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#1 Inlet Manifold Throttle Cam Binding

Posted: Thu Jul 25, 2024 6:27 pm
by caveman
Part way through tuning my SU's, ive just noticed my inlet manifold throttle linkage is catching the engine frame. :doh:
It's the linkage cam/lobe that connects to the carburettor nearest to the bulkhead and the cam is clearly longer than the neighbouring linkage that attaches to the centre carb, which has plenty of clearance.

What stops the throttles at maximum open travel? (throttle butterfly/linkage etc?)
I've never had an issue with hard acceleration but note my accelerator pedal full travel is now being restricted by the frame.

My initial thoughts:

1. Engine mounts have gone soft? Looks like thay are standard rubber.
2. Engine/Gearbox stabiliser needs tightening (rubbers replaced last year)?
3. Gearbox rear spring gone soft? I think it's the original.
4. Inlet manifold casting is lower on bulkhead end (manifold was a replacement some years ago)? Unlikely as I seem to remember a small mark always being there in the paint and prior to its replacement.

Thoughts/advice welcome.

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#2 Re: Inlet Manifold Throttle Cam Binding

Posted: Thu Jul 25, 2024 10:13 pm
by tim wood
Do you have the spacing plate sometimes fitted under the right side engine mount?
This is present to avoid the throttle linkage catching on the engine frame

Part number c18242


Tim

#3 Re: Inlet Manifold Throttle Cam Binding

Posted: Thu Jul 25, 2024 10:26 pm
by caveman
Hi Tim,
Many thanks, it looks like it is missing so just ordered along with uprated mounts :salute:

#4 Re: Inlet Manifold Throttle Cam Binding

Posted: Thu Jul 25, 2024 11:18 pm
by abowie
Replacing your engine mounts should fix this.

Also check that your engine isn't cocked right hand side down.

#5 Re: Inlet Manifold Throttle Cam Binding

Posted: Fri Jul 26, 2024 5:41 am
by caveman
Thanks Andrew,

I'll get the spirit level onto it.

I've been trying to gain knowledge of the engine mount shim/spacers as they are sold in pairs.......should they be on each side to keep engine level or is it accepted that the engine sits higher on the RH side to maintain throttle/carb frame clearance?

#6 Re: Inlet Manifold Throttle Cam Binding

Posted: Fri Jul 26, 2024 6:28 am
by mgcjag
Hi Steve...spacers were an "as required" item...Steve

#7 Re: Inlet Manifold Throttle Cam Binding

Posted: Fri Jul 26, 2024 7:30 am
by caveman
Thanks Steve,
I’ll order a couple along with mounts and adjust accordingly once installed.

#8 Re: Inlet Manifold Throttle Cam Binding

Posted: Fri Jul 26, 2024 7:37 am
by mgcjag
Carefull closeing the bonnet after fitting...the carb tops are close..

#9 Re: Inlet Manifold Throttle Cam Binding

Posted: Fri Jul 26, 2024 7:41 am
by caveman
:salute:

#10 Re: Inlet Manifold Throttle Cam Binding - Solved.

Posted: Sat Aug 03, 2024 11:18 am
by caveman
A quick update and thanks to those who took the time to reply to my original request.
Having just fitted new & upgraded engine mounts (M.Robey) I now have good clearance on the throttle cam. No shims were required (& none fitted originally):

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Worth checking or replacing if you're using standard mounts:

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#11 Re: Inlet Manifold Throttle Cam Binding

Posted: Sat Aug 03, 2024 11:23 am
by tim wood
Those mounts look knackered !

As mentioned check carefully on carb to bonnet clearance ( although with products from Rob Beere you should be ok )