FE-FC Holden Discussion Forum

Hi all,am looking for 45-48 carby jets x2 for my twins.I know this topic has been raised before but I can't find info on how jets can be soldered up and redrilled using number drills.Can you use normal solder or do they have to be brazed up?Have hunted high and low for the jets so am leaning toward redrilling.Do venturi restrictors still need to be used if you go lower with the jet sizes say 45's or so?My engine is a 138 and only has Speco exhaust manifolds and better breathing exhaust and I have only gone with the twins for the nostalgia factor.Any more help (other than what I have already read on the forum) greatly appreciated.Cheers,Jamie.

Hi Jamie,

I have been going through this lately and still haven't come to a positive conclusion. I trust the master carby guru Harv will offer some further thought to what I have to say and I would encourage you to look at his comprehensive Carby Guide. He has been wealth of information to me. I have twins and used them as stock with 48 mains for a few years. After much research here and over at the FB EK forum I placed restrictors in (got them at American Auto's). These alone made a huge difference particularly down low. Eliminated a flat spot. As I understand with my limited knowledge it will help low down but there is a trade off at higher speeds. By having two carbys on you are increasing (double)the size of the venturi. By doing this the air flow is reduced compared to a single carby. By placing restrictors in it increases the vacuum and velocity of air flow.

With this increased "suck" you need to reduce the Power Bypass Jets. I went from a standard 67 to a recommended 70 (this is a reduction in size). I will discuss how I did that in a minute. I originally put in 48 mains but the fuel economy was shocking (see my recent thread). I must say I also had the throttle spindles rebushed and this would have contributed to the extra "suck". I have played around with different jets and are currently running 46' looking at possibly reducing these because the fuel economy is not at the level it was before I started these mods.

Now for the jets. I searched high and low also. I had a mate who knew someone with jet drills. He plugged up the jets (not soldered) pressing in. He then redrilled. As for the Power Jets when I made the change I soldered them up and redrilled these myself. I searched on the net and was able to buy No:70 jet drill bits from a hobby shop in Melbourne rather cheaply. I didn't redrill these through the solder as you would have to with the mains. I drilled slightly off through virgin brass. You must be extra careful in not drilling through to far to damage the internal spring.

Anyway things got the better of me and I was after some more jets. I wasn't happy either that the tension of the springs in the Power Jets. I source some Stromberg 97 jets from Summit Racing in the states. The postage was a killer. I got two 70 Power Bypass Jets and three pairs of mains (46,47,48). The power bypass jets were 12.95 us each, and the mains 9.95 per pair. The postage was the killer and all items cost- wait for it $90 US (slightly less AU at the time due to the exchange rate).

Since then I decided to get some smaller main jets- 44 and 45's but decided against Summit due to their shipping costs (I have seen somewhere recently however that that have reduced their international shipping rates). I investigated further and received them through searching on ebay US. I contacted So-Cal_Speed_Shop. They were absolutely magic to deal with. Not only did they have very cheap shipping -$9.99 but they went out of their way for a small order. They made a special listing on ebay for me to order. To cap it off I received the jets in less than a week.

So in summary
1. Restrictors - Yes.
2. Reduce Power By Pass Jets to No:70 (either buy new or solder up and redrill - can get drills on net but will need to have a small drill mandrel / chuck- dremel???)
3. Reduce main jet sizes to somewhere between 46-48 to start with. If like me you may need to play around with it ie: smaller (once again you can get new or solder up)
4. I used normal solder.

I hope this info is of help but I am sure Harv will clarify some of my points.

Cheers

Rod

Jeez i love a single strommie... ;D
Good luck jamie sounds like fun.

Thats what I am thinking too. Often wonder why I went down that path.

Jamie,

Rods advice is great. A lot of guys throw a set of twins on, downsize the jets a little and are happy with the extra grunt (or extra nostalgia  ;D). Rod is doing the right thing (IMHO) - tuning the twins so they perform well (better than a single) without being thirsty. Takes patience, but worth it in the end.

The document Rod is referring to is here:
http://fefcholden.org.au/forum/index.php/topic,20117.0.html

Jet drilling is OK, though the pedant in me says that it is fiddly and somehow not quite right. I'd suggest solder/drilling until you find the right jet size, then order new ones from SoCal (American EE Stromberg jets are identical to Aussie BX Strommie jets  ;D). Lead solder is acceptable to use as the typical lead solder melting point is around 180ºC –petrol boils between about 20ºC and 210ºC… if the carburettor is hot enough to melt the solder, it‟s already boiling out most of the fuel. Care must be taken though as lead solder is very soft, and easily damaged (like by wobbling the drill bits around as you drill). Silver solder (melting point above 450ºC) is somewhat harder, but needs a lot more heat to get it to braze (more likely to distort the fiddly little brass parts or burn the spring out of a bypass jet).

Cheers,
Harv.

The jets are available locally, I am now running 44's with venturi restrictors without any issues in my triples ;D

Got them from the Carburettor Service Company (0297474066) good guys to deal with ;)

Mick 8)

Well I am sorry to put you all through this topic again but I must say I am overwhelmed by the awesome response from you all.The advice is invaluable and I'm glad I asked.I soldered the jets up tonight and redrilled them and without changing anything else at this stage it is already running better and not churning out heaps of black smoke at idle and smells less fuely if that makes sense.Will look into the new jets and venturi restrictors next.Anyone have a picture of the venturi restrictor?Thanks again to all.Jamie.

Mate just download this

http://fefcholden.org.au/forum/index.php/topic,20117.0.html

Everything you wanted to know about strombergs but were too afraid to ask ;D ;D ;D ;D

Mick 8)

P.S. plenty of diagrams and pictures and well written ;)