Stromberg Carbs
Discussion
Recently acquired a Defender V8 with a pair of Strombergs on it. Runs, but runs like a pig at present, so amongst other things a carb rebuild was prescribed. Kit arrived today and I set about it.....only to discover that the piston in one carb weighs twice what the one in the other carb does! Which won't have helped the running!
Other than trying to find a pair of gash carbs to buy and rebuild, I'm wondering what my other options are. I doubt that the pistons can be purchased new these days? I'm wondering whether to have a go at relieving the heavy piston with a Dremel? They look identical, but one is clearly made of more dense metal. Don't think I can easily ADD weight to the light one. Then again I don't know whether a heavy or light piston is good either!
Anyone got any thoughts?
Other than trying to find a pair of gash carbs to buy and rebuild, I'm wondering what my other options are. I doubt that the pistons can be purchased new these days? I'm wondering whether to have a go at relieving the heavy piston with a Dremel? They look identical, but one is clearly made of more dense metal. Don't think I can easily ADD weight to the light one. Then again I don't know whether a heavy or light piston is good either!
Anyone got any thoughts?
i don't think you have strombergs on there, should be SU's, the strombergs didnt have pistons IIRC.
Have you weighed the pistons or are they just different in the amount you have to lift them in the carb? if 1 is difficult but the other is easy it's often the wrong oil in there, too thick means more difficult to lift it.
If the pistons move up and down very easily it means the response is better. the harder it is to move them then it will be sluggish and as you have said, horrible to drive.
Have you weighed the pistons or are they just different in the amount you have to lift them in the carb? if 1 is difficult but the other is easy it's often the wrong oil in there, too thick means more difficult to lift it.
If the pistons move up and down very easily it means the response is better. the harder it is to move them then it will be sluggish and as you have said, horrible to drive.
Absolutely definitely Strombergs, not SUs! I've weighed the pistons, when I took them out I noticed the difference immediately, one weighs approx 120g whilst the other weighs 230g! They look identical in size (obviously!) but one seems to be made of a much more dense metal than the other, as apart from a slightly different colour, there is no obvious physical difference. I do know about the oil weight too, made that mistake once many years ago, if the oil is too heavy the car wont start at all.
The piston is item 29 in this diagram:
and looks like this once stripped and with the needle still fitted:
The piston is item 29 in this diagram:
and looks like this once stripped and with the needle still fitted:
CAPP0 said:
Hmm, I guess that's a possibility - what's involved in fitting EFI to an old tractor like this?
Megasquirt would be the best bet. Bit of work and will a little. But should make a massive difference. I guess other options are to buy some used Strombergs and try and get the best you can, convert to SU's or look into something like a Weber 500 cfm 4 barrel. Strombergs and SU's. IMVHO a design for the time, but unless you need to keep it original, I am completed converted to EFI.
Have now done 2 megasquirts, one of which was converting my V8 defender to megasquirt. (Admittedly the efi manifold was also bolted on top of a different engine). I wouldn't go back to carbs unless I had no choice.
Have now done 2 megasquirts, one of which was converting my V8 defender to megasquirt. (Admittedly the efi manifold was also bolted on top of a different engine). I wouldn't go back to carbs unless I had no choice.
The HIF style SUs are just as good for off road as the strombergs as they both have integral floats below the main jet and are not prone to as much fuel surge as old side float SU carbs.
Some SD1s were fitted with Strombergs, my Mum and Dad had an 84 Vanden Plas on Strombergs, it made good power but seemed to run on fart gas at cruise! I assumed ( don't forget that assume makes ass out of u and me) they were fitted for economy. Not so I have been informed by a customer who over saw the carb use....they were cheaper than SU to buy. And we all thought everything was factory fitted for us tuning folk
Strombergs have few needle variants available for tuning purposes.
Peter
Some SD1s were fitted with Strombergs, my Mum and Dad had an 84 Vanden Plas on Strombergs, it made good power but seemed to run on fart gas at cruise! I assumed ( don't forget that assume makes ass out of u and me) they were fitted for economy. Not so I have been informed by a customer who over saw the carb use....they were cheaper than SU to buy. And we all thought everything was factory fitted for us tuning folk
Strombergs have few needle variants available for tuning purposes.
Peter
Thanks for all this. FI would be good but looks pricey at first glance.
Seeing as I have the Strombergs (not to mention £100-worth of rebuild kit) and I know it did run on those, I think I'll see if I can get hold of a piston/pistons which are similar weight and get it going again on those before I decide on any other options. Seen one or two possibles for spares - it's just frustrating having to wait to get it running again!
Seeing as I have the Strombergs (not to mention £100-worth of rebuild kit) and I know it did run on those, I think I'll see if I can get hold of a piston/pistons which are similar weight and get it going again on those before I decide on any other options. Seen one or two possibles for spares - it's just frustrating having to wait to get it running again!
Quite right about the diaphragms. Some of the earlier TR ones are getting difficult to obtain as they are different fitting pattern than later ones.
It is a shame the carbs do not seem to be a matched pair. Some research needed to see which piston is correct for your application then match the wrong one. You need a Range Rover Guru to tell you.
If you are running a non standard air filter system you will have fun sorting the fuelling to be rich enough for cruise and maybe for full power too.
Peter
It is a shame the carbs do not seem to be a matched pair. Some research needed to see which piston is correct for your application then match the wrong one. You need a Range Rover Guru to tell you.
If you are running a non standard air filter system you will have fun sorting the fuelling to be rich enough for cruise and maybe for full power too.
Peter
Yes, new diaphragms will be going in as a matter of course, although there are no visible holes/splits.
Not been able to ascertain which weight piston I should be using. For the short term they guy at SCI thinks I could add weight to the light piston (piece of lead or similar wrapped around the piston shaft) and see how that runs. I'm on the trail of a couple of pairs of cheap/scrap carbs at the moment so I'd hope I can get a matched pair out of one of those. Maybe even two pairs then I can experiment. I'm sure it's all good fun really!
Not been able to ascertain which weight piston I should be using. For the short term they guy at SCI thinks I could add weight to the light piston (piece of lead or similar wrapped around the piston shaft) and see how that runs. I'm on the trail of a couple of pairs of cheap/scrap carbs at the moment so I'd hope I can get a matched pair out of one of those. Maybe even two pairs then I can experiment. I'm sure it's all good fun really!
@M4A - sent you a PM, let me know when you're about.
If anyone else has a pair of carbs for this engine I'd appreciate a PM. Not getting anywhere with the ones I have here so I need to try something else. Won't rule out FI but I'm trying to keep things simple.....
If anyone else has a pair of carbs for this engine I'd appreciate a PM. Not getting anywhere with the ones I have here so I need to try something else. Won't rule out FI but I'm trying to keep things simple.....
Edited by CAPP0 on Saturday 2nd March 21:36
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