1600m webers GT cam
Discussion
I have just fitted a "CAMOHVGT" Kent cam (i'm a sunday driver now) in my 1600m. Engine is also 1700cc, balanced, Gasflowed head, Duplex timing chain. Lucas non advance Dizzy.
I have twin 40 dcoe Webers fitted and set timing to 14° advance for the moment to get it running.
My question is does anyone have a similar setup because i would like to know what Jets you have fitted in Webers.
The car runs well but just a little hesitation when accelerating.
Weber jets fitted: Choke 31, mains 120, idle 50f11, air corrector 190.
thanks in advance for your comments boys
Alan
I have twin 40 dcoe Webers fitted and set timing to 14° advance for the moment to get it running.
My question is does anyone have a similar setup because i would like to know what Jets you have fitted in Webers.
The car runs well but just a little hesitation when accelerating.
Weber jets fitted: Choke 31, mains 120, idle 50f11, air corrector 190.
thanks in advance for your comments boys
Alan
Practically every engine is different so comparing to a "similar setup" might not get you much closer to curing the hesitation.e.g. "Gasflowed head" could mean anything and having someone pop up and say "ooh, yes, I have a gasflowed head too and I used X" is highly unlikely to help.
Have you started by checking all the jets are spotlessly clean and that the carbs are correctly balanced?
Are the carb bodies a matching pair ?(important because of the progression hole drillings).
Are the progression holes clear?
What pump jets are fitted? Are the alloy sealing washers in place? (pump jets get dribbly without these)
Witht that checklist complete then you can start trying different jetting if the hesitation is still present.
Have you started by checking all the jets are spotlessly clean and that the carbs are correctly balanced?
Are the carb bodies a matching pair ?(important because of the progression hole drillings).
Are the progression holes clear?
What pump jets are fitted? Are the alloy sealing washers in place? (pump jets get dribbly without these)
Witht that checklist complete then you can start trying different jetting if the hesitation is still present.
many thanks monkeythree,
i will check your ideas. It was fitted with a piper 285/2 and was very flat below 2200rpm. That's why i have changed the cam for Sunday driving. Maybe i will fit a single weber as it left the factory. I must say that i like to keep the cars original as possible BUT with TVR it is not SO easy to know HOW it left the Factory!!!!!!!!
Alan
i will check your ideas. It was fitted with a piper 285/2 and was very flat below 2200rpm. That's why i have changed the cam for Sunday driving. Maybe i will fit a single weber as it left the factory. I must say that i like to keep the cars original as possible BUT with TVR it is not SO easy to know HOW it left the Factory!!!!!!!!
Alan
Correct, non-vac distributor only with dcoe carbs, I am running my 1600M with a Kent 234 cam, still drivable but slightly hotter than the GT cam. Mine peaks at 100hp at the wheels at 5250rpm but still has over 80hp at 2500rpm and a good flat torque range. Can't help with the jetting, it was done many years ago! Geoff
I agree with Monkeythree in that all setups will be very different so giving you the jet prescription that works for my twin 40 setup won't necessarily work for you. I have a fixed dizzy and no vacuum advance and have no problems other than a slight lumpy idle at 800rpm but no issues once you throw fuel and air at it.
A couple of thoughts. It sounds to me as if a single twin-choke down-draft would be perfectly ok for your needs but the reality is the twin side drafts can be effectively tuned, even for a Sunday afternoon car.
I think the mistake many make is to go for big chokes. I'm not saying that 31mm chokes are excessive but you might get more "low-down" grunt with 30mm or even 28mm chokes. I would also do a plug test against your idle circuit (this was an area where I struggled to get the car to run smoothly). I'm guessing if you are flat spotting in the progression phase then having a play with your E-tubes might be worthwhile but only once you've checked you haven't got any blockages. I'm running F11s but I'm told that F16 or F9 can work well with the xflow.
A couple of thoughts. It sounds to me as if a single twin-choke down-draft would be perfectly ok for your needs but the reality is the twin side drafts can be effectively tuned, even for a Sunday afternoon car.
I think the mistake many make is to go for big chokes. I'm not saying that 31mm chokes are excessive but you might get more "low-down" grunt with 30mm or even 28mm chokes. I would also do a plug test against your idle circuit (this was an area where I struggled to get the car to run smoothly). I'm guessing if you are flat spotting in the progression phase then having a play with your E-tubes might be worthwhile but only once you've checked you haven't got any blockages. I'm running F11s but I'm told that F16 or F9 can work well with the xflow.
Monkeythree said:
You need to drill and tap the top of each inlet runner and join them up with vacuum hose and run that to the distributor.
Sorry but I have never seen someone tap the top of each inlet runner to run that to the Dizzy, imho that is not correct.I see no reason that my Kent 1700 with a GT cam cannot run well with twin 40 dcoe carbs.
Many kent crossflows run with 34mm chokes albeit with Wilder cams. I think 31mm chokes imho seem correct for a GT cam which will help torque . Normaly 28mm chokes are for 250cc per cylinder= 1000cc engine (ref "How to build and Power tune Weber and Dellorto" Des Hammill" page 67)
Alan
Alan,
My Crossflow with twin 40's is just fine running on Sunday cruises or going for a blast. So you should not have any difficulty getting what you want.
I suggest a RR setup will probably give you the most benefit you'll get in return for £150 ish, and done well will be right for your specific car. Finding an operator who knows what he's doing with Webers is the harder bit as most guys seem to be lost if they can't plug in a laptop.
As already advised, most Kent engines will be running different build specs, so replicating another cars choke sizes will probably not work for you.
Good luck
Steve
My Crossflow with twin 40's is just fine running on Sunday cruises or going for a blast. So you should not have any difficulty getting what you want.
I suggest a RR setup will probably give you the most benefit you'll get in return for £150 ish, and done well will be right for your specific car. Finding an operator who knows what he's doing with Webers is the harder bit as most guys seem to be lost if they can't plug in a laptop.
As already advised, most Kent engines will be running different build specs, so replicating another cars choke sizes will probably not work for you.
Good luck
Steve
thanks Steve,
at the moment with the "CAMOHVGT" GT Cam fitted the engine makes much more relaxed driving than the Piper 285/2.
NO SPLUTTERING and pulls from tickover with a nice roar from the webers.
I'm sure with some fine tuning of the webers i can arrive to have a nice relaxed car to drive.
I'm not looking for a track day car or bhp, just relaxed driving and changing gear when i want to and not need to.
I do prefer the look of twin webers than a single carb for a sports car.
I will see if i can find someone to do a Rolling road setup and who knows webers.
Alan
at the moment with the "CAMOHVGT" GT Cam fitted the engine makes much more relaxed driving than the Piper 285/2.
NO SPLUTTERING and pulls from tickover with a nice roar from the webers.
I'm sure with some fine tuning of the webers i can arrive to have a nice relaxed car to drive.
I'm not looking for a track day car or bhp, just relaxed driving and changing gear when i want to and not need to.
I do prefer the look of twin webers than a single carb for a sports car.
I will see if i can find someone to do a Rolling road setup and who knows webers.
Alan
Edited by plasticpig72 on Wednesday 6th May 18:25
"Normaly 28mm chokes are for 250cc per cylinder= 1000cc engine (ref "How to build and Power tune Weber and Dellorto" Des Hammill" page 67)"
thats one of those other mistakes going around the web:
the chocke size is not only depending on the cc-size of the enigne.
alfa romeo fitted similar carbs from the factory. the 1300 came with 28 chokes, the 1600 with 30 and the 1750&2000 with 32´s
most x/flows in the typical tuing stage: gt-valves (also named "stage2"), 1700cc, a mild cam run mostly on 32´s
but, have seen same spec engines fitted with 28´s and running well.
the smaller the choke, the more the air speedens up, the better for torque.
the bigger the choke, the more air flow, espec. with higher revs, the more mixture will pass throught the carbs into the engine, the better the top-end power.
thats one of those other mistakes going around the web:
the chocke size is not only depending on the cc-size of the enigne.
alfa romeo fitted similar carbs from the factory. the 1300 came with 28 chokes, the 1600 with 30 and the 1750&2000 with 32´s
most x/flows in the typical tuing stage: gt-valves (also named "stage2"), 1700cc, a mild cam run mostly on 32´s
but, have seen same spec engines fitted with 28´s and running well.
the smaller the choke, the more the air speedens up, the better for torque.
the bigger the choke, the more air flow, espec. with higher revs, the more mixture will pass throught the carbs into the engine, the better the top-end power.
With the caveat of knowing nothing about your gasflowed head or what compression ratio you have, for a generic 1700 xflow with the objective of low down torque I would start with:
30mm chokes
115 mains
F11 emulsion tubes
200 air correctors
45f9 idle jets
35 pump jets
But without cleanliness and balance, the jetting is irrelevant. Start with getting those spot on and then start fiddling with the jetting.
30mm chokes
115 mains
F11 emulsion tubes
200 air correctors
45f9 idle jets
35 pump jets
But without cleanliness and balance, the jetting is irrelevant. Start with getting those spot on and then start fiddling with the jetting.
plasticpig72 said:
hi monkeythree,
with twin weber dcoe carbs a Dizzy with vacuum advance cannot be used, only with single carb!!!!
correct me if i am wrong!
Alan
wrong!!with twin weber dcoe carbs a Dizzy with vacuum advance cannot be used, only with single carb!!!!
correct me if i am wrong!
Alan
alfa romeo used vacuum advance in certain cars with double sidedraught carbs.
certain dellorto DHLA carbs have such a vacuum connection on the first chamber of the front carb
its true that most tuned engines fitted with twin sidedraughts do not have a vacuum advance dizzy fitted or it has not been connected.
but thats mostly due to lack of a vacuum take-off on the carbs.
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