14 inch tyres and gearing.

[nmauduit]

Elan3:

Thanks for this, it looks like I will be trying to figure out my cars first gear ratio before anything else happens. The guy at the local differential shop, who has done quite a few British Cars, is hesitant on this one, as he thinks a 3.0 is for V8's.

I'm not sure the first gear is the only one to take in account... by overdriving the whole gearbox by about 20% (the 4th with a 3:1 becoming similar in gearing to a Lotus 5th with a 3.77:1 for example), one actually sacrifices the use of the 4th to highway cruising, leaving mostly 2nd and 3rd for regular (spirited? ) Elan driving ... True, the first could potentially offer a 3rd gear, but even on track with a high revving engine few people actually use it, so I would think the conditions on the road are not likely to come up ofter to properly use the first besides launching.

I'm glad that TBG is happy with his setup, but I am pretty sure that such setup is not for everyone... in any case not for me : even if my street elan is only 130 hp (5 speed Lotus + 3.7:1 diff), I do use 2-3-4 while 5th is only for highway. There is a reason why a gearing is set for a given car by the manufacturer and the purpose is to use every gear evenly - overdriving it will result in exactly that : overdriving it, then the 4th won't be useable at 6500 or nearby (then one can always back up from that stance by fitting extremely low profile tires... which is an other can of worms).

[TBG]

"one actually sacrifices the use of the 4th to highway cruising"

Actually no you don't! As I have said from the start you need a torquey engine with sufficient power. Mine is, and top gear,4th, is splendid. Pulls like a train and is relaxing when you relax.

"There is a reason why a gearing is set for a given car by the manufacturer and the purpose is to use every gear evenly"

True but that does not take into account chaps like me adding power and torque. The whole ball park then changes and new horizons are possible.

[billmoore42]

TBG, Rohan, and mnauduit:

Thanks for your generous insight and replies, I have two things to do now:

1. Figure out my first gear ratio on my 67 FHC, I think a 2.5 first gear would kill this project.

2. If it is a 2.97, work with my local gear shop and convince him that I will not ask for a refund if I can't get it out of the driveway after the change. I will also be changing the Rotoflex to R Dent CV driveshafts during this which should make starting from first a less of a chore, which should be economical as not much more labor is involved.

I find the Elan a perfect car for driving on back roads here in California, but need to get on the freeway for stretches (some quite long, say 100 miles at 70 plus MPH to keep up with traffic) to get to the choice back roads. I love driving with the Twin Cam at 3200 rpm or less, I guess because I am now 65 years of age, and like to treat things like engines and valve trains gently, or maybe l like to listen to my newly installed Pioneer stereo at times.

To mnauduit, a 5 speed would be ideal, I agree, and I would love one, I just do not see an easy way to do this, as the conversion kit from Alan Voight sounds like a bit of a nightmare to install or have installed.

It is funny how this little car can be so much more fun than say, a Porsche Cayman. That is all for now until I find my first gear ratio.

[TBG]

Good luck Bill. Keep us informed as to how you get on. I have just been for a run to get some flowers for our 54th wedding anniversary and so the car is now covered in mud!! I am thirteen years older than you and never go slowly enough to listen to the radio!! Happy Christmas all, D

[billmoore42]

It looks like I have a close ratio box in my 67 Elan FHC, as I marked a rear tire, and the crank engine pulley rotated 2.5 times for one revolution of the tire in first gear. Probably explains why with the 4 Rotoflex coupling drivetrain, starting in traffic takes a bit of clutch slippage, and also explains why the previous owner cautioned me against a 3.55 rear diff.

At any rate, I will now continue to ponder the pros and cons of a 5 speed, as well as a 3.55 diff combined with solid rear shafts, which should make starting off the line in traffic more bearable.

[TBG]

Bill - giving up on the 3:1 then?

[billmoore42]

TBG: Not in spirit at least, but I think I need a 2.97 first gear with this instead of my 2.51. Time to ponder things, the only 5 speed appears to be the Voight option, and from what I have read this is something that might be a lot of trouble to fit properly. I will research the Voight transmission some more, as it sounds like way too much work to change my gearbox ratio and fit the 3.0 differential, although this is certainly another possibility!

[1owner69Elan]

It looks like I have a close ratio box in my 67 Elan FHC, as I marked a rear tire, and the crank engine pulley rotated 2.5 times for one revolution of the tire in first gear. Probably explains why with the 4 Rotoflex coupling drivetrain, starting in traffic takes a bit of clutch slippage, and also explains why the previous owner cautioned me against a 3.55 rear diff.

Not sure I understand how you determined that your first gear is 2.5:1, unless I am missing something.

Having the crank rotate 2.5 turns, the first gear output of the gearbox would be 1 turn of the propshaft. Then that gets reduced to the wheels by the diff (3.77). I don't understand how this can result in a single revolution of your tire.

You can do the same thing of rotating the crank (presumably with spark plugs out to make it easier) and observe the number of turns on the propshaft (as it goes into the diff) while in first gear. Number of turns on the crank for one turn of the prop gives you your 1st gear ratio without involving the diff.

I checked the gear ratios delivered to me on my Voigt 5-speed, using the method above, but admittedly with the gearbox out of the car. Marked the clutch plate to measure rotations of the engine and observed the number of those rotations for 1 rotation of the prop yoke. This is when I discovered, to my surprise, that my 5th gear which was specified to yield 0.82 was in fact 0.75. Another Voigts glitch, but one I was OK with.

Fifth gear, clutch plate started at 12 o'clock and shows 3/4 of a rotation for one rotation of the prop yoke. Thus, equal to a 0.75 gear ratio.

(BTW: the clutch plate shown was not going to be used ,so I was not worried about affixing tape to it, though it wasn't really compromising the surface anyway).

[billmoore42]

Dear OneOwner69Elan:

Thanks for the information on finding my first gear ratio. I am a bit of amateur as far as being a mechanic, okay with doing things like replacing Rotoflex couplings, and have even taken out the dashboard to put in a new heater core.

This gear ratio business is new for me, and I will try your method of finding my first gear ratio.

[billmoore42]

Anyone tried the 3.3 CWP from Tony Thompson Racing?

https://www.tonythompsonracing.co.uk/parts/final-drive/

Wondering how this compares to the 3.0 as an everyday road car that has to stop and start at stop lights, and go up California hills.

Doing some research, the MGC originally was fitted with a 3.07, and had about 136 hp and weighed about 2300 lbs. A 1700cc Elan which has at least say 120 hp and only weighs 1550 lbs. would seem to bear out TBG's results that the Elan can easily handle a 3.0 CWP. However, in the second year of production, the MGC switched to a 3.3 CWP which was the standard differential ratio for the rest of its short life. I read they did this because the first year MGC was a bit of a dog off the line.

Anyway, if anyone has more experience with the 3.3 or 3.0 CWP I would appreciate hearing it. Particularly, is it quiet or does it whine when properly set up? The 5 speed option is off the table, just too hard and difficult from everything I read.

[TBG]

Bill - Hullo once again! I have now done a few thousand miles with my 3:1 cwp and would not change it for the world. It transforms the car without it would seem losing any of the fun factor. Yes the acceleration has moved down a gear, but seems even better than before and top is a hoot - plenty of overtaking power and of course relaxed cruising at quite high speeds.80 mph at 3600 what's not to like. As to noise it is silent at most times except a bit of whine as you enter over run and that seems to be getting quieter as time goes on. Mind you with the roof down you cannot hear it anyway once you are up to speed. I do hope your experience is as good as mine. D

[vstibbard]

I've had a number of Elans now with the 2.5 first close ratio gearset and 3.55 diff, the first was a S3 SE Elan, I had no issues pulling to of uphill corners etc, it went like the wind and fine cruising, I did a few Sydney to Brisbane (900+km's) with only a fuel stop and same return, same experience only better economy in a S4SE same gears and ratio's, it had Strombergs with the D type cams, so slightly more powerful.

I'm interested in 3.3 as the 3:1 feel rather big step unless used with stroked TC or significantly higher spec more powerful engine. Having said that I've been pleased to hear all the positive feedback about it, and would go 3 or 3.3 over a 5 speed conversion based on ease and cost.

[billmoore42]

To TBG and Vstibbard:

Thanks for the feedback on this, it is greatly appreciated. As I have a 3.9 first gear, I believe I could pull either a 3.0 or a 3.3 CWP rear differential. My TC features a 1700 CC tall block with a standard weber head, so I think I have the power to do this also. I also have an older Spyder chassis, which I believe precludes even thinking about installing a 5 speed.

I am going to play around with this calculator for a while with 3.0 and 3.3 ratios :

http://westfield-world.com/gtc.html

Again, thanks for the feedback, and TBG, I am glad to hear this has transformed your car.

[GreyElan]

I have posted this elsewhere on the site but it also seems relevant here.

ELAN box with 3 and 3.3 diffs.pdf

(1.29 MiB) Downloaded 126 times

Cheers