Dellorto DRLA 40 B. What jetting for a 2110cc Type 1 engine?

Hi Paul. Thanks for tagging but not sure I've got a great deal to bring to the party here, particularly given the way the discussion has gone. If you've had good service from the motor and a rebuild isn't on the cards anytime soon then talk of the cam type and characteristics are somewhat irrelevant other than for gaining an understanding of what's in there and where you might go to in the future (or not). Best to leave to those who have amassed the experience over the years and know what works or provides the desired outcome. Id guess you've done significantly more mileage than its advised your cam is good for so who knows how close to the mark that is. going back to the dells then I have some 30s should that itch need to be scratched you can try! I've always steered away from 009s based on advice and that, as described, might be n area of interest or development! I guess it was fitted for a reason but possibly the reason is they are cheap and available new or indeed that there's no vacuum take off on the carbs.

 

My type of DRLA 40 doesn't have the external orrifice/is not suitable to be moddied to provide a vac take off

 

Cheers Chris you were tagged for the jet/carb side of the debate, before i derailed it with talk about CAM's. I only mentioned what type of cam in case it impacted people's thoughts on jet sizes etc!

I've know you like a fiddle with your dells and the offer of a loan of your 30 vents would be most appreciated! Thank you

The 009 has been in place since approx 1997 as far as i know/remember. If your carbs don't have a vacuum take off then i guess the distributor choice is somewhat limited.

I know the 009 always gets slated, but it's funny as when my VW friend saw it the other day he was showing it some real love, not only is it German it appraently still has it's original cap!

Your CAM comments are correct and i've done more than 5000 miles on it. Still interesting for me in case it contributed to my issue last year.

I'm not planning a rebuild and keep my fingers crossed it won't need one for a long time!

 

Are you quite sure ?

 

Dells are made in pairs aren't they? More than likely the RH one isn't adaptable I'd think.

The cam does impact on the venturi selection - if your engine was a revver you'd want a bigger venturi. But it's a slogger with that cam - I'd love to see the RR torque/HP graph for your engine.

 

I'll try and find it. If memory serves me right the printout is quite faint

 

I sent photos to eurocarb and that is what they told me.
Both of my carbs are the same DRLA 40 b's. Originally for an inline engine, the right hand one has been modified with a bracket welded on for the throttle stop.

This is a case of if it's not broke, don't fix it.
This posted was originally meant to be about jets/vents after i discovered what some of mine where last week.
I may do something with jets/vents.
I still would like a 123 dissy when funds allow. I would keep my old 009 and clamp as in vehicle spares.
I'm not clear what major benefit a vacuum take off may bring me, eurocarb told me to leave it alone & i'm going to leave it alone
I'm not doing anything with the CAM until the engine has to be split for another reason, which hopefully won't be any time soon.

 

get the felt tips out!

 

Found these notes i made. Will try and dig out original graph
Engine power (corrected) 99.hp@93mph/4925 1/min
Torque (corrected) 119lbs/ft @3911 1/min (engine)

He said it would have been 125hp if he had 'tuned/tested it to 6k revs

Engine power (measured) 95.1hp@93mph/4925 1/min
Wheel power (measured) 71.4hp@93mph/4925 1/min

2nd rolling rd

125lbs/ft @3303 1/mon

 

Yes please!
At least the second one realised your peak torque wasn't revving the nuts. These RR folk seem to be obsessed with high revs = power, which it does, but they tend rev it past peak torque without looking even if it's a grunty engine, something doesn't compute - maybe it's that their normal customers are only interested in peak HP bragging numbers, not really so bothered about how it actually drives! Peak torque on mine is way down at 1750 rpm.

 

I’ve read elsewhere a fair few people having loose valve guides with mofoco heads
So I reckon your problem may have arisen from poorly manufactured heads.

 

I doubt it and he'd have been tuning it "wrong" for it's cam.

 

This is a very good article on aircooled.net which gives a good understanding of jetting.
Worth investing in an AF gauge if you want to play Paul

https://www.aircooled.net/how-to-use-a-wideband-to-tune-your-carburetors-on-the-vw-flat-4-engine/

 

Well I've dug them out, just uploading now!
Very interesting.
Rolling rd August 2013.

My instructions say I never rev over 5k.

Receipt says Dyno Tune, ReJet & Balance carbs. Optimise Ignition Timing.
My notes on the back say:
160 Main Jet
215 Air Corrector
Idle same as 55

So I've no idea if that is what they were before being changed at the rolling road or if it is what jets I left with, which doesn't correspond to the numbers I wrote down the other day from the jets! Confused




Trying to edit so image right way round

 

back on the jetting, my 2056 is currently on 28 venturis and 130 mains and 53 idles and 33 Pump jets i think.. could do with a tune but seems to run ok , well would if the accelerator peddle hadn't rusted off the floor pan at the hinge point!..

As above 30 vents's would prob suit yours fine with 130 - 135 from all the collected set ups I looked at but they are very much engine specific with all the other factors cam , valves , exhaust dizzy etc

 

I think there are a series of vacuum profiles on one of the 123's where the vacuum advance is settable at all-in at different, decreasing vacuums relative to stock vacuum from air rushing down a small choke on a 34PICT-3 feeding all 4 cylinders.

Either a 123 or a MegaSquirt EFI ECU/MegaJolt ignition ECU or similar will do the trick,

I looked at the 123 website and its this one : basically everything is programmble so you can say 10 degrees of vacuum at 50kPa plus 20 degrees of centrifugal all-in by 2500 rpm or whatever.

And chuck in some idle retard ..
123/TUNE+ 4-A-V-V

 

Rolling Rd 2. April 2014
Can't even remember why I went back, but I had a Pressure regulator fitted (Filter King)
Receipt says retune as necessary (doesn't say anythung about changing jets)
No idea why i cant post pictures the right way round today. Ill edit at somepoint

 

Rolling Rd 3. July 2017
Just to add further confusion this is at a different Rolling Rd, i think the original one was busy.
This was well after my stud down carb related engine repairs were completed!
Absolutely f all happened at this one except it go on a rolling road, i was there and videoed it and they changed nothing jet wise etc. Told me it was all set up fine

 

Your graph shows the torque falling off a cliff at 4,000rpm. The power does increase above that due to more revs, but at a much slower rate. It's a bit like mine in that respect - it keeps accelerating but it feels a bit thrashy/strangled so we change gear?
Interesting how your first RR went for 160/215 then later someone changed that for a more "normal" 145/175. I say more normal because it appears to be herd DRLA40 wisdom to fit a 180 air and a .2 emulsion for every conceivable engine.

I can't vouch for this, but geezer who wrote it explains clearly enough to be believable?

"If you find that the engine runs perfectly at WOT near the torque peak, but becomes lean toward redline, select smaller main air jets. Conversely, if the engine runs perfectly near the torque peak but richens toward redline, select larger main air jets. Changes in air jets may require changing the main fuel jet. Say you have good performance at engine speeds leading to the torque peak under wide open throttle with a 150 main fuel jet and 200 main air jet. Should you need to richen the mixture at full revs and full throttle and select a 180 main air jet, you may need to go down to a 145 or 140 main fuel jet to keep the lower rpm mixture the same as with the 150/200 combination."

 

@Zed

Any jetting info must be taken with a pinch of salt.



We have my reading of various numbers from a long main jet the other day. No idea if these are what is actually in it or if they have been re drilled but not marked.

The 2013 jetting figures are what i had written on the back of the my first rolling rd trip receipt. I dont know if i have written down what was in it before he re jetted the carbs. Or what they are after he has re jetted the carbs at that rolling rd session.

What i wrote down in 2013, doesnt correspond to what i saw written on the jets last week!