694speed350

tpfarm

Hi Jordan , I also bought a 73 L82 about six months ago, welcome to the forum and the 73 club. Google the "73 spot" and you will find a plethora of information on the 73. I know my 73 4 speed M21 came with a 3.70 rear gear as standard and a 3.55 was available as an option for economy. Do check the bottom of your diff for the numbers but that will only tell you what came in it from the factory . You can jack the car up , mark the drive shaft and then spin the rear wheel once while counting the revolutions of the drive shaft. If it turns just under 4 revs you probably have 3.70 .

gbvette62

Years ago, I had a 74 L-82, 4 speed car, with a 3:70 rear. It was all stock, with about 35,000 miles on it, and turned mid 14's in the quarter. L-48's were were about a second slower. For the time, the L-82 was decent running engine.

The gear ratio in your car, was partly determined by the transmission and options.

73 L-82's with the wide ratio (2:52) first gear, came standard with 3.55 posi rear. A 3.36 was offered as an optional economy ratio, and a 3.70 could be ordered as a performance ratio, if you didn't have air conditioning.

If your L-82 came with the close ratio 4 speed, the standard rear was the 3.70, and the 3.55 was offered as an economy option. Having air conditioning, didn't effect the ratios available, when ordered with the close ratio trans.

Automatic backed L-82's, came with the 3.55 rear, and the 3.36 and 3.70, were both offered as options. Like the close ratio 4 speed L-82 combination, air conditioning didn't effect the rear end ratios offered, when ordered with an automatic.

Jordan73

Thanks guys. I will be getting under the car this afternoon to check out the rear diff.

I have a buddy that is selling an edelbrock performer aluminum intake for $50. Aside from a reduction in weight vs the stock cast iron, will there be any performance gains?
Is this worth buying or should I just stick with the stock intake and quad jet carb?

Jordan73

Also, what are the best performance parts to add while the motor is still in the car?

Shark Racer

I think it is worth buying, yes, but would hold off on installing until you had a tangible reason to do so. IE, vacuum leak, cam swap/replacement, etc. You may gain 1-2 hp if that.

Headers and ignition recurve. If the carburetor is poorly tuned, getting it correctly tuned will also be worth a fair bit of performance. Despite what Mike Ward said, I measured a sizable improvement in 0-60 times switching from manifolds into dual 2.25" exhaust (with cats) to headers. With dual 2.5" exhaust it would be even better. The 0-60 time went from a 7.1sec average to a 6.5 sec average. This was with an L-48. An L-82 would benefit even more as it pushes more air.

The L-82 already has a pretty good cam which is already maxing out what the stock heads can support. I'd say to do a cam and head swap in lieu of just a cam swap, but that's a much larger bit of work than swapping in a pair of headers.

Jordan73

What do you mean by intake re-curve?

Shark Racer

Oops. ignition re-curve.

LS4 PILOT

Back in the 70 s , yes before LS motors and such ....we use to hop up our cars ......

I bought a set of 65 Fuelie heads , had them tweeked, and installed on my 74 350 back then it was pretty fast or wild . The builder did everything ....he was a short track engine expert builder . I think he used a 350 350hp hyd.GM cam.

All I know is it was very fast and loud and I was one lucky teen I didn't kill myself .

Headers, higher compression, mine had cherry bomb mufflers .....it was loud and obnoxious ....as described by my then girlfriends father

Lobzila

Jordan, I just went through engine hell myself and feel your pain. Find a local builder and see what he can do for you to get you the most bang for your buck. You can find some local deals when you look. My builder had a guy come into the shop with a pair of GM Aluminum heads with brand new bronze guides and valves that he let me have for the pair for 700.00 for my 454. Leave your motor alone for now and enjoy your car. Shop around and find a good builder. It will be cheaper than a crate motor and if you have a problem with the motor you have someone to take it to locally. Summit, Jegs, are good as well, but if you have a problem with the motor, you have to ship it back to them. Warranty service has improved from what I have seen, but you can find builders all over who do great work, it will cost you less, and a local point of contact. Enjoy the car now, build the motor of your dreams and then drop that in there and scare the neighbors. Good luck.
Also when you get the monster motor in it, make sure the brakes work well.

Jordan73

I'm fine with using the car as it is, it's a blast to drive! My plan is to "collect" some performance parts throughout the summer and then work on it this winter. (Not much else to do in the winter in Canada!)
I might do something with the exhaust yet this summer as it is bone stock and while I don't want something too loud, I do want some rumble!

Overall I'm very pleased with my purchase. Its pretty hard to find a '73 that hasn't been messed with in some way. Other than being painted from the factory silver to red, this car is 100% original and everything works. No frame rust, no bird cage rust, tight steering and suspension, I've completely fallen in love with my car!

Jordan73

So I've decided that first on my list is exhaust. I want to run ceramic headers but I don't know which brand would be best. I looked at the Patriot shorties with down pipes as part of the Magnaflow package but was told they don't offer much performance gains beyond stock. The shop in town was trying to sell me Hooker long tubes but I'm worried about ground clearance. I was thinking a nice mid length, can anyone steer me in the right direction? Then for the rest the local shop recommended a "crossmember back" kit from Pypes. What does everyone think?
I want to run midlength ceramic headers, electric exhaust cutouts, and then whatever for the rest that will give me a stock look with a decent growl. Also, I want to run whatever system is going to go in the nicest and fit best. I'd like to maximise the performance gains and money really isn't an issue. (within reason!!)
Keep in mind my car is a 73 L82 with a 4 speed.

Thanks guys, I'd appreciate all the help, advise and guidance you can offer.

Revi

You may find this article interesting. The L82 is just a lower compression version of the 1969-70 L46. There's only about a 40hp difference between them. http://www.superchevy.com/how-to/eng...g/viewall.html

L46 - 351hp/393tq (Gross)
L82 - 313hp/355tq (Gross) 250hp (Net)

I don't know all of the differences that exist between my rebuilt L46 compared to the L46 used in the Superchevy article, nor do I know the difference in Lab dynos used. So this may be a bit like comparing apples to oranges, but my rebuilt L46 with 10.4:1cr made 341hp/387tq. I was within 10hp/6tq, pretty close considering the variables.
The cast iron intake manifold does limit max horsepower to around 350. It just doesn't flow well above 5600rpm.
So if you want more than 350hp, you'll need to change the heads, cam, intake manifold and up the compression a bit.

As for headers, that's up to you. A nice 2.5" under car exhaust with N11 off road mufflers will give you a nice sound and won't cost an arm and a leg. I believe Corvette Central, Paragon, etc., offer similar systems in the $350-$400 range.

Shark Racer

Ground clearance is worse with long tubes, but not much worse. What kind of situations are you worrying about? I've been running the Hedman 68301s in a lowered car for over a decade; they only scrape on REALLY nasty speed bumps or lots with very sharp apexes on entry.

Jordan73

I saw a couple of pictures of C3's with the Hooker long tubes installed and when looking under the car from the side the collector flange was only like 2" from the ground. Do you have any pictures of your headers? I just want something that is going to install without having to dimple or tweak, and keep ground clearance within factory spec or close to it. I don't want to spend money on nice shiny ceramic coated headers and then be scraping them all the time. I live in Saskatchewan remember!

Jordan73

Anyone else run electric cutouts on their C3? What brand did you use? Location? Pictures? Thanks in advance.

AirborneSilva

I took off a set of unknown type headers and put on a set of the headman headers, the unknown never scraped but the headman's do a little so I have to be careful when going over speed bumps.