Changing jets in a 4150

[427James]

Hi guys,

My 1970 running a 4150 DP has been running rich for what feels like for ever so I took it off the car yesterday and stipped off the float bowls.

For some reason the jets in the sodding thing refuse to come out - the old 4160 required a light flick of the wrist on a suitable screwdriver, but these are completely immovable.

Does Holley make metering blocks where you cant remove the jets?

ETA its an Ultra Double Pumper with billet metering blocks.

Edited by 427James on Saturday 29th December 07:59

[roscobbc]

427James said:

Hi guys,

My 1970 running a 4150 DP has been running rich for what feels like for ever so I took it off the car yesterday and stipped off the float bowls.

For some reason the jets in the sodding thing refuse to come out - the old 4160 required a light flick of the wrist on a suitable screwdriver, but these are completely immovable.

Does Holley make metering blocks where you cant remove the jets?

ETA its an Ultra Double Pumper with billet metering blocks.

Edited by 427James on Saturday 29th December 07:59

I would have thought that being a 'hi-spec' carb it certainly would have removable primary and secondary jetting. It was only the lower spec' 4160's and their equiv's that generally had a secondary metering plate with fixed jetting. Perhaps you need a specific jet removing tool (a screwdriver type tool with a 'shrouded' head - would a 'Snap-on' van man keep something like this?) or try and grip the offending jet in a vice whilst 'turning' the metering block. Don't worry too much about the secondaries - concentrate on the primaries - you OK on checking out the mixture the 'old school' way?

[427James]

roscobbc said:

I would have thought that being a 'hi-spec' carb it certainly would have removable primary and secondary jetting. It was only the lower spec' 4160's and their equiv's that generally had a secondary metering plate with fixed jetting. Perhaps you need a specific jet removing tool (a screwdriver type tool with a 'shrouded' head - would a 'Snap-on' van man keep something like this?) or try and grip the offending jet in a vice whilst 'turning' the metering block. Don't worry too much about the secondaries - concentrate on the primaries - you OK on checking out the mixture the 'old school' way?

Cheers Ross. I think the problem is that the Ultra uses an Aluminium block and the brass has a different tendancy to expand in heat, so it becomes welded into the bloody metering block. Have ordered the jet removing tool and will try again in a week or so with a freeze your nuts off can and the right tool - one of the jets may need drilling out carefully in any event now.

[427James]

427James said:

Cheers Ross. I think the problem is that the Ultra uses an Aluminium block and the brass has a different tendancy to expand in heat, so it becomes welded into the bloody metering block. Have ordered the jet removing tool and will try again in a week or so with a freeze your nuts off can and the right tool - one of the jets may need drilling out carefully in any event now.

Ross, by way of update on the 383 swapped the jets down in the primaries to 68s (leaving the 2ndaries rich) and it runs a treat. Also adjusted the auto choke to come off a lot quicker. No more fouling plugs after 150 miles. Thanks for all the help.

[roscobbc]

427James said:

427James said:

Cheers Ross. I think the problem is that the Ultra uses an Aluminium block and the brass has a different tendancy to expand in heat, so it becomes welded into the bloody metering block. Have ordered the jet removing tool and will try again in a week or so with a freeze your nuts off can and the right tool - one of the jets may need drilling out carefully in any event now.

Ross, by way of update on the 383 swapped the jets down in the primaries to 68s (leaving the 2ndaries rich) and it runs a treat. Also adjusted the auto choke to come off a lot quicker. No more fouling plugs after 150 miles. Thanks for all the help.

If you wanted to be really 'brave' you could (if still having issues) try different idle air bleed jets (if the carb has them)