SU HD8 Rebuild and Restore How To Video

I created a how to video on rebuilding SU HD8s from an E type, but they’re on my XJ6, so I threw it here in the XK engine section in hopes of it helping more than just XJ6 guys. Enjoy!

I did NOT replace the needles, and I have not done shaft seals. Appreciate any input on what I did wrong, if needles are worth replacing vs just cleaning the old ones, etc. Cheers!

I personally do not replace needles

I have debated this before, as some say they are wear items, but as they are tapered, they can just be adjusted slightly

I have not seen evidence of wear

In the instance of shaft seals, I have not seen yr video yet ( I will look)

I have a lot of HD8 carbs, the test is to wiggle the shaft. If you can detect lateral play, it will be suspect as air is drawn in

I have never used a dial gauge to measure, its just by feel, and any movement is a reject, nearly half would fail this test, I believe the bush is very tricky, and best done by a pro, but have a look on the archives

( I just watched the vid, nice job, I would take more time over checking the shaft play)

I also put anti-seize on all dissimilar metals

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The needles are generally not wear items, unless the carb has been misadjusted or mistreated. But…over the years, fuel has changed. The stochiometric ratio of E10 is 14.1:1, as opposed to pure gasoline, which was 14.7:1. As a result, you may find that the car will perform better with a richer needle.

The Service representative from the unnamed official supplier of SU parts wanted to sell me new Jets and Needles, and when I enquired why, he stated the Jets could become ovalized from contact, and upon further questioning, that particulate matter in the fuel could “wear out” needles

I did then, and still do believe he was trying to upsize my order, he sounded a bit lame

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Well the main jets were definitely trash because the diaphram was junk on the bottom of it. so those needed to go for sure. Also multiple floats were bad, and the needle/seat in the float looked kind of bad too. And the choke linkages were gummed up.

very true for a diaphragm pump, the early H6 carbs have just a jet and needle

Not that I probably would, but I almost certain someone recently did just replace the rubber diaphragm, using the old jet

I also tend to prefer to leave original non-wear parts alone, rather than replace them , mainly because replacement parts are of unkown quality & fit

for sure the diaphragms normally need replacing, and I would also replace the jet springs that push them up, as they collapse from rust and cause tuning problems.

I used slightly stronger generic SS springs on mine

I wouldn’t trust that the float forks were adjusted correctly. You can end up chasing seriously frustrating issues like flooding and fuel starvation if they’re off. Since you’re changing float type, the factory spec for the fork might actually not even be correct any longer. But you need a consistent starting place so you know which way to move them.

Given the hassle you had accessing the banjo bolts in your application, you’re going to be a might bit disappointed if you reassemble it all and find your carbs are all flooding. I would suggest that you set the carbs to the factory initial startup settings, then figure out a way to plumb a single carb to the supply line and test the fuel level by removing the dash pot and piston, activating the pump, and measuring the fuel level inside the jet. There is a heuristic for that level. For security it be worth it to repeat for all 3 and verify the levels are consistently correct.