"I am looking for suggestions for a more responsive and powerful carb setup for my 1985 Plus 8. I presently have the original Zenith Strombergs. The car will be used as a road car and
dependability is a must.  H. Smith"


Chris Crane

It has to be a Weber 500 conversion (aka Edelbrock Performer 500). There is no other simplistic and power, efficiency resultant upgrade. Previously, the only affordable upgrade carb option was the Holly 390cfm. Its problems have always been that it is too large (390cfm) for part throttle economy/torque, and too small for more serious top end power gains. So, unless you are into drag racing then my advice would be to forget it.

Unlike the Weber, the Holly float bowls are mounted, both in front and behind of the carburettor, causing fuel starvation and fuel flooding problems when hill climbing or fast cornering. The Weber float bowls are either side of the carburettor, completely alleviating the problem.

To re-jet the Holly (normally essential) it is required to remove the primary & secondary float bowls (plus Two hours removing the glued on gaskets) and another two mopping up  all the petrol that has spilled onto the intake manifold, (does wonders for new paintwork).  The primary side is easy enough to re-jet, but in most cases is fine as standard.  However, to re-jet the secondary's it is first required to purchase a "Metering Plate" this replaces the standard item between the carb and secondary float chamber and allows a fitment of various jet sizes. Because the Holly is vacuum only/secondary activation, a great deal of fuel is wasted in high load driving situations, where engine vacuum would activate the secondaries, even though not required. The Weber overcomes this problem by making the secondaries both vacuum and
 mechanically operated, This means, if your foot is not on the floor, you won't be wasting fuel or engine power, infact the torque gains on part throttle with the Weber carburettor is quite amazing, as is the cruise fuel economy. When set up properly it is not unusual for this system to surpass that of  fuel injection, and its certainly a lot less trouble. The Weber 500 can be re-jetted in minutes through the top and it has an adjustable power valve, so no need to buy up-rated ones. It can uses the same manifolds, filters and
linkages of the Holly. You will never regret the upgrade to this carb and you will get better mileage, better power or more reliable power than the Holly.

Bill Fink


Suggest Edelbrock intake manifold with smallest Holley 4-barrel (vacuum secondaries) available, Moroso type "drop center" air filter  housing, Cadillac diesel air filter.



John Sheally II

Dear H. Smith,

Throw the Stroms away or use them for a door stop. Order you a Offenhauser 360 intake for a Buick 215 and Install a 390 Holley Carb them your 1985 Plus-8 will be able to breath and run with the big


John H. Sheally II

John Worrall

I think your car had STROMBERG carbs as original.

A good replacement is the 4 choke Webber carb which you can buy complete as kit with all the fitting required. It comes with Inlet Manifold, Valley Gasket, Linkages, chrome pancake air filter etc. Gives substantially better performance and fits neatly under the Morgan Bonnet.

Hope this helps

John Worrall