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MG TD TF 1500 - Drop in RPMs if depress clutch

I have a 1951 TD and the engine has run well for years.
If I have run the car so it is up to operating temperature and the engine is idling at 900 rpms, is there any significance that my rpms drop when I fully depress the clutch pedal?
Milton
Milton Babirak

The clutch release bearing is a carbon block. The is some resistance when the clutch is pushed in, it is not uncommon for the RPMs to drop slightly.
David
D. Sander

Milton

The only things I can think of that would reduce engine rpm when the clutch is depressed are
1. Not enough clutch pedal clearance (3/4" min) and too much clutch throw or
2. The clutch release bearing is worn down and dragging down rpm when the clutch is depressed.

Just thinking out loud. Is the drop significant or just a small amount? If small it is probably nothing to worry about.

Stuart
S Grimm

Agree with David...perfectly normal. Remember, when you depress the clutch you're forcing the flywheel forward very slightly against the center thrust bearing.
Gene Gillam

I've found that if the engine, transmission and/or engine steady mounts are soft and worn, that depressing the clutch moves the engine enough that the throttle can be affected.

Tom Lange
MGT Repair
t lange

Milton - In addition to the above reasons, there is an additional cause that is not well known. Has the cable assembly for the clutch pedal to the clutch lever at the clutch housing been replaced with clutch rods? If so and the clutch stop bolt was never installed (primarily because no one knew of its existence) when the change over was done, resulting in the clutch throwout bearing traveling too far. E-mail me at SUfuelpumps@donobi.net and I'll send you a write up on the clutch stop bolt. Cheers - Dave
D.W. DuBois

I'll agree with David S. Been watching that happen for a bunch of years. I trust that the drop is not significant, i.e., <200 rpm. Dave D. has a very good point for any car. Bud
Bud Krueger

Dave DuBois:The clutch cable was replaced with a rod. I do not know if a clutch stop bolt was ever installed. I will email you for the write up. Thanks.
I did check to see how many rpms are lost but I have forgotten already. I will check again tonight.
Milton
Milton Babirak

Milton: I had the same problem several years ago and posted a thread. You will be able to find it if you search. My TF had the stop bolt in place and was still losing revs when I pressed the clutch. The solution for my car was to make the changes in rod geometry by drilling the hole in the lever and adjusting the rod length. It made a major,major difference to everything to do with the clutch operation. It is much smoother now and the revs hardly drop at all. If you search you will find what you need to do to make the same changes. Ron
Ron Coates

Ron, thanks for your comment. I still have not had a chance to get my car on a lift to see if I have a stop bolt. I am only loosing about a 100 rpm. My clutch operation seems to be smooth.
Milton Babirak

Slight drop perfectly normal, I would not worry at all. But do check engine mounts as Tom says. George
George Butz

This thread was discussed between 10/06/2015 and 15/06/2015

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