MGB Weber 45 DCOE help
Discussion
Anyone got any knowledge of what jets/choke for a 45 Weber on a 1800cc with a fast road Kent Cam 2" sports manifold/exhaust and open trumpets? Just had it all put together and the engine is new so I don't want to put it on a rolling road as yet. I bought the carb 2nd hand it was set up for a standard MGB engine. I don't know what sizes are in at the moment has anyone any ideas?
Thanks.
Thanks.
Are you chasing max power at WOT only (in other words racing?) if not sell it and stick SUs on it. Genuine advice from someone who's been there and backed up by the men who know what they are talking about. Your going to gain one or 2 HP at peak power, possibly lose power and driveability through the rest of the rev range and certainly use a lot more fuel. They just don't suit the Siamesed port A and B series all that well.
If however you are going with the carb, fit as is, take to rolling road and let them match it to your engine, you need a man who knows them, if your anywhere near Yorks I can recommend one to you I trust with Webers. If not then you need to find someone local. Do not consider going with a vague set up and leaving as is. It will end up rich or weak in parts of the rev range and will either wash bores or burn pistons/valves. Had a few engines in B and midgets with webers fitted by previous owners and destroyed because the carb wasn't set up. Made for cheap cars for me, with a very sellable carb that more than paid for the repairs......Wasn't good for the POs.
If however you are going with the carb, fit as is, take to rolling road and let them match it to your engine, you need a man who knows them, if your anywhere near Yorks I can recommend one to you I trust with Webers. If not then you need to find someone local. Do not consider going with a vague set up and leaving as is. It will end up rich or weak in parts of the rev range and will either wash bores or burn pistons/valves. Had a few engines in B and midgets with webers fitted by previous owners and destroyed because the carb wasn't set up. Made for cheap cars for me, with a very sellable carb that more than paid for the repairs......Wasn't good for the POs.
Actually sold the original SU's and bought the weber the engine is a brand new Unipart one from 1978 that I bought from the classifieds on here. It was still crated covered in wax paper so I have had a Kent cam and Peco manifold and 2" system put on it all from Moss and had the head sorted for unleaded. I just want it for the road and really didnt want to sell it on and go back to the SU's. I was going to take it to Minisport in Padiham on their RR but with being brand new I wanted to get a few miles on it 1st and wondered if anyone else had this set up so I can get a little bit closer to the correct sizes so as not to do the damage you have mentioned while I run it in. I take your ponts on board but still if possible want to keep the Weber.
Would be willing to travel if not too far where/who is the one you recommend, I live nr Preston?
Would be willing to travel if not too far where/who is the one you recommend, I live nr Preston?
Edited by barefoot on Wednesday 15th June 20:58
Edited by barefoot on Wednesday 15th June 20:59
No point in travelling from preston, these guys aren't that rare. The one I use is Dave Boggs in Luttons near Sledmere.
Going off that spec I strongly advise you to use a set of late B HIF4 carbs lightly flowed. You need a much heavier worked engine to get any real benefit from that carb.
Also don't run open trumpets you will screw the engine in a few thousand miles (been there done it). Run standard alloy air cleaners (as fitted to the B as standard) with either K+N elements in the standard housings or the K+N MGB plate type filters. Which cam are you using?
Going off that spec I strongly advise you to use a set of late B HIF4 carbs lightly flowed. You need a much heavier worked engine to get any real benefit from that carb.
Also don't run open trumpets you will screw the engine in a few thousand miles (been there done it). Run standard alloy air cleaners (as fitted to the B as standard) with either K+N elements in the standard housings or the K+N MGB plate type filters. Which cam are you using?
Haven't been on for a while but these Weber on MGB topics always make me feel like I need to play "Yer Old Man Telling you Whats Right" etc.
First and foremost; Unles you are intending to drive everywhere at between 3 and 4000 RPM with a reasonably spikey cam, don't bother.
SUs are designed to be progressive accross a range and can be far nicer to drive with than the occasional "hitting the sweet-spot" roar of a Weber.
A 45 is really only for track days and racing and a 40 will only be tractable on a long inlet manifold and even then you will be (should be) changing your oil every 2000 miles. The simple fact is that the standard design of a B head without major porting and over-sized valves leads to wasted fuel - most of which is forced past rings and IV seals.
And as stated previously a sidedraught will only add about 4bhp even with a decent extractor manifold (There are some real shiny but garbage manifolds out there atm)
So instead of shortening the life of what sounds like a very nice engine, invest some time rebulding the SUs that you have OR find some decent HS4s or even 6s and play with those - your rewards will be far greater. If you are a tart for a deep throaty suck then by all means put some trumpets on but get some nice furry socks for them - 100 miles on a dusty road with no protection will take about 3 microns off your bores.....honestly....we have done it!
The biggest single improvement you can do to a B for the least cost is a decent leccy dizzy (I was so impressed I bought the franchise etc) I won't mention names but experience has shown that plugs, leads, cap and especially rotor arms in good nick with a trigger type module and fat coil will add/give back anything between 3 and 10 bhp to your engine. And you don't have to pay silly money for them - ultimately they all use the same basic components.
I know that nothing looks better than a B engine with a Weber and extractor and lots of shiny pipework but you are wasting money unless you are going racing.
If you really, really, really, want a list of jets/needles etc for different applications for Webers (and Dellortos) - contact me via here or Liskeard Classic Cars and I will help as much as possible.
Somewhere out there is a green and yellow Robin Hood with a 2 litre Alfa twink engine running 4 x 1 and a quarter SUs....and it produced more bhp than the twin 40s - let me know if you know where "Grenville" is.
'til next time......
First and foremost; Unles you are intending to drive everywhere at between 3 and 4000 RPM with a reasonably spikey cam, don't bother.
SUs are designed to be progressive accross a range and can be far nicer to drive with than the occasional "hitting the sweet-spot" roar of a Weber.
A 45 is really only for track days and racing and a 40 will only be tractable on a long inlet manifold and even then you will be (should be) changing your oil every 2000 miles. The simple fact is that the standard design of a B head without major porting and over-sized valves leads to wasted fuel - most of which is forced past rings and IV seals.
And as stated previously a sidedraught will only add about 4bhp even with a decent extractor manifold (There are some real shiny but garbage manifolds out there atm)
So instead of shortening the life of what sounds like a very nice engine, invest some time rebulding the SUs that you have OR find some decent HS4s or even 6s and play with those - your rewards will be far greater. If you are a tart for a deep throaty suck then by all means put some trumpets on but get some nice furry socks for them - 100 miles on a dusty road with no protection will take about 3 microns off your bores.....honestly....we have done it!
The biggest single improvement you can do to a B for the least cost is a decent leccy dizzy (I was so impressed I bought the franchise etc) I won't mention names but experience has shown that plugs, leads, cap and especially rotor arms in good nick with a trigger type module and fat coil will add/give back anything between 3 and 10 bhp to your engine. And you don't have to pay silly money for them - ultimately they all use the same basic components.
I know that nothing looks better than a B engine with a Weber and extractor and lots of shiny pipework but you are wasting money unless you are going racing.
If you really, really, really, want a list of jets/needles etc for different applications for Webers (and Dellortos) - contact me via here or Liskeard Classic Cars and I will help as much as possible.
Somewhere out there is a green and yellow Robin Hood with a 2 litre Alfa twink engine running 4 x 1 and a quarter SUs....and it produced more bhp than the twin 40s - let me know if you know where "Grenville" is.
'til next time......
my two pen'th as a owner of road going classics only - you've been given great advice already but I'll add mine -
personally I've not heard good stuff abour sock filters and if you go electronic ignition which I think is preferable don't forget you're putting the new part into the old and no doubt worn and inaccurate rest of dissy, better still is to had a new electronic dissy, I can recommend a fully electronic 123 dissy and you can get programable one for those cars with entirely different set ups
I'd also recommend performanceleads HT lead set made by the people who make leads for other well known name(s)
personally I've not heard good stuff abour sock filters and if you go electronic ignition which I think is preferable don't forget you're putting the new part into the old and no doubt worn and inaccurate rest of dissy, better still is to had a new electronic dissy, I can recommend a fully electronic 123 dissy and you can get programable one for those cars with entirely different set ups
I'd also recommend performanceleads HT lead set made by the people who make leads for other well known name(s)
Barefoot, just seen this thread. All the chaps advice above ref' SU's v's Webers is bang-on. Unless you're into shiny bits on your MG or planning to race, don't bother with Webers. Even most of the period rally cars run with HIF4 or HS6 SU's.
The reason is that the only real advantage with Webers is on pick-up. A Weber has better pick-up than a std SU, and, a Weber will always increase your fuel consumption. However, and this is where it gets exciting, a slightly modified/tuned SU can be made to perform nearly as well as a Weber[!]
Realistically, if you've got a slightly mod'ed engine then a well set-up pair of HIF4's will really do the job. Do fit K&N's as advised + change needles [see MOSS catalogue] + change throttle discs to non-poppet types. There are other tweaks you can read up on and do as and when. If wallet's feeling full this month do think about changing the manifold+exhaust for better balanced flow. The 123 distributors are very good!! But, you should think about ensuring your timing chain has no slack too. If so, fit a Duplex with Vernier which will ensure timing is spot-on.
Once you've chosen and made changes, do get set-up on a rolling road. The 123 advance curves can be set-up correctly at this point. Good luck and have fun tinkering!
The reason is that the only real advantage with Webers is on pick-up. A Weber has better pick-up than a std SU, and, a Weber will always increase your fuel consumption. However, and this is where it gets exciting, a slightly modified/tuned SU can be made to perform nearly as well as a Weber[!]
Realistically, if you've got a slightly mod'ed engine then a well set-up pair of HIF4's will really do the job. Do fit K&N's as advised + change needles [see MOSS catalogue] + change throttle discs to non-poppet types. There are other tweaks you can read up on and do as and when. If wallet's feeling full this month do think about changing the manifold+exhaust for better balanced flow. The 123 distributors are very good!! But, you should think about ensuring your timing chain has no slack too. If so, fit a Duplex with Vernier which will ensure timing is spot-on.
Once you've chosen and made changes, do get set-up on a rolling road. The 123 advance curves can be set-up correctly at this point. Good luck and have fun tinkering!
v8250 said:
do get set-up on a rolling road. The 123 advance curves can be set-up correctly at this point. Good luck and have fun tinkering!
I’ve put a hint in the link here (sounds like a village) see the Home pagena said:
I can recommend a fully electronic 123 dissy
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