Replacement manifold gasket

I am planning to replace the manifold gasket on my 75 TR6 due to what I suspect is a vacuum leak causing rough idle and backfires on deceleration. The Bentley manual describes doing this 2 ways: One with the carbs removed from the intake manifold and one with the carbs in place. Any one with advice here? Do I completely drain the cooling system before and if only partial, how much? I appreciate any help. Mike. /ubbthreads/images/graemlins/patriot.gif

Leave the carbs on the manifold. Only a small amount of coolant will drain from the pipe that runs through the intake manifold. Just undo the hoses at either end and you'll be fine. Top off the rad after your first startup.

I agree, don't take the carbs off. It is a pain to get them linked back up again. I may be a bit tougher to get to some nuts but you will save time in the long run by leaving them on.

You might want to take it all apart to check the mating surfaces of the manifolds to see if they are cupped or warped.Nothing like doing the same job twiceded. Also, NEW lock washer upon reassembly.

FWIW, there are tests for manifold leaks that can usually be done with everything in place. Some, however, are controversial as to whether or not they are safe.

If you have already satisfied yourself that you have a leak then ignore... otherwise you might search the archives for some tests.

You could try spraying WD40 around the gasket to check if leaks. If the idle increases, then you know you have a leak. If it doesn't, the problem isn't the gasket.

or use an unlit propane torch, so as to avoid the oily mess of wd40

/ubbthreads/images/graemlins/cheers.gif

Thankyou everyone for your help. The problem may not be as simple as I hoped. I sprayed carbeurator cleaner around the intake manifold tonight with no change in idle speed. Can i ask for some help here? The problem manifests itself with "missing" under acceleration as well. This LBC just had her carbs cleaned and rebuilt, all new plugs, points, filters, fluids. She had sat for more than four years before I got her. She ran great for about 300 miles after the above work was done. Is this a valve? Should I look at something in the ignition system? Does anyone have a logical approach to the problem? Thanks!

You didnt mention the rest of the fuel system(tank,pump,lines) If the car as set for some time you should make a clean sheet of things. It will save you tons of trouble, grief and bad language.You will NEVER be able to tune it untill it gets a good clean supply of gas!!!!
MD(mad dog)