As I Live & Breath (427/390 Auto w/ 3.08 final Drive) Yeah...Me!

[Bob S.]

First off, I want to thank all of you for your input. I'm the guy looking to change from a 3.08 Final Drive to something lower for more off the line. My mechanic was dead against it....I received so many responses from this forum, my head was spinning...Don't get me wrong..I appreciated each and every one.

That said, ONE of the reasons my '68 was in the shop was for a new carb. I got a call from the mechanic, asking me to come be and test drive my car. Seems when he was removing the old carb, he noticed a few things that were not kosher...Remember, this car is very new to me. After explaining a few things to me, he says..."So, what I'm thinking is, you've been driving this car with only TWO BARRELS!" He was almost sure the back barrels weren't opening when "CALLED UPON"

I started her up, took her out and headed for a strip of road that was to be, "Pretty safe for what you wanna do"....and, it was far enough away to let the engine warm up very nicely. Well, I pulled over, waited 'till it was clear, started a slight roll, and HAMMERED her!!!!!

Like I was driving another Vette all together!!! This thing squatted, broke lose a bit and took off like the preverbal BAT OUTTA HELL!!!! 3.08's and all, she was pulling like the Tiger I knew she had to be!!! Three our four times, same routine...just to make sure I wasn't dreaming....

I came back, (No lie) took the paper off the floor, spread it out on my mechanic's floor, knelt on it and BOWED IN HOMAGE, to the man who knew all along I wouldn't be happy with a 3.55! He was right.

Neither of us knew the carb was that bad off, but once the new one was installed and all four functioning, I now have my rip snorter, and a great final drive for the freeway as well!!!!!

Thanks again for all the input...Just wish we'd had an idea WHY my car was not performing like I knew is should!

Bob

(9944)

[Chuck G.]

Re: As I Live & Breath (427/390 Auto w/ 3.08 final Drive) Yeah...Me!

Sounds like you got to the basis of your problem.

It's fun to punch it and hear and feel those rear barrels open up.

Chuck

[Larry M.]

Re: As I Live & Breath (427/390 Auto w/ 3.08 final Drive) Yeah...Me!

Bob:

Glad you and the mechanic got it sorted out. If you do some additional "tune up" measures that were recommended, you may pick up even more horsepower.

But just think about this same ride with a 3.70 rear gear and a high stall converter.

Larry

[William C.]

Re: As I Live & Breath (427/390 Auto w/ 3.08 final Drive) Yeah...Me!

If you really want to top it off, blueprint the distributor curve if you haven't already.

[Bob S.]

Re: As I Live & Breath (427/390 Auto w/ 3.08 final Drive) Yeah...Me!

sounds like you got to the basis of your problem.

It's fun to punch it and hear and feel those rear barrels open up. :d

chuck

without question!!!

[Bob S.]

Re: As I Live & Breath (427/390 Auto w/ 3.08 final Drive) Yeah...Me!

bob:

Glad you and the mechanic got it sorted out. If you do some additional "tune up" measures that were recommended, you may pick up even more horsepower.

But just think about this same ride with a 3.70 rear gear and a high stall converter. :d :d :d

larry

just may do that!!!!!

[Bob S.]

Re: As I Live & Breath (427/390 Auto w/ 3.08 final Drive) Yeah...Me!

If you really want to top it off, blueprint the distributor curve if you haven't already.

Just might do that!!!

[Michael J.]

Re: As I Live & Breath (427/390 Auto w/ 3.08 final Drive) Yeah...Me!

A very interesting story. When I first got my '67 L71, I too thought the 3.55 in her was not enough to make her snap, she seemed docile off the line without the fire and fury I expected from this solid lifter monster motor. Then a friend reminded me it was just a 2 barrel car until you got her above 4000 rpm, and the vacuum actuated 2 other 2 barrels opened up. I then just floored it and held on, and when those other carbs were open, it was a true monster motor alright, sounded like a supercharger had kicked in. It was a thing of beauty all the way to 6500 rpm to the next shift point.

[Paul H.]

Re: As I Live & Breath (427/390 Auto w/ 3.08 final Drive) Yeah...Me!

Glad you sorted it out. When I bought my 68 427/390 with a Turbo 400 and 3:08 rear 7 years ago it just wasn't doing what it should. It was the carb. After sorting that out I am very pleased with the acceleration. Plenty of pull down low and the 3:08 keeps the revs down on the highway. To me it's the best of both worlds.

[Steven B.]

Re: As I Live & Breath (427/390 Auto w/ 3.08 final Drive) Yeah...Me!

A simple, and no cost, way to improve acceleration is to bend the tang on the carb linkage and elongate the hole to cause the secondaries to kick in faster. It makes a noticeable difference. After ignition mapping this is the second modification I made. This mod. may be in the Q-jet book, I can't recall. If you want to highway cruise it will increase your fuel flow ($).

[William C.]

Re: As I Live & Breath (427/390 Auto w/ 3.08 final Drive) Yeah...Me!

Distributor mapping is a MUST on any of these old beaters. Most of them didn't meet their target curves when they were new.

[Steven B.]

Re: As I Live & Breath (427/390 Auto w/ 3.08 final Drive) Yeah...Me!

That is right! In my case the map from the factory to spec. I wondered why it wouldn't accelerate with the 3.55's. Ignition was the culprit. To further improve acceleration I installed a B&M reprogramming kit. Mods are still in it nearly 36 years later.

[Kenneth B.]

Re: As I Live & Breath (427/390 Auto w/ 3.08 final Drive) Yeah...Me!

Glad you got it figured out. Old carbs are ususlly the sorce of the problem.

[Chris H.]

Re: As I Live & Breath (427/390 Auto w/ 3.08 final Drive) Yeah...Me!

I enjoy the "kick" of Rochester secondaries opening up, actuated by its mechanical linkage. It's not as smooth as the vacuum operated Holley secondaries.

My '70 LS5 will chirp the tires when the secondaries kick open.

[Tom L.]

Re: As I Live & Breath (427/390 Auto w/ 3.08 final Drive) Yeah...Me!

Had a similar problem with my '72 LS-5. Turned out that the last owner used real thick insulation under the carpet. The secondaries barely cracked. Have fun, I am now!!!