Twin 1 5/32 Strombergs on 186?

[Bjamo]

First off, I hope you can excuse me but this engine is actually in a HR. It just seems that there are some folks here that are very cluey about Strombergs so I thought I'd ask.

Anyway. It has a stock 186 & Powerglide. I've got X2 Headers and a 9 port head with some port work, bigger valves and dual springs to go on. I bought a twin downdraft Stromberg set (Carbs, manifold, linkages) but they're both 1 5/32 - am I correct in thinking the X2s used 1 3/32? Does anyone know if I'll have any trouble setting these up, getting them running right, or whether it's worth sourcing the smaller carbs?

Cheers,
Blake

[Trev]

Hi Blake, I would get the smaller carbs, especially on a stock 186.

I ran an X2 setup (1/3-32 carbs) on my stock 179 and I thought they were good untill I tried a single carb (1/5-32) and the power increase was so good I will never go for twin carbs on a stock motor again.

Hope this helps, Trev.

[Harv]

G'day Blake,

The HR 186 motors had a variety of Strommies fitted - single 1 3/32" on the taxi motors, 1 5/32" on most, and 1 28/32" WW Strommie on the 186S (Craig - correct me if I'm wrong here... I'm no late model expert ).

The larger carbs will run, and will give it more highway legs than the smaller ones. You may find however that the lower venturi velocityies on the larger carbs can cause poor throttle response down low, and a bog off idle... not to bad if this thing is a drag strip warrior or speedway vehicle, but can be annoying around town. If it was mine, I'd use the existing carbs and fit venturi restrictors (cheap and easy to fit). If it was still boggy, I'd go for the smaller carbs.

No matter what carbs you are running, you are going to need to jet them way down. Some guidance on jetting here:
http://www.fbekholden.com/forum/viewtop ... 25&t=14756
and an open offer to help out here:
http://www.fbekholden.com/forum/viewtop ... 25&t=17922

In any case, I'd pull one carb off and measure the inlet manifold carb hole size. If if is 1 5/16", the manifold has been set up for the 1 3/32" carbs (they had 1 5/16" throttle bodies). Running larger 1 5/32" carbs (which had a 1 7/16" means on that manifold means the air flow comes down into the throttle body then hits a ridge... not good for air flow. Either bore out the manifold to 1 7/16", or use the smaller 1 5/16" throttle bodies.

Cheers,
Harv (deputy apprentice Stromberg fiddler).

[Bjamo]

Cheers! This car is my daily driver. I'll give it a go with the venturi restrictors and come back with results - this will likely be a couple months away though. With the manifold holes, will there be a noticeable difference if the carbs and manifold are not the same size, i.e. bigger carbs on a manifold meant for smaller carbs? Or is it more of a fine difference? I'll measure the manifold in the next couple of days.

Cheers for the advice!
Blake

[Harv]

G'day Blake,

If you are just tooling around town, you won't notice a huge difference due to the mismatch in hole size. The manifold lip will tend to condense some fuel, making mixtures a little erratic but not massively so (it's only a 3mm or so gap). You'd notice it more on the top-end. Where people notice a big restriction is using the adaptor plates to mount bigger carbs(eg Holley) to the standard Strommie manifold. The adaptor plates effectively have a "dead end" that condenses fuel badly.

Cheers,
Harv

[Bjamo]

Cheers! I'll probably stick with the 1 5/32 on the manifold with smaller holes - I get that it's not ideal, but I'm not after a drag car. Twin carbs are just cool. I'll get a hold of some venturi restrictors, do you (or anyone else) have a ballpark figure for jetting?

I really appreciate the help!
Blake

[Harv]

G'day Blake,

For guidance on jetting, try here:


Cheers,
Harv