I’m just going through changing spark plug wires, rotor
And installing new ignition coil.
I thought I would set up and measure the gaps on the
Throttle body openings to ensure they’re opening and
Closing to the same gap settings.
I measured my throttle pulley rods at the capstan and they
Appear to be the same length.
One seems fairly taught but the other one
Seems to have quite a bit of waggle at the ball joint
Connections at each end of the rod. My question is, is
There a way to make these a more snug fit.
Do the little ball joint connections or the rod connection
Points wear out? Do you just order new ones?
Wear inevitably occurs throughout the entire linkage system.
As for the rods specifically they can be adjusted to take up excess slack, leaving a mere trace. If you can’t roll the rods between thumb and forefinger they’re a bit too tight.
The essential thing isn’t that the rods are exactly the same length but, rather, that both throttles open at the exact same instant.
Cheers
DD
2 Likes
It’s a very tedious adjustment as I have discovered - I would venture to say if one of the throttle plates is just two nut flats (adjustment nut for .002") out from the other, slight misfires at idle and lags when hitting acceleration from stop can happen. This may be equal to .0005"-.001" difference! It’s so much a ‘feel’ in how the .002" feeler slips out that you need to match. And top/bottom. I had to readjust my throttle plate screws because they were not perfectly aligned.
And then when those nuts are adjusted, the throttle rods need fine tuning so each throttle opens same time. I’ve spent many weekends playing around with this. In the end, it really helps with a smooth idle and smooth acceleration from stop. Oh, and finally idle screw to get back to around 750RPM.
Dual throttles on cars have always been a huge PITA. Although I hear the Etype V12 was a nightmare, and needed adjustment regularly.
Thanks Greg, I was thinking the same thing, but as I change the plug wires , the rotor , the ignition coil, I thought I might as
Well go through the system and check all the throttle linkage,
Timing and kick-down switch.
Here’s one more question, I received my plug wires from
SNG , I notice they don’t have the brass connectors, not
Sure if it’ll make much of a difference, but I’ll smear some
Dielectric grease on the connection points (boots).
Does it matter or should you use dielectric grease on top
Of the rotor contact point. I’ll drop some synthetic on on
The felt pad.
Also notice you changed your picture on your JL’s sign in.
Did you realize there’s someone sitting in the trunk of your
Car?
Did you have any issues getting the screws loose holding the plates? I’ve got one throttle body where I need to do this. Can’t get a consistent .002" with the feeler.
Jon
Caveat !!! An odd place to adjust throttle opening at rest!!!
Teh screws that aecure the plates to the shat are swedged. Not a goo thing to come adrift and enter the combustion chamber…
I understand that, but the plate is hanging up in the throttle bore. The plate isn’t centered properly in the bore.
A binding throttle blade might be the result of the axle/shaft being a bit sloppy where it goes through the throttle body. I think the bushings are replaceable…… but foggy memory disclosures apply!
Cheers
DD
No slop; car only has 50k miles. And bore is clean, no gunk.
Jon
I replaced screws with throttle body off and on the bench. The screws are slit at end, and bent slightly out, so they won’t come loose. Don’t try to unbend in car, one of those split pieces could easily fall off into intake manifold.
I bought new screws, and used blue thread lock, and reattached/adjusted on bench.
Thanks, thats what i figured. The only way to safely do it is on the bench. Did you use original Jag screws or just get them locally?
I went ahead and ordered Jag screws. One of the usual retailers we use had them for a buck or two each.
Dual throttles, there’s always something! All this talk, so I took a 216th look at mine and guess what? One throttle rod was a bit off at full throttle. The B bank throttle was open all the way, but the A bank rod was maybe 1 cm shy in opening it’s throttle all the way. Probably not that much of a difference in the amount of air getting in. But now it’s correct, we shall see if this makes any difference at full throttle.
I hope you meant a millimeter not a centimeter. A centimeter would be quite large of a difference.
I remember a couple of years ago watching an episode of Chasing Classic Cars. Wayne acquired an E-type and when they got the car to his shop his chief mechanic (I can’t remember the older gentleman’s name but he is a hoot) set about tuning up that dual carburetted V12. When he was done he placed a champagne flute of champagne (or some liquid) on top of the engine. A nice steady shimmer to the liquid’s surface but no sloshing or spilling.
Ok, more like 1/4" (0.6cm) But quite a bit. Looking at throttle plate, without that extra movement the throttle plate was still quite open.
The full throttle stop screw at capstan was adjusted for A bank, so both banks were never at 100% open throttle. I had to push back the full throttle stop a tiny bit with this new adjustment. Does that mean i just added a bit more power at full throttle?
Yes. Racers always make durn sure the plates are all the way open.
Odd as to how a plate could get askew.
I always thought the .002 was set by the idle speed screw. Not by plate adjustment on the sheft???
A Hoit rod “trick” was to acheve o opening. Plates fully seated in the bore. idle speed set by drilling a pair of small holes in the plates/
1/4" seems a lot!!!
Carl
2 Likes
Yes, the 0.002" is set by idle speed screw at the throttle. I got that perfect last year.
The plates got askew because the part that the throttle rod attaches to is secured to the long shaft for the throttle with a set screw around some grooved portion of it. I had removed the entire thing last year when I removed throttle bodies. When I set it back up, I got it perfect at idle, but forgot to check full throttle.
Is there really a noticeable difference between 95% and 100% throttle? I guess I’ll find out soon enough!
Went for test drive, really didn’t notice much difference at full throttle. Maybe need to get on the track to really find out 
Roger Barr . Suffered a leg injury while working on an F 40 I believe
Saw many a stock motorcycle carb with holes in the throttle plates.