Need some advice on Carburettors
Discussion
i have had a number of issues with my spitfire but namely it seems to be the fault of the carburettor, its an aftermarket Weber DCOE 45 that was put on for competition use a few years ago, and the engine has a high lift cam fitted and different valve springs. but at the moment it seems to be fouling the plugs every time it is driven, so we took it to the local garage , he tarted around a bit and peeked inside the carb, he said that it needed to be rebuilt. so i bought a rebuild kit and set to it, replacing the main jet and the gaskets (not touching the tune) took me all day to finish but it seemed to do the job because as we took it back to the garage it was all working fine, a few days later i get a call from the mechanic saying 'its fouled the plugs again, and as much as i tune it it doesn't make any difference!'
He said that the Carb on the car isn't suitable and really isn't necessary, as webers are designed for cross flow heads and this isn't one. he suggests buying some stock SU's and fitting them instead. i just wanted some advice on where to go from here, is it an issue that can be solved without new carbs? or should i just buy them?
and yes i have given everything a good clean since the picture was taken
thanks again.
He said that the Carb on the car isn't suitable and really isn't necessary, as webers are designed for cross flow heads and this isn't one. he suggests buying some stock SU's and fitting them instead. i just wanted some advice on where to go from here, is it an issue that can be solved without new carbs? or should i just buy them?
and yes i have given everything a good clean since the picture was taken
thanks again.
adamliptrot said:
I know people run that type of carb on MGBs, but generally from what I've read it's only worth the hassle of setting up if you are competing. If not the general advice looks to be go back to SUs.
That's great info thanks, been searching ebay for a complete set To refurb. Daniel,
I might be wrong but when you had problems before you got the same advice about SU's over Webbers on your car but Webbers can be made to work on your car
however if you can sell the Webber to finance a set or single SU then that would probably be better but be aware if you need to change other things like manifold, cables, filter(s)
also be aware that SUs can be worn mismatched, incomplete, wrong parts and fittings so buy carefully
once you have the (whole) car serviced and set well the carbs, if in good condition, can be set and left alone - no fiddling with them later - this means sometimes they are slightly at a compromise but that's carbs for ya and why they're not on cars now
set in this order - tappets, points, plugs, timing then mixture
to check you're getting the best out of your carb(s) and have the correct needles take your car to Peter Burgess for an excellent value rolling road tune (best done after your car has been fully serviced and tested) - http://www.peter-burgess.com/index.html
I might be wrong but when you had problems before you got the same advice about SU's over Webbers on your car but Webbers can be made to work on your car
however if you can sell the Webber to finance a set or single SU then that would probably be better but be aware if you need to change other things like manifold, cables, filter(s)
also be aware that SUs can be worn mismatched, incomplete, wrong parts and fittings so buy carefully
once you have the (whole) car serviced and set well the carbs, if in good condition, can be set and left alone - no fiddling with them later - this means sometimes they are slightly at a compromise but that's carbs for ya and why they're not on cars now
set in this order - tappets, points, plugs, timing then mixture
to check you're getting the best out of your carb(s) and have the correct needles take your car to Peter Burgess for an excellent value rolling road tune (best done after your car has been fully serviced and tested) - http://www.peter-burgess.com/index.html
Edited by na on Wednesday 21st November 21:25
As above, two options really.
1)Go back to SUs. This would be a sensible option IMO. They're plenty enough carb for the engine even in a warm tune (The same ones quite happily do the job on my 1850cc Dolomite or on an MGB). They're easier to get running properly at home than a DCOE, and the bonus is that you'll be able to flog your current carb and manifold for more than the SUs and manifold will cost you.
2)Get the DCOE sorted. You've got a lot of running issues at the moment, some of which will be down to the carb, some to the ignition, and some down to the camshaft. If you get it to a rolling road you should be able to get it to run a lot better, but the DCOE really isn't a "pottering around town" carburettor, if you know what I mean.
1)Go back to SUs. This would be a sensible option IMO. They're plenty enough carb for the engine even in a warm tune (The same ones quite happily do the job on my 1850cc Dolomite or on an MGB). They're easier to get running properly at home than a DCOE, and the bonus is that you'll be able to flog your current carb and manifold for more than the SUs and manifold will cost you.
2)Get the DCOE sorted. You've got a lot of running issues at the moment, some of which will be down to the carb, some to the ignition, and some down to the camshaft. If you get it to a rolling road you should be able to get it to run a lot better, but the DCOE really isn't a "pottering around town" carburettor, if you know what I mean.
OP, na and davepoth have both given good advice. i have a considerable preference for SU's over Webers so the following recommendation is biased; but with good reason. a carefully tuned/mod'ed SU will perform as well as any comparable to application Weber except in one area...from standing start. SU's are far easier to set-up, tune, modify, maintain than other carburettors.
your Spitfire is not designed as a fire-breathing dragon all-out racer. one imagine's the previous owner was trying to get a reliable fast'ish road spec' but did not match up ignition, cam, and carb's...a classic error.
price-wise, have you spoken directly with Burlen Fuels yet? they are able to supply either brand new, and/or, beautifully refurbished units. also, if you talk with them ref' your Spitfire giving them the profile of you cam they'll be able to recommend the state of tune you need for your SU's i.e. needles & springs. also, Burlen have a VERY well respected ref' guide which covers nearly every SU application known to man.
if you know you've then got good/correct/accurate ignition, good clean fuel/air supply, and known carb' status...then your ready for a rolling road set up. if peter burgess is near to you, use him. he has a very good reputation.
lastly, you mention the current state of 'tune' was designed for competition. when this work was done, were the block and head skimmed? if so, your engine could be running hotter; does it? if it does give your complete cooling system a thorough reverse flushing until crystal clear both ways. then refill with 50:50.
your Spitfire is not designed as a fire-breathing dragon all-out racer. one imagine's the previous owner was trying to get a reliable fast'ish road spec' but did not match up ignition, cam, and carb's...a classic error.
price-wise, have you spoken directly with Burlen Fuels yet? they are able to supply either brand new, and/or, beautifully refurbished units. also, if you talk with them ref' your Spitfire giving them the profile of you cam they'll be able to recommend the state of tune you need for your SU's i.e. needles & springs. also, Burlen have a VERY well respected ref' guide which covers nearly every SU application known to man.
if you know you've then got good/correct/accurate ignition, good clean fuel/air supply, and known carb' status...then your ready for a rolling road set up. if peter burgess is near to you, use him. he has a very good reputation.
lastly, you mention the current state of 'tune' was designed for competition. when this work was done, were the block and head skimmed? if so, your engine could be running hotter; does it? if it does give your complete cooling system a thorough reverse flushing until crystal clear both ways. then refill with 50:50.
more good advice from davepoth and v8250 and I certainly not saying that because we all agree because often we don't
I will add you can get your SUs reconditioned/rebuilt from a couple of other specialist too (I forget who I was recommended)
I can't remember (much at all) your previous problems, except the carb one (if I'm right)
there are various levels of competition and competition tune, I have a slightly tuned car that might be at a very low level of competition tune (but I don't know the regs so it might not be) it has higher lift cam, modest head work, tubular manifold and K&Ns but the standard SUs are well within the range of this and lots more, only needing different needles
good point about block and head, if skimmed a fair bit you might then be on higher compression ratio wanting the higher octane fuel and different plugs ect.
another good point was getting the components matched and in balance with each other, same as for the suspension, tyres and braking and all elements balanced to the car overall
even a standard car needs good cooling, I have a simple thorough method of cleaning the coolant system I can send you if you wanted it
also remember your oil system is a secondary cooling system so thorough oil changes will help (and filter)
I know it’s boring and unsexy but the best tuning you can do on a car is regular full and proper servicing, maintenance and repairs – plus frequent use over reasonable distances
I will add you can get your SUs reconditioned/rebuilt from a couple of other specialist too (I forget who I was recommended)
I can't remember (much at all) your previous problems, except the carb one (if I'm right)
there are various levels of competition and competition tune, I have a slightly tuned car that might be at a very low level of competition tune (but I don't know the regs so it might not be) it has higher lift cam, modest head work, tubular manifold and K&Ns but the standard SUs are well within the range of this and lots more, only needing different needles
good point about block and head, if skimmed a fair bit you might then be on higher compression ratio wanting the higher octane fuel and different plugs ect.
another good point was getting the components matched and in balance with each other, same as for the suspension, tyres and braking and all elements balanced to the car overall
even a standard car needs good cooling, I have a simple thorough method of cleaning the coolant system I can send you if you wanted it
also remember your oil system is a secondary cooling system so thorough oil changes will help (and filter)
I know it’s boring and unsexy but the best tuning you can do on a car is regular full and proper servicing, maintenance and repairs – plus frequent use over reasonable distances
Edited by na on Thursday 22 November 22:29
If your high lift cam is also high overlap and the rest of the engine is modified to match you'll find that a well set up Weber is better than SU's in every respect, except fuel consuption. SU's really struggle at lowish revs with a high overlap cam when the vaccuum is all over the place. Once you're certain all the electricals and basic mechanicals are correct take the car to a reputable Weber expert to set it up correctly on a rolling road, Chris Conoly at Mass Racing in Great Gransden near Cambridge is fantastic. One additional point, the works Spitfires when new had twin 40's not a single 45, a much better system with an 8 port head.
that's a good point and also brings us back to balancing out all the components
as there's a lack of history information about the engine it would require an expert to judge what might have been done to the engine
as this is a road car if the dissy hasn't already been rebuilt or modified to suit the engine I'd rather invest my money (and have done) in a fully electronic dissy, I'm very happy with my 123
for more tuned engines you can get fully a programmable 123
having a tuned engine on a old worn dissy would mean frequent fiddling with the car
although I didn't get mine from there because I didn't know of him at the time again Peter Burgess sells 123 and programmable 123 and obviously it could be installed at the time of the rolling road set up
I'm not sure if I put this before on this car so, what makes a car good on the track doesn't necessarily make it good for road use
as there's a lack of history information about the engine it would require an expert to judge what might have been done to the engine
as this is a road car if the dissy hasn't already been rebuilt or modified to suit the engine I'd rather invest my money (and have done) in a fully electronic dissy, I'm very happy with my 123
for more tuned engines you can get fully a programmable 123
having a tuned engine on a old worn dissy would mean frequent fiddling with the car
although I didn't get mine from there because I didn't know of him at the time again Peter Burgess sells 123 and programmable 123 and obviously it could be installed at the time of the rolling road set up
I'm not sure if I put this before on this car so, what makes a car good on the track doesn't necessarily make it good for road use
great info guys.
some more info on the car, its mildly tuned for basic competition. as it has:
stainless exhaust/tubular header.
stage 2 ported head
stiffer valve springs.
Weber DCOE 45.
triumph tune manifold.
lightened flywheel.
oil cooler.
electronic ignition.
and a host of other bits and bobs...
talked to a good friend i bumped into on the bus today. he owns a mini clubman with a metro turbo engine.. he knows a local specialist who tunes mini's and other leyland stuff, so i might drop it into him. but for now i think i will buy some su's from 'spitfire graveyard' and give them a good rebuild. then drop it in to the garage specialist, and get it all sorted.
some more info on the car, its mildly tuned for basic competition. as it has:
stainless exhaust/tubular header.
stage 2 ported head
stiffer valve springs.
Weber DCOE 45.
triumph tune manifold.
lightened flywheel.
oil cooler.
electronic ignition.
and a host of other bits and bobs...
talked to a good friend i bumped into on the bus today. he owns a mini clubman with a metro turbo engine.. he knows a local specialist who tunes mini's and other leyland stuff, so i might drop it into him. but for now i think i will buy some su's from 'spitfire graveyard' and give them a good rebuild. then drop it in to the garage specialist, and get it all sorted.
One 45DCOE Weber will flow more than 2 HS4 SUs so it may be woirth trying a bit harder. I would go to someone who understands Webers, I'm sure it just needs re-jetting. I was impressed with Aldon when we did the MGB register rolling road "shoot out" day. There was one track day car with a 45DCOE and they got another 5 horses by rejetting the main jet. You may need a leaner idle jet but all will be revealed on an RR. Second hand SUs may be a problem, they can for example need spindles rebushed before they can be set up.They will give you better economy and do not need such careful "handling" at low RPM where you can get "Weber Gasp" if you snap the throttle open.
With that spec of engine you will need a different needle in the SUs anyway.
With that spec of engine you will need a different needle in the SUs anyway.
My thoughts are that for a road going 1300 a 45 is a tad on the big side, even on a mildly tuned lump. One thing not mentioned is float height, this is critical on these so it needs setting up properly. Another area is fuel pump, some mechanicals can force the float jet off its seat & flood up that way. Aside from that it needs going to someone who knows what they are doing (a dying breed these days) & setting up properly. You could weaken it off on the idle screws a little & see if that helps.
yorkebar said:
let me reiterate... its a 1977 spitfire '1500'
a 1500 cc engine. not a 1300...
OK but not a huge amount of difference in the scheme of things (compare a Mk3 1300 to a Mk4 1500 power outputs!). The 1500 is quite a low revving long stroke engine. Capacity is only part of the issue of the over size carbs, rev limit is another.a 1500 cc engine. not a 1300...
yorkebar said:
great info guys.
some more info on the car, its mildly tuned for basic competition. as it has:
stainless exhaust/tubular header.
stage 2 ported head
stiffer valve springs.
Weber DCOE 45.
triumph tune manifold.
lightened flywheel.
oil cooler.
electronic ignition
is there a standard for 'stage 2' ported head or does it vary depending on who does the work(?)some more info on the car, its mildly tuned for basic competition. as it has:
stainless exhaust/tubular header.
stage 2 ported head
stiffer valve springs.
Weber DCOE 45.
triumph tune manifold.
lightened flywheel.
oil cooler.
electronic ignition
are stiffer valve springs just for performance on Triumph
(I'd forgotten about the lighten flywheel on mine)
oil cooler, I think I've put before that with an oil cooler it's best to have a thermostat (for those cars that need an oil cooler and most Midget 1500 didn't back in the day)
with the dissy having an electronic igniter won't overcome a worn and often not oil and lubed rest of dissy, just new trying to compensate for old - to me an igniter head is a good step in the right direction and I had an Aldon until the correct 123 became available for my car, one of the best bits of 'tuning' kit on my car making the car better for all types of use but importantly for me reliable and spirited frequent use
ETA: I've just noticed you've put it's mildly tuned for basic competition if you mean that aren't we back to it's possibly over carbed(?)
Edited by na on Thursday 22 November 19:38
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