Jensen Healey IT Prep Progress III

[Ron Earp]

A few folks have asked what is happening with the JH and why isn't it running! I'd like to know too, but the short answer is it is a British car and while building it Jeff and I run into many little snags. The latest "snag" was building the motor, which, on most cars is no big deal.

But for those of you that do not know the Jensen motor is of course the Lotus 2.0L twin cam motor that lived a long life in the Esprit in various states of tune. The motor is quite strong in that the crank and rods are very, very, very beefy for a 4 banger. In fact, too beefy and I wish it could be lightened.

The head is a DOHC 4 valve per cylinder design that for 1972 was pretty high tech. It flows well and can make a lot of power with a good cam, of course, we really don't get a good cam in IT trim but I digress. The valve train is very "motorcycle like" in that there are no lifters - the cam actuates the valves directly via a little follower that acts as a valve spring "cap". And there in lies the beef.

The valve clearances are adjusted by shims, much like a motorcycle. Easy you say, measure the clearance and put in the shim? Not so fast.

The cams come in "carriers that sit directly on top of the valve train. The shims are trapped under the follower, which is trapped under the cam. So, a valve clearance adjustment goes somelike like this:

1) Install cam carrier
2) Measure clearances
3) Calculate shim thicknesses
4) Remove cam carrier
5) Insert shims
6) Install cam carrier
7) Measure clearances

And at step (7) you find that when things are all torqued down for some damn reason a couple, one, or maybe a few are now a few thousands off. So, you start at (1) again and repeat about 4 times for the intake cam and about 4 times for the exhaust cam.

Lots of fun. But we picks our picks and makes our choices.

At any rate here are some shots of the little motor. It sits at a 45 degree angle in the car to clear the hood thus putting the header damn near on the ground and the carbs (2 Strombergs) have to have bend in the intake so they don't go through the hood. The entire motor is aluminum and dressed all out with everything installed weighs about 310lbs or so, not too bad really.

She won't make VIR I am afraid, but we're shooting for Roebling Road in April and I think that is entirely possible. Jeff and I work on it when we can but I've been sick and traveling, same as he, and we've not made a lot of headway in the last few weeks.

I'll post more here as we make progress, enjoy.

Ron

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Ron Earp
NC Region
Ford Lightning Tow Beast
RF GT40 Replica
Jensen-Healey ITS
1/2 a 260Z ITS - Zero

[This message has been edited by rlearp (edited March 08, 2005).]

[This message has been edited by rlearp (edited March 08, 2005).]

 

[cherokee]

Thanks for the update, I love hearing about the progress. I too have slowed down a-bit, got the car tech'ed then started looking for a new job. It is still snowing here so I have some time....yea just keep telling yourself that, you have plenty of time.

 

[trd77]

It sounds like your valve shims are like that of a Triumph TR7. I raced a TR7 for many years and I know the pain it can be to shim, install crank and rotate and measure and then calculate the difference and install new shim. If the shims are like the TR7's, I have some of those. If you want to email me I have a trick to help speed this process up. It works for the TR7, it my work for the JH, it depends how the shims sit on the valve and the tappet covers. [email protected]

 

[trd77]

Also, the engine looks great. You are building a good looking car. Noew you need to talk Jeff and yourself to run Mid-ohio this year and we can be a all british team. I do not know what people would think seening 3 TR8s and a JH.

 

[grayracer]

They'd think "Hope the EPA doesn't show up lest this track be added to a superfund site"

 

[JeffYoung]

You know I might do that. Always wanted to run Mid-Ohio. What dates are you going up there?

That's a neat motor. 140 hp in European trim (Dellortos). 120 with smogged out Strombergs. De-smog the Strombergs and they flow decent (380 cfm or so)and I bet they get close to or more than the "stock" 140 hp. Add a header, the allowed compression bump and some gasket matching....maybe 160-170 at the crank.

At 2240 race weight, the car could be fast.....

 

[trd77]

I will be interested to see how it does.

We always run the Mid-Ohio (Brat Bash) race, and that on July 30-31. There is also a race there the following weekend, but we will not run that one. Then we will run the Mid-Ohio race in Sept. just after Labor Day, the date is Sept 10-11.

However, that Sept race is tentative this year because if all goes as planned, my brother will be going to the Run Offs later that month.