200r4 vs. 700r4

[Larry D.]

First timer here, so be gentle. Have a 1966 Coupe, 327, Powerglide ( not original engine). Looking for more fuel mileage and lower cruising rpm. Thought a 200r4 was the way to go ( don't want to mess with any computers, wiring, etc) but Bow Tie Overdrive says go with a 700r4 because that does not require cutting the tranny mount to install the tranny.

Any advice would be MORE than welcome

[Joe R.]

Re: 200r4 vs. 700r4

First timer here, so be gentle. Have a 1966 Coupe, 327, Powerglide ( not original engine). Looking for more fuel mileage and lower cruising rpm. Thought a 200r4 was the way to go ( don't want to mess with any computers, wiring, etc) but Bow Tie Overdrive says go with a 700r4 because that does not require cutting the tranny mount to install the tranny.

Any advice would be MORE than welcome

Hi Larry,

Welcome aboard!!! How many MPG are you getting? How many RPM are you turning at say, 70 MPH? I'm going to guess that you would have to drive a ton of miles to pay for the new tranny. Most of us don't drive these cars very far in a year. Do you have side pipes? If you feel the need to change something, I think the rear axle ratio is a better bet. What is the ratio now?

Joe

[Joe C.]

Re: 200r4 vs. 700r4

First timer here, so be gentle. Have a 1966 Coupe, 327, Powerglide ( not original engine). Looking for more fuel mileage and lower cruising rpm. Thought a 200r4 was the way to go ( don't want to mess with any computers, wiring, etc) but Bow Tie Overdrive says go with a 700r4 because that does not require cutting the tranny mount to install the tranny.

Any advice would be MORE than welcome

Wrong place to post.
You'll get no help here because these people consider any modification as tantamount to murder of a human.
Post your question on the Corvette Forum.

[Joe L.]

Re: 200r4 vs. 700r4

Hi Larry,

Welcome aboard!!! How many MPG are you getting? How many RPM are you turning at say, 70 MPH? I'm going to guess that you would have to drive a ton of miles to pay for the new tranny. Most of us don't drive these cars very far in a year. Do you have side pipes? If you feel the need to change something, I think the rear axle ratio is a better bet. What is the ratio now?

Joe

Joe and Larry------


I agree. If MPG improvement is your primary goal, you're going to be GREATLY disappointed whether you convert to either 200R4 or 700R4. You might see a minor improvement in highway mileage but that's about it. The cost of the conversion + the loss in resale value of the vehicle will be FAR, FAR more than any fuel savings you could possibly achieve.

[Larry D.]

Re: 200r4 vs. 700r4

Turning 2600 RPM at 58 miles per hour. Tranny cost me nothing, bought a bunch and sold them at enough of a profit that this one is free. Getting 10 mph, if I do not turn on the A/C. Not sure of rear ratio, but am in high gear at 15 to 20 MPH

[Gene M.]

Re: 200r4 vs. 700r4

Larry,
If you only get 10 MPG you must have 4.11 gears or a hot rodded engine. Is tach working correctly? Speedo gear correct? Carb too big? Big cam? Consider investigation in what you have. Make corrections back to stock configuration and tune. Standard tranny with over drive will out do an automatic in efficiency.

A '66 base engine automatic should get 16-18 MPG no problem. And yes a hot rod site may have more response for modifications as previous stated.

[Terry D.]

Re: 200r4 vs. 700r4

Larry
If you do indeed have a 4:11 rear end you will be turning 2000 rpm at 58 mph with a 200r4. I would guess this will greatly improve your gas mileage. I run a Tremec 5-speed behind a 383 crate motor in a 62. It gets 22-24 mpg on the hiway running a 3:73 rear end. There are some of us here who like to drive our cars as much as possible and a 4;11 with a powerglide makes that difficult. Don't get me wrong, there is nothing wrong with a bone stock car, but if you have a Corvette that is far from stock then make it as drivable as possible. And being able to cruise at 60-70 mph without stopping every hundred miles to get gas makes it much more enjoyable to drive. Before I put the 5-speed in I averaged about 2000 to 2500 miles a year, now I average over 6000 miles.

[Joe C.]

Re: 200r4 vs. 700r4

Larry,
There are a few essential improvements that should be made to any classic car that will be driven on a regular basis:
1. Convert to 12 volt from 6 volt if applicable
2. Use radial tires
3. Upgrade the headlights to DOT beams, non halogen OK but halogen preferred.
4. Install air conditioning
5. Install a new and updated carburetor
6. Replace old ignition with modern high energy system using a Hall Effect transducer as triggering device
7. Install an overdrive transmission...........5 or 6 speed manual........4 or 5 speed automatic.

Now, I can say that my Corvette benefits from # 2,5,6 and 7, as well as having a "hot rodded" 327 with a big solid roller cam and a big 750 CFM dual inlet/dual pump carburetor.

It makes close to 500 HP (414 RWHP or about 485 crank HP SAE net).

Here is how much fun I have with my Corvette:

1. I can take 270 degree exit ramps at 50-55 MPH while "lesser" modern cars crawl along at 40-45 MPH. I recently passed a BMW driven by a Millennial hipster who was messing with me by coming alongside him on a single lane 270 degree exit ramp and passing him while going 55 MPH. The look on his face was priceless. Caution: Don't try this yourself............... "Professional" driver used on a "closed course".

2. The engine fires immediately...hot or cold.............and runs flawlessly. No warmup necessary. Drive immediately after cold start. No stalls, no leaks. Idles beautifully. Oh........did I mention that my carb is a race model with no choke horn?

3. Engine never overheats. I installed a 160 thermostat to keep the intake and heads cool for a denser intake charge (i.e.: torque and power). The temp gauge (verified with IR thermomometer) never varies from a 160-165 degree reading, even on 100+ degree days, in traffic, in parades, during race activity.

4. Engine runs like a champ up to it's race shift point of 7500 RPM. Never misses a beat and I no longer have to change plugs like I did before with the stock ignition system. Currently, plugs have about 5000 miles on them. They still fire beautifully, even when pushed to 7500 RPM.

5. The RS600 5 speed keeps the revs down at 2400 RPM @ 75 MPH.

6. It's fun to blow away C5 Z06s and C6s with LS3s.

7. When I put my foot into it at say, 60 MPH in 5th gear, the speed climbs so fast that I'm quickly up to 135 MPH and accelerating fast. Frankly, I have to get out of the throttle because, I'll admit, I'm afraid of the front end getting airborne when I look at the speedo and see the speed.

8. It's fun to have a hot rodded RWX STI challenge you on the highway only to have him in your rear view mirror at 140 MPH and then see him fade as he gets out of the throttle.

9. It's economical $$$$$$ to get 26 highway MPG if I drive conservatively and try to keep it at 60 - 65 MPH.

10. It is VERY streetable and makes way too much torque below 2000 RPM for the 205-70R-15 tires.

[Gene M.]

Re: 200r4 vs. 700r4

Joe, I suggest add an alternator with more output and brakes should be up to standards to enhance spirited driving. I find the old WCFB very economical. Also the stock ignition with solid core wires is sufficient with a stock or near stock 327. Yes it does run out of breath at red line speeds but street manors are excellent. I know your car is quite built and needs more ignition & fuel............

I run slightly bigger 215 in the rear but your suggestion of 205 is best in the front so no fender damage is incurred.

You provided a lot of excellent text on your car in this and previous treads that is always of interest. thank you

[Joe C.]

Re: 200r4 vs. 700r4

Joe, I suggest add an alternator with more output and brakes should be up to standards to enhance spirited driving. I find the old WCFB very economical. Also the stock ignition with solid core wires is sufficient with a stock or near stock 327. Yes it does run out of breath at red line speeds but street manors are excellent. I know your car is quite built and needs more ignition & fuel............

I run slightly bigger 215 in the rear but your suggestion of 205 is best in the front so no fender damage is incurred.

You provided a lot of excellent text on your car in this and previous treads that is always of interest. thank you

Gene,
A couple things might clear your perspective on what I have. First of all, I have not (yet?) added Vintage Air. Secondly, I use original, non DOT T3 sealed beams which I modified to make them permanently air-tight. They have been in continuous duty since 2003, and although very dim, they have been reliable and trouble free. They also draw less current than the "modern" DOT T3s sold by LL.

I had John Pirkle Sr. restore my alternator, and although it is stamped "37A", it has C60 optioned guts, which I think means that it puts out 60-63 amps. In any event, this alternator has and still does serve me very well. The state of charge of the battery is always near optimal in all driving conditions. If I have to drive with the "brights" on, the same holds true.

If and when I install air conditioning and/or Halogen headlamps, I'll take your excellent advice and study the alternator's rated output very carefully, as well as wire gauge size to the front pigtails, etc.

As far as brakes are concerned, my Corvette has and always will be "no power anything", except engine output. I have Bendix riveted pads installed at all 4 corners. Lifetime guarantee on premature wear, and I believe that they are what is now known as "organic". I have DOT 5 (silicone based) brake fluid holding up against stainless steel lined calipers running lip-seal piston seals. All I can tell you is that at 115 MPH at the end of the quarter mile, the brakes are more than sufficient to slow me down in time to make the first exit opening in the concrete barrier.