Throttle Linkage

[PAUL MORRIS]

Dear All,

I wanted to change the Throttle Linkage but seem to be 2 diff models ? One with 15 & other 17 parts on SC Catalog ?

Part number: 206836
Throttle linkage stainless steel, polished, set of 17 E-Type 4.2 Series I (LHD models only)

Part number: 206835
Throttle linkage stainless steel, polished, set of 15 E-Type 4.2 Series I (LHD models only)

[Vegard]

As some of you've read, my dad just bought an E-type. Although it's fitted with Strombergs it should perform OKish. It doesn't

One of the reasons is that the butterflies won't fully open because of, Ok, I hate to admit it, the PIECE OF RUBBISH throttle linkage. Are they all like this?

I counted 11 pivots/linkages and they are all sloppy. Pushing the pedal to the metal only results in 50% throttle opening, and I cannot really see how I could adjust all the slack away.

Oh, while trying to adjust the points afterwards, I made all spark disappear. So, from a poorly performing E-type to a notn-performing E-type in 30 minutes :)

They joy of old English cars I guess

[abowie]

PIECE OF RUBBISH throttle linkage. Are they all like this?

Yes. Patience and a few hours can improve it a lot though.

[PeterCrespin]

A common issue is that correct timing of the secondary throttle linkage depends on using the correct heat insulators, which are different in thickness from the triple SU version.

There's no denying it is a lash-up though. Jaguar and other car makers of the period were desperate to meet emissions at any cost, since failure to do so would threaten their very survival as a business. Thankfully, it is very easy to circumvent the the system. Go to www.jag-lovers.org and do a forum search for the Crespin mod or 'five minute Strangleberg fix'. Make the adjustment, drive the car again and report back.

http://forums.jag-lovers.org/av.php?1546928n14

Pete

[Vegard]

Thanks guys.
I'm not a member on there, so the link didn't show.

A five minute Strangleberg fix sure sounds promising :)

[Heuer]

From Jag-Lovers:

"The 'Crespin mod' just needs you to disconnect the secondary throttle link at the carb end and leave it dangling attached to the secondary plate quadrant. The secondary throttle plate (on E-types at least) is spring-loaded to close. If you wriggle the link around, you can jam it against the engine side of the manifold (for which you need to open the secondary plate to make room) and the return spring holds it tight against the manifold. In doing so. the secondary closes a very slight amount, so it's not as good as complete removal, although it does jam the secondary almost totally open. It therefore eliminates the major obstruction that causes the mixture to divert at lower revs and messes up gas flow at medium revs too. It also avoids all possible secondary throttle mis-timing (which is pretty common), be it from maladjustment or due to incorrect carb spacer thickness that messes up the opening geometry. "

[PeterCrespin]

I didn't think you had to be a member to read a thread link? Register on Jag-lovers (takes 5 minutes) and see the whole thread, because there is a fully-marked-up photo of the linkage that somebody put up there. It takes longer to explain than to do. The thread includes feedback from people who went out and did it and reported back.

Of course if your main throttles aren't opening fully then you need to fix that too, but the mod would probably still help and also reduce the number of bits you need to concern yourself with.

The one bit of advice you need to be careful with is I think the person who suggested removing the secondary throttle plates but leaving the spindle in place. That's fine, but the spindle is prevented from coming out by the plate, so you can end up with problems if a bare unconnected spindle vibrates out or even just allows air leaks.

Pete

[E55 Bulldog]

I had a question, I tried this mod with my 69 and when I pinned the linkage to the engine side the idle jumped from 700 to 1700.... is that normal?

[PeterCrespin]

I had a question, I tried this mod with my 69 and when I pinned the linkage to the engine side the idle jumped from 700 to 1700.... is that normal?

No. This question has been answered on Jag-lovers.

[Herzeg]

Peter

Thanks for this answer. It sounds to good to be true so definitely will give it a try.