well i'm already excited for spring, considering after my tranny blew up my car officially came off the road a couple weeks ago. problem is i wanna re-rebuild my motor, and i need some help. right now i have a Lg4 305 (the non H.O.) bored .030, decked .030, with H.O. heads (from an L69 305). on top i have an edelbrock performer intake (3701) edelbrock performer 600cfm EGR carb (1400) and a crane energizer cam (100052). i'm just guessing but this combo should only be worth maybe a touch over 200 hp and somewhere around 250-260 lb/ft torque. basically i wanna know the easiest way to get lots of power. so far my ideas are getting a 350 block and bore it out and get some higher compression 350 pistons to throw in it (maybe like 10.5:1?), and use everything else from my motor to make a better motor. now my questions are, could i go .060" over on the 350 without worry of it being to thin? or should i just go .030"? if i had a bored 350 would 600 cfm be enough? would my 305 heads flow enough(ive heard of guys putting 305 heads on 350s)? what else could i do to bump the power? does anyone suggest a better cam/intake/carb combo? could i make more power out of my 305 if i get the right parts?
sorry for the lenth, but tuning/parts matching is the one thing i don't know enough about.
thanks, Adam

 

Never bore an engine any more than you have too. Boring an engine is for maintenance, not performance. It will net you a zero HP gain. As for .060 boring, take the block in and have it sonic checked, only way to be sure. But dont do it unless it needs it, you are wasting a block. As for the carb, the overbore really doesnt make any difference there (like noted above). What matters is your ability to move air. Do you need the 600cfm? What kind of heads are you running? Intake? Camshaft? Exhaust? These are all important. Some 350's only need a 500, some a 600, others a 750--or bigger.

 

all those are listed above. as for specs on the cam, its .454" lift in both intake and exhaust. i have flowtech cheapo shorty headers with a 2.5" Y pipe and stock 2.75" mid pipe, then a flowmaster 80 series muffler and 2" tailpipes. that exhaust will most likely change but if i don't need to i wont (headers might change).

basically in a smaller version, im asking for making big power using a 350 with 305 H.O. heads, or if 350 heads could make better power, and what intake/cam/carb combo would make damn nice streetable power if my combo right now cant (with either set of heads).
-Adam

 

Emissions. Do you have it? That is a big factor.

Although the main journals and stroke are the same as a 350's the crank cannot be used in a 350. The balancing would be off. The 305 counterweights are lighter, designed for the smaller pistons the 305 uses. Best bet would be a junkyard 350.

<A HREF="https://www.thirdgen.org/techbb2/showthread.php?s=&threadid=256235">Here's a good thread that I've helped in that spells out a budget 350 build with 305 heads</A>

 

right now the car is setup for emissions (if you mean EGR) most other emissions stuff was ditched.

also, two different machinists have told me the 350 crank and 305 crank were the exact same, and these are like 60 y/o+ machinists that have been in the business their whole life. now no offence to you but that makes me wanna lean toward them pretty strongly. but most likely whatever block i get will be a shortblock from a JY, so it probably wont matter. anyway, thanks for the help so far- Adam.

ps: also what are vortec heads? where do i get them? how much do they cost?

 

Emissions means emission testing.

Vortec heads are raised runner heads with different 8 bolt mounting patterns. They have pretty decent intake ports and the standard SB-crap exhaust ports. They max out at about .450"-.480" valve lift. The Xe262 is about as much as I would dare go on them untouched. Maybe even that's too much. The heads themselves come on the 96-later 350 Vortec L-31 trucks.

 

The 305 and 350 cranks are the same casting; but depending on what rods came in the motor they were in, may be balanced differently. But, you can use a 305 rotating ***'y in a 350 with 350 pistons, or a 350 rotating ***'y in a 305 with 305 pistons, and it will almost always be within easy re-balancing tolerances.

Here's a link to another board where somebody actually measured the pitiful garbage grade hardware that comes on theose heads from the factory, and measured the maximum possible lift, on an untouched factory set. http://www.chevelles.com/forum/ultim...c/4/22338.html They are simply the stock heads off of a 96-up truck 350. They have their intake ports re-located, upwards, such that the incoming intake charge has a much straighter shot at the back of the intake valve. Their intake flow is therefore better than any other stock heads, and even some aftermarket heads. Excellent castings, as far as making horsepower. On the other hand, they are built in such a way that they are so far from a "performance" setup, that it costs almost as much to turn them into a performance head, as it does to buy new heads outright.

305 HO heads are the same as 305 LG4 heads. There is no difference whatsoever. Of all the differences between the LG4 and L69, the heads isn't one of them.

It's possible to make decent power with the 305 heads, and it's also possible to end up with so much compression, that the finished produict won't run on pump gas. If you have 1.94" intake valves installed in them and port them, especially in the bowl area right behind the valves and around the valve guide, they make a decent "performance" head, as stock heads go.

I would suggest that you lose the Performer intake; it's basically a stock replacement, very little improvement. The Performer RPM is a better running piece at every RPM. Or, the ZZ4 intake (which you can find for cheap from people who buy ZZ4s and put some other intake such as TPI on it) is an excellent one, with better fit & finish and overall compatibility with the car, than any aftermarket one.