Lotus Elan

Carb trumpet studs - refitting

PostPost by: RichardS » Mon Apr 26, 2010 12:51 pm

I've had my airbox back plate off - and a couple of the trumpet securing studs have come out with the nuts when removing the trumpets.

Have googled and looked back through the archives but cant find an answer on the correct way to refit the studs.,

The manual quotes a figure of 8lb ft for torqueing the nuts - so should the studs be put back at about 10lb ft? I dont want any stripped threads! Other thought was to put them back with a spot of blue loctite and "fairly tight" by feel.

Thanks

Richard
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PostPost by: RichardS » Tue Apr 27, 2010 12:49 pm

Silence!

Anyone got a minute to point me in the right direction? I am planning to refit the studs this evening.

Thanks

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PostPost by: paddy » Tue Apr 27, 2010 1:08 pm

This is not definitive advice, but if you want advice urgently, it's what I'd do (right or wrong, and I'm sure if I'm wrong someone will correct me).

My understanding is that it is bad practice to bottom-out the studs, and also bad practice to "shoulder" them, ie screw them in so far that the unthreaded part of the stud starts to engage with the threaded hole. Instead, apply some Loctite studlocker, and screw the studs in as far as they will go without tightening them (perhaps backing off by a small fraction of a turn). Assemble everything once the Loctite has set.

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PostPost by: GrUmPyBoDgEr » Tue Apr 27, 2010 1:26 pm

To screw a Stud down until the Thread run out engages is "standard practice" & provides to some extent a self locking effect due to the Stud cutting a partial Thread into the parent Material of the Component it is screwed into.
Paddy's advice to use Thread locking Fluid on them is the way to go.
In fact I use the stuff on the Nuts as well. I'd rather struggle getting those nuts off than pulling a broken Engine apart to find out where they landed when they came loose.

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PostPost by: RichardS » Tue Apr 27, 2010 7:08 pm

Paddy/John

Thanks very much for the advice

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PostPost by: ecamiel » Wed Apr 28, 2010 2:17 pm

A bit of gasket compound securing the nuts and studs to the inside of the air box back is a worthwhile trick to keep those things in place and out of the combustion chambers.


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PostPost by: rgh0 » Thu Apr 29, 2010 1:11 pm

Personally I prefer to use bolts rather than studs and nuts to secure the trumpets. That way you only have to worry about locking 1 thread versus 2 to keep the bits out of the combustion chambers.

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PostPost by: billwill » Thu Apr 29, 2010 10:48 pm

Oddly enough my Delortos now have bolts in the top holes and studs in the lower holes.

I'm not sure which of my professional engine overhaulers did that.
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PostPost by: RichardS » Fri Apr 30, 2010 8:17 am

rgh0 wrote:Personally I prefer to use bolts rather than studs and nuts to secure the trumpets. That way you only have to worry about locking 1 thread versus 2 to keep the bits out of the combustion chambers.

cheers
Rohan


I had wondered about some nice stainless 1/4" UNC socket head machine screws with a drop of loctite - perhaps I will try these next time I do the job.

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PostPost by: GrUmPyBoDgEr » Fri Apr 30, 2010 8:56 am

I tend to agree with the use of Bolts rather than those fiddly little Nuts along with those tiny Trumpet clamps, it makes the "Mechanic's" Life easier.
However it should be taken into consideration how often you will be fitting or removing those Bolts.
The Studs with Nuts is the "Engineering solution" so long as the studs remain fixed in the Carb' Body Casting.
Aluminium Castings don't like having their Threads used too much, they will eventually strip, which will result in a tricky re-work.

Nix f?r ungut.
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PostPost by: rgh0 » Fri Apr 30, 2010 11:36 am

Hi John
Dont worry mate ( no wuckin furries ) - du machst Dir zuviel Sorgen

When and if the threads ever strip you just use a longer bolt with a nyloc on the other side of the carb body flange. I always pull the carbs off as a unit with the air intake back plate in place so I only remove the trumpets when doing a carb overhaul which is about a 1 in 20 years event.

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PostPost by: GrUmPyBoDgEr » Fri Apr 30, 2010 2:21 pm

rgh0 wrote:Hi John
Dont worry mate ( no wuckin furries ) - du machst Dir zuviel Sorgen

When and if the threads ever strip you just use a longer bolt with a nyloc on the other side of the carb body flange. I always pull the carbs off as a unit with the air intake back plate in place so I only remove the trumpets when doing a carb overhaul which is about a 1 in 20 years event.

cheers
Rohan


Ha, ha, love it! :lol:
I enjoyed your "Spoonerism" & the German.
I'd forgotten that those Studs went into thro' Holes & not Blind Holes; far less of a problem.
The Zetec is blessed with a separate Intake Manifold so like yourself I take the whole assembly off when necessary.

Must fly now & get the Shopping in, the Shops are closed Tomorrow; 1st May.
Just cut the Grass as we can't do that on Holidays or Sundays, it'll be nice & peaceful for the next couple of days. :D

Cheers
John
Last edited by GrUmPyBoDgEr on Sun May 02, 2010 6:15 am, edited 1 time in total.
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PostPost by: billwill » Fri Apr 30, 2010 3:25 pm

rgh0 wrote:Hi John
Dont worry mate ( no wuckin furries ) - du machst Dir zuviel Sorgen

When and if the threads ever strip you just use a longer bolt with a nyloc on the other side of the carb body flange. I always pull the carbs off as a unit with the air intake back plate in place so I only remove the trumpets when doing a carb overhaul which is about a 1 in 20 years event.

cheers
Rohan



?? I cannot reach the lower nuts holding the carbs to the manifold with the air box & trumpets in place. In fact its extremely difficult to reach those of the rear carb until the front carb has been removed.
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PostPost by: rgh0 » Sat May 01, 2010 1:45 am

I use a cut off 3 inch long open ended spanner as my special tool for getting to those 4 underneath carb to head manifold nuts.

They are not easy to access but it is doable. The 2 nuts on the front carb are easy enough. The one on the front of the rear carb is hardest to get at due to the reach in past the front carb . The rear most nut is not to bad as you can guide the spanner with a hand down the rear of the carb despite the even longer reach. I also take the dizzy cap off first to get the wires out of the way and better access when reaching under.

Generally I find i can remove the carbs in about 20 minutes and not even have to adjust the balance when refitting them if i remove them as a unit with the intake back plate to get at something like the oil pump or engine mount.

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PostPost by: billwill » Sun May 02, 2010 3:14 am

I find I can get these delortos off one at a time and just slip the balance adjuster off without moving the adjuster screw, so they should still be balanced on putting them back.
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