The V8 Owners Forum -

Hi guys,
I need an additional two Vacuum take off's, one for the adjustable fuel pressure regulator and the second for the vacuum gauge.
There is only one at the moment and that's at the inlet for the distributor.
Can I drill and tap a new take off on the plenum chamber and if so is there an ideal location?
Many thanks.

Can you not just tee off the current vacuum?

paulsv8manta wrote:Hi guys,
I need an additional two Vacuum take off's, one for the adjustable fuel pressure regulator and the second for the vacuum gauge.
There is only one at the moment and that's at the inlet for the distributor.
Can I drill and tap a new take off on the plenum chamber and if so is there an ideal location?
Many thanks.

If this is an EFI RV8. there should already be a vacuum take off for the fuel reg. I just added an additional one for the MS MAP sensor along side it. Found a suitable brass barbed tube threaded at one end from Demon Tweeks or similar.

However, if that is awkward, the trumpet base has three bosses where takeoffs are provided depending on model. Be easy to drill and tap those.

I am using one vacuum take off from the plenum to both my MAP sensor and fuel pressure reg and dump valve.

Seems to work fine, Is there any advantage/reason I should have a separate take of point for each vacuum device?

Thanks for getting back to me, I wasn't sure I could t-off the existing vacuum. thought it might impair the performance of the distributor.

Think I'll drill and tap the spare boss at the base of plenum.
Cheers Guys

paulsv8manta wrote:Thanks for getting back to me, I wasn't sure I could t-off the existing vacuum. thought it might impair the performance of the distributor.

Think I'll drill and tap the spare boss at the base of plenum.
Cheers Guys

You are correct, the distributor vacuum pipe should not be used as it will not give full manifold vacuum and would only give vacuum on light throttle. This is known as a timed vacuum port.

SuperV8 wrote:I am using one vacuum take off from the plenum to both my MAP sensor and fuel pressure reg and dump valve.

Seems to work fine, Is there any advantage/reason I should have a separate take of point for each vacuum device?

If your dump valve has a bleed system like the HKS two stage progressive type, then that should have a separate vacuum take off.

If your dump valve has a bleed system like the HKS two stage progressive type, then that should have a separate vacuum take off.

No, just a standard/simple dump valve, so i'll leave as is then, thanks.

Tom.