i bought what i thought was a 350 but didnt look at the casting numbers and now found out that it is a 305 clean motor but totally off on what to do now i am complettly tearing down and building back up and this is a low budget build for most part doing alot of price comparing but anyways what kinda hp gain could i expect with boring .30 over and what would the piston size be for that and with changeing all components roller arms valves and all cam thinking a 270 duration comp cam i really dont know what all i can do for this motor to get a good hp rating with out spending a fortune for a little motor? and idea and info thanks

 

Few questions:

1. Can you take it back because ide be pretty mad if i bought a "350" only to find out its a 305.

2. What kind of perpouse do you intend for this car? The first thing you want to do for a project like this is to first figure out the perpouse for the car and then figure out how to best achieve that goal. The term horsepower is kinda a missleading anyways the way people throw it around without really a true understanding as to what it really means in terms of performance. I mean if your talking about a drag car that sees no street time yea you want lots of HP but for a strictly street car that spends most of its time in the low RPMs you want lots of torque and a strong mid range. A 350 would be better reguardless but we might be able to meet your goals with what you have as long as there not too demanding for a 305.


To answer your questions:

1. For .030 over pistons you dont really need to know the actual size of the pistons you just have to order a set of pistons for the 305 .030 oversized and they will be listed that way rather than a specific diameter. I would not expect much horsepower from punching the block out 30 over and would only do it if the block needs it as the gains do not justify the expence or the fact that you will not have less material for a future rebuild or repairs. However you will probably have to punch it out if its an older high mileage motor.

2. For mods there really no different than any motor. I cant really talk specifics as i dont know the goals for this motor are yet but reasonably speaking with all the basic mods for a hot street car i can see a mid high 200 to a low 300 number with a radical stip only set up i could see as much as high 300s maby even breaking into the low 400s. NA and no power adders. Although again it all depends on your requirements for the motor if it will be possable to make the power you want and meet your needs as far as streetability ect is concerned.

 

im looking for a motor for my 83 camaro that i can have on the street but also take it on the strip when available i had heard on a 350 the hp gain for bore .30 on a 350 would increase about 200 and to get that done where i live is about 250 which aint bad im not really sure what to do i only paid 150 for the motor so not a big amount to get all mad about i should have done my research a little better but i would like to have about 400 hp when done but done as cheap as possible not spending 1000s any more ideas

 

a 30 overbore is worth maybe 5 horses, depending on the build. For a stock rebuild it's worth masybe 2 horses. Seriously. If you do it with Vortec heads, a COMP XE268 cam, an RPMAirGap and full exhaust with headers, then you could have 370 hp @ 6100 rpm, but really, sell the 305 and go find a real 350.

 

Yea no way is punching out a motor 30 over worth 200 hp. To get 400 hp out of a 305 it will cost 1000s and not be particularly streetable. Ide say a reasonable amount to get out of a 305 while maintaing good streetability would be high 200s low 300s. However even that will require heads cam intake exhaust and rebuilt the works so that will run a few thousand too.