MG MGB and MGB GT Tech Talk
As someone trying to determine the best puchase option on a MGB, what are the advantages verses disadvantages on a B with & without overdrive. If I purchase a B without overdrive how will I be limited or is it more about preference. Any and all perspectives are welcome as I get closer to a purchase.
OD is GREAT thing to have for freeway...but it cost more to buy. Get it if you can.
Running in o/d gives you the same speed at lower rpms. Each engine has a finite number of rpms in its' life. So, o/d extends the life over miles. This also improves your mpg.
O/D allows you to do speed at a quieter level also.
Plus, it is just too cool to be going along and flick the switch.
It is a personal choice/preference...and does not inhibit the performance of the MGB at all. Neither my 1968 MGC nor my 1978 MGB have O/D at present. I will be adding O/D to the MGB this spring, but only because I got a good deal on it.
I've driven across country in the MGB at sustained highway speeds with no ill effects...to the car or to my ears.
It is my opinion that we are now accustomed to the lower RPMs of our Japanese/other import cars....and that those lower RPM have become the "norm"....our MGBs were designed for high RPM....you're not going to hurt the engine (as long as you stay below constant speeds at Yellow or Red Line).
FWIW - YOMV
If we could all have ODs we would!!! there is no down side to them.
I agree with Rick. My B has OD and I love it, but I wouldn't let it be a deal breaker. I would much rather buy a nicely sorted out, rust free non-OD car rather than an OD rust bucket.
Basically, as others have said, OD lowers the RPMs in top gear by approx. 500 turns. It makes long highway driving a bit more comfortable but the B is designed to run at high RPMS all day long.
OD's are some what rare. I once heard that when the B was origially imported about 1 in 20 had one. If you scour ebay, they turn up from time to time for anywhere from $500-700 for one of unknown condition. About $1200 for a rebuilt one.
Bottom line. Find a good car, if it has OD great if not no big deal. It can be added later if you really want it.
Advantage without. On average you pay less (always ambigious buying something like a B).
Performance, not a accel or realistic top speed factor. OD does help gas mileage and the engine is quieter.
The thing about buying a B is being patient and not falling in love before you buy. And from a money perspective, but nice as possible. Let someone else fix it. Probably ceaper to buy a $15K B in great shape than a $5K daily driver in good shape if getting the thing nice as possible is the objective. Mine are closer to the $5K variety, and I have ni issues taking them across the country.
Like many, I have a minor thing for the older Bs, pre 68, but their transmissions, while effective, are not smooth. They work, but my wife won't drive a 3 synco. Also, how much will you drive. If this is a 100 mile per day driver, get the OD. If this is a hobby, sometimes on weekend car, OD is for bragging, you lose more gas in evaporation in the garage than from the 3MPG drop if you nurse a B on the highway.
Speaking of driving and RPMs, can you tell me what a reasonable RPM range is to run a B on the highway for extended periods without stressing the engine too much?
I've always stuck under 3500 for long trips. Is that being overtly cautious?
The overdrive is like having a fifth gear. So just as everyone said, you can run at highway speeds and be at a lower RPM. I don't think it makes the car any faster than an non-overdrive.
I like mine.
According to my appraisal it can add about 10% to the value of the car.
Now the bad news is it can be the source of problems. Because it is an electric overdrive, you find that some cars that have overdrive, the overdrive itself is not working because of an electrical issue like a bad solinoid. The time and effort to figure out what the problems is, is more costly than the part itself.
I have made it my mission to make sure mine is working. And I try to at least engage it once every trip just to keep it operating.
I see people suggesting it is cheaper and more practical to convert to a five speed tranmission rather than install or repair an overdrive. It wouldn't be "original", but it would work. I recall Moss selling these conversions.
I found the use of the overdrive not so jerky if I push in the clutch, flick the switch, and then bring the clutch back out. Just as if it was a fifth gear.
I think if I had a non-overdrive car, and wanted the benefit, a five speed would make the most sense.
John, I learned how to drive manual on a 3 sync tranny! It is all I know.
Rorie
Everyone wants a fifth gear. Like many I bought my OD tranny after I bought my car. :)
Chris,
If I'm doing 60-65mph on the highway I'm usually at 4000-4500 rpm. I usually don't go much faster than that. I do not currently have OD.
Overdrive is the best thing for LBC's that anyone invented.. Don't miss a good car because of a lack of it, but add it later..
The car runs so much quieter and doesn't seem like you going 106 when you only doing 93.
Gary
Thanks Daniel. It'd be nice to be able to keep up with traffic without stressing the old lady (the car that is!).
I know Chris,
She sound like she's eating her inards up inside but all is well. :)
cgill Wrote:
I've had B's with both. I have also driven both cross country. The GT without O/D was nice since it was winter, and the weather was bad. The 67 Roadster was an absolute dream on the long stretches of pure hiway driving. Suddenly, my B is a long-legged road warrior that can suck up 750 miles before I have to take a break. Nothing like cruisin 80-85 at a reasonable RPM.
If you don't have one, get one.
Have fun
The advantages are not just better gas mileage at freeway speed. High speed driving without an O/D is fine, if your just driving high speed in spurts. But, extended high speed driving CAN cause problems such as your exhaust pipe nuts to loosen. If there is a low oil condition, high speed driving can cause a lot of engine damage in a very short amount of time. Also, Think about how fast modern cars travel on the freeway. Without a O/D you will be relegated to the slow lane, unless you don't mind winding your 40 yr old engine out to 5500 rpm for extended periods. I get real nervous about doing that with my MG, call me paranoid.
Call me a maniac, but I have faith in these cars. If your motor is built properly, you shouldn't have a problem sustaining speeds of 80-90 mph. Recently, as an experiment I got my motor up to 120 mph. It will cruise very nicely at 80-85 without an overdrive. Drive it like you've got Rhino nuts!
Whorst
I have OD and find that it is really great on the highway. The RPM's do drop significantly and the car is quieter. The top end speed seems to be the same regardless of whether or not I use the OD but it does slow the engine down. Expect to pay around 800 dollars more for a car with OD but you will not be sorry.
I'm putting in a 5-speed in a few weeks, for all the reasons stated. BUT - These cars like high revs. On the highway I'm always at 4000-4500 rpm, and have to consciously keep my foot off the gas to keep from winding it out more. This has me going a steady 70mph very comfortably.
R.
Oh, I'd have to say that it is far more an issue of performance than preference.
The non-OD trans MGB will have a speed ceiling that cannot be crossed. In other words, you will run out of rpms before you're going as fast as you want.
That was always the biggest drawback and thing I wanted to change on my NON-OD car. I hated the fact the the grandmother with her 3 granddaughters in their big SUV could run right up behind me and pass right by me like I was standing still. The three little faces having their noses pressed up against the window saying "Grandma look at that cute little car" - as they pass right by. I'd have to move over a lane because I was already at redline and couldn't go any faster.
Most cars start to shake or get hard to control before they run out of gears. My MGB could have gone another 50-60 mph without having handling problems, but there's no more gears.
I opted to buy a 5 spd trans, rather than the OD. But, whether it's OD or 5-spd, the bottom line is you're getting another gear. Rather than topping out at 1.00:1, you are at .80:1. Meaning that the wheels are moving faster around than the engine is.
Bottom line: you'll get a higher top speed with an OD or 5-spd, all things being equal. Performance stays the same up through the gears.
The other advantage: Cruising at 60-70 is done at a lower rpm.
Here in Southern Califonria everyone travels at around 100 mph on the freeway, it was a matter of survival for me, the grille of grandma's Suburban is awfully big in my 67 MGBs rear view mirror!
Brian
BManBrian67 Wrote:
Brian,
What is the highway driving ceiling on a B without overdrive?
Orange is 5500, redline is 6000. 5500 is about 85mph, +/-. 5000 rpm is about 80mph.
R.
interesting seeing the mph variation over the years. I have no problem running my non od B all day long at 75mph gps verified which for mine is at 4000 rpm. For mine around 5000 is 90mph and 5500 is 95 and that's where I chicken out as I am not a fan of silver bracelets, uber high insurance and huge fines.
I have found in my 77 BGT that in overdrive I am cruising at 70mph at about 3000 rpm
Brian's driving environment is my rule, not the exception. I do baby my car. I guess I never got over cracking the head on my old 1965 "b" while driving it 85 MPH on the freeway...and that was 25 years ago!
After spending time behind the wheel of a non OD car, an OD car, and 5 speed conversion, I have come to the conclusion that the extra gear or gears is no big deal.
Sure it is nice for extended straight highway cruising, but definitely not necessary.
The high rpms in the B don't scare me.
I tend to run all the cars at about 4000 rpm on the highway for extended cruising. With OD or the 5speed, I just go faster in the fifth gear and the rpms end up in the same place.
My B engines don't really feel like they might be getting taxed till they hit the better side of 4500 rpms.
I'm never in the extra gears if the road isn't straight.
OD is great, but these are tough little cars and they are a lot more fun to drive if you wind them up a bit.
> I've always stuck under 3500 for long trips. Is that being overtly cautious?
4 cylinder engines have a characteristic vibration at certain RPMs. I actually find that on the MGB it is most severe at about 3500 RPM. By 4000 RPM it is singing sweetly.
The factory manual recommended against sustained operation above 4500 RPM. Since that is 80 MPH that isn't too severe of a constraint. I think these cars start to float around 90 MPH unless you've got air dams on them.
After hearing testimonial after testimonial, I just picked up a used one and it's being serviced. No rush, as it's for my swap over project.
The mechanicals are from a 74, the shell is from a 72 and the O/D is from a 77 or 78. I'd like to get some advice for what will be needed, presumably, a new shifter with an O/D switch and to recalibrate my 74 speedometer. People tell me that the wiring harness should be ok.
Guidance?
Thanks.
Peter
And you have to have a pilots license to drive a B that fast.
4000 rpm seems to be about 72 mph without OD in 4th.
With OD 4000 rpm is about 88 or so.
Either way 4000 rpm is the sweet spot!
Yeeee Haaaaaw!
No, John that guy was in dreamland about the costs. I picked one up from your your friends at Coveland. I'll be coming up your way to get it in about a month. I sent you an e-mail with details.
My B is a daily driver. I've even made a couple of round trips from Texas to CA loaded with an attrative passenger and luggage on the rack, without problems.
Every engine I have ever owned seemed to have a sweet spot and they were all different. This one seems to smooth out at about 3700 to 4500 RPM...every thing from carb springs to suspension and muffler tone. I don't usually concern myself with the speedo too much since it has never been right on since it was new, but if you go by the owners manual, 18mph per 1000 rpm 4000 should give you about 72mph.
I don't really worry about what speed others are driving. I do my thing and let them do their thing...and I enjoy the company and the ride.
Warmest regards,
ray h