Lotus Elan and Lotus Elan Plus 2 Forums

These cars are still all new to me, but this looks like it?s been modified. For an otherwise stock S4 is this a problem?

Thanks!

This depends on how deep the apparent plugs are. What you have is the Federal Stromberg crossover manifold. As delivered there were pipes that connected to the cast exhaust manifold. These pipes took the intake mixture over to the exhaust manifold for preheating (to reduce emissions) and back, at part throttle. What most people have done with his setup is to remove the crossover pipes, cover the holes in the intake crossover manifold with plates, and removed or oriented the (first) butterfly in this manifold so that only the secondary butterfly is in effect.

The crossover manifold needs to allow for balancing between the carbs like the non-emission Stromberg setup which has a balance tube. The Federal manifold effects this same balancing by its internal channels - but if the plugs you have shown extend into these channels this could deleteriously effect the balance function.

It might make sense to remove these apparent plugs and simply apply a plate(s) to cover the holes like what is done by others.

I do have a spare Stromberg crossover manifold if it is of interest, with the holes covered by two plates.

Thank you for a very thorough reply, super helpful. In my case it looks like this was welded closed, so not easily reversible and I suppose I should just go with what I have?

Here is a picture of the non-federal version, a three-piecer. The goal is to allow airflow between the stromberg carbs for balancing - well explained in prior threads - so as long as your federal version similarly allows the proper airflow between the 2 sides you should be ok. If the filler goes deep enough to prevent the 2 sides from connecting, you'll have issues.

Thanks Henry, I'll check that.

Confirmed that I have good flow between the sides still, going to call this good.

Thanks!