Lotus Elan

L14 Cam Install and performance

PostPost by: Pfreen » Sun Oct 25, 2020 5:59 pm

My covid hibernation required that I do something while locked up in a rental house waiting for my new house to be completed.
So, I did a lot of investigating of cams for the twin cam and decided that the QED 420 or the Kent cams L14 cam would be the cam to try. Theoretically, the Q55 valve springs and retainers allowed the cam to be installed without the machining of the valve spring pockets.
In May, Someone offered me some reground L14 Europa cams. Sold!

Anyway, then I got serious. The big decision was what MOP to set the cams at. It seems there are a lot of opinions on the subject. Anyway, I downloaded an engine model called Engine Analyzer Pro v3.9B (you get one month for free). I first modeled the current engine which is a Stromberg head, 10.2:1 CR, and a Sprint cam set at 110/110 deg MOP. I calibrated the flow coefficients and such so the performance matched my chassis dyno data (Inertia dyno sprint cam 110.png). I then did a lot of runs at different MOP settings. I found that the best compromise was to use the Kent cam recommendation 0f 106/106 deg. The QED 420 cam recommends a 100 int/106exh MOP settings which I found to be unusual, thus the modeling effort.

Anyway, I bought the Q55 valve springs, Q55 valve retainers, new collets, spring seats, vernier cam sprockets and thick pad lifters. I needed the thick pad lifters to reduce the shim thickness since the cams had been reground and the base circle was quite small. I did not have to do anything to the head except clean it up. No machining. It is ported and polished so I know it flows really well.

The attached an excel spreadsheet which documents the build.

Before I took the head off, I took the car to a new chassis dyno in Orlando (my new home) so I could do a one to one evaluation of the new cam. The max HP was 105 at the wheels whereas the max hp on the inertia chassis dyno in Fort Lauderdale was 115. Hmm I thought.

So, I just took the car back to the dyno place in Orlando and I was shocked when I saw 130 HP. They could not produce curves because they were not at all computer savy. I will not go back there.

In conclusion, I find it difficult to believe the cam change added 25 BHP, but I guess you never know. That's the problem with some dyno shops. This shop did not give me much confidence.
I did clean and lap the valves so they were totally bubble tight. That took a fair amount of work. They were not bubble tight when I removed the head, but none of the valves or seats were worn or burned. Maybe that added HP. I don't know.

Anyway, the seat of my pants says the car is a lot quicker. Another funny thing is the exhaust sounds a lot deeper and it revs forever. However, my rev limiter is set to 6800, so no rods out the side.

So, in conclusion, I am very happy with the cam. The idle is slightly less stable, but there is more than enough low end torque. I suspect the mileage is worse, but that is not my number one concern. I retorqued the head and checked the valves after 500 miles and all was well.

If some of you are looking for a project, I think this is a good one to add a lot of spice to your Lotus.
Also, thanks to Rohan for his advice.
Load dyno L14 cam 106.jpg and
Load Chassis Dyno L14 cam
Load Dyno Sprint cam 110.pdf
Load Chassis Dyno Sprint Cam
(71.05 KiB) Downloaded 24 times
Model final.pdf
Modeled Sprint vs L14 cam
(137.26 KiB) Downloaded 24 times
Kent cams l14.pdf
L14 cam spec sheet
(101.13 KiB) Downloaded 22 times
Inertia dyno sprint cam 110.png and
Inertia Chassis Dyno Sprint cam
Kent Cams L14.xls
Installation spreadsheet
(31 KiB) Downloaded 21 times
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PostPost by: gjz30075 » Mon Oct 26, 2020 2:21 pm

Thanks for posting. I see '2000' for vehicle weight. I assume pounds? I think the weight
of a twin cam Europa is closer to 1,600 or so. Would that affect the other numbers?
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PostPost by: Pfreen » Mon Oct 26, 2020 4:11 pm

I have weighed my car and it is 1530 lbs. I told the operator that but the software would not accept under 2000 pounds. Thus, 2000 pounds.
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PostPost by: denicholls2 » Mon Oct 26, 2020 5:55 pm

Pfreen wrote:I have weighed my car and it is 1530 lbs. I told the operator that but the software would not accept under 2000 pounds. Thus, 2000 pounds.

Ah, Lotuses have such trouble being understood. :)

I don't find your experience surprising and suspect that all is good and your modifications added about 25 flywheel horsepower. The key is in understanding that the intended purpose of a dynamometer is not to determine how many horsepower your car makes within some small margin of error, but to tune your car for optimum power and torque to your specific needs by using the numbers from each run as benchmarks and understanding the dynamometer as a sizable variable which is controlled by using the same one for each run.

Dynamometer operators know about bragging rights, and some cater to them by setting up the system to return nice high bragging numbers. Others focus on different clients and don't play those games.

On the dyno day I attended, there was a guy with a Maserati Biturbo just tweaked in some way I forget who came to see how much over 500 horsepower the car now had. I think the dyno (wheel dyno) showed him just under 300. And boy, was he ripped.

However, the same presumably pessimistic dyno (and it was the operator who explained the above in the context of the Biturbo owner) told me I was seeing more than 10 horsepower more at the wheels than I should be expecting at the flywheel of a stock S2 Europa. And that my distributor had some issues. Because this is an S2 Europa with Hermes mods, that much margin for error just didn't exist, so I left a whole lot happier than the Biturbo guy. My happiness was affirmed by my numbers closely matching a Cortina Twincam's. And that owner (the same owner as GKN-47D) learned that although his new-to-him Cortina was ex-Alan Mann, the engine most likely was not one that had spent much time on the track.

If you're not concerned particularly about bragging rights and in the Boston area, the dyno was Northeast in Marlboro, Massachusetts. I'd recommend them as nice guys who seemed to know their stuff. And they gave me the graphs as well as the numbers.

As my brother's tag line used to say (he was a junk artist), "It's all in how you look at things."
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PostPost by: denicholls2 » Mon Oct 26, 2020 6:00 pm

Just realized I hit 600 posts. Now I only need 2/3 as many as I've managed since 2006 to hit the coveted fifth gear. Will I live that long? And will I die owning one more Elan or one less Europa?

These are the truly important questions in life. :wink:
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