1971 Lotus Seven S4 Transmission Questions

[73TwinCamSpecial]

Hi -

I'm the new owner of the recent Seven S4 auction on BAT. The car is on it's way to me from Philadelphia and I'm starting to gather information on what I'll need to make it roadworthy. As purchased the car does not have an engine or transmission. From my experience with a 1500cc Cortina GT and now a Twin-Cam Europa I am looking at a Ford based engine to put in the car. A Twin-Cam would be nice but I just got my newly rebuilt Twin-Cam engine for the Europa back and don't think I can afford another one just now. I'm leaning toward a Cortina 1600 crossflow GT engine. I think this is what the car originally had in it. I would also consider a non-crossflow 1500 Cortina GT engine.

 

In researching what would be the easiest engine/transmission combination to install, it looks like the Kent crossflow with a Corsair 2000E 4-speed might be a good choice. I understand the Corsair transmission was also used in the Twin-Cam Sevens. I've also read of a "Cortina close-ratio 4-speed" and a Ford Type 9 5-speed. 

 

I'd like to get a better understanding of what transmissions are recommended if I decide to use a Kent/crossflow engine in the car. The following are a few of my questions/concerns -

 

1. Assuming a Kent engine, what transmissions will bolt directly to the existing (stock) transmission mounts? 

 

2. I'm guessing bellhousings for the Kent - Ford transmissions are nothing special for this application?

 

3. Are there any specific model/type/designation for the Ford transmissions I mentioned above?

 

4. Other than the "close ratio" designation, is there anything specific about a Seven S4 transmission?

 

5. A friend has offered me an Elan transmission. Would that work in a Seven S4?

 

I know these are all pretty basic questions and I've tried to search for answers but so far have not been successful. I certainly appreciate any information anyone can provide me. I'm sure this will not be my last request for help.

 

Thanks

 

Larry Mullen

 

[7Westfield]

All this is based on my Westfield 7 conversion---it's a pretty good S2 copy    with a xflow

First    if you want to do a lot of highway driving, a 5 speed is a def plus

        the only thing T9s came in this country in was the Merkur xr4ti    but they are the wrong input shaft for a crossflow without tinkering   they are too long

        you can easily shorten them (I did)    or buy a short one and install     or get a spacer plate that moves the box back about 1"    also, 1st gear is lower than needed, but not horrible      alternate sets are available ($)

the mount is several inches back from the 4sp location   in mine the plate welded in the frame was long enough that I just drilled new holes, but had to cut away part of the front end cuz the T9 is fatty brute   had to use the 4sp rubber mount, as T9 type was too wide for tunnel

If using a cable clutch, you may have issues with clearance for the arm...no way to fit it in mine, so I went concentric hydraulic

Burton has a nice bellhousing   4sp + T9 are different  Merkur item won't work  try to keep the starter on the right side so it's cooler

The shift lever came in exactly the same place as the 4sp, straight under the dash bar

Propshaft will be tricky    I got mine from England, but with tariffs and so forth.........the problem is finding the yokes for both ends    the Merkur used a guibo at the front end, and it's too big for the tunnel    needs a regular ujoint type   there are several sizes of flange for the rear--need to measure

the 4sp I took out is a T3    I presume just a Cortina unit

 

need any pics or dimensions?    PM me your email

Charlie

Edited Friday at 08:36 PM by 7Westfield

[Ian7]

If the budget allows, consider a custom Quaife unit. You can pick the ratios you want (most street boxes out of 'normal' cars have uselessly short first gears), and the input shaft length and spline. And if inclined (as I did), get straight cut gears for the aural fun :-)

[SENC]

Congratulations!

 

Yes, get your friend's Elan gearbox (assuming it isn't the 5-speed +2 variant).  In general, a 116e or 2821e gearbox will work with any of the Kent engines (pre crossflow, crossflow, twink).  Your bellhousing choice will have implications for clutch size and clutch fork/release bearing selections (some of the bellhousings need internal relief to fit larger clutches, as on the Elan, and some require spacers to correctly position the release bearing).  Tony Weale's book will be helpful to you, and I also recommend the old Dave Bean English Ford Racers catalog, if you can find one.  I'll try to grab some photos of the gearbox and clutch sections this weekend, as I recall that catalog describes several of the variants.

 

If you get the Elan gearbox, you will need to find a remote and shift lever for it (the Elan didn't use a remote - Cortinas did).  I haven't looked in a while, but seem to recall them popping up on ebay from time-to-time.

 

There were some Elans with CR boxes, but not many - so you'll have to check on what your friend has.  Most were semi-close ratio.  But, depending on your differential gearing and your intended use for the car, semi-close may fit your needs.  If you can find close ratio gear sets, a semi-close box can be changed to close ratio with a relatively simple rebuild, but I don't see CR gear sets (or boxes) come up for sale very often.  Note that there were variations of mainshafts throughout the 116e/2821e life - meaning there were also variations in the baulk rings and gear sets.  @joe7 knows these gearboxes as well as anyone here, he may chime in with additional thoughts or to correct mine.

[IamScotticus]

If it hasn't already been said, 

you should have the Tony Weale book and the Caterham reprint of the Lotus 7 owners manual (pink softcover).  these two books are essential.

[SENC]

I misremembered... it was the regular Dave Bean catalog that had the gearbox and clutch info.  Adding pictures of relevant pages in the event that is helpful.  I also think there is an S4 manual in the resources section of this site.

 

 

[SENC]

[SENC]

[73TwinCamSpecial]

Henry -

Thanks so much for the information. Pretty sure I have the Dave Bean catalogue somewhere, my Europa has needed several things and between them and RD Ent. I've spent quite a bit already. The Tony Weale book is already on my Christmas list and I've burned through a bit of paper copying the reference material on this site. 

 

My searching so far for a Cortina GT crossflow and gearbox hasn't turned up much. As mentioned earlier I do have a source for a 1500 non-crossflow Cortina GT engine so am not too worried I won't find anything. 

 

Just to make things a bit more confusing (and showing my ignorance for Kent engines) is the Kent 2.0 L engine a suitable candidate for a Seven? They seem to be in the same category as a 1600 crossflow in the vintage open wheel car group.

 

I am really impressed with the outpouring of information from this group and am glad to have found it. Reminds me of the Europa groups I'm associated with.

 

Thanks again

 

Larry Mullen

[JohnCh]

Do you mean the 2.0L SOHC Pinto engine? It's not part of the Kent engine family but did succeed it in some applications, which might create some confusion. It's a lot heavier than the crossflow and doesn't have the same reputation for character. Personally, I wouldn't consider it and would target a crossflow, which is a great little engine.

[7Westfield]

As John said, it's a big lump   and it's taller as well, esp the front end, with that cam pulley

 

And the exhaust is on the right side, opposite from a Kent    intake on left 

[73TwinCamSpecial]

Thanks for the continuing education. As I said, my ignorance is showing.

 

Larry

[joe7]

Henry posted all the info you will need. To summarize: Starting with the engine. I had a 1500 non crossflow bored out to the same displacement as the Elan twincam, 1558cc. Worked out very nice as the engine needed a complete rebuild. I think a 1600 crossflow would also do nicely. Much cheaper than a twin cam as the head work isn't cheap. Going down the stroker path on a 1600 to a 1750 probably isn't worth it either. Cost add up quickly however if a massive rebuild is required, that might be a maybe or just a simple over bore. If you don't have them the next thing is the motor mounts. Bell housings are a bit different and the Elan type would be the proper one. 

3 rail transmissions from an Elan or early Cortina's will work fine, but you will need to get a gear box extension. There are Ford sourced heavy cast iron ones and also lighter aluminum ones to chose from. Early 7s used a Triumph sourced extension with a Lotus adapter to bolt on. Another option is the later trans from a Cortina's with an integrated shifter single rail. 

Then make sure you get the proper bearing that fits the trans input shaft and flywheel. There are 2 clutch types so make sure its a compatible set, clutch plate, disc, bearing and bearing carrier. You also need to source a complete drive shaft.

Hope this helps. Any more ? just ask the forum is full of knowledge people.

[San Augustine]

@73TwinCamSpecial I have chassis s4 3123 GTS which is a RHD car imported to the states in 1974. It originally came with a Kent crossflow 711m 1600 and had a single Weber downdraft carburetor but at some point was upgraded to twin Weber 40 DCOEs. The gearbox is a 2000e four speed also known as the 2821e. According to Tony Weale S4s came with three different style bonnets. At first there were separate bonnets for the twin cam and the Kent cross flow. The twin cam had a rh side bulge to give room for the air cleaners on the twin cam while the Kent crossflows had the bulge on top for the downdraft carb. Later bonnets incorporated both features to accommodate both engines. Looking at the pictures on BAT your car has the earlier Kent crossflow bonnet. My car has the later style bonnet but the previous owner still elected to use skinny air filters for clearance when they converted to dual webers. Since you have the original unobtainable engine mount brackets I would elect to keep it stock and find a Kent 711m 1600 with a 2000e box. If you use the style of air cleaners I have you could still go with twin carbs or keep it totally stock and go with the downdraft. I worry that if you used a 1500 non crossflow there would not be clearance for a downdraft carburetor, but you also might not be able use side drafts as well. Also the engine mount brackets might not fit since 1500s share the same block as the twincam not the crossflow.   FYI - I included a pic of my radiator as well. I don’t think it’s specifically designed for the s4 and is probably used for triumphs or something else. Good luck with getting this special time capsule back on the road. 

Edited 4 hours ago by San Augustine