what would you guys recommend for jets for a single blow through 40DRLA on a 1914 with 40x 35.5 heads with some P&P and an engle 120?
i would like to jet it mostly for power. i will probably be running no more than 10-12 PSI
dellorto jetting help please
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blue thunder
Dell jetting
I'd go for a 145 main jet, 180 airjets and 55 idle's.
Thats a good starting-point.
Remember not to get more than 24 BTDC total advance, or otherwise it's possible to kill your engine.
Another tip: use a far stronger acceleratorpump spring, cause it wil have to feed 4 cilinder instead of 2 in a dual setup.
This setup should be in the ballpark. Use a 02/lambda sensor to get it right. (rather a little rich than lean).
Good luck,
Robin (Holland, Europe)
Thats a good starting-point.
Remember not to get more than 24 BTDC total advance, or otherwise it's possible to kill your engine.
Another tip: use a far stronger acceleratorpump spring, cause it wil have to feed 4 cilinder instead of 2 in a dual setup.
This setup should be in the ballpark. Use a 02/lambda sensor to get it right. (rather a little rich than lean).
Good luck,
Robin (Holland, Europe)
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bumblebee
Actually I forgot to mention them in my former message.
The turbo emulsiontubes help lean out the mixture at low airspeeds through the turbo (better fuel economy) and fattens up the mixture at high velocities (on boost).
The jetting as in my former message should be in the ballpark, but always be carefull: a lean mixture on boost can distroy your engine in no time!!
That's why it's important to stay on the safe side during startup:
Don't exceed 24 degrees of maximum advance with your ignition, and rather start with slightly bigger mains and idles and smaller air-correction jets (rich mixture).
Use a O2/lambda gauge to get it right!!! The only way to check it!
Good luck,
Robin
The turbo emulsiontubes help lean out the mixture at low airspeeds through the turbo (better fuel economy) and fattens up the mixture at high velocities (on boost).
The jetting as in my former message should be in the ballpark, but always be carefull: a lean mixture on boost can distroy your engine in no time!!
That's why it's important to stay on the safe side during startup:
Don't exceed 24 degrees of maximum advance with your ignition, and rather start with slightly bigger mains and idles and smaller air-correction jets (rich mixture).
Use a O2/lambda gauge to get it right!!! The only way to check it!
Good luck,
Robin
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blue thunder
I used 32mm venturi's, and they worked fine. 30mm are quite small, especially cause it's a single Dell. One advantage of smaller vent. is a richer mixture, but it would probably be quite restrictive for your power-output.
I've also heard of a few guys using 34mm venturi's with good results.
However you'll have to use larger mains to keep the mixture rich enough (bad fuel economy)
Good luck,
Robin
I've also heard of a few guys using 34mm venturi's with good results.
However you'll have to use larger mains to keep the mixture rich enough (bad fuel economy)
Good luck,
Robin
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Hi Octane
inlet needle valve
I am also using a single 40drla in blowthrough. What size inlet needle valve will I need? I have a #225 which I was gonna use as a starting point.
HO
HO
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blue thunder
first question: I would start off with 155 mains, 170 aircorrection and 60 idles and then work your way down from there when using 34mm venturi's.
This should be a little too rich, but it's safe for your engine.
Get it right with a lamda-gauge.
second question: I'd use a larger needle and seat in a single setup.
Something like 275 would be fine, but this also depends on the boost you'd like to drive with.
Cross-drilling just under the seat of the valve helps aswell.
Trim the stop-tab of the float so it can get lower in the float-bay and pull the needle further from the seat.
Don't go over 290, or you might experiance overflowing the float.
If you are serious about making boost (10psi of more), it's possible to use a glass-ball or gross-jet to supply enough fuel.
I used two 275 in my dual setup.
Also remeber to use a good fuelpump and progressive pressure regulator (Malpassi) to keep the fuel flowing.
The pump must be able to flow enough fuel, but also be able to generate enough pressure!
Not all pumps are suitable. If your looking for one in a junkyard, look for a large Bosch rotary pump or similar.
I hope this answers both your questions.
Good luck,
Robin
This should be a little too rich, but it's safe for your engine.
Get it right with a lamda-gauge.
second question: I'd use a larger needle and seat in a single setup.
Something like 275 would be fine, but this also depends on the boost you'd like to drive with.
Cross-drilling just under the seat of the valve helps aswell.
Trim the stop-tab of the float so it can get lower in the float-bay and pull the needle further from the seat.
Don't go over 290, or you might experiance overflowing the float.
If you are serious about making boost (10psi of more), it's possible to use a glass-ball or gross-jet to supply enough fuel.
I used two 275 in my dual setup.
Also remeber to use a good fuelpump and progressive pressure regulator (Malpassi) to keep the fuel flowing.
The pump must be able to flow enough fuel, but also be able to generate enough pressure!
Not all pumps are suitable. If your looking for one in a junkyard, look for a large Bosch rotary pump or similar.
I hope this answers both your questions.
Good luck,
Robin
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Guest
""""""""" I would start off with 155 mains, 170 aircorrection and 60 idles and then work your way down from there when using 34mm venturi's.
This should be a little too rich, but it's safe for your engine.
Get it right with a lamda-gauge. """""""""
The chart in the Dellorto book suggests otherwise. I looks like a #200 main and a 180 air??????????
This should be a little too rich, but it's safe for your engine.
Get it right with a lamda-gauge. """""""""
The chart in the Dellorto book suggests otherwise. I looks like a #200 main and a 180 air??????????
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purple69
- Posts: 534
- Joined: Mon Apr 15, 2002 1:01 am
Re: Dell jetting
would you guys still recommend these jets with 30mm venturies or would you recommend finding some larger ones?blue thunder wrote:I'd go for a 145 main jet, 180 airjets and 55 idle's.
Thats a good starting-point.
Remember not to get more than 24 BTDC total advance, or otherwise it's possible to kill your engine.
Another tip: use a far stronger acceleratorpump spring, cause it wil have to feed 4 cilinder instead of 2 in a dual setup.
This setup should be in the ballpark. Use a 02/lambda sensor to get it right. (rather a little rich than lean).
Good luck,
Robin (Holland, Europe)
-
blue thunder
When using smaller venturi's, you'll need smaller mains/idle's and possibly larger aircorrection-jets.
Remember: smaller venturi's give a richer mixture, larger venturi's lean out the mixture.
For the question from our guest: a 200 main?????? If your running a 777 jumbojet engine perhaps...
P.s. we're talking about a rather small engine in blow-through setup.
Also don't forget to install secondary venturi's (somthing like a velocity-stack) on top of the carbs. A suitable size would be 32mm.
You can purchase them at CB Performance in Farmersville.
A lot of your questions are covered in the book 'Turbomania' written by Rick Tomlinson from CB.
Have fun,
Robin
Remember: smaller venturi's give a richer mixture, larger venturi's lean out the mixture.
For the question from our guest: a 200 main?????? If your running a 777 jumbojet engine perhaps...
P.s. we're talking about a rather small engine in blow-through setup.
Also don't forget to install secondary venturi's (somthing like a velocity-stack) on top of the carbs. A suitable size would be 32mm.
You can purchase them at CB Performance in Farmersville.
A lot of your questions are covered in the book 'Turbomania' written by Rick Tomlinson from CB.
Have fun,
Robin
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blue thunder
It's possible to plug one of the inlets (if they differ in size, plug the smallest one) and use the other. Remove the filter behind it, and use a large filter between the tank and the pump instead.
I used 8mm rubber fuelline and used copper lines in the tunnel to the tank.
Just make sure never to use lines with a smalled i.d. of 6mm, as it can cause serious problems (this goes for the return line aswell).
Good luck,
Robin
I used 8mm rubber fuelline and used copper lines in the tunnel to the tank.
Just make sure never to use lines with a smalled i.d. of 6mm, as it can cause serious problems (this goes for the return line aswell).
Good luck,
Robin