• Hi Guest!
    You can help ensure that British Car Forum (BCF) continues to provide a great place to engage in the British car hobby! If you find BCF a beneficial community, please consider supporting our efforts with a subscription.
    There are some perks with a member upgrade!
    **Upgrade Now**
    (PS: Subscribers don't see this gawd-aweful banner
Tips
Tips

SU caruretor rebuild

Share this page

BOBBYR

BOBBYR

Jedi Trainee
Country flag
Offline
Hello Gang,
I hope you're all doing good tonight.Because my 3000 sat in storage for so long,the fuel system is in poor shape.(The fuel sat in the tank and carbs for 18 years).Being a mechanic for a living,I'm not too worried about tackleing this problem.Still I knew I had to get some imformation before ripping into these SU carbs.I just read an article writen by Jim Taylor and it was great.This guy really explains SU carbs to a science.Anyone interested,go to Google and type in "hd8 carburetor"and then go to "su carburetor notes".Anyone working on these,really should read this first.
Bobby R
 
Rebuilding these carbs is one of the more pleasant tasks in the restoration process, and should not be a problem for anyone who is patient and reads up first. They are not that complicated. The greatest tip I can give anyone is to do the carbs one at a time, always leaving one carb assembled for reference.
 
Hi Cutlass,
Thanks for the advice.I would think these carbs are pretty loaded up inside.
Bobby R
 
I'm just an amateur mechanic and am always intimidated by carbs. However I've been reading about the SU carbs. I really like the design so far. It is incredibly simple (the SU carb was invented in 1905 and has not really changed). I can rarely say this about a carburetor, but after reading about the design I feel like I completely understand how it works.

Here's a few articles about them:

https://www.classiccarclub.org/SU%20Carbskb.htm

https://mossmotors.com/forum/forums/thread/10464.aspx

https://mossmotors.com/forum/forums/thread/10469.aspx

https://sw-em.com/su_carbs.htm

The last article is particularly good.

I was just looking at one of my carbs last night. My car sat for almost the exact same amount of time, 18 years or so. I just took off four screws and removed the dashpot. There was the spring, piston, and needle. Easy.

As far as I can tell all I need to do is clean out the piston chamber and the fuel supply (float and bottom of the carb, to the jet) and I think it will run. It's really nice not dealing with multiple jets, accelerator pump, etc.
 
The only really bothersome part of the rebuild process is the price of the kit. But once past that, things are straightforward. You can get a one gallon carb cleaner dip, with basket, which is just enough for one carb. I would recommend it wholeheartedly. The only thing I would do differently, and may still do, is have some of the linkage parts zinc plated.
 
Yeah I can't believe how expensive the kits are. I think over $100 everywhere for each carb? Why so much? A complete carb rebuild is overkill for me right now since I'm just getting my car back on the road in driver status. Nice polished restoration later. I'm thinking I can just clean the important bits. An article or two that I've read seems to agree with me.
 
Hi Bobby, with your experience you won't have any trouble with these carbs. they are really quite simple and many downdraft carbs on typical american v/8s are easier to screw up. the su's can be cleaned up pretty well even while on the car, but i would recommend removal if they haven't been in use in a while. Three significant things about the HD8s which help to keep your mind in the right focus, (1)the main jet is adjusted by a verical screw along the main body in leu of an adjusting nut on the bottom of the other model SUs. (2)To do your final adjusting, the throttle plates are to be kept completely closed. Other SUs, the idle speed is adjusted by openning the throttle alittle. and (3) On the HD8, the idle speed is adjusted by use of an idle speed adjusting screw (similar to the idle screws of traditional American carbs) which is one of the larges slotted head screws on the carb and it controls a stream of "mixture" already mixed by the adjustment of the main jet around the closed throttle plate. Anyway, when you look at it, you will readily see it.
 
Just make sure the needle shoulder is set correctly to the bottom of the piston, and the choke is centred correctly, and from memory the bottom choke nut is wound up fully snug (gently!) and then backed off 3/4 of a turn as a start point
 
Hey Vette,
Thanks for the help.I'm looking foward to this job.I haven't been doing much other than buying parts lately.I'm basically going to rebuild the carbs and replace the fuel pump and the gas tank.
Thanks again,
Bobby R
 
Hi Carlivar,
I've already got a new solid state pump, although I'm planning on rebuilding the old one and keeping it as a spare.If I ever get my 3000 in the shape I want,it wouldn'tbe a bad idea to store in the trunk.
Bobby R
 
Back
Top