Discussions board for the classic MG MGA.
While building my A coupe, I have a chance to pick up a fairly cheap roadster. Has anyone ever transplanted a B eng/trans in one. I've read where people have but looking at it...I think the trans. crossmember mount and tunnel would pose a problem. I know purists are gagging but its not like I'm dropping a Hemi in the thing. I have seven or eight complete B set-ups so I thought it might make it a bit more powerful. Any help would be greatly appreciated.
Not a stupid question - this was recently discussed in some detail when Eddie Saunders started planning the same thing for his coupe. It is not a simple bolt-in matter, but it can happen without moving a mountain.
[url] http://www.mgbmga.com/tech/mga2.htm[/url]
I think Eddie eventually found an early MGB transmission modified using an MGA transmission tailpiece. That kept the shifter in the same position and allowed use of the stock rear mount with no chassis mods. It also allowed the MGB flywheel and clutch. Sounded like the most painless way to do it.
A assume the (absolutely not stupid) question relates primarily to the gearbox (there are no big issues with the engine).
Bill Spohn has done this with the overdrive gearbox, as I understand, and will no doubt 'chip in' here...
I've never torn down and MG trans...dosen't look like it would be too difficult. I pondered the problem for hours...have a low milage engine from a BGT(about 60k miles) and was measuring the tailshafts and everything looks the same. The mod. listed on that site looks like way more than I have time for as I'm currently building a pals 71 BGT...total engine, paint, interior etc....my A coupe, two B roadsters that are mine as well as numerous VWs..my Porsche 911 I'm doing the engine on and various other things. If changing the trans. tailshaft will do it, thats what I'll do. Thx. for the help.
A fellow club member did an 1800 with OD into his A roadster. The tunnel has to be modified since the OD is larger. The simple swap is to do a 3-main 1800 which should bolt right on to the A transmission.
Jack,
As Wray mentioned:
Wray Wrote:
My guy's conversion worked out really well. We went down to a show in Hilton Head on I-95, nothing could keep up with us. I was in the 73B (w/OD) running behind him.
The only hitch I see to installing a 3-main B is that, unless I'm mistaken, you have to install the MGA engine backplate on the MGB block, and use the MGA flywheel which is a smaller diameter. Then you use the MGA clutch which isn't quite as stout as the MGB clutch. But all this said, I think this would be a satisfactory bolt-on conversion with no cutting, welding, machining. The differential change certainly sounds like a good idea.
The biggest problem with using a completely stock MGB transmission is the rear mount is totally different between the A and B transmissions and the shift lever of the B is a few inches forward of the MGA's. There are mods you can make to both the transmission and to the car's chassis to accomodate these differences. But you're getting into cutting and welding, or placing an MGA transmission tailpiece on an EARLY MGB gearbox.
Jack and Wray,
I guess the law of diminishing returns kicks in here pretty quickly...
I have both a '57 A and a '66 B. The B, hands down, provides more pep, shifts smoother, and has a much more solid feel to it than that of the A..... It is much more fun to 'drive' than the A...
Increasing the HP in the A is something that I will do, eventually... I will, however, opt out of anything that will require cutting, bending, or welding to accomplish the goal...
'IF' having a B or B/OD tranny in your A has an overwhelming draw and you are not adverse to the cutting, bending, and welding... then transplanting a B 1800 and B tranny will result in a much peppier and easier to shift car.... Sort of a B in A's clothing ;-)
Either way, I do recommend the Differential change...
...I have done 3 of them,if I were to suggest it, I would say go for the 5 main 4sync-O/D box. I also used the B 3.9 salsbury axle. The only thing I had to farm out was the driveshaft was cut and balanced.
Bughut. get it in there and you will figure it out, I did it and I am the kinda guy who forgets what he had for dinner.
I cant find my trans pix...
So Wyatt,
Now you have my interest.....
I have been told that a great deal of hacking and hueing is required for this conversion. Tranny tunnel and center crossmember being the most affected.
Since I have not done this conversion...
Should I buy a plasma cutter and start hacking away.. or have the pundits lead me astray????
Thank you oh guru of MGB in MGA clothing...
I must unabashedly admit that my A with the perk of my B has a great deal of attraction to me....
OK - to install a 3 main MGB engine in an MGA:
- swap the MGA rear engine plate onto the MGB engine and use the gearbox, clutch and transmission from the MGA
Upgrade - use the lighter flywheel of the 3 main MGB - this has a different bolt pattern for the clutch. Might as well change to the MGB diaphragm clutch as it is stronger anyway. The only thing you have to do to accomplish this is to swap in the front trans cover with a higher fulcrum point for the release arm, along with that release arm. A good idea as it also uses a better seal.
Want to use the MGB trans? Swap the shifter and tower as well as the rear trans casing - IF you have a 15GD or later transmission with a flange instead of a sliding spline as used on the earlier MGAs. Then you essentially have an original MGA trans, albeit with MGB front case - so you have to use the MGB rear engine plate as well, to mate with the trans casing.
Want to use a 5 main engine? Easiest way is to take the MGA rear engine plate and have it machined to take the 5 main rear main seal, and away you go - BUT the input shaft on the 5 main engine is larger diameter, so you'll lneed a special crank bushing that has the 5 main OD and the earlier 3 main ID - Moss sells these, I believe.
Confused yet?
Now it gets more complicated. Want an OD trans? Don't want to hack up the frame? Remove the two squarish MGB rubber mounts and creat a sheet steel piece that looks like a "W" without the centre point. Drill it to mate up with the 4 threaded holes in the mounts on the transmission tailhousing.
Now measure the distance between the 'ears' on the MGA frame mount. Get a piece of steel pipe and cut it to that length, then weld it onto the "W" piece you made so that it drops into the MGA mount and you can pass the original MGA bolt through it.
Things to bear in mind if you do this:
- the rear of the transmission will be higher than the original one was - this misalignment will keep your U joints exercised, but has never seemed to cause any problems, and is in my view superior to rudely hacking out the MGA frame mount for something else.
- the shifter from the MGA cannot be used. This means that the MGB shifter has your knuckles right under the heater panel where you will bark them. You can heat and bend the shifter into a tighter 'S' shape to move it back a bit.
- you need to move the top tunnel cover forward a little or modify it to clear the new shifter loacation. All will be concealed under carpet, so not a big problem
- your drive shaft is now 1 1/8" too short. Either pay big bucks to have it sectioned and rebalanced, or do what I do and have a 1 1/8" alloy spacer made up to go between the third member and driveshaft, obviously with longer bolts
- the OD unit will probably have minor interference in the solenoid area with the handbrake assembly, but nothing that a little judicious banging won't alleviate.
- the 'F' for fog light switch on the MGA dash lends itself to use as an OD switch - F = faster, no?
You are on your own as far as recalibrating the speedo
PS - it all looks nicer if you use the MGA carbs, and the 3 main already has the mechanical tach drive.
Can you tell this isn't an MGA engine......
...hey Bills way is good for me, I did it slightly differently I used the 4 sync LH O/D, is this the OD you are talking about Bills. If it is a little banging wont get it. It must be cut and pieced together. the trans tunnel has a flange for the floor bolts that must be kept. I lowered my trans to line up better with my dif and if it is left sitting high it interferes with the top of the tunnel and a lot more stuff.
I am poor at explaining and when the weather breaks I will try to get pix. Right now it is stuffed in my barn wrapped up like a present.
I am using a 5 main B engine with a converted TR6 Dist to run my tac. I will have to get it to the guy who rebuilds them because I tore it apart and now it does not run correctly. I think I have the weights and springs messed up.
Bills who made your spacer?
Wyatt, I was talking about the early non-synch trans. A bit more banging is required if you use the all synch (which I don't like as much). Ther non-synch doesn't foul as much as the larger all synch.
Bill,
This is wonderful... now I have ANOTHER forum besides BCF to take up my time when I should be working!!!
Anyway.. to quote you...
"OK - to install a 3 main MGB engine in an MGA:
- swap the MGA rear engine plate onto the MGB engine and use the gearbox, clutch and transmission from the MGA "
With all of the money I dumped into the 1500cc engine to make it as good as new.. Now you tell me this.... ;-) woulda, shoulda, coulda....
Ah well....
I think I'll do the diff conversion on the A and leave well enough alone, at least until the B is finished...several years and many $$$ later...
The 1500 will be a bit doggy with the 3.9, but as long as you don't mind that.
And your axles are coarse spline while the 3.9 will be fine. Either use the MGB axle shafts or get the spiders swapped out by a trans shop.
Bill,
Thanks for the advice and the heads up....
When the '66 B goes under the knife, I will likely swap the differential from it to the A and buy a replacement for the B when the time is right....
As for the performance with the 3.9:1 in the A.... 'tis a cruiser so will not be a concern, at least while I sit here pondering....
why do you want to change to a b engine and trans? IMO you will not have an A. Drive the car like it was made. Don't change it. If you want it to have an 1800 engine and an od then buy a B. When you change everything to a B you lose that A feeling.
mga60t Wrote:
I have an 1800 3 main, 3 sync OD in my MGA.. regretably I hacked the transmission mount and cross member to lower the height of the transmission tail piece. The frame on this car was pretty bad, and at the time (5 years ago) did not think I would restore it to that level I have...The right side of the transmission tunnel must be cut and pieced in to make room for the OD solenoid and the hand brake bent. I had the shifter linkage lenghtened to use the stock location, but the MGB shifter is taller then the MGAs so its still a knuckle buster and will be bending mine more or cutting it off. Instead of using a spacer I had a local shop make me a new drive shaft, I think they charged me $125 for this. If I had to do it over? I would use the same engine but use a Datsun Z 5 speed transmission. I also used a late model MGB 3.9 rear end for the car as well as MGB front suspension. There is a local guy who has an 1800 with a Datsun 5 speed who is using HIF carbs, and the way he did it only MGA owners really notice, but he drives that car all over..
At the moment I have what looks like an MG eng/trans swap meet in one bay of my shop. I have early and late engines...transmissions of every type o/d and non o/d...The one thing I don't want to do is hack and cut even though I have all the hacking and cutting tools. I'm still debating and I do appreciate all the advice and help. I'll post a pic or two of the confusion this evening.
...what hack and cut? you shave off the trans mount ears clean with the frame, then if you want to go back some day, no problem they are a clean fit to weld back on. Welding is how they got there in the first place. Plus two extra holes in the floor rails for your fab'd trans mount. EEEsss Cleeeen yob.
Well I'm not sure you are going to get the mount a lot lower by cutting the mounting eyes off (I think you might have to cut the corssmember down or relace it), but if you want to do it that way, do a future owner a favour - tack weld the 'ears' you removed to a handy bit of frame so they are always available for restoration. They won't get in the way and believe me, it is the only way they will ever stay where they can be found.
mga60t Wrote:
Bills, yes I saved the mounts,and no crossmember hacking......bills...this is the 3rd one I did.....but who knows...maybe I did them wrong...
How much lower did removing the ears allow you to go? 1/2 - 3/4"? Probably all that's needed.
...I had a guy out, you probably know him, who gave me the scoop on the planes of the u-joints being paralle with the diff. An old MG racer guy...
IMO when you change to anything that wasn't available then you are changing the car to something it wasn't. If the technology wasn't available say OD, 5 speed, then a car built in that year should not have it. Just my 2 cents:)
Tom,
Sooo.... How do you really feel about this??? ;-)
Go Navy....
Ron,
However, I did gleen information on BCF about changing the 4.3:1 differential on the A with a 3.9:1 from an early B. Easy conversion and about a 20% decrease in RPMs on the freeway.
mga60t Wrote:
However, I did gleen information on BCF about changing the 4.3:1 differential on the A with a 3.9:1 from an early B. Easy conversion and about a 20% decrease in RPMs on the freeway.
Ron,
I'm not sure what BCF is or what information they are saying about changing the MGA 4.3 diff for an MGB 3.9 diff and getting a 20% decrease in RPMs but that is not accurate. Dividing 3.9 by 4.3 equals .906. Thus you will realize approx. 9% decrease in RPMs.
I'm just finishing some winter maintenance on my A (put the wheels back on tonight) which included replacing my 4.3 diff with a 4.1 diff from a 1961 MK11. This will decrease the RPMs by approx. 5%. I chose this diff because I stripped out a MK11 last winter so I had the diff and I didn't have to mess with changing the actual diff gears to accept the axles that are currently in the car as you would have to with the MGB gears. During the process of the change over I decided to replace the pinion bearings and made a couple of tools to hold the diff in the vice and hold the pinion flange from turning when tightening the nut.
I'm hoping for dry weather this weekend to take it for a test run.
John
I guess nobody is in my corner:) I really like all kind of cars and hope to own some kind of hot rod in my lifetime. I don't hold it against anyone who changes the engine and trans on an A. It is your car and you can do what you like. I personally wouldn't do it as I like the car to drive and act like it did when made.
About time we had a post go on and on. So many posts get one or two responses and ends. It is good to disagree/agree. What a dull world we would live in if we all agreed on something. OH I guess we do the A is the best of all MG's. or can we agree on that?
mga60t Wrote: [quote]
I guess nobody is in my corner
Tom,
I'd say I'm in the same corner as you. I try to keep my car original too but I don't think changing the diff ratio to one that was actually an option at the time is bad. I wouldn't put a B engine or gearbox in an A. Just buy a B if you want that.
On the mg-tabc list there is quite a discussion at times regarding changing the Bishop cam steering box to either a Datsun or a VW box. Some people feel that you can't get the original boxes to steer well or even rebuild them. I'm in the long, slow and expensive process (I stopped so I could work on the A this winter) of rebuilding the original Bishop cam box for my TC. Why? Because that's what the car came with when new and I know of at least one person who races one of his TC's at speeds exceeding 100 MPH with his rebuilt Bishop cam box and he is quite comfortable in doing this.
John
Here is the solution. Anybody..... i have started a new thread to not loose the existing topic.
bills Wrote:
I never expected a response like this..but I 'm glad it happened. I've been prowling my collection of MG parts ...A..B..and C. Then I go back and look at the A coupe sitting there gutted like a dead carp. I'll have the original 1600 from it stripped and inspected today, and a engine builder pal has a block vat and all the toys to do anything. Maybe I should just leave it stock, forget the roadster I have a line on and enjoy what I have. If I need speed I can drive one of my Mustang GTs..or on the rare occasion My 911. Jury is still out...I'll ponder it while rebuilding my pals 71 BGT.
Tom,
Through all of this thread we have bantered about with views expressed and opinions tendered... All in fun...
I have just completed a five year frame off with my A. Although I have considered making a few 'improvements' (the old Hot Rodder in me) I have not opted to make any changes -- any major changes are not in the plan.
The 1498cc engine purrs, the tranny has been rebuilt, the body and chrome is perfect, it is a BLAST to drive, and the car is restored to its original condition and remains as it was manufactured.
As long as I have the car, it will remain in this original condition... except the change in differential gearing ratios...
MGJohn...
The math was my very loose approximation.... You are absolutely correct; 9.09% is the expected decrease in RPMs which is still worth the effort to change... The BCF is the 'British Car Forum'; another LBC site that I have belonged to for a few years...
mga60t Wrote:
Tom,
I need to add that I am, in most ways, in your corner -- Being a like minded purist, although I do have lingering hot rodder proclivities... My goal, with this car, has always been to restore it, not update it.
However, I agree with Bills that a few 'enhancements' could be reasonably considered if it makes the car safer or more drivable on todays highways and byways... A few more ponies, maybe a higher top end ratio, or even seat belts, do not detract from the car in any way.
The car was designed and built to be driven in English country roads and byways at 45mph. not the 70+ mph super highways that we drive today...
If you want to Concours it, then by all means, keep it EXACT. If you want to drive it, then adding a few 'enhancements' will make the car that much more fun, and safer, to drive.
IMHO.....
Ronz Wrote:
Bills,
I have yet to install lap belts in my A.... I know, dumb, dumb, dumb....
A couple of weeks ago I took the A on its first outing with the Club... ended up rear ending a truck! Actually impailing the A on the huge Trailer hitch... No damage to the truck except for scratched paint on the hitch.... My A's original freshly rechomed bumpers and Brand new grille now just so much shiney metal with the front of the body nicely crunched.... No injuries but WOW do I need to put seat belts in it....
...I pretty much agree with bills opinions on the MGA also..
...Tires...I get the JC whitney cat for Vws, they have 4- 165x15 on sale 209.00 for 4. Thats a good deal.
wyatt Wrote: