I'm not terribly concerned about top end with 3.73 gears, but I am curious since most of my driving is on the highway (stock 3.23s). There is an HO car in a yard with the rear end in place ($50). Wise idea or would the gas mileage be prohibitive? Speaking of gas mileage, what does the L69 get?

JamesC

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I have an L69, some mods done to the engine that have made my milage a little worse, but even before that, my milage was absolutely pathetic.

I never exactly figured it out for highway and for in traffic, but my average before the mods was about 18 mph or so. And that's with mostly highway, and maybe 1/3 traffic.

With that in mind, I really love the L69.

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http://www.gruveb.com/z28

 

I've got a K&N and a Flowmaster 80 and I averaged 14.5mpg once, mostly city traffic. Kinda sucks, huh. I'm doing that a few more times to find an average of multiple times. I think I've got a 3.42 rear end though. For that reason alone I'm glad I don't have a 350 b/c this is my daily driver.

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1984 Z-28, 305HO 4bbl, t-tops, K&N, Flowmaster 80 Series with 3" tips. Planning a massive modfest. It's gonna be one gangsta of a street demon.

 

Dauntless,

It's my understanding that HO cars came stock with 3.73s (RPO GT4).

JamesC

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James

I asked about what kind of gears I had, and someone suggested to do 70mph in Drive (not OD) and if the tach read 3420, it meant I had 3.42s. The tach was reading almost 3500. But hey, if I've got 3.73s, that's cool too.

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1984 Z-28, 305HO 4bbl, t-tops, K&N, Flowmaster 80 Series with 3" tips. Planning a massive modfest. It's gonna be one gangsta of a street demon.

 

Dauntless,

If you're planning on headers any time soon, I'm looking for the L69 exhaust manifolds, complete with air tubes and heat stove--I'm trying to upgrade my LG4 on the cheap.

JamesC

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Top end? By the way, what are you guys running with 3.73s at 70 mph?

JamesC

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JamesC,

With 373's at 75 I am running 2250 rpm, give or take a few depending on wind, hills and so on.


------------------
http://www.gruveb.com/z28

 

Wow! I was just looking over some old paperwork I got when I rescued my car, and I found an old "Car and Driver" article comparing a 1983 L69 Z28 against a bunch of other cars. It says 17 MPG average, 134 MPH top speed, and 15.0 in the quarter mile.
If I had a scanner, I'd post it.

BTW - I think '83 was the first year of the "H.O." version, built to try and keep up with the 5.0 Rustangs of the time.

I also found one of those color photo dealer pamphlets that advertise the 83 Camaro line.

In 1983, only the BW T-5 was available with the L69, no automatic offered. And 3.73:1 rear was L69 only. The 1984 and newer offered more options like Auto trans, different gears etc....

BTW...I have a question about my muffler on the exhaust board if anyone could help.



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-1983 L69 Camaro Z28 305 H.O. (Bored .030 over,Teflon oil seals,Melling H.V. oil pump,Hyperetic pistons,chrome-moly rings,2040 Crane compu-cam) T-tops, 3:73 Open rear, BW T-5, Rebuilt E4ME 4 Barrel, Duel Snorkle Air Cleaner w/K&N Filter , Rhino Clutch, Crane 2040 Compu-cam, LS1 valve springs, porting, PST front end kit. Now for paint, interior, etc...etc.... Also:
2000 S10 4.3L 4WD LS
1995 Ford Thunderchicken, 4.6 V-8

 

Gruveb,
I think your tachometer is off. According to the equations page you would have to have 30in tall tires to run 2250rpm at 75mph. The equation shows you should be running 2600rpm assuming 26" tall tires and a .70 overdrive gear with the 3.73's.
later,
Craig

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84 Z28 305HO, 5spd, 222,000 miles, Edelbrock intake, Hedman headers, low restriction exh(w/cat), K&N air filter, 14.630 at 93.17mph
Del-A-lum front control arm bushings, Moog ball-joints, Energy suspension front sway bar end links, Moog rear sway bar end links, Eibach pro-kit springs, tokico shocks/struts, AU secondary rods
www.indycamaro.com

 

Craig,

New tach. It's not off. Scout's honor.
I'm not a boy scout, but seriously, the tach is right.

Speedo is right too. There are plenty of those displays that show your actual speed and the speedlimit.

Doing 2600 rpm, I'm doing about 85 or so, if I remember correctly. I know I am correct about the 75 though. I've checked it.


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http://www.gruveb.com/z28

 

I have 3.73s with a 5 speed also.

My speedo is inop but according to my equation above and the equations page, i am turning 2639 rpms at 75 mph. At 70, I am turning 2463 rpms.

My tire is a 245/60/r15 and is about 26 inches in diameter. The overdrive ratio in the T5 is .73 and when multiplied by 3.73 gear ratio, you get 2.72. This is the final drive ratio that you use when calculating these speeds.

Gruveb, unless you have really tall tires or do not have a 3.73, your tach is wrong, also, on the equations page, it asks for tire radius, half of the diameter.

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84 Z28 L69. 5 speed with 3.73 posi (broken)Ported heads, intake, 10:1 comp. 230/230 .480 lift cam @.050"

 

JamesC... As for top end, I ran my car to 4900 rpms in fifth. It was about out of breath, but to be fair, i was going slightly uphill and i probably chickened out before it stopped pulling.

This figures out to 139 mph and this gives me reason to believe there was more left because a stock L69 is supposed to go like 138 mph.




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84 Z28 L69. 5 speed with 3.73 posi (broken)Ported heads, intake, 10:1 comp. 230/230 .480 lift cam @.050"

 

Gruveb,
If I put 3.23 in the equation it comes out to the rpm you are saying. The equation page is here:
https://www.thirdgen.org/newdesign/t...ulations.shtml
If your doing 2600rpm @ 85 you must have 2.73 rear gears. Use the equations and you'll see what I mean. My car runs 2600rpm at 75mph.
You have a nice website. You might want to have your car dynoed to get a baseline before you try to estimate hp. Very tricky.
Hope this helps,
Craig

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84 Z28 305HO, 5spd, 222,000 miles, Edelbrock intake, Hedman headers, low restriction exh(w/cat), K&N air filter, 14.630 at 93.17mph
Del-A-lum front control arm bushings, Moog ball-joints, Energy suspension front sway bar end links, Moog rear sway bar end links, Eibach pro-kit springs, tokico shocks/struts, AU secondary rods
www.indycamaro.com