Will recon throttle bodies solve my problem

[Tim D.]

hi chaps

Ok so here's the issue. Since I have had the car (a cp) I have struggled with getting a low idle. 1200 rpm is the best i have ever had but that was with sub optimal ignition timing. 1500 rpm is more normal..

Over the last 5 years I have ignored this annoying problem but as part of the general renovation of the car I have replaced much of the PI system including injectors, MU, pressure regulator and TB linkages. The TBs have also been on and off the car a few times during various bits of work. I have also tried resetting the throttles on a number of occasions and the best is always 14-1500 rpm with the air bleed shut. Note I have never cleaned the bodies so haven't disturbed any gunk that might be helping seal the butterflies.

So my question is.. Would getting the TBs reconditioned help? I am pretty sure the butterflies are leaking air as if can detect flow when fully closed. How would reconditioning help this?

Cheers

Tim

[TriumphV8]

Hi Tim, difficult to judge from here what causes the high idle

but I would not like to drive a car with such an idle....

 

Mostly misalignment of linkage causes high idle, next is wrong air from

the connection to cylinder head or the rubber pipes between the bodies.

The linkage could be disconnected from the spindles to check.

 

Last idea is the black mud in the manifold to block the spindle and plate from

moving and seating in the manifold. Can also be checked with linkage disconnected

by trying to close the spindles by hand when idling.

 

Anyway a proper bearing for the spindles is the base for a PI that makes fun!

But also the whole linkage should be checked for wear.

[Tim D.]

Thanks Andreas. Was going to do the linkage disconnection check before it commit to new TBs. Will also double check pipes and gaskets etc.

cheers

Tim

[Guest ntc]

You need to check for air leak's and yes can be done Very carefully

[DaveN]

On the question of throttle bodies, any recommendations for the rework and mods, new ball races, seals etc? I have a set that I was considering reworking.

[k_raven_smith]

Tim is your in box full

[Tim D.]

Inbox now has space

[Tim D.]

Ok so have done the linkage disconnect test. Idle is the same. The seems to be quite a lot of movement of the throttle spindles along the same axis as the spindles.

Going to talk to Neil F.

Tim

[TriumphV8]

Tim did you try to press the disconnected levers

by hand a bit more into close position when idling?

 

Ask Neil what he will do beyond fitting new spindles

because that is only half the way cutting away the play.

Best remedy is switching to ball bearings like Webers have:

 

 

combined with nice new homemade spindles:

 

[Tim D.]

Yes tried pushing down and nothing changed. Also wiggled the spindles and nothing happened.

Will talk to Neil.

Cheers

Tim

[YankeeTR5]

Well, a simple way to tell if air is leaking in from the spindles is to:

a)make sure the plenum is attached to the throttle bodies.

b)spray some carb cleaner (or WD40) or other type of misting spray around the spindle area with the car running.

 

A change in idle will indicate a leak from the spindles. You don't need to blast the area, just a small amount will do and, given its over the exhaust make sure your in a well ventilated area, preferably with the engine not hot. I find this method to be a relatively quick way to isolate the area where a vacuum leak is occurring.

[John L]

I still have a lot of play in the spindles on #2,4,6 cylinders, but I can get still a very low idle, as low as 500rpm.

I would suggest that you loosen the 4 screws per inlet group, and shut the lever this will centre the butterfly plates, then retighten the screws. If you have a carbon ring build up in the throats this has to be removed first.

You can check after tightening the 4 screws you should be able to trap a 0.002" feeler gauge, or cigarette silver paper if you still smoke, with the butterflies fully closed.

If this has been done, you must have air leaking in from somewhere else.

Cap off the servo take off point and the MU pipe and run the engine.

John

[Red 6]

I have only just read this so maybe a little late.

 

Firstly the inlet butterflies need regular maintenance, it is actually part of the service schedule.

 

The process is very simple but you will need to buy a gunson carb balancer to do it (V cheap on ebay)

 

This is what you do:

 

Remove plenum chamber

 

Disconnect the throttle bodies from the choke and accelerator cable and MU.

 

Loosen all screws and adjusters so as to effectively disconnect the throttle linkage from having any effect on the butterflies

 

Shut off the air bleed. Before doing this it is a good idea to remover the screw and thoroughly clean the pointed end and the mating surface inside the housing. Carb cleaner will do fine.

 

Now with the butterflies within each manifold totally free of any interference and the engine idling put the carb balancer on each butterfly and note the difference in airflow.

 

What I would expect to see is a different reading for each individual butterfly.

 

Once that has been done undo both screws on each butterfly so they are loose and snap them shut several times to re position the butterfly.

 

That should do the trick.

 

However when I do this I remove the manifolds, thoroughly clean the throats and butterflies with carb cleaner and then snap shut each one. Doing it this way allows you to see and adjust each butterfly disc.

 

Put them back on and using the carb balancer set up the throttle linkage as you would do if you were setting up SU's.

 

Sorry to be brief but I am being shouted at to get off the pc and get in the car to go out.

 

Hope this helps.

 

ps All spindles are worn to some extent but not enough to give you the idle you have so I think it is the butterflies.

 

Run the engine until warmed up.