Ok, apparently everyone thinks this is crazy but honestly I dont really feel like dealing with different engine mounts and completely diff proms and different intakes. I spoze it's kinda unique to build upp a 305 cuz everyone and they're brother puts a 350 in these cars... If all i wanna do is build this engine up alittle (my goal is like 300hp) which is only like 60 above stock which i dont see it being that hard to gain. So if i were to build up my 305 what limits do I have with piston compression and cam lift before its gonna cause a whole S*** ton of computer problems and headaches?? Im pulling it and deleting the cats, a/c delete, smog delete, and tubular headers. please help instead of saying get a 350...but still thank you to those of you who have responded anything helps.

305/350 mounts and intake are exactly the same. The PROM is different, but very easily swappable.

I meant to say and older 350, i mistyped lol do u happen to kno what kinda cam size i should go with and what compression pistons i can go to without making alot of problems??

Well just to let you know the older 350s are the same too. There all gen 1 SBCs which ran unchanged from 1968-1985 and although they changed a few things in the 1986-1995 block there still the same motor just with provisions for roller cams and a slightly different intake bolt angle (still the same pattern just 4 of the holes are drilled at a different angle so the intakes can fit with alittle grinding on 4 of the holes). The reason i mention this is a new GMPP 350 can go for as little as $1500 so its kinda hard to justify rebuilding a 305 when youll end up spending the same amount and have a rebuilt block vs a bran new larger motor. Seeing as how your planning on doing mods the prom will require some changes anyways. Although if your intent on going with rebuilding the 305 theres a few things we need to know to help you pick parts and a few things you should know. First when ever you make some moderate mods the ECM should be reprogrammed although you can get away with small changes and remain drivable still it really should be reprogrammed. Some motors are more tolerant to mods and some are pretty intolerant. So before we talk about what parts and specs we need to know what motor your currently have so we can get an idea of how tolerant your motor is to mods. Next 300 hp although definitely not imposable that will take a fairly well built motor nothing crazy but not really near stock either meaning that youll have to use parts the will require your prom to be re-programmed. Again 300 hp would be much better accomplished on a 350 in virtually ever sence even in gas mileage because you can get this number useing much tamer parts and still have better torque. I think with a 305 ide hope for the best but shoot for 250 or so. Also keep in mind unless your talking about a non original motor its not just 60 hp. The best performing 305 was the tpi motors of 85 and later stick shift tpi motors and they only produced 215 so were talking 85 hp tpi 350s put out 240 hp. Depending on which 305 you have it may be even worse like the lg4 with i believe only 145 hp? That would leave u 155 hp short.

Rolling Thunder is correct - it will cost you virtually the same to build either a 305 or 350. You will have to tune the computer, but even if you mod the 305 you will still have to mod the computer. Other than that, literally all of the parts are interchangeable - headers, heads, cam, intake, etc. The reason "everyone and they're brother puts a 350 in these cars" is because it makes sense to do, versus building a 305.

i have a 91 rs with a 350 out of a van its carberated and i have 4:10 s in the rear my uncle has a bone stock 96 impala he wants to race for a hundred bucks should i pull it........

can my 91 rs with carberated 350 out of a van beet my uncles 96 impala ss

pobably not. as the van sits stock, its only about 260-275 hp, if ur lucky. more like 240-250. the impala is sitting at about 300ish, and is a stout machine. depends also on what mods ur gonna do to the motor. head to head, stock to stock, u will get crushed.

Rolling thunder is right for the most part, but if memory serves me correctly the best tpi 305 was 230hp in 88 & up with stick. And the highest hp in a 305 from the factory was i think in 2001 version in the vans 240hp. Gm is still producing the 305 for marine applications. The 2010 model is putting out 253 hp and 302 lbft.
http://www.gm.com/experience/technol...000_Marine.pdf

None the less, it's always nice to do something different than the usual 350 build. If every1 did the same build it would be very boring. I support the 305 builld even though u get more bang for your buck with a 350..

Hehe, that would be sick if someone put that in their car!

i second 1qk4mula
i have a tpi 305 sitting in my garage that i plan on building up

-lunati voodoo cam
-hyperutectic pistons
-pollished intake runners and manifold
-larger throttle body, bbk
-long tube headers, with 3 to 3.5 inch exaust
-electric water pump
-mabie some difrent heads, if not ill just port and polish them, with some difrent valve springs
- roller rockers
-larger injectors
................
thaught about punching it out to a 327
...............................................

and of course reprograming my prom for the engine
and i need a painless harness too
...................

should turn out quite ballsy

or a nice set of slp intake runner

alrite well im pretty sure now im gonna go with a 350 lol..i just gotta find one. and for rolling thunder my 305 is the 230hp 300ft lb of torque version. with the t5 tranny and g92 rear diff with the 3.42 gears. I have 2 questions though now... Can you run long tube headers on that with a 350? and can the computer run anything modest? like lets say i wanted to put my tpi setup on a 350 with about 10:1 compression with like a .500 lift cam.. what would i have to do to the computer and injectors etc to make it all work???

Well to answer your question it depends on which TPI set up you have. There was the MAF type tpi set up from 85-89 which is fairly tolerant to mods and then there was the 90-92 MAP style TPI set up which is pretty intolerant to mods. Either way it would be a good idea to get a tune but if you have a MAF style TPI set up and the cam wasnt too radical (a lot more to it than just lift) you could probably get by however if its MAP syle TPI you will need a tune. Stuff like headers and exhaust you could do without much problem even with a MAP style TPI (although even then it would benefit from a tune). However im unaware of any manufacturers that make long tube headers for stick shift f bodys due to the clutch linkages being in the way. I have heard there out there though. Course either way it may not matter. Swapping to a 350 will mean that you need the PROM for a 350 or reprogram your current prom to 350 specs. If you were going to ]do the latter you could program it to match your new motor at the same time as well as eliminate emissions controls (cant really just un plug them and call it a day have to program them to not run) although i recommend leaving the emissions stuff as it really dosnt hurt performance too much and would keep you legal.

I have the MAP style TPI, and I have to buy a new prom for my engine now which my local gm dealer quoted me at a wonderful $350... does like a napa or something sell a generic prom that you can have burned?? and i dont need any emmissions stuff in Massachusetts...Just safety inspections anything without obd2.. And thank u for your good help so far

Well you already have a the prom its just a matter of getting it reprogrammed. If it was a tamer build (with MAF) you could have just bought the stock 350 PROM and been done with it although because you have MAP even if you bought a 350 MAP PROM you would still need it programmed. So just send the prom you have now in and give them your specs that should take care of the ECM part of things. What thell do is program it for the mods and to compensate for the fact youve changed to a 350.

thanks rolling Thunder..Do you know any companies that will do that?

Off hand not really i haven't had to deal with that maybe someone else has more experience in that area than me will speak up. I believe we have a site sponsor PMC for less that has done business with some of our members and yielded good results. You may want to try contacting them about what they can do and prices. Beyond that a Google search would be your best bet.

there are a couple on google search that you can send it to and they will do it

i think i might have seen a link on chevythunder.com

I'm kind of torn. I know someday I'll have to rebuild/swap but I don't know which to do. Would a rebuilding a 305 without any upgrades still be the same cost as swapping a 350? What costs are associated with building the 305 and swapping a 350?

rebuilds are generally cheaper, provided you don't have too many parts you have to replace, but, my question would be, if you are going to rebuild it, why would you NOT want to add some cool new pieces, to get more power? If you are feelin' froggy, why not get in to tuning your own proms? (caution, this practice seems to be highly addictive, and the folks that do so are endlessly tweaking their tunes..... to the detriment of interpersonal relationships. I.E. girlfriends/wives....) For what GM wants for one prom, you could buy the equipment to tune an infinite number of them. (although you really only need one, or two....) Just gotta have a laptop that will run windows 98..... which can be picked up for under a hundred bucks these days....)

The cost of just rebulding it will be cheaper and easier. If its fuel injected the electronic end of things must be dealt with to make up for this change which already makes the difference in the 305s favor of cost. Let alone assuming if the 305 isnt damaged beyond economical repair you have the 305 vs having to get a 350. I mean the way i see it these are the cheapest ways to do it. Rebuilding a 350 vs a 305 is basically the same cost wise so if you bought a used block and had it rebuilt you'd only be out the money for the motor which you might be able to find cheap. Or you could get a new 350. If you reused alot of the 305s stuff you could buy a GMPP short block fairly cheap (considering what your getting) and pull it off (though still costing more than just rebuilding the 305). The only real cheap way to do it is to just get a junkyard 350 and run it but i personally wouldnt as you never know what your getting and its too much work to find out the motors shot. Honestly if your considering rebuilding your 305 with no performance stuff it sounds like performance is a low priority and if thats the case the 350 just isnt going to be worth while because thats really the only reason you swap to a 350. If you were considering doing a performance build then it would be cheaper to go to the 350 as many of the new GMPP 350s already come with good stuff in them and its cheaper to buy it like that than piece by piece.

My reasoning: cost. I think it would be awesome to have a 350 but if the price is that much more expensive then I'm going to rebuild I have because the swap can always be done sometime down the road if I have the extra money. But if it's not a significant amount more than I'd go with the 350 in a heartbeat, but from what I'm seeing it gets pretty pricey compared to a rebuild.


And to Rolling Thunder, the extra performance is definitely fun which is why I would like to eventually do it, I was just trying to get an idea on which one is most cost effective until I have the money to start building up. For now I'd just like to get the car to what it should be.

The only difference you are going to see here, is the 350 itself. Rebuilding the 305 will end up being cheaper, simply because you already have it. Leaving out that particular consideration, it cost pretty much the same to rebuild either motor. You just get more bang for your buck with the 350.

What other costs are there? Fuel pump, would I need a different trans for the extra power, different injectors, ECM/PROM, other stuff? I have a friend with a 91 RS and the previous owner did a half ... job on a 350 swap and it seems like there is a new problem every day. I just worry about not getting everything I need in order for it to run like it should.

There was a post in the last couple days that had a list of everything needed to go from a 305 to a 350.... PROM, Injectors, Knock sensor, and some other minor stuff I can't remember. Check some of the other swap threads, or, try a search. It was an excellent write up.