Technical Piss-poor mileage from a 700r4 ??

I have the TCI throttle/tv bracket, as well as their TV cable corrector for the edlebrock carb, so I don't think that is an issue

 

Good. Just making sure. That can be an expensive omission.

 

Somewhere on the net I had read that the TV cable really only has one setting, that it's not meant to "tune" the shifts . Is that correct?

 

Technically, yes, it has one correct setting. The adjustibility is not for tuning, but to accommodate manufacturing variances.

Tuning shifts should be done via the valve body plate, and the governor.

 

It sounds like your TV adjustment needs a little work as mentioned here. That said, I've never gotten particularly good milage out of Edelbrock carbs, and while they've always worked (as in the engine starts and runs) I've never been excited about the performance or milage. Maybe see if you have a buddy with a Holley or a 500 cfm Edelbrock with smaller jets in it. If you're running a 305 to begin with, I doubt high performance is your first priority.

 

I'd just go with the 3.08 and forget the 700r4.

 

and only if he runs highway speeds where it is in 4th gear and lock-up. Around town he will see no difference in mileage.

 

Google 700R4 TV cable adjustment. The constant downshifts (when it seems unnecessary) is an indication that the transmission thinks that your throttle position is something other than what it really is, so it downshifts at the wrong time. All this talk about changing the transmission back out is silly. For a 2500 pound car, the rear end gear ratios and tire sizes should not have that much affect on proper shift points, unless your 305 is VERY low on torque, causing you to have to push your gas pedal down more to maintain speed when you are in lockup. Another poster mentioned that you should be sure that you really are going into lockup at highway speeds. Mathematically, the new transmission, at highway speeds and with lockup working, there should be no difference in your mileage. If that excess energy in mileage drop is not getting to the wheels, I'd expect your transmission to catch on fire sooner or later.... haha....I can only guess that you never are going into lockup, but that's just a guess at this point. Hell, upgrade your engine to get more torque if that's the problem - high torque cam, be sure timing is correct, be sure your advance is working, etc. I'm running a 2.08 Jag rear end with 700r4 in a 3600 pound car, but with 383 stroker (torque out the ASS) and it runs juuuuust fine. Just thought of something. Find somebody with a chassis dyno and run the numbers on what's really going on. Just my two cents.

 

As others have said, rpm is everything. Lets review, 3400 pound car,305 engine,edl carb,308 gears in the rear. Non aerodynamic body .

Low rpm mpg works with fuel injected, computer controlled engines, not with carburetor engines with vacuum advance distributors, or mechanical advance for that matter.
Make sure the spark plugs are set and clean, make sure the timing is spot on, make sure the carb is set and working perfectly, have a large clean air filter.
There are calculators showing rear gearing and rpm somewhere on the internet, find one and enter tire diameter, desired engine rpm and that will calculate rear gearing at a selected speed. Play with that calculator until you have lets say, 2400 rpm at 65mph, 2400 is going to give you full spark advance and no lugging and no wasteful over revving. The 700 has a 0.72 over drive gear which must be entered into the math to get the correct rpm. Who knows, you may find the th350 is a better choice. The 700 with let's say 4.11 gears should be more peppy around town, good luck.

 

Have you actually tuned one, or just run them the way they come, right out of the box?

Why all the 305 hate?

My A can turn 140, and leave a pair of black strips as far as you want, or have road.

It has a 305.

At 65, it gets 28MPG.

 

I imagine it's because of the same reason people don't like 307s. They really weren't much to cheer about from the factory. Such a small bore and only smog era to boot so lots of junky heads as originally equipped. My dad had an 81 or 82 c10 with a 305 and as far as I recall it received new heads on a schedule that rivaled the LOF regimen.
I've had no respect for them but if you stand behind them then my prejudice is uncalled for.

 

I agree with FourSpeed..........it's not a matter of hate, it's just that if somebody/anybody goes to the trouble to build a cool ass car, why would they put a piece of crap engine in it, and then complain about performance? Shoot me, then.

 

If you cannot get good performance out of a 305, then don't blame the engine, blame your tuning skills.

 

Here's something for you

 

Or click this link if the PDF doesn't download for you. http://www.langdonsstovebolt.com/tech/professor-langdon-grades-your-235-driveline/

 

right, there is nothing wrong with the 305. the motor takes a beating because of the 350. back in the day both engines were available, in most vehicles, as an option so phrases like; "it only has a 305" or "too bad it doesn't have a 350"or "if your going through all that work you should have put a 350 in that" made that, decent engine the ugly step child.
just one retired multibezillionairs opinion

 

According to the Chevrolet SAE paper the original 1955 265 made decent torque and almost 60 HP down around 1200 rpm.
Seems like that should be plenty to move a full size vehicle down the road at 70 mph with 25 HP to spare for slight hills or leisurely passing.
http://www.newsteamengine.com/images/figure07.jpg.

Chevy showed similar (full throttle) BSFC fuel curve from 1200 rpm to 3200 rpm too, making me think the working power band goes down at least that far with mild engines in good tune with reasonable centrifugal and vacuum advance curves .

 

You could just leave the car out of OD and it should be the same as before, or real close to it.
You might try reading this thread:
http://www.jalopyjournal.com/forum/...-for-all-the-old-times-305-chevy-post.713719/
for some ideas on using your existing motor.
Good Luck!

 

What is mpg? lol

 

I have to smile at these posts. So the guy has a turbo 350 ,puts in an overdrive to lower cruise rpm ,and you guys want him to now change the rear gear ratio to raise the rpm back up. If its running 2200 rpm at 60 with the 350 trans and you change to a overdrive, lower the rear end ratio and it still is running 2200 rpm at at 60 what have you accomplished? Put the 350 back in it ,sell the 700r4 , don't spend the $$ on rear end gears and use the money you save to buy gas.

 

I wondered how long it would take before someone would say it. 3 pages of throwing good money after bad.

 

Or, just leave it in 3rd...

 

The problem is that this transmission with a 235 kills it on both ends. You will be incredibly doggy at a light, and the engine noise will be very noisy at any highway speed. So for this reason, we don't recommend the TH350 trans on the 235. For a SBC? Go for it. You have the horsepower then to overcome the first gear... You can't compare apples to oranges in this way.

 

I should state that the info I am giving is in relation to some of the other comments. Since this car has a 305, he would gain some fuel mileage with an overdrive and a good rear end. It just depends on what he wants to do. I am building my small block with a 3.08 rear and a TH350... But ultimately as I can afford it, I plan on installing a 700R4 since I drive really long distances with my '59 Chevy. For the guy with the stock engine in his '55, you would never want the TH350...

 

I guess there are some interesting discussions on here regarding efficiency, power bands, and torque. Seems there is some trains of thought that more RPM's = less gas mileage. I would have thought the same, but can see now that with (700R4) 1800RPM= 11 MPG, and with (TH350) 2500RPM = 14MPG.

I will update this thread whenever I make any changes to the driveline or tuning.

Thanks for the responses.

 

Yeah, you have a lot of good info to hash over. For now I would keep it out of 4th and work on the tuning while scouting out a lower rear option. Start with 4.5 - 5 psi fuel into your Edel. Setting floats a "tad" lower than spec can be good too.

 

One of my Suburban beaters was, for some unknown reason, built with a 350/700R4 and a 2.73 gear.

I managed to pull 17 MPG or so out of it one time, driving 75-80 down the interstate. The rest of the time, 14 was typical.

Interestingly, I had one right after that that was almost the same, but had a 3,73. Maybe the motor was more worn out, but it got the same MPG, and it was a dog, no power up hills like the other one had.

Being lazy, was this my car I'd just shift it into D and only use the OD on the flat.