Cam Shaft Timing.

Useful Tools For Correct Cam Shaft Timing of The Twin Cam Lotus Engine.

Obtaining the correct cam timing of the twin cam lotus can be a fiddly, and sometimes exasperating process.

But it can be a big help using the correct tools, plus a bit of knowledge to make the job easier, and almost guarantee that the cam timing will be dead accurate.

We have put together a short video below to help explain what tools we have used, and why we use them. What we attempt to explain here may differ to what you might read elsewhere, but that’s OK, take what you from this to sort out what will work for you or not, because that’s what we have done.

We wont be giving you any fool proof way of how to time the cams that you have, because they will all differ, and there are plenty of cam timing experts out there to show you the finer points of cam timing.

Some cam timing articles are easy to follow and understand, while others choose the path of confusion, and you’ll be left scratching your head afterwards.

The further apart your chosen cams are from the standard timing, the more need there is to degree and correctly time the opening and closing of the valves, especially with an overlap period that differs wildly from standard, just be very careful.

What we outline here are the tools you will require, the most important being a good degree wheel and a DTI or Dial Test Indicator, and if you are handy with tools and metal, the rest of the bits can be made in your home workshop.

A quick word about the degree wheel, a very effective degree wheel can be made from a 360Deg plastic or sheet metal protractor, stay away from those huge degree wheels that you often see in the youtube videos, you don’t need them, and its been said that the bigger the degree wheel, the harder it will be to time your twin cam engine. The disc in the video on this page is about 8′ or 10″ Dia, and about the right size .

The most important item you will need is the cam shaft data sheet that your cam grinder should supply you with- Yes, they all supply cam data cards, but that is not enough, ask for a cam shaft data sheet, which will expand on the numbers they give you on the cam card or ticket.

The data sheet will provide all of the valve opening and closing points, and crank shaft degree checks that can be made with various amounts of valve lift.

The standard valve timing opening point these days seems to be at a valve lift of 050″,(Just off the seat) which is what we adopted for our project, and it turns out that is correct.

I can remember many decades ago (1980s) with my first association with the Twin cam engine began, a very prominent Melbourne engine builder of that time, explained to me the process of placing a .001″ feeler gauge between the cam shaft and the cam follower, he explained to me that the timing point, or valve opening point was when the cam lobe just nipped the feeler gauge, so that was the opening or timing point that we chose, it must have been fairly accurate, because the engine performed really well for about 80,000 miles before a rebuild was required, which is where we are at right now, but this time around we are building 1700cc twink using 1600 cross-flow crank and the twin cam L block.

Back in the early days, I did not understand or know about a cam timing degree wheel or disc, and the only means of adjusting the cam timing was with those fiddly, time consuming and frustrating offset dowel pins.

These days, we have adjustable (Vernier) cam sprockets, and boy, do they make the job of cam shaft timing so much easier, they provide everything from a micro adjustment, to several degrees of change without much hassle.

The adjustable cam sprockets you will see in the video have been re-manufactured from the original Twin Cam Lotus sprockets, so take a look at those also, that’s another project we completed a long time ago. There’s just one other thing I will say here re the single row twin cam timing chain, since the mid 1980s, I have used a split link cam chain…. no real back in horror, its perfectly Ok on a road engine, even if you touch 6000RPM here and there, remember the chain and sprockets are only travelling at 3000 RPM. So with the elan ownership reaching forty three years, I’ve not had any issues with the split link timing chain.

We may even do another article on the vernier or adjustable cam sprocket items in the near future.

Cam timing can be as simple as lining up the cam sprocket marks or dots after TDC or top dead centre has been found, and then hoping that its correct, well it will be to a point. BUT, if you are installing high lift cams with a different duration than the standard cams, you will need to familiarise your self with the in-depth method of dialing in the cams, you wont do it in one hour, it will be possibly more like three hours once you go through a trial build, and checking, then double checking everything.

It doesn’t matter how much time you spend on your own engine build project, your time is only pub time, or love time, take as long as you like.