305 heads on a 350 good or bad idea

[RockReadyYJ]

i am trying to find a decent priced 350 to go in my YJ wrangler, blew up the 258 again, i'm decideing whether to buy it , rebuild it, or buy it used. a friend of a friend has a 350 that he will give me for a pretty good price but it has 305 heads. he says it boosts compression and horsepower i don't need a kick ass engine just something better than the 258 i just killed, but i hate to waste money on a boat anchor, seems like you might put 350 heads on a 305 but not the other way around.
whats the bad and good about running a engine like this, he's been driving it for a while and says it screams but i just wanted to get some opinions. whats the good and bad of this combo
thanks

[a1supersport]

A 350 with 305 heads will give you higher compression (the chambers are smaller), but the valves and the ports are smaller. You'll have more velocity because of the smaller ports, but it'll get "winded" faster. It's like a person sipping a soda through one of those skinney coffee stirring straws, compared to slurping a soda through a piece of garden hose. The air/fuel mixture will move quicker in the smaller ports, but it won't be able to keep up with the engine as the rpm increases. So it'll "get up and go" real good, then fall flat on it's face eventually. The opposite, a 305 with 350 heads wouldn't work. I actually measured the diameter of "normal" 350 combustion chambers, and it's a little bigger than the diameter of a 305 cylinder. The valves will most likely hit the cylinder. So to sum it up, the 350 with the 305 heads might work good for you. You'll get good response in the lower rpm range. Any engine can "scream"...whether it's putting out as much power to match the screaming, is a different story. The down side is the compression. More compression means you'll need more octane, or the engine will start "pinging". Unless you install a cam with a lot of overlap (which will let some cylinder pressure out), you're going to need more octane. I don't think 92 octane pump gas will be enough. Hope I haven't confused you . Good Luck.

[RockReadyYJ]

nope didn't confuse me, actually made it pretty clear. this engine is going it a daily driver so another question i have is do you think the engine would be about to handle long drives like 5 to 10 hours straight getting to where i go wheeling. the guy has been running on pump gas for a while from what i understand so i guess its working.
thanks for the info and Please keep it coming

[a1supersport]

Wow, 5 to 10 hours of driving...and then go wheelin? How many hours/miles are on this engine already, and how much is a "pretty good price"? It'll also be good to know at what temperature it runs. By the way, how did you "blow up" your 258? What exactly happened to it? I can see you'll definitely need something reliable, as well as something that's easy to repair and find parts for...and a smallblock Chevy is the answer. Whether or not this engine is the right one for you, it's hard to say. The reason I asked about the temperature is because of the compression and the smaller ports in the heads. More compression creates more heat. Smaller ports, especially if they're smaller than what that engine demands, will make the engine run a little "leaner", which also could create more heat. Even with the old theory that "Heat is Power", after a certain point, heat becomes detrimental to reliability...and reliability is definitely what you need, not power. Whatever happened to your 258 should partially determine what your next move will be. I have more to add, but I'll wait for your reply .

[RockReadyYJ]

well i have decided not to waste my time with this engine, i found another guy with a built up 350 intake carb headers bored 30 over brand new rebuild still on the stand for 800 so i'm gonna go look at it and probaly get it.
i just blew the head gasket on this one and the last one the piston ring went to shit, not that i'm Real hard on them it was just their times to go and i don't want to spend money on the six, on the trail it was fine but street it just didn't have enough ass
thanks for the info

[a1supersport]

Sounds good. 800 sounds decent for a complete motor...700 sounds better though . Remember, so long as you have the money, YOU'RE in control. Once you give him the money, HE'S in control. Hope to hear good news .