I have a 305 in a package that, according to GM, made 230hp and 300lbs torque when new. I have a 3.42 posi rear-end with 5-speed and as a whole this package works really well. In fact a co-worker has a '97 LT1 that I can keep up to without much ado until around 60mph (after which all I see is his tail-lights). I find my 305 setup to be great for 0-60 but obviously not much use in the 1/4 -- it lacks the roll-on power of a 350 as well.

Question:
If I wanted to swap out the 305 for a 350 and didn't want to change anything I absolutely did not have to -- could I keep my reciprocating gear, get new pistons, rings, bearings, etc, and substitute a 350 roller block for my 305 block ?

I suppose the 305 heads would then be a liability. Would these have to be swapped out for some decent 350 center-bolt heads ? Has anyone built power out of these heads ?

I'm not specifically trying to built an HP motor but am looking for about 350lbs torque (aka '91-92 L98s). This has to have been done by someone before -- any comments ?

Thx in advance,
RP.

Unless your planning on racing circle track, you should prolly forget about 305 heads on a 350.

As for the reciprocating gear... it's balanced for a 305, so you would need to have the rotating assembly re-balanced if you wish to reuse it in a 350. It is prolly cheaper and smarter to get stuff that's already balanced for a 350.

Bottom line as with most car stuff is you get what you pay for... shortcuts usually burn you in the end.

I'm not sure what your budget is, I think your best bet would be getting a re-man tpi long block. Then remove the mystery cam that it will come with and replace it with a regular LT-4 cam. The 305 heads would probably hold you back. The B2L 350 heads can be made to work quite well. If you where to have a valve job done, the bowls cleaned up and the decks shaved to a real 60-62cc's, LT-1's would be easy pickin's. You will need to get the 350 knock sensor and a 350 prom for it to run properly. An "off the shelf chip" for a 350 would work (SLP's are on sale for $65). You could also retain your stock 19lb injectors. I expect you would be well over 350 ft/lbs

how about my non computer controlled lg4 what would i have to do to switch to a 350 remember i have no computer

Step #1.........Remove 305

Step #2.........Replace 305 with 350

Step #3.........Install 350

Step #4.........Tune carb for bigger engine

Step #5.........Replace entire LG4 exhaust system

Step #6.........Abuse imports

You've got it easy Hughes BTW, I think you do have an ECM, at least you should. I thought they went to the 'puter contolled carbs in '86

canadian lg4 are not computer controlled and my carb has no electrical hookups. My exhaust is already changed

Oh, my bad. A 350 does not deserve to have LG4 exhaust bricks bolted to it. Are you thinking of a swap?

Its on the list but my first priority is bodywork and paint. I am getting 2 new fenders and a ram air hood maybe a different spoiler

I didn't know that I'd have to have the crank re-balanced. Guess that means a new dampener too ? If I do the swap it sounds like the heads should go so why bother keeping any internals -- just buy a new long-block and have it done with.

I am trying to avoid short-cuts but don't want to waste $$$ either. Having built up a few cars already I am reluctant to make a decision to spend the bucks yet KNOW that come spring when I put the car on the road again I will want more power and as you point out there really are no short-cuts.

Waffling, mulling it over,
RP.

I have a healthy budget which means within reason I can pretty much do whatever I want to, to make more power. It sounds like you have built this motor before ? Or one like it ? I haven't built a 350 in about 8 years so am pretty much out of date on cams and head combos. I think whatever I built I will want to take advantage of SLPs shelf for parts.

I am waffling over the swap -- whether or not I want to dump a low mileage (70k) 305 that does not leak or burn oil and runs perfectly, for a custom built 350 that will probably cost me about $5000-6000 CDN before I am done.

I was considering this -- what about putting a blower on my 305 ? That way I can run another 30-40k on the existing motor and when it starts to pack it in upgrade to the 350 and use the blower on it too.

Has anyone on the Ontario group blown a TPI 305 before ?
Comments ? Suggestions ?

thx,
RP.

Hey Paul, I was understanding that from 1986-1987 LG4's had come with the feedback carburetor that was controlled by the ECM. My '87 used to have this setup, but was butchered by it's previous
owner. In order to eliminate the feedback, they had to replace the original distributer with an older model ie. from an '85 LG4. I know another guy who owns an '87 Formula with the feedback setup, and he says it works great.
The electronic feedback was GM's experiment into
computer controlled F-bodies. They eventually came out with the TBI and then TPI. Either way we look at it, it's still an easier swap to a 350 than if it was TPI.

Blowers are great but they reduce engine life on stock short blocks. But, the power they add is undeniable. If you choose to go with the 350, I'd recommend the GMPP ZZ4 partial engine. It's the short block from the ZZ4's and RamJet engines. I'd then add a well suited set of heads and cam. SLP's shelf for parts is getting a little thin these days. I wouldn't be surprised if they completely move away from thirdgens in the next year. Just wait until they start making Mustang parts next year.