ok guys i have a LG4 (Class H) and i was wonderinf how much horsepwer the folling would provide

1. hooker competition headers
2. flowmaster 40 muffler
3. Holley Competition intake manifold
4. holly 4150 750cfm carb

also what are some of the best power adding parts

 

If you slap on some headers and a full 3'' exhaust with a performence muffler, an edelbrocker performer manifold(never heard of a holley comp. manifold), and just tune your Qjet ( a 750cfm carb is way to much for a 305, the qjet is more than enough) you could probably gain around 40 hp. Good Luck.

 

If you change the carb, then for best results, you will also need to change the distributor, to a non-computer-controlled one. IMHO yanking off the carb and slapping another one on there is not a real high bang-for-the-buck move.

Exhaust, all the way from the heads to the street, BUT NOT FOR LG4; then a cam; then a torque converter; then gears; then head work. Somewhere along the line, a dual snorkel breather from a L69 Z28.

After you've done all that, then maybe a different carb would be an upgrade. Until then, it's not the bottleneck, so leave it alone, and work on the parts that ARE the bottleneck.

 

Looking at other people's results, I'd say just adding a good exhaust to your car (headers and a catback) would net you at least 25-30HP.

 

When I took my CC carb off my 86 Camaro I was a happy man. I put in a 600cfm Holley and was just happy that I wasn't dealing with the computer anymore. I can't say that I gained gobs of horsepower but it sure felt good to get rid of the cc carb. My 305 did ok with that 600 with some tuning . Then later on came the biggest change to my engine , I switched to a 383. I installed Hooker long tubes, 3" two exhaust pipes , tci converter ...oh well, take a look at my sig and my mods are included.

 

oops sorry . I guess I changed my sig .

 

Agreed. Find an exhaust system for a 305/350 TPI or an L69 motor, not one for an LG4.

I saw a few posts up someone said not to use a 750cfm carb... I don't see whats wrong with that. The stock Qjet is 780cfm.

 

There are only a few Qjets that are rated at 780 cfm. None came on 305s. The average QJet on a 305 has the potential to do 750 cfm but I think GM did something to limit them to 680 cfm or so.

RB meant to get a header and exhaust system meant for a 350, not the so-called 305 headers, which are only 1.5" in diameter. The good stuff has 1 5/8 primaries. The intermediate pipe should be 3" then a good high performance muffler. Some of the car mags have claimed to get 40 hp or more just from decent headers and exhaust on an LG4.