I just received a set of SLP runners and after some digging around on the various F body sites I've come to the conclusion that I really shouldn't put them on my car in it's current state.
Here's the current state:
LO3 305 with TPI speed density conversion
Stock PROM with TPIParts adapter
SLP CAI
Edelbrock headers, no cat, slp/Flowmaster exhaust
Stock 700R4 with TCI shift kit and vette servo
9 bolt with 2.77 gears
Holley AFPR
MSD ignition
A/C and AIR removed
I've been "told" that the runners will hurt low end torque and that I don't need them until I upgrade the cam and heads. I know the TBI heads are not a good choice for performance but I read comments stating that they actually do well with a TPI conversion.I've actually thought of putting some 1.6 rockers on to try and get a little more from the cam. The mainstream logic is to put a 350 in and call it done but I've never been one to follow the mainstream (hence why I own a Formula instead of a T/A or Z28). I've seen this combination once before and it seemed to be a stout little street performer, what's your thoughts on it for my 305:
Corvette "113" or World Products S/R heads or similar
LT4 Hotcam with 1.6 rockers
The SLP runners ported and polished along with the plenum
Edelbrock TPI base ported and polished
Definitely some tuning
Would you do this to an engine very well cared for but with 160K+ miles on it?
I already have 22# injectors in the car (adapter corrects for them) and I'm not sure I would need 24#ers. I've got another 9 bolt with 3.27 gears waiting to be gone through so some better gearing would be available but I would like to see how this would run with the 2.77s in the car now. I'm not interested in getting every hp out of the car nor am I a drag racer, I do however love a good torque curve and I love a snappy throttle so suffice it to say my main concern is performance on the street. I do take the car out on the interstate from time to time to stretch her legs and she does very well but I know she could be better. Give me some honest opinions here folks, a 350 isn't out of the question but I've always been the type to take the road less travelled. Thanks in advance for your input.

Bigger ports and bigger valves mean more hp & torque. However,it's where that power is made that will determine port volume and cam size that will be needed. I dont think the Hot Cam would be a good torque cam for a 305. It will make more toque,but it will be higher in the rpm range than you may want. Likewise,if the head porting is to much bottom end power will suffer because you dont have enough displacement to take advantage of the increased port size. Another thing to find out before you buy a set of heads is the combustion chamber volume. A bigger volume helps flame travel & the combustion process but it kills compression. I had a 262 V8 that was stock in a Monza I once had. I obtained a set of 300 hp heads (used on the early 300 hp 350's & 327's). These had alot bigger ports & valves than the stock 262 so I put them on there. The car ran sick. The small 262 used tiny combustion chambers since the cylinder volume was much less than that of a bigger motor so it was needed to get compression up. The 305 is in the same boat. The heads use smaller combustion chambers. Do some research on this before you buy. Slightly porting & cleaning of the stock heads along with a little bigger valves would be the thing to do if you cant find a suitable set. As far as cam selection goes,call your favorite cam maker and tell them what you are after. They will know better than anyone else what would work best.

As far as head choices go I'm leaning more towards the World Products S/R heads with 58cc chambers and 1.94I/1.50E valves and wasn't looking to do much in the way of porting them but moreso just polishing and smoothing them out with little if any changes to volume and such. After doing some more research I'm inclined to agree with you on the LT4 hotcam. I'll make the rounds with the cam companies to see what they recommend and then start the slow process of rounding up the pieces (as budget allows).

With that kind of mileage I wouldn't cam or head it. A good way to tell the condition of the engine is a compression test. I'd do that if you are going to consider doing the swap anyway. I hear you about building a 305, it can be done usually doesn't cost anything more then a 350, you just have to keep in mind they like different things because of the small bore. They actually like forced induction a lot. There are 2 people I know of with supercharged 305's in the 5-600 hp range!!! Also, when looking at cam specs they are usually rated for a 350, the same cam in a 305 will have a higher rpm range, just an FYI. TPI's are known to run out of breath in the 5280rpm area, with your runners/base probably 5500, but in a street application that is fine, just plan the combo accordingly.

To answer your question about parts though: I would lean towards the vette heads, they have much better flow potential, and can always be opened up in the long run as you go faster. Plus they are aluminum and will save weight. The new comp cams XFI grinds are really nice, I'll be running the XFI280 in my 355. The XFI260 is an excellent choice and the XFI268 would be on the extreme side. I would shy away from porting the base and runners, just match them to each other and maybe siamesse the plenum to match the runners. Those parts will flow enough for the 305, and making them any bigger will cause a loss in low end torque, and with a 305 it is the exact opposite of what you want to do, especially in your street and 2.77 gear application.

-Jim

With all the info I've been sorting through from the various F body boards I'm giving serious thought to putting the runners up for sale and stepping back from the idea for a while.