Discussion
You can wreck a std engine fitting one of these carbs...They are known for putting bucket loads of fuel into an engine and can give bore wash and increased wear to relatively mild engines which have not had some serious headwork and cam swaps carried out to make the best of the increased fueling.
I am no expert of the essex but the old 38 DGAS is a good carb and more than capable of fueling even a good fast road essex let alone a std one..
You would be far better off investing your money elsewhere with the engine, A cam change would be a good first step, followed by port matching and an exhaust..
The Carb could be jetted and made to work but you will then find that you are back to where a good 38 DGAS would have had you anyhow??
N.
I am no expert of the essex but the old 38 DGAS is a good carb and more than capable of fueling even a good fast road essex let alone a std one..
You would be far better off investing your money elsewhere with the engine, A cam change would be a good first step, followed by port matching and an exhaust..
The Carb could be jetted and made to work but you will then find that you are back to where a good 38 DGAS would have had you anyhow??
N.
Edited by heightswitch on Saturday 5th May 09:36
Sorry to resurrect this, just going through looking for something else and noticed it.
We've got a 40DFAV, which we got for peanuts, and it looks in good condition, with what looks like all new gaskets etc. The engine is going to be standard bore and compression. We've got some stage2/3 heads with larger valves and porting work, and a Piper 270 cam. Stainless steel exhaust manifolds (still TVR design I believe, 3 into 1).
Would a 40DFAV still be too much for this stage of tune?
We've got a 40DFAV, which we got for peanuts, and it looks in good condition, with what looks like all new gaskets etc. The engine is going to be standard bore and compression. We've got some stage2/3 heads with larger valves and porting work, and a Piper 270 cam. Stainless steel exhaust manifolds (still TVR design I believe, 3 into 1).
Would a 40DFAV still be too much for this stage of tune?
Adrian@ said:
Fine on point and squirt type of driving...but cannot handle high speed cruising, I have had 2 cars that this carb has been attributed for the blown engines.
Adrian@
Adrian, Adrian@
I can't imagine that being the case. Why? At sustained high revolutions, the vast majority of the fuel is coming from the main circuit. There's virtually no way a carb can let you down that way, but a person who selects the wrong main air jets, main fuel jets, emulsion tubes, or auxiliary venturis could.
I would think that tradition still has value, and if these engines were running too lean, a plug check, at various rpm would have caught the problem.
Who attributed the failure to the carbs, and why?
Best,
B.
The 40DFAV was fitted to the Zodiac for a period of time and was offered as a performance upgrade to the 38DGAS by Ford during the 70's. They also offered the 40DFI (which I had). The 40DFAV has a power valve so should retain some of the economy (cough) of the 38DGAS, whereas the 40DFI is really a 'race' carb with no fuel saving measures and just throws fuel at the engine.
In my (very) humble opinion, the 38DGAS with correct filtration is good for at least 170bhp, and only above that figure should you be considering a 40 carb. Above 200bhp, you really need to look at the exhaust flow (especially on a TVR) as this is the limiting factor.
If you want a mediumly fast road car with half reasonable cruising mpg (25-27) then stick with the 38DGAS, my car with a trick engine (and exhaust + 40DFI) would only manage about 20mpog at cruise). With stock cams stay with the 38DGAS, improving the breathing will give the engine more of an edge than throwing a 40DFAV on.
The 40DFI was difficult to fuel, especially for around town work (if you didn't want to sacrifice the top end performance, my car really was a track day toy, so was built for higher than average rpm), but on several occasions I had flames both under the bonnet (even with a filter) and out the exhaust. The former, I could see through the SE vent, and experience told me to press the loud pedal to suck it back through the engine!!! Fire and plastic cars don't mix. Flames on the overrun were cool though!
Of course if you want to go mad. follow GAjon and fit triple 40's but here all the gains will be at the top end (above 4000rpm), and you will need a fuel tanker to follow you around!!
In my (very) humble opinion, the 38DGAS with correct filtration is good for at least 170bhp, and only above that figure should you be considering a 40 carb. Above 200bhp, you really need to look at the exhaust flow (especially on a TVR) as this is the limiting factor.
If you want a mediumly fast road car with half reasonable cruising mpg (25-27) then stick with the 38DGAS, my car with a trick engine (and exhaust + 40DFI) would only manage about 20mpog at cruise). With stock cams stay with the 38DGAS, improving the breathing will give the engine more of an edge than throwing a 40DFAV on.
The 40DFI was difficult to fuel, especially for around town work (if you didn't want to sacrifice the top end performance, my car really was a track day toy, so was built for higher than average rpm), but on several occasions I had flames both under the bonnet (even with a filter) and out the exhaust. The former, I could see through the SE vent, and experience told me to press the loud pedal to suck it back through the engine!!! Fire and plastic cars don't mix. Flames on the overrun were cool though!
Of course if you want to go mad. follow GAjon and fit triple 40's but here all the gains will be at the top end (above 4000rpm), and you will need a fuel tanker to follow you around!!
Edited by DavidY on Saturday 1st December 09:00
DavidY said:
The 40DFAV was fitted to the Zodiac for a period of time and was offered as a performance upgrade to the 38DGAS by Ford during the 70's. They also offered the 40DFI (which I had). The 40DFAV has a power valve so should retain some of the economy (cough) of the 38DGAS, whereas the 40DFI is really a 'race' carb with no fuel saving measures and just throws fuel at the engine.
In my (very) humble opinion, the 38DGAS with correct filtration is good for at least 170bhp, and only above that figure should you be considering a 40 carb. Above 200bhp, you really need to look at the exhaust flow (especially on a TVR) as this is the limiting factor.
If you want a mediumly fast road car with half reasonable cruising mpg (25-27) then stick with the 38DGAS, my car with a trick engine (and exhaust + 40DFI) would only manage about 20mpog at cruise). With stock cams stay with the 38DGAS, improving the breathing will give the engine more of an edge than throwing a 40DFAV on.
The 40DFI was difficult to fuel, especially for around town work (if you didn't want to sacrifice the top end performance, my car really was a track day toy, so was built for higher than average rpm), but on several occasions I had flames both under the bonnet (even with a filter) and out the exhaust. The former, I could see through the SE vent, and experience told me to press the loud pedal to suck it back through the engine!!! Fire and plastic cars don't mix. Flames on the overrun were cool though!
Of course if you want to go mad. follow GAjon and fit triple 40's but here all the gains will be at the top end (above 4000rpm), and you will need a fuel tanker to follow you around!!
In my (very) humble opinion, the 38DGAS with correct filtration is good for at least 170bhp, and only above that figure should you be considering a 40 carb. Above 200bhp, you really need to look at the exhaust flow (especially on a TVR) as this is the limiting factor.
If you want a mediumly fast road car with half reasonable cruising mpg (25-27) then stick with the 38DGAS, my car with a trick engine (and exhaust + 40DFI) would only manage about 20mpog at cruise). With stock cams stay with the 38DGAS, improving the breathing will give the engine more of an edge than throwing a 40DFAV on.
The 40DFI was difficult to fuel, especially for around town work (if you didn't want to sacrifice the top end performance, my car really was a track day toy, so was built for higher than average rpm), but on several occasions I had flames both under the bonnet (even with a filter) and out the exhaust. The former, I could see through the SE vent, and experience told me to press the loud pedal to suck it back through the engine!!! Fire and plastic cars don't mix. Flames on the overrun were cool though!
Of course if you want to go mad. follow GAjon and fit triple 40's but here all the gains will be at the top end (above 4000rpm), and you will need a fuel tanker to follow you around!!
Edited by DavidY on Saturday 1st December 09:00
Adrian@ said:
Both cars came in as break downs, new customers, both after being on long motorway high speed cruises, one with an unleaded insert having gone through the engine and the other with no oil pressure and a broken rocker arm (hence the no oil pressure) both faults assigned to running lean. B you are not wrong, their is no sense in it, but neither car could be set up for high speed running without over-fueling in the normal range, and the dynamic range just was not there. Both are now running on the 40's after I put lambda ports into the exhaust and left the customers running with a digital display for them to feedback to me.
Adrian@
I would rather take the 38DGAS and bore it out and tweek the high speed running jets...
DavidY, Adrian@
I would rather take the 38DGAS and bore it out and tweek the high speed running jets...
Edited by Adrian@ on Saturday 1st December 11:34
Sounds as though those 40DFIs have a similar reputation to a Hilborn fuel injection set-up. You're either accelerating, or you're not. No such thing as steady state. They must have well developed accelerator pump circuits.
Adrian,
Are you sure they're DFAV? Could they have sat long enough for varnish build-up to have caused the lean condition? Did you change the jetting after the rebuilds?
Best,
B.
phillpot said:
Stop messing around with little Webers and get a proper carb... 
Then you would need some of these... 
Adrian@
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