ok, can you tell me what's the output, if we do this:

we've got a 305 packed with all the high performance parts (exhaust, heads, cam, larger tbi...) good for, let us say, 300hp and "?"lbs of torque.

now we take all these parts and put 'em into a 350!

how many hp and torque will we have now?

your turn!
greetz

S!MON

 

Prolly 250 horsepower.

The flow through 305 heads would be crap on a 350, the combustion chambers are too small, resulting in your running AV gas or retarding your timing to all hell to avoid detonation, the exhaust is now too small. If you got headers, sell 'em, the primaries are either not matched for a 305 in the first place (meaning you wouldn't have 300 hp on it) or they're too small. Cam .... you might be able to keep the cam

EDIT --- oh, and you'll be fine on the tbi and intake manifold =)

EDIT 2 --- If you did the swap using slightly different parts, you'd end up with approx 344.2 horsepower going with your same hp/cid ... but the actual parts on the 305 just wouldn't quite work if they were done correctly for the 305

 

my fault, I have ment the same parts for a 350 (mostly the same price)!
it's clearly that heads or something else wouldn't work right on a 350.

it's like:
I pay 2500 bucks for my 305
and
I pay 2500 bucks for my 350

greetz

S!MON

 

so 305 heads on a 350 block would run like crap?

some guy was trying to sell me an engine with 305 heads on it, he said 305 heads make it run better.. (i don't know that much about engines so i believed him)

 

kristopheer, the guy trying to sell you the engine may have been correct, some 305 heads are actually very good heads if they've had porting work done on them. Many guys on these boards run 350's with the 416 casting 305 heads, if you port them and put in bigger valves they can flow really well. I know of a few guys I think maybe Sitting bull had some of the 416 heads flow tested that flowed more than stock vortecs. Also, a lot of 305 heads have 58cc combustion chambers which would boost compression up on a 350 that came stock with 64cc chambers.

 

Yes, if you modify the crap out of some 305 heads they will run a 350, and will introduce about a half point of extra compression, but for the most part, such a head is no longer tuned to run on a 305. Idea being you've more or less turned it into a small-chamber 350 head. I mean, it'll still run a 305, but the powerband they'd react best with on the 305 would be higher in the rpm range than on a 350.

Simon, I understand the reasoning behind your question perfectly now.. and honestly, the hp-per-cid calculation, while nice, isn't going to be entirely accurate. From what I understand, 350s tend to respond better to modification than the 305s, however that could also be many people just performing the wrong mods to the 305s to begin with. Only main note i'd add here is the 350's mains are going to be stronger.. never seen a 4 bolt 305

 

lol. that's right.
but I can't decide if I should swap to a 350 or stay by my 305. it's my daily driver and maybe you know the gas prices here in germany
so I think if i would build up a 350 with all the good stuff it would be too much (ok, I know, there is no "too much")
but with a 305 I would have a naturally restriction
and it's a lot cheaper if I won't need new pistons a new crank and stuff like that...I'm a trainee!!! so it's hard enough to keep the car going! for example I have to pay over 500bucks fot tax a year, the gas is over 1$ per liter (maybe 3$ for a gallon) and so on...
it's hard but it's worth it

greetz

S!MON

 

Simon, You can do it and the difference between the two engines are just bore and stroke as far as interchangability.. Is that a word ? LOL Anyway, You'll hear diffrent things but mainly, You should run a higher fuel pressure to compensate for the fuel curve or injector size given to the 350 compaired to the 305. A 90-92 or map car will react to the change easier with out any component changes. Such as knock sensor , prom or other items.

I didn't see you asking anything about heads in this ? However I gotta get my jabs in here. You don't find any litature any place writen by Lingenfelter, Emanual, batchel say that the heads are not recommended. Vizard say the valves are pushed closer together on 305 heads to clear the cylinder walls and heat transfer to the intake from the exhaust is a big problem and not to use them.... Big valve 350 heads rule ...