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On Jul 23, 2022, at 4:24 PM, Tim Engel <TSEngel@...> wrote:

?Ian,
I don't have either an E-cam or 110 pulleys for you, but...

What is your preference for how the engine will run? Do you prefer higher performance at the top of the rev range, or milder manners/ easier driveability/ better low end torque? You can't have both stronger top-end power and better low-end torque. You must choose, and one comes at the expense of the other. If you're going to spend money to sort this out, then you should at least get what you want in the end.

The pre-1974 Lotus cars (Coventy-Climax, Lotus-Ford Twin Cam... etc) were meant to be flogged, and their owners were boy-racers rat-racing through the countryside. I think they would have loved the early 907. But I think Lotus failed to realize that buyers for the Jensen-Healey, and for the new 4-seat Elite 'Executive Express' were not going to be members of the previous crowd. And Lotus got a lot of complaints from early owners about the 907 being too high-strung, having to be driven hard in order to perform, and not having enough torque at low rpm.

In the 2nd & 3rd years of production, Lotus made some relatively minor carb changes aimed at taming the 907. But it wasn't until later that they actually made an internal change. The E-cam was Lotus first attempt to de-tune the 907. It helped, but the silk scarf & wicker basket crowd still complained. Next, Lotus introduced the 107 cam... more of the same (milder). If the E-cam was one step toward milder, then the 107 cam was two steps milder.

So, what do you prefer? More low-end torque and easier driveability? Or full-throttle, top-end performance?

C & D cams are biased more toward top end performance. They're at their best at full throttle above 4000 rpm. Not 'racey', but not mild-mannered either.

The 107 cam leans heavily toward the low-end torque part of the spectrum. Given time, it will eventually pull redline, but you have to wait for it. It's pretty much all done by 4500-5000 rpm, then it's pretty lazy the rest of the way to redline.

The E-cam is somewhere between the above two. It's specific target was low-end driveability and torque, but it didn't go as low as the 107 cam.

The 'street-hot' 104 cam targets top end performance. It doesn't really wake-up until 4500 rpm, then it will scream right past redline. It's up to you to lift off, because the engine will just keep going.

So, which personality do you want your car to have? Both/ All aren't options. Pick the appropriate cam, then install the correct MOP pulleys for the cam's used.

C & D Cams = 110 MOP = Red dot
E Cam = 102.5 MOP = Yellow dot.
104 & 107 Cams = 104 MOP = Green dot.

The stock C-cam and the later, street-hot 104 cam both have 272 duration. The difference is in the 104 lobe's very aggressive opening & closing ramps banging the valves open & closed, and the greater valve lift. Plus the stock C-cam runs milder 110 MOP pulleys, and the 104 cam runs hotter 104 MOP pulleys. "IF" you put the 104 MOP pulleys on the stock C-cam, it will have the same event-timing as the 104-cam, but not the aggressive lobes and lift. If you wished to autocross in a STOCK class, but want to 'sneak in' a little more top-end performance ("If you don't get caught, it's not cheatin"), then the 104 MOP pulleys on the stock C-cams would give you sort of a baby 104 cam set-up. It would produce more top-end power at the expense of low-end torque and driveability... just not as much as the 'street-hot' 104-cam would). Either plan on spending most of your time above 4500 rpm during an autocross run, or don't bother with the 104 MOP 'cheat'.

Running the 102.5 MOP, yellow-dot pulleys on the C-cam is 1.5 degrees further down that 'stockish-cheat' path. Even stronger top-end performance even higher up the rev range, and at greater expense to low end torque and driveability. If you prefer driving your Esprit with your foot on the floor, you might like the result. If you prefer taking your lady for a drive through the park, then you're probably not going to like it.

None of those combinations are going to bend valves... that's not the issue. The difference will be in the engine's personality (milquetoast, or bonkers) and performance (down low, or bouncing off redline) verses what you like. "Dissapointment is a function of expectations".

Choose.

*~*~*
I don't know which vender has a supply of all the pulley MOPs, but there are some parts suppliers who are selling incorrect pulleys. Some owners have received pulleys from Kent-Cams that have one MOP, but are marked as another. And some of the 'Lotus' vendors are getting their pulleys from Kent-Cams. You need to be careful.

Adjustable pulleys are an option... they are what you make them during installation. The problem is that they are much more complicated to set-up, and you need to KNOW what you're doing. It's easy to make mistakes, and bad mistakes can bend valves. If you don't know how to set-up adjustable pulleys, or don't have a knowledgeable fried who can look over your shoulder on your first attempt, then adjustables probably come with too much risk for a beginner.

So, first question first... what do you want your engine to be?
Low-end torque and easy driveability, or
top-end performance.
"Both" isn't an answer.

Later,
Tim


07/22/2022, 11:35AM, Ian Munro, <webdudeca@...> wrote:

Folks,

I have recently rebuilt my engine following what I now believe to have been an oil delivery problem to my exhaust camshaft. I purchased a used cam carrier and a used camshaft to replace the failed ones but failed to notice my replacement camshaft was a "C" version while my original one was an "E" version. As you all likely know (and I have now learned) they use different pulleys which are keyed to provide different MOP degrees.

I have at least three options to sort this out. One is to obtain a replacement "E" camshaft and return everything to stock using my existing pulleys. Two is to purchase a "red dot" pulley for the "C" camshaft and operate the engine with a mix of camshafts (Tim advises this is workable.) Three is to purchase two "red dot" pulleys and convert the engine to full "C" camshaft spec (I actually already have two "C" camshafts.)

My question to the group is do any of you have any of these items (qty 1 "E" camshaft and/or qty 1 or 2 "red dot" pulleys) available for sale?

Thanks.

Ian Munro
JPS commemorative #32