Hi all - great forum !!

I just picked up a sweet '73 vert with an LS4/TH400 - I think the rear-end on it is a 3.77 (not a factory combo).

The car runs well and I'm using it as a daily driver on my blissfully short commute. I'd like to juice it up a bit without losing the reliability I've got and without dropping a brick of gold into it. Any suggestions?

thanks!

 

The first thing you should do is get a set of headers and a 2 1/2" exhaust on it. If you want more do a street port job on the heads.

BigBlockk

Later.....

 

That is a great start. The rear is a 3.70 (GM gears) or 3.73 is the aftermarket gear. Also make sure the dist is set correct and you have a good advance curve. If the dist. has some miles it probably is out of adjustment.

 

Headers & cam.

 

Won't headers change the low RPM performance - what's the tradeoff here?



As in smooth and polish the intake manifold? What should I expect to pay for that / what am I gonna get for it?

thanks!

 

Then it's a 3.70 - thanks (I know it's GM).


Ok, thanks for the tip - I'll go read up a bit.

 

There is no performance trade off with headers. Any modifications you make that increase performance will put more demands on the exhaust system. It is a good idea to get this one out of the way early on. A good exhaust system will help everything that comes later perform better.

No! A street port job is done on the cylinder heads. Take a look at this for more info. http://www.sa-motorsports.com/diyguide.shtm
It involves smoothing (not polishing) the area just under the valve heads. This area is a very complex casting with many ridges and folds that need to be blended and smoothed to allow the port to flow more air/fuel mixture and exhaust gas. It's also a good idea to match the runners in the intake manifold to the intake ports in the heads. This is worth a few hp. This is also a good time to get a good three angle valve job. I have no idea how much a port job costs, I do all my own work.

All in all headers are worth about 15 to 20 hp by themselves. The same goes for the port job. But done together they can add up to 50 or 60 hp. If you reach this point you will probably not be able to afford a camshaft, intake manifold and carburetor because you'll be spending all your money on rear tires.

BigBlockk

Later.....

 

I can already "sit" at a green light as long as I want - just looking for a bit more .

Thanks for the advice.

 

Here's what you can do in afternoon to wake up the ol' 454:

1) Ignition...trade the points and condensor for the Pertronix conversion kit...part # 1181. Use the pertronix coil as well...part # 40011. Plug Wires...use the original braided AC/Delco wires...part #458W. Plugs...I like Autolites, part # 26.

2) Carb...change the secondary metering rods to "DA"s...(.044"). Replace the little POS carb filter...AC Delco part # GF427. Change Air Filter, AC Delco part # A329C.

3) If street legal isn't a concern, remove the AIR system (if it's still there).

4) Make sure your cowl induciton is operational. If you'e missing parts or air cleaner parts to make it work, try ebay. CI makes a good bit a diff at WOT.

Down the road:

1) Heads...GM Performance Alum Oval Port heads, part # 12363392
2) Pistons...a good forged set to bring you up 10 or 10.5:1 comp ratio
3) Intake...finda a GM Q-Jet Aluminum low profile (will fits under your hood as your original, and can still utilize the cowl induciton system)...casting number 3937793 or 3947801.
5) Headers...I like long tube Hookers...1 7/8 primaries.
6) Use the original Q-Jet rebuilt to "Doug Roe" performance specs (if you don't have his book, " Rochester Carburetors" you should get it...good stuff)
7) Cam...how about a Comp Cams 280H Magnum...should work well with your auto and raise the usable rpm a bit to work with your 3.70's.

Paint the heads and intake "Chevy Engine Orange" and with the stock appearing ditributor, stock air cleaner, etc, you'd have a very rowdy sleeper.

Sounds like a fun car!
Wes

 

I am also planning to wake up my stock LS4 a bit when I get home late next month. Consider Edelbrock's 100cc Al heads. Those plus the stock pistons (implying no need to rebuild bottom end...do a compression check, etc) will get you in the mid 9's for CR. I have a few posts running considering my plans...