Thackery Washer Gap

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After pulling the motor and transaxle to replace all four coolant pipes running through the box section of the frame, I'm attaching the Stromberg carbs to the motor in my 73 TCS and have run into a mounting question.  The shop manual shows a Flange Adapter between the Secondary Throttle Assembly and the carburetor.  I don't have the adapter and the carbs are mounted directly to the Secondary Throttle Assembly.

The shop manual calls for a clearance of 0.070"  between the adapter and carb.  I used this clearance between the carb and Secondary Throttle Assembly.  The picture below shows the assembly as I now have it.

If I set the gap to 0.070", there is no pressure on the Thackery washers and the nuts are essentially loose.  I tightened this gap down to 0.40 to 0.45" which is what is in the picture.  This gap secures the connection.

I don't know what effect this smaller gap will have but remember reading somewhere that the purpose of the Thackery washers  is to isolate/minimize the motor vibrations transferring to the carbs.  The vibrations cause the fuel in the carbs to foam, which is undesirable.

If there are other considerations I should take here, I would appreciate your input.  Thanks as always.

[SwiftDB4]

.040" is about right.

[Bainford]

Are the o-rings in place between the adaptors and the manifold?
Are the carbs flexibly mounted with the current gap?

I've recently been playing with my carbs and have had them off and back on a half dozen times a couple weeks ago, so have been messing with mounting quite o lot. The .070" gap was not difficult to achieve, and the carb mounting is quite flexible, i.e. you can wiggle the carb around a fair amount.

By the way, the adaptors are shown in the photo you posted. They are the three-hole flanges that are fastened to the downstream side of the carb, through which the mounting studs pass, and against which the thackery washers apply their force.

[jbcollier]

These are where the o-rings go that Mr Bainford mentions:

http://www.lotus-europa.com/manuals/tcparts/e/ek.htm

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Thanks guys.  I didn't realize that the adapters were already mounted to the carbs but that is quite apparent now that you point it out.  Wish I could say I didn't have my glasses but that's not the case.
The O rings are in place appropriately.  They required a slight stretch to get in place and then would pop off before I could mount the carb.  After a few tries I got them in.
The current fit for the carbs provides some, but not much, flexibility.  I could do a trial and error method of creating more gap/flex .  When I set it to the .070" everything was so loose I was concerned the nuts would vibrate off.  Suppose I could gradually enlarge the gap to get a balance of flex and secure mounting.
I could also try nylock nuts and not worry about the loosening issue.

[BDA]

Somebody who has Strombergs can correct me but I believe the 0.070" gap you're referring to is between "the adaptor flange/carburetter to the adaptor blocks" and not the Thackery washer gap.

I would use lock nuts of some kind everywhere (except a very few specific places like rubber isolation mounts) on the car but especially here. You want to maintain a particular gap and as you say, you want to make sure the nut doesn't vibrate loose.

[jbcollier]

Nylock nuts will not hold an adjustment if subject to engine vibrations.  I had a pair of Webers vibrate loose when using nylocks and thackery washers.  I would drill and wire the nuts.  If cleanses are tight, then you could do this:

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I did go back and adjust the gap to .060" and the nuts appear to be under tension and the carbs are "flexible".  I think I will keep a close eye on the juncture for a while until I'm satisfied it doesn't change .

BDA I think I understand your point to mean the gap has t be .070" and not the width of the Thackery washers under compression.  I don't think one could compress the washer to a .070" width, they would be way over that when fully compressed.  If I'm not understanding this correctly please let me know.

[Bainford]

The O rings are in place appropriately.  They required a slight stretch to get in place and then would pop off before I could mount the carb.  After a few tries I got them in.
The current fit for the carbs provides some, but not much, flexibility. 

It sounds as though you may have o-rings thinner than original spec. If so, then you will have to go with a thinner gap. The set-up could be compromised, though, and ideally the original spec is best.

Also, when you say, "...required a slight stretch to get in place...", it makes me think the overall diameter of the o-ring is also too small. I presume you are stretching them some over the spigot on the face of the adaptor. The o-rings, on their own, should be a comfortable fit into the bore of the manifold (i.e. a size for size fit or very slight interference). When I fit my carbs, the o-ring is sitting snug in its seat in the manifold, and I offer the carb up to it.

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That's how I ended up fitting the O rings Bainford.  They wouldn't stay in place on the spigot of the adapter but sat nicely in the bore of the manifold.  I assume I have the correct size O ring since they came from Joe Curto when he rebuilt my carbs.

With any luck, I can get it fired up and running today.

[Bryan Boyle]

That's how I ended up fitting the O rings Bainford.  They wouldn't stay in place on the spigot of the adapter but sat nicely in the bore of the manifold.  I assume I have the correct size O ring since they came from Joe Curto when he rebuilt my carbs.

With any luck, I can get it fired up and running today.

One thing I did when I reinstalled mine was to mount the secondary throttle body (minus the throttle plates and spindle, all blocked off) to the head, then the adapter plate and o-rings (without the carbs mounted...less weight) which allowed me to feel around the bore to make sure the ring was in place and not collapsed or offcenter...get the clearances right (some guidance was to get the thackery clearance where it needed to be and accept the gap that resulted, others advised getting the adapter clearance and live with looser thackery clearance..I chose the former, and the adapter clearance ended up for me at .6) them mount the carb rack and set up from there. 

Mine seems to be just fine; it starts nicely, plugs are a tan-ish brown, and my fuel consumption is not out of line (admittedly, I do like to put my boot into the loud pedal and listen to the exhaust note when accelerating...).  I figure, they aren't Rolex watches, and barely up to Timex standard.  So, within .1mm is good enough for normal driving. 

[Footer]

Brian, could you post a picture of your setup?  I'd like to compare it.
Thanks.

[Bryan Boyle]

Brian, could you post a picture of your setup?  I'd like to compare it.
Thanks.

Sure...when I get back to MA...on business travel right now, so it will be a few days.

[Footer]

Okay, thanks

[cazman]

My car does not have the original tube, but has an aftermarket adapter with crossover tube. I suspect that there is no o-ring, as there are not Thackery Washers either. Did some of these aftermarket set ups work without the "flex"?