im stuck between the 2, at first i was going to swap in a 400 but there are none around here that i can afford, even at the junk yards.

ive come between the 305 in my car already and swapping in a 350, here is a list of what each motor would have

305
-hedman shorty headers
-decked heads and some P&P
-.4xx lift cam
-unknown aftermarket intake and possibly a better carb
-MSD ignition
-smog/emissions equip. removed

350
-hedman shorty headers
-.4xx cam
-MSD ignition
-smog/emissions equip. removed

which would be better for me as far as HP goes and ease as far as modifying it? im 17 and have never done an engine swap before but my dad has done lots of them, so he would help me, but if we swapped in an engine it would take the rest of the winter probably and i dont want to do that. i want to have it in the yard waxing it the first day it hits 60 degrees.

the reason why there is more stuff on the 305 is that i would be taking the money otherwise spent on a new engine and putting it towards the 305 and i would have the time otherwise spent on the swap going into the 305

so what do you think? this car wont be for drag racing, i might take it to the track a couple times but it will be on the road 90% of the time

 

If you're going to be rebuilding anything, rebuild a 350. If you aren't going to rebuild the 305, then I guess you could stick with it for awhile til it needs to be rebuilt...then throw in the 350.

 

I just got a short block (350) for 70 dollars, and even had some smogger heads, springs, cam, and 7 of 8 pushrods. Though I wont be using them, it just goes to show that the price for a 350 over a 305 really isnt that much. For 70 dollars more to your rebuild you can add 45 cubes, and it'll add much more horsepower than any other performance mod that you can get for 70 dollars.

 

If you find anyone who says the 305 is the better engine to tinker with, I'll eat my ragtop.

:shrug:

 

Depending on what the casting numbers are, it might be worthwhile to use your 305 heads on the 350.

 

Do the 305.

Since the car is 90+% street use, you won't be able to find a better carb than you have now. You may need to improve its capabilities, but that doesn't mean replacing it.

The LG4 has weaknesses that aren't fixed by putting in a 350. They are: air cleaner, exhaust, & cam. In that order. After you fix them, the heads become the limiting factor, but like the carb, don't need to be replaced but to have their capabilities improved - 1.94" intake valves, and the aforementioned porting. Decking only required if the head sealing surface(s) isn't flat. Aftermarket intake optional. All of this stuff will transfer over to a 350 shortblock.

The 305 is a better engine to tinker with. The improvements above will produce more power than just putting a 350 in. However, a 350 is a better shortblock to rebuild.

 

305 is better to tinker with

there

lets see this buddy tell me how it tastes

 

350 small block Chevy. I'll stick with my TPI. You could try those 70s Caddy big blocks as a build up performance engine.
I guess tinkering ain't really my bag, I just like to drive 'em!
Bill

 

i say go with the 305. if you're 17, you'll learn much more about what actually makes power as you're modding it than a 350. a 350 responds to just about anything with some success where as a 305 is a big more touchy. much more of a learning experience starting with the 305.

 

They should both respond very similarly to similar mods. They are designed the exact same way. Granted, the 350 will make (assuming its built to the same specs) 15% more power, so each mod will make 15% more power on the 350 than the same mod would make on a 305. But still, they should both respond similarly. Of course, that's after you remove the stock bottlenecks. The 350 has a few more bottlenecks than the 305 (exhaust, intake, etc.).

Anyways, I still say to stick with the 305 unless you were planning on rebuilding it. If you're going to REBUILD (i.e. machinework, new rotating assy., etc.) then go with something larger, but if you're just going to add parts to the car and not mess with engine internals, stick with the 305 for a while. Do all the supporting mods first before throwing in a bigger engine. Do the suspension work, do the bolt-ons. If you do anything to the engine, make sure its something that can be bolted onto the 350 (such as headers, or a new intake).

 

doesnt decking the heads give it a bit more compression? and its my understanding that compression=HP pretty much, or am i just wasting my time? its 8.6:1 right now at stock, i was thinking if i bumped it up to 10:1 or somewhere close to that i could run 92 pump gas and get more HP, could i even come close 10:1 with just decking the heads and adding a cam?

and i have to replace the intake manifold because it has a crack in it and it leaks coolant, so id be doing that no matter what, im probably gonna go with an air gap or weiland manifold because that seems to be the universal best bang for the buck

oh and i wont be 'rebuilding' the 305, it runs nice the way it is, i will just be building up, the only machine work will be on the heads if i decide to go that route

part of the reason why id rather go with the 305 is because it would be alot of work swapping in the 350, i have to go to school and work so i dont have much time in between, plus i have to do other stuff like put new brakes on all 4 corners, plus i want everything done before spring so i have to do everything with frozen hands

so your saying i dont need to get a new carb? i know carbs are expensive but i have a holley 4bbl 400cfm that i could use, would that be a waste of time?

 

Decking refers to the block, not the heads. "Milling" is the word used when you grind down your heads to gain compression.

 

Who's the guy to look at my heads in Western Minnesota, BTW...or put in a new vert top for me? Still waiting for some tips there
Good call

 

aaah i see, thanks for clearing that up. my dads a machinist and ive taken lots of machining courses over my highschool career (we have a really nice machine shop at our school) so im pretty knowledgable with machining and stuff, since 'Milling' is such a broad term i just thought it was best to use the term decking so people know exactly what im talking about. but now i know what to use and i wont look like an idiot when i go to the auto parts store and tell them to do the wrong thing.

i could probably have my dad mill the heads on his CNC at work, but depending on the cost the local auto/machine shop will do it for it might be worth it to have it done professionally. about how much would i need to take off the heads to bump the compression? the cam i will be using is about a .410 or so lift cam

 

i know theres a shop near Dassel MN that builds race cars, like really really nice ones, i cant remember what town it is in though,and i dont know if he does engines but if you talk to him im sure he could give you a number to a nice machine shop in that area.

i grew up in Dassel, my best friend was from Cokato, and i was born in Litchfield

 

That will depend on your existing parts, your current compression ratio and the type of heads (some can only handle a little milling while others can handle a lot more). Also, the same head on a 350 will have a higher compression than a 305.

Your choice of cam will also affect the compression ratio you should run. Longer duration cams need more compression and short duration cams tend to detonate more with high compression.

I do recommend having the heads "angle milled" so the intake will bolt up properly.

 

Depending on how much you take off, this isn't necessary. I know around here it costs about $50 to get a pair of heads milled. Angle milling starts around $70-80 due to the extra work of setting it up for the angle, etc.

 

when it comes to the smaller cubic inch engines, especially those with a small bore, there is a much larger area to screw of the velocity by chosing the incorrect part.

 

Yes, but only a very small amount; usually just only enough to "true" the heads. For the typical milling that is done to make a 1/2 point or more increase in compression ratio, angle milling is the preferred route to go. This is something that is best discussed with the machine shop that will be doing the heads since in the whole scheme of things (when rebuilding or modding the engine), the price difference is insignificant.

 

Don't bother trying to raise the compression, even though it is low. The "right" way to do that would be to put flat top pistons in it, but the expense isn't justified for the gain that would be realized. Milling the heads enough to affect the compression ratio would also require milling the intake manifold, would would effectively disqualify them for future use on a 350.

Are you sure the intake is cracked? Mine leaked because of deteriorated gaskets.

 

You've got a V6 therefore your opinion doesn't count.

My point was that in the long run, the 350 will disappoint you less than the 305. If you want to tinker with an engine that will never see the strip then sure... mess with the 305.

 

At 17, a 305 is probably the better choice for spending limited funds on bolt-ons that will transfer to a 350 later, when funds are more plentiful, and insurance rates are lower.

 

best advice.

I'm 19 and doing the 350 swap out of necessity... swapping to a 350 "seemed" like a good idea for cheap horsepower and getting my car back on the road when I spun bearings... boy was I wrong! More expensive than you may think since you'll need to rebuild the shortblock, and then while you're doing that you should replace valve springs, and since you're replacing valve springs and everything's out of the block you may as well buy a new cam... oh then you need new lifters to go with that, and then the rockers, etc... you're best off buying a short block from your local machinist. then get a cam package (K package on summitracing.com is what I'm going to use), and then get a rebuild kit from summit as well, that includes heads, bearings, gaskets galore.

Then again, you can also just go and buy a 350 from the newspaper, and hope it doesnt have any real problems for about 400 dollars (with high miles) and see where it gets yah.

 

Not with angle milling. That is why I recommend "angle milling" to ensure a stock intake will bolt up properly.

 

If the purpose is to get the car back on the road, then there are a lot of 305's lying around cheap. If you're building from the ground up then the 350 is actually a cheaper engine because parts for those are dime-a-dozen. If you start dumping money into machine work for the 350 then the 305 becomes the better deal.
Of couse, many of the 305 parts could be used on the 350.
Do this, use the info you get here, develop a plan, add 25% for overage on the budget and see where you end up.
You could also check on the price of a GM longblock (targetmaster)
Not the highest horsepower engine ever built, but it comes with a warranty.

 

there is no replacment for displacment

 

The only thing faster than cubic inches is cubic dollars.

 

..which i dont have, lol



guys thanks for the help and i have been thinking a terrible lot lately and still dont know what to do, i want to swap a bigger engine in, my dad keeps trying to convince me that putting the bigger engine in will be 10 times as better and is really easy. lol i know that kinda sounds funny, my dad trying to convince me to swap a bigger engine in, but its the truth

so let me get this straight, if i put my 305 heads on a 350 block, they will fit perfectly and will give me more compression? how about on a 400? im assuming they will bolt up just fine but what about the compression?

can anyone tell me the HP and TQ numbers for a stock carbed 350 and a stock 400 SB? ive tried googling but all i come up with is buld sheets of modded SBs and no stock numbers

i got new brakes today and while i was at the auto parts store they can get me a nice intake manifold (they said it outflowed the edelbrock performer intake manifold) and a remanufactured holley 600 CFM carb for under $350... $190 for the carb and $125 for the manifold, so if i can get ahold of just a block of a 350 or 400, swap the 305 heads on and get that hell of a deal intake.... hmmmmmmm but we'll see

so many options its frustrating yet joyful at the same time

 

Yes 305 heads will fit onto either a 350 or a 400 block.

350s came stock with anywhere from 160 HP up to 375 HP. Most 400s were about 175 HP. Those numbers don't matter though; you most likely won't ever see a stock one. If you do, you don't want it, except as a core to make into something else.

 

I sure hope you plan to rework those 305 heads. Stock, they will choke a 350 due to the small valves. Frankly, I would look for L98 heads (iron) if you are tight on cash and use those. They are cheaper than dirt. And, depending on the head gasket (.015-.051), assumming flat top pistons (6cc valve reliefs) and minmal decking of the block (.010" just to true it) you will be any where from 9.6-10.4:1. Frankly, I would keep it under 10:1 with iron heads.

Your 305 heads (assuming 58cc) will be 10.25-11.25:1...a bit high for iron heads - you could live with the lower range if they were aluminum. So you will end up needing dished pistons, and now the primary reason for running 305 heads (compression) is gone.