SU height shortening
Discussion
Hi all
Hopefully you can help I have an MGB V8 which I want to fit SU on an aftermarket copy of the trouser manifold unfortunately the carbs are about 10mm to high.
When looking at the internet noticed a firm selling shortened SUs. I could do this my self if I knew the procedure. Anyone know what’s required. I’ve attached a picture and there description
You are looking at a HIF 44 SU Carb. The carb has been modified to suit a 1275cc MG MIDGET / HEALEY SPRITE The Dashpot and Piston have been machined to reduce the overall height of the carb and it is fitted with a flat topped damper. This reduces the carb height by approx. 15mm and allows fitting to most aftermarket inlet manifolds.
Hopefully you can help I have an MGB V8 which I want to fit SU on an aftermarket copy of the trouser manifold unfortunately the carbs are about 10mm to high.
When looking at the internet noticed a firm selling shortened SUs. I could do this my self if I knew the procedure. Anyone know what’s required. I’ve attached a picture and there description
You are looking at a HIF 44 SU Carb. The carb has been modified to suit a 1275cc MG MIDGET / HEALEY SPRITE The Dashpot and Piston have been machined to reduce the overall height of the carb and it is fitted with a flat topped damper. This reduces the carb height by approx. 15mm and allows fitting to most aftermarket inlet manifolds.
You need a lathe as a minimum.
If it was me, I would check the thread where the damper cap screws in to make sure the thread is long enough to allow a few mm to be faced off the top of the dashpot. This would require the dashpot to be held using external jaws in either a a three jaw (CC) or, if you're fussy, a four jaw chuck. If there aren't enough threads, I'd be investing in or making an 11/16"-24tpi tap to lengthen the threaded section - I've never had much success picking up an already cut internal thread with a single point threading tool.
Next, using internal jaws, I would set up the dashpot the other way round to allow the bottom flange to be faced by half its thickness (looks like half in the photo).
Finally, the top end of the piston's damper tube needs turning down by the same amount as came off the top of the dashpot.
Couple this with an earlier style damper cap and Bob's your auntie's live in lover!
Then it just needs a mirror finish polishing into it.
Note: I think there's enough room in the damper tube to prevent the damper bottoming out (could be wrong though)
If it was me, I would check the thread where the damper cap screws in to make sure the thread is long enough to allow a few mm to be faced off the top of the dashpot. This would require the dashpot to be held using external jaws in either a a three jaw (CC) or, if you're fussy, a four jaw chuck. If there aren't enough threads, I'd be investing in or making an 11/16"-24tpi tap to lengthen the threaded section - I've never had much success picking up an already cut internal thread with a single point threading tool.
Next, using internal jaws, I would set up the dashpot the other way round to allow the bottom flange to be faced by half its thickness (looks like half in the photo).
Finally, the top end of the piston's damper tube needs turning down by the same amount as came off the top of the dashpot.
Couple this with an earlier style damper cap and Bob's your auntie's live in lover!
Then it just needs a mirror finish polishing into it.
Note: I think there's enough room in the damper tube to prevent the damper bottoming out (could be wrong though)
Thanks for the reply
Looking at it quite a bit over the last couple of days (measure twice cut once) I have ordered flat top dampers and I think they will give enough clearance. The issue then is the Dashpot being to long. (the Dashpot go into the top hat top) so need to cut down the Dashpot, so this is the plan.
This way if it doesn’t run right I only need to new Dashpots to put back to standard.
Mick
Looking at it quite a bit over the last couple of days (measure twice cut once) I have ordered flat top dampers and I think they will give enough clearance. The issue then is the Dashpot being to long. (the Dashpot go into the top hat top) so need to cut down the Dashpot, so this is the plan.
This way if it doesn’t run right I only need to new Dashpots to put back to standard.
Mick
Gassing Station | Home Mechanics | Top of Page | What's New | My Stuff