unreasonably hard throttle pedal....what gives?

[JamesH]

my stock-ish 1980 TR7 DHC has an unreasonably stiff pedal. it has the US standard ZS carbs and a new throttle cable. (the old cable was broken at the firewall when i bought the car...i replaced it recently. i have used zip-ties to anchor the cable and give it gentle curves and not sharp angles.) so, is there a trick here? lighter springs on the carbs? anybody have insight? i am at a risk to chirp the tires coming off red-lights because i have to punch the pedal to break it away from its resting position.

[Beans]

Is it stiff all the way down or only on the first part of its travel?
If it's the last, check the linkage. Pictures below is the SU version but the Stromberg should be more or less the same.
Problem is the linkage rod that wears out, giving a lot of initial resistance when opening the throttle.
Easily sorted with two ball joints and matching threaded rod (on the right).

[Spike]

Had a similar problem with mine, check everything for wear. Mine had also worn on the main pivot on the mounting bracket, as well as the rod, also check the throttle spindles for wear as well.

Replaced, throttle mounting bracket, rod with ball joints, new throttle cable, new throttle spindles and cleaned and greased the throttle peddle. When I replaced the rod with ball joints I've adjusted it to be slightly longer as this also seems to give a slightly smoother throttle action.

regards

Graham

[Spike]

I used one of these to replace the rod http://www.ebay.co.uk/itm/Weber-Throttl ... XQROxRF4Wy

on SU's you need to trim it slightly. You can also by generic stuff cheaper.

[sonscar]

Best £15 I spent on my car.Steve.

[tr8]

I once had a similar problem, can't remember if it was an MGB or TR8, but doesn't change the cause. Found the throttle sticky and when I went to check it I found that it was GLOWING red. It was acting as the ground cable!! Pretty sure this was after a recent engine switch.

[Spike]

had that on my MG Metro, strap came loose with a lovely smell of burning plastic in the car.

[JamesH]

thought you might be interested in the solution. the linkage arm that comes up and hooks the over head spring was fouling on a hose clamp on the vacuum line elbow that attaches to the front carb. you know, the 2 cent problem that fouls up operation of the multiple-thousand dollar car. i twisted the clamp a quarter way around and now the pedal doesn't take extra force to get it moving. miraculous!

[tr8]

Glad you found the cause. Looking at your signature, with 5 project cars, I think you like detective work...

[JamesH]

i appreciate your kind comment....thats not what my wife calls it...she uses unkind words like "obsession" and "insanity."

[tr8]

Having had LBCs for a very long time I think of it as a PHD...permanent head damage

[JamesH]

i sure won't say that you are wrong....but will add that i have a pretty short commute and a stressful day job. my car "habit" is a partial antidote for my day job at pretty minimal risk, (because of the short commute) usually.

[FI Spyder]

Sometimes (most often?) the most complex and/or most difficult to diagnose problems have the simplest solutions.