305 engine suggestions

Before anyone tells me the 350 is better, I know this and am just building the 305 since I got sort of screwed on the deal and the 305 is in very good shape with little wear. I was planning on rebuilding what I thought was a 350 out of my '89 T/A to a near stock rebuild with a few performance enhancements to get a little kick out of it. Now I find Ive got this 305.
Anyway, I want to build a reliable everyday fuel efficiant motor with a little more kick than stock. That was my plan with the 350, except it had more to begin with. I want to keep it a low end to mid range torquer that it was from the factory so my off the line is quick even though I don't plan on running quarter miles with it really. Essentially, I want a fast off the line car up to speed limit.
Right now I plan on dumping the A.I.R. system crap and rerouting the belt to get rid of the A.I.R. pump. I am going to put more or less the stock cam from a 350 TPI corvette/Trans-Am setup in (its the hydraulic cam which is at least one bonus to this letdown). I am also going to put the Edelbrock street legal headers on it. I want to port the intake and exhaust to match the gaskets and polish it up a little while I'm in the heads, nothing crazy, just a little better than it is stock. My question is this, what compression ratio does this come with and how hard would it be to bump it up about a point, like from 9.5:1 to say 10.5:1? What ignition would go well with this setup? Any other suggestions? Thanks in advance.

Hot Rod magazine (or maybe car craft) built up a 305 a couple of years back and made a 300 hp 305. I highly reccomend digging up this article.

as for compression ratio, it would help to know what engine you have. then it's just a matter of looking it up. example- the compression ratio on the LG4 305 is lower than the L69 305. these were the 2 enngines offered for the T/A in 1984. (I don't know them offhand, but they can easily be looked up)

I'd guess your 305 is in the 8-8.: 1 range.

Furthermore, if you plan on running over 10:1 compression, you may want to consider some aftermarket aluminum heads to keep the ability to use pump gas. Iron heads may require even higher octane to suppress detonation (the aluminum draws the heat away faster than the iron which keeps temperatures down and reduces detonation)

ways to increase compression can be any of the following: reduced head gasket thickness, milled heads, swapping heads with smaller chambers, swapping pistons, longer connecting rods, larger throw crankshaft, etc..

of course, if you mill your heads then you create alignment issues with the intake manifold and valvetrain geometry. you need to also machine the intake and set up the valvetrain. not for the novice engine builder

if you swap pistons or increase stroke, then you need to be sure you maintain clearance from your valves.

I would reccomend you call edelbrock or the like and see what kind of "performance" packages they have. chances are, they have a cam, intake, and possibly heads you can bolt on to give your 305 some pep. it'll be engineered to work together (which makes it so much easier) and then you can run harder.


for the power you'll be making you can retain your HEI distributor. you could swap in a better coil or a unit like an MSD 6a or 6AL control unit. they also make an ignition module that replaces the stock version that locates under your distribtor cap. also include a good set of wires and plugs for maximum efficiency.

the headers will be good, but be sure you also include a good cat back system too. the headers will be worthless if they're corked up further down the exhaust system.

I hope this is helpful!

Yes, thanks. Any info. is helpful. I am not trying to run over 10:1 compression, I just wanted to add some to whatever the stock number is. so if it is at 8.5:1 than 9.5:1 is what Id be looking for. I dont mind having to run a 93 octane, but Id like to stay away from having to buy race fuel...like I said, it is just a 305 and I wanted to add a little to stock not race it or anything. Im also not looking to spend too much money on an engine that doesnt respond as well as a 350. So aluminum heads and kits are a little past my budget. I might have done it with the 350.
My other question then I guess is my engine is an '88 305 with an LB 4 head? maybe...it wasnt the LG4. Im pretty sure it was a "B" in there. Anyway, it has a standard ignition with seperate coil. I was thinking about putting an HEI in there or at least a stronger coil though Im not sure it will be completely necessary with the mild upgrading I plan on doing. The biggest or most radical modification I was planning on was installing a 100 shot nitrous kit maybe. Not enough to blow the engine apart, but enough to bring her back up even with a stocker 350 probably. So I will probably just use pistons to raise the compression to whatever pistons alone are capable of up to the 1 point over stock, the cam, some head work to increase efficiency, and dumping the emissions. Anyway, all the advice is appreciated.
I actually forgot about the geometry involved in head shaving til you mentioned it...I can see it now. I would have been sitting there trying to bolt on an intake thats off just enough to piss me off and then realizing what happened... its been a while since I built my last engine.