

If you are asking if theres more power to be made at .060 over, I'd say its a really bad idea to bore the engine out more for more power.

 

How come you just don't look for a 350 to rebuild?

Boring a motor .60 over is a little risky for a daily driver. You better make sure you have no core shifts. The cylinder walls are pretty thin @ 60 over!

 

I would go along with the 350 idea. A 350 core wouldn't cost that much plus most of the parts on a 305 would fit the 350 as well. Boring to .060 over is risky with the thinness of the walls and you could easily create a overheating problem.

 

The extra power your going to get from going an extra .030 is marginal at best. Maybe 5hp on a 300+hp 350.

I don't agree with the people who say the walls are too thin @ 60 over, I have seen too many engines 60 over that have lived a long happy life with no problems. Going any farther becomes an issue, pistons and rings will no longer be off the shelf items and then the walls are starting to get thin.

Alot of how far any specific block can go is what year the block is. IIRC pre-70's blocks have thicker walls than most and I've heard of some castings being able to go .120, but they don't last long and aren't meant for the street.

 

The reason why i ask is that my 305 is still a very strong motor and can usually beat or at least hang with the 350's.
I just wan't that extra kick so i can ask them if they can read my licence plate I thought about NOS but i don't really know much about it and i don't know if i would use much, and would be a waste of money?

 

If your 305 is still "very strong", why are you rebuilding it?

Assuming 1 hp/cu in, you'll gain exactly 5 hp with .060" over vs. .030" over. You can lose/gain that much from poor/good tuning. And, 1 hp/cu in is not "normal".

Obviously from my sig, I'm doing a 305 build. But, I have a usable shortblock to start with. If you have to spend any money on the bottom end (pistons, boring, crank turning, etc.), it makes more sense to get a 350 core and build it. The "unique" factor is only worth so much. Making a 305 work can be done with a serviceable bottom end, however, and does not involve a "rebuild". If your bottom end is "still strong", then follow my sig (you'll have to get a non-roller cam for an '84, though).

If you want to go NOx, the first recommendation is to use forged pistons to help it hold up. Now, see preceeding paragraph.

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82 Berlinetta, orig V-6 car, now w/86 LG4/TH700R4. 2.93 limited slip. 2-1/2" cat-back, ZZ3 intake, Accel HEI SuperCoil. AMSOIL syn lubes bumper-to-bumper. Daily driver, work-in-progress (LG4 CC system w/'87 LB9 block, ZZ3 cam, ported World 305 heads, Hooker 2055 headers, 3" Catco cat & 3" catback, restalled TC, Spohn SFCs).
57 Bel Air, my 1st car. '66 396, 9.7 CR forged TRWs, Weiand Action+, Holley 750VS w/4150 conversion, GK 270 cam, Magnum rockers, Jacobs Omnipack, 1-3/4" Hedders & 3" Warlocks, TH400 w/TCI Sat Night Special conv & Trans-Scat shift kit, MegaShifter, 3.08 8.2" 10-bolt w/Powertrax, AMSOIL syn lubes bumper-to-bumper. Idles smooth @ 600 RPM in D. Best 15.02/95.06 @ 5800' Bandimere (corrected 13.93/102.4 @ sea level).

 

One advantage to boring the 305 over is to create more compression. All the new area will now hold more air that can be compressed. If you overbore it to .030 or .060 you might be able to run 350 heads that normally would have too big of a combustion chamber.

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-Tas
'89 Formula WS.6

 

.13 more of compression for each .030 you go... I wouldnt say thats a very significant amount.

 

The reason i'm going to rebuild is that i'm already going to have the engine out so why not, My buddy that is going to do this is GM certified and he's not charging me anything but the parts for the motor. I was just trying to get some ideas before so i could make my mind up before he started.

 

Everything said above still applies.

Why not rebuild? a) If it isn't needed, it's money spent that could be used elsewhere. b) Believe it or not, 305 parts are slightly more expensive than 350 parts. c) In their latest edition, Chevy High Performance mag in their "My Generation Camaro" series used the same logic as you when they decided to put on the World 305 heads. When they got inside, they found that it had already been bored .030" over, had some messed up pieces (rockers), and a cracked block. They found a sound stock-bore 305 core and bored it, using their old pistons and a PAW rebuild kit, but when they got done, they had spent as much as they would have had they gone out and gotten a 350 core. d) When they got it all put together, the resulting performance was improved, but I wouldn't call it "impressive".

Look, go ahead and build your 305 for some more spunk. But, my advice would be to first do a compression check; if it's okay, take the heads off and look at the cylinders and lifter valley (I just discovered my own '87 305 block is cracked in the lifter valley). If still okay, pull the pan and check the bearings. If there is ANY problem with any of those steps, stop all 305 work and go out and get a 350. If everything is okay up to that point, then I like my selection of bolt-ons, and would recommend them (based only on research - not results).

BUT, not if you want to go NOx sometime down the road.

[This message has been edited by five7kid (edited October 27, 2001).]

 

Thanks for all the help it was very useful.