Inlet manifold 'nipples'.

[M.J.S]

I'm determined to put the car back on the road before the summer is out. I'm about to pull the engine to have the water pump overhauled, clean up and repaint the block and head, and carry out a list of other jobs.

One such job concerns the four 'nipples' on the inlets. I assume these are for tuning purposes to set the airflow?

One of them is snapped off; has been for years by the look of it.

1. Is it worthwhile to go to the effort of having the broken one drilled out, tapped and the nipple replaced?
2. Do they really serve a purpose? Most twin cams I see do not appear to have them.
2. Are the original nipples available, or something comparable?
3. Is it likely I might end up having to do all four? I've not tried slackening them off yet, but they don't look very sturdy.

I've tried to find a thread on the subject, but the word 'nipple' doesn't bring the right results;-)
Thanks.

[john1180]

Pic would help a lot

[billwill]

I suspect that those were an owner modification.

[mbell]

As been said probably an owner modification. I'd guess for balancing the carbs v vacuum signal.

[M.J.S]

Photo attached. They don't have look of an owner's aftermarket addition, but perhaps they are. Car is a December 1972 +2 130/5.

[ElliottN]

They're a PO modification. I'd leave well enough alone and wouldn't mess with them.

[denicholls2]

Hooked up to four independent vacuum gauges and provided that they have close to the same throughput, these would have the same role as carb synchronizers attached in place or in way of the trumpets but be a lot less expensive than buying four and allow modification with all of the other hardware in place.

They might also be suitable for nitrous oxide injection if you're willing to take a walk on the wild side.

I vote for "ignore them" except:
- You don't want any of them open, they will suck unfiltered crap into your engine. They look like brake bleeders, but are they designed to close when screwed in? Simple fix is either a same size rubber cap or a hose connecting the pair on the same carb. (mini balance tube)
- It's worth assessing their protrusion into the intake. They will have an impact on intake flow, how negative that is depends on how much the topography of the intake runner is affected.

I doubt they were intended to affect runtime performance (other than negatively as above), a balance tube would need to be larger in diameter. See same on Stromberg heads.

[bill308]

Hi M.J.S.

The proper term for these fittings are "hose barbs". They are indeed used for synchronization of the carbs or to balance the airflows through each carb. It appears you have a Weber head, so the 4-hose barbs are appropriate and very useful if you learn how to use them and acquire the necessary instrumentation. These hose barbs tap into the intake bore and enable the resulting vacuum signal of each intake tract to be measured with a suitable instrument. The most suitable instrument is a 4-bank manometer system as used by 4-cylinder motorcycles for tuning. When not tuning, they hose barbs are capped off, I use a short piece of silicone tubing with a plug in one end. I installed a similar set on my Elan decades ago and also on my carb 308 Ferrari. On the Elan, I installed them on the bottom of the intake runners for operational and cosmetic purposes.

Bill

[Quart Meg Miles]

I drilled and tapped the manifold on my first rebuild (1970?) but sealed them with screws, for normal running, as my home-made "nipples" were just tubes. I would remove yours and fit bolts with a sealant as on a recent head-test mine were found to be leaking.

Weber 151s include monitor points and a quad vac meter at ?50 makes it very simple to set them up.

[billwill]

Delortos also include these ports.