Lotus Elan

Engine upgrades

PostPost by: europatek » Mon May 30, 2016 9:24 pm

I haven?t posted here for a while but thought I?d share my latest Elan upgrades with you. As purchased, my Elan had inappropriate cams for the road ? good top end but at the sacrifice of bottom and mid-range torque ? performance that I have never been happy with. I had them checked at Clive Cams here in Melbourne and they measure up like L1/L2 with low lift of 0.352?, which explained the performance.
I?ve been collecting parts to rebuild the engine to 1700cc spec with a 711M crank etc?. to make a punchy and torquey road engine just like I have in my Cortina. I?ve collected most things needed but I?ve also collected a couple of small children along the way so now with limited time and redirected funds that project is on hold. I did however decide to progress with some interim upgrades, those being;
- New cams
- 2? exhaust
- Pertronix ignition
I undertook each upgrade one at time to fully appreciate the change each one made.
First step ? the cams. I took a spare set of cams to Clive Cams in Melbourne to be reprofiled and had what is commonly known here in Australia as a Wade 205 grind, 70/30-30/70 with 0.375 lift. Installed with new followers and shims I now have a much better road engine. Bottom and mid-range torque and response is much better.
Next up was the exhaust. My car has what appears to be a standard sprint exhaust. I decided to upgrade the main central pipe to 2? first. $50 later I had the pipe with O2 socket and modified collector. Again, success, with further improvements in torque. I?ll do the muffler next. I?m thinking the Tony Thompson fast road version.
Third up was the Pertronix ignition. I had tried this before but it actually made the engine worse. However now, with the new cams and exhaust it works great.
So, success on all fronts. A bonus is the upgrades have helped the carburetion. I have Dellortos that have always had an off idle stumble regardless of jetting. I am happy to report that this stumble has pretty well disappeared and the low speed running is a lot nicer as is the idle. I figure that the old combination of cams and exhaust just didn?t work well together or maybe they also needed a bigger exhaust to work properly. Either way they would not produce the torque the 205?s do.
Next on the list will be the muffler and another distributor that is in better condition than the one currently in use. I also have some Webers that I may try using some of Keith Franks Hypo jets and tubes.
Finally I?ll rebuild the lot to 1700cc spec and if my Cortina is a bench mark then the Elan will be a real flyer once completed. I look forward to this stage.
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PostPost by: rgh0 » Tue Jul 05, 2016 12:44 pm

keep on with the developments - lots of joy in an Elan with a 150 hp high torque engine :D

cheers
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PostPost by: Certified Lotus » Tue Jul 05, 2016 11:42 pm

Yes, I drive my 150HP Elan as much as I can because smiles never go away. Had my engine built for mid-range torque. A bit lumpy below 2500 rpm, but after that the power just doesn't stop :mrgreen: it's addictive, you will be glad you rebuilt the engine.
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PostPost by: seniorchristo » Wed Jul 06, 2016 1:28 am

Euro
I have a 1650 tall block with Sprint like cams. I have a smooth idle at 800 rpms but a long flat spot lasting from 1000-2500 rpms. What jets are you using? Did you change jets when you changed cams? I am studying up on Keith Francks Weber modifications but would prefer to dial in the basic Weber jets before experimenting with Keith's seemingly infinitely adjustable tubes and hyperjets. Have you used the O2 sensor for carb tuning? My name is Chris Herr and I am Elanaholic. :)
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PostPost by: nmauduit » Wed Jul 06, 2016 7:52 am

seniorchristo wrote:I have a smooth idle at 800 rpms but a long flat spot lasting from 1000-2500 rpms.

Chris I'm not sure what your expectations are below 2500, but I would think it is natural to have less power there. People usually refer to a flat spot around 3000 or 3500, incidentally near the transition region between idle jets and main jets. To help selecting jets, idle jets included, I have used an O2 (lambda) sensor, which I found very convenient - but one can sure do without, as was done back then (checking spark plug color etc).

Even if my engine would go lower, I personally set idle around 1000, which I hope will help making bearing last longer, and possibly help taking off by reducing the rpm zone to be covered by the accelerator pump spray.
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PostPost by: europatek » Sat Sep 24, 2016 1:47 pm

As of two weeks ago my latest round of upgrades is complete. I fitted the Tony Thompson muffler and a pair of 40DCOE's that I had. Chokes are now at 34mm, emulsion tubes are my own design using the F16 as a base and the idle jets are from Keith Frank - the hypo-jets size 20. My Elan has never run so well. It has its mo-jo back and I look forward to the next drive.
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PostPost by: gjz30075 » Sun Sep 25, 2016 8:49 am

How did the base F16 work? What did you do for "your own design"?
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PostPost by: europatek » Sun Sep 25, 2016 11:06 pm

The F16 as is was terrible. It produced a horrible lean stumble in the transition.
I also tried F2 and F11. The F2 had great performance but still suffered a lean stumble. F11 just felt flat.
I've spent time changing the OD, counter bore depth and diameter and adding
cross drillings of different diameters at different heights. Lots of experimenting.
The F16 is a good base as it has plenty of material to work with.
I installed an Innovate Motorsport digital AFR gauge so I can see the results of the changes immediately.
The two sets I have currently are kind of hybrids of the F16 and F2. I have another set yet to modify and try.
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