Griff 500 vacuum leak

[Das882]

I bought a project pre serp about 10 days ago, one of the issues is that it obviously have a vacuum leak…. the car will idle perfectly with the base idle all the way in and the hose to the stepper clamped shut. The butterfly is also shut. I have checked the plenum and re sealed with Hylomar. Blanked off the servo and Carbon canister nipples. Checked the Fuel pressure regulator hose. PTFE on the Stepper valve. So except for the throttle spindle bush/seals and the rocker cover breathers there isn’t much else that I can think of. I would have thought that there would be something fairly obvious as a V8 at idle would need a fair volume of air even at idle.
Any ideas anyone?

[Belle427]

Try some carb or brake clean sprayed on the suspect areas such as gasket seals etc, do it on a colder engine though just for safety reasons.

[gavgavgav]

get a smoke machine, I was surprised where it was leaking for me: https://www.pistonheads.com/gassing/topic.asp?h=0&...

[eliot]

is the throttle heater fitted underneath the throttle - if it’s missing two of the four resulting bolt holes need to be plugged otherwise you end up with a unmetered air leak

[Das882]

I tried spraying Aero start around the potential leak areas without success, I’ve now decided to wait until I can get it smoke tested. I’m just about to strip the car down for a body lift, so I’ll attend to it later when the engine is either in the chassis or out.
Thanks for all the suggestions.

[Belle427]

Probably easier to do it when the body is off access wise.

[Das882]

[quote=Belle427]Probably easier to do it when the body is off access wise.
[ yes it definitely will, body is now off so I’ll concentrate on the chassis strip down and outriggers first ]

[Sardonicus]

You sure no one has cracked the butterfly open? (poor practice) i.e rather than having a slight air gap ... well just enough to stop the disc jamming in the housing instead the stop screw is wound up to open the disc further

[Das882]

[quote=Sardonicus]You sure no one has cracked the butterfly open? (poor practice) i.e rather than having a slight air gap ... well just enough to stop the disc jamming in the housing instead the stop screw is wound up to open the disc further [Ill have a look again, I know I did check that the butterfly was closed]

[eliot]

Sardonicus said:

You sure no one has cracked the butterfly open? (poor practice) i.e rather than having a slight air gap ... well just enough to stop the disc jamming in the housing instead the stop screw is wound up to open the disc further

as long as the plate is correctly centered on the shaft it shouldn’t jam even when closed.

[Sardonicus]

eliot said:

Sardonicus said:

You sure no one has cracked the butterfly open? (poor practice) i.e rather than having a slight air gap ... well just enough to stop the disc jamming in the housing instead the stop screw is wound up to open the disc further

as long as the plate is correctly centered on the shaft it shouldn’t jam even when closed.

They do under the triple springs pressure hence the air gap this also reduces the brass butterfly wearing the alloy bore/housing

[eliot]

Sardonicus said:

hey do under the triple springs pressure hence the air gap this also reduces the brass butterfly wearing the alloy bore/housing

I may of modified 1 or 30 of these plenums to 72mm..

[Sardonicus]

eliot said:

Sardonicus said:

hey do under the triple springs pressure hence the air gap this also reduces the brass butterfly wearing the alloy bore/housing

I may of modified 1 or 30 of these plenums to 72mm..

I know you did mine about 8 years ago