carby parts ..power JET

[my8thholden]

Hi all ..Stromberg carby ..Item 21 ,power by pass jet in section 6-35 of FE FC shop manual ..I have a few of these and one has 56 stamped on top of it and other 64 and another with no number ..what do these numbers mean ?

[Dr_Terry]

AFAIK these numbers are using the American gauge measurement system for the size if the jet.

No. 56 is 0.0465", & No. 64 is 0.036".

Dr Terry

[Jolls]

Hi all ..Stromberg carby ..Item 21 ,power by pass jet in section 6-35 of FE FC shop manual ..I have a few of these and one has 56 stamped on top of it and other 64 and another with no number ..what do these numbers mean ?

Hi Vern,

The pump bypass jets are stamped with the jet size in drill number (e.g. a jet stamped 56 has a 0.0465” diameter hole drilled in it). Not sure of the unstamped one.

Harv has produced a brilliant guide on Strombergs that has all of the information you need on different jet sizes etc. It can be sourced here: https://www.scribd.com/doc/238223610/FB-EK-Holden-Stromberg-Carburettion-Enthusiasts-Guide-Addendum-1

However, if you don't have access to it the jets are as follows:

56: 0.0465” diameter. Standard fitment to EH, HD, HR (149ci); HR (161ci); HD normal and economy excluding X2 (179ci), HR X2 and economy (186ci)
64: 0.0360” diameter. Not standard fitment.

Cheers

[Harv]

Yep, power bypass valves are sized in drill number. Larger drill number = smaller hole = less flow. Main metering jets are different - they are sized in thousands of an inch (larger number = larger hole = more flow).

Assuming there are only Holdens in the garage, the #56 has probably come out of a EH, HD, HR (149ci), HR (161ci), HD normal and economy excluding X2 (179ci) or HR X2 and economy (186ci). The #64 has probably not come out of a Holden, but would suit a grey (they were #63, #65 and #67 from factory).

From 1970, GMH used power bypass jets with two holes on the B-model carbs, and also on the WW's. Sometimes the holes are the same size, sometimes different depending on the engine they were going into. To complicate matters even more, from LC Torana and HQ Holden onwards, two stage power bypass jets were utilised, with the first stage opening at approximately 3-7” Hg (1½-3½psi), and the second stage at 10-12”Hg (5-6psi). From 1976 onwards, the settings were closer to 3-6”Hg (1½-3psi) and 8-10”Hg (4-5spi).

Cheers,
Harv

[my8thholden]

Thanks for the information gents ..firstly I made a typo , the one I thought was a 64 is actually a 65 ..and yes it is intended for a grey engine ...SO ! do I conclude correctly this valve was sized by GMH to the engine capacity , and therefore to the particular series of carby that was also fitted to that engine .

[Harv]

Yes - they were specific to engine and vehicle. Can you feel a difference if you put the wrong one in? Most of the time, probably not. For the greys:

Jet      Diameter Vehicle
#63     0.0370”   48, 53 (132.5ci)
#65     0.0350”   FB, EK, EJ (138ci)
#67   0.0320”   FJ, FE, FC (132.5ci)

Cheers,
Harv