I Have a 305 chevy s/b that i'm gonna build up to put into my 1985 firebird. what i want to know is what kind of pistons would be best suited for this engine that will bring the compression up to about 9.5 to 1. The block is already bored .030 over. Also i want to use the same cylinder heads that are already on the engine they are the cast iron 1.84/1.50 valve size heads casting no.14022601. Thanks in advance for all your feedback.

PS. i dont want to go out and buy a 350 block for this car i want to keep the 305 in it.

 

The '83-'86 L69 and '85-'86 LG4 had 9.5:1 compression. So, pistons for either of those specific applications, along with the proper shim-type head gasket, will result in that compression (slightly higher with the .030"-overbore, but not enough to quibble about).

 

thanks for the info now i just need to find some part numbers for the pistons and camshaft used in the LG4 engines.

 

I think you're short-changing yourself out of the cheapest power money can buy.

You will have a minimum of $2000 tied up in this before it runs again; I can guarantee that. You'll run up a $400 bill at the machine shop on block work alone. So, just for the sake of it, let's assume that all your parts, plus all your labor, plus any other costs such as fluids, misc parts you "might as well" replace like water pump and spark plugs and hoses, comes up to $2000.

You can buy a 350 short block core for $100. Every other piece - EVERY OTHER - costs exactly the same as for a 305, or less. So if you build a 350 under the identical circumstances, you'll have $2100 in it.

$2100 - $2000 = $100 that's the incremental cost in increasing your inches.

Let's also assume that you build a killer 305, and come out with 1 HP per cu in. OK, you got 305 HP for your $2000.

Now let's assume that you take those same parts and build an equally killer 350 with 1 HP per cu in. For $2100 you get 350 HP. That means those extra 45 HP cost you a grand total of $100.

Rule of thumb for a rough evaluation, is that if you can get HP for less than $10 apiece, it's a good deal. Yet here we are looking at a simple, easy, readily available upgrade, that gets you 45 extra HP at just over $2 apiece.

That's the cheapest power you will ever be able to buy.

Why would you not want to step up and claim your 45 HP at $2 apiece?

But if you're determined to short yourself out of what you could get for your money and instead you want to deliberately settle for less and get beat by people with superior arithmetic and/or decision-making skills, you'll find it very difficult to buy any kind of performance parts for a 305 (pistons specifically) because there's so little market. About the best you can do is the Sterling / Speed Pro hypereutectics, which are available in flat-top with 4 valve reliefs.

 

you're not going to put it together with the stock cam are you? If you have it all apart anyway, why not put a better cam in it. It would really compliment the ported heads.

 

Now, I didn't say anything about the camshaft.

I love the cam I've got in my car now. If you go off and put an LG4 cam in this engine, I'm not speaking to you anymore.

You don't "need" a p/n for the pistons. Just ask/order them for the application (I'd say "L69", VIN code "G", if I were you).

FWIW, the '82 & '83 LU5 also had 9.5:1 compression.

 

Forged, flat-top, 4-valve relief, .030"-over 305 pistons http://www.partsamerica.com/PartDeta...e=1268&PTSet=A .

Almost $90 a piece.

 

No i'm not gonna use the same cam i just wanted to know what works best with the LG4 pistons

 

http://store.summitracing.com/partde...rt=STL-H534P30

 

You say that your engine is on roids what is your set up (pistons cam lifters ect.)

 

RB thanks for the info on the pistons as far as the 305/350 change goes i want to keep the 305 in the car because that is the same as what was offered in 1985 and i want to keep the car as stock as i can.

 

In the sig of my first response.

Bottom end is completely stock (crank, bearings, rods, pistons). Cam, oil pump, oil pan replaced as noted.

If it wasn't stock, it wouldn't be there (it would be a 350).