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DHLA 40 vs. 45  Rating:  Rating
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 Posted: 11-03-2005 02:50 pm
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Brett Gibson JH5 20497
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And before the Idle Circuit or Main Circuit can establish a fuel flow and take over,  the shot-gush will be flushed out and the engine will go way lean and stumble again.   Sound familiar?


Bingo !!!                 Thanks Tim I really think you nailed it for me.........

Man I love this message board and all the great members helping each other out.

Brett.

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 Posted: 11-04-2005 03:19 am
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John Finch
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I just helped a local owner of a new-old J-H install Lotus Spec-5 DHLA 45's  with 36mm chokes on his 907.   The only not-spec setting is bumping-up the idle jets from 50 to 55.    I think he'll tell you that the car runs great and is very driveable on the street.

I am the guy who was fortunate enough to have Tim bring 1111-18309 back to life after sitting in Phoenix for 15 years. I have put almost 1,000 miles on it in the past two weeks. No back fires and it pulls strong into high rpms. Tim is a genius with these engines IMHO. He had mine running smooth within minuets after first firing it up! Lots of prep before we turned the key though. We are very fortunate to have this forum. My car would not be running without the input from this forum and Tim's hands on knowledge and unselfish time spent in my garage. Safe and reliable travels to all. John FYI I've attached a current jpeg of the engine.

Attachment: Dellortos Drivers Side A.JPG (Downloaded 295 times)

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 Posted: 04-05-2012 01:22 am
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Bob 13902
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Having a problem with significant hesitation between 2000-3000 RPM with my Dell 45's. Idling and >3000 is smooth and strong. Reading the various JHPS posts and the Des Hammill bible I would conclude I should changeout my idle jet holder from a 7850.9 to perhaps a 7850.7 and/or a richer emulsion tube, perhaps moving from 7772.8 to 7772.7. Before I start dumping money on jets, I would like to see what others might suggest.
Just completed my rebuild which included replacing the Strombergs with Dell 45's. The DHLA 45's are off a 1974 Elite and I rebuilt them prior to installation. Below is some background on the engine rebuild and my current Dell 45 specs:
Choke: 36mm
Main jet: 160
Main A/C jet: 230
Main Emulsion tube: 7772.8
Idle jet: 58
Idle jet holder: 7850.9
Pump jet: 42.38
Starter jet: 95
Starter emulsion tube: 7482.3
Butterfly: 8010.1
Progression Hole Pattern: 5-hole
Long jet idle mixture jet: 4.5T

Engine Performance mods:
Cams are the JHPS 107's with HTD Green Dot Pulleys
Cylinders bored +0.030 and Hi Compression (9.5:1) pistons
Advanced Distributors modified/tuned Distributor (Existing Electronic ignition)
JHPS Oversize Stainless Steel Valves; Intakes & exhaust
Ported and polished intake and exhaust
Ceramic Coated performance headers and exhaust
Iridium plugs

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 Posted: 04-05-2012 02:57 pm
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Jensen Healey
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Hi Bob, The main jet and emulsion tube are not functioning in the 2- 3k range. Your issue is in the idle circuit which operates to around 3000 rpm.

You are correct that the idle jet holder is the likely problem. The 7850.7 Would be my guess also but since the air corrector is what adjusts the air/ fuel mixture to 14.7:1 it must be spot on.

If it turns out the idle jets are the wrong size, the process will need to repeated.

Once the idle circuit is sorted, the main circuit can be evaluated. The 160 main jet seems quite large for this engine.

Kurt

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 Posted: 04-08-2012 08:53 pm
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Bob 13902
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I've got the 7850.7's on order to see if that is the cure.

I have also come across another issue which shows up when I'm out driving for an hour or so...fuel seems to splatter into my K&N air cleaners - enough that it seeps out of the bottom of the air cleaner so I get a film on the attachment plate. Any ideas on that problem's solution?

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 Posted: 04-09-2012 03:47 am
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Jensen Healey
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I've had that happen on #4. I would re-check the timing, (12 degrees BTDC,) the float levels and the needle valves. Stick a finger in each venturi with the engine off to check for leakage.

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 Posted: 04-21-2012 11:18 pm
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Bob 13902
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I seem to be thru all my issues with the Dell 45's - here's what I did/found...I've attached a pic to help with the explanation... (1) The hesitation was caused by low float level. I did not change to the "richer" idle holder jet. To get the right float level with the 7gram floats that I have, they need to be set at 10mm (not 15mm per Hammill). The other important thing about the 10mm measurement is that it needs to be the same at any point from the top surface of the float.

I bent the floats so the tops were "level" with the carb top at the measurement point (so the measurement dimension is the same to the gasket surface anywhere from the float top - I find it interesting that I've never seen a float setting procedure that addresses this. The floats were far from even before I did this and the effect on float level was 4mm). I set the floats targeting a bowl level of 27mm (distance down from top of float bowl) at the centerline between the main and idle jets. With the tilt of my carbs, the measurement on the main jet side was 27mm down and on  the idle jet side was 31mm down. I was going to make another adjustment to get to 25mm and 29mm, respectively (so the average was 27mm), but decided to save that for another day since engine performance is strong throughout the RPM range where they are. At the current setting, the 7g floats measurement is 12mm (I also readjusted to the appropriate 25mm droop). However, to get the 27mm average, that makes the correct setting for these floats at 10mm - which is where I'll put them next time I open them up again.
(2) Fuel leakage into the K&N air cleaners was caused by not using the correct trumpet gasket. Fuel was getting into the annulus between the venturi and barrel (likely at the joint between the venturi and choke). As a result of air pressure distribution and/or capillary action, it had a path to K&N's.
When I had installed the trumpets, I chose not to use the rebuild kit gasket because it had a smaller OD than the venturi (and trumpets) and would disrupt air inflow...which I wasn't keen on since maximum HP increase was a goal on this rebuild. Rather than trimming it, I had decided to install the gaskets provided with the K&N filters only since they were larger than the trumpet inner diameter. The problem is that they are the diameter of the barrel so the annulus (where gas was leaking from) had a free path to the K&N's...and I guess the aerodynamics got me. I did check the venturi to barrel clearances which are supposed to be 0.004 mils and they were ~right. The venturi and choke were both held tight together once the venturi positioning/lock screws were installed. I also verified the fuel pressure at the carbs - which was fine at 3psi and the new inlet valves seal fine at the 3 psi.

Attachment: Dell45-Float Set_JH-Apr2012.jpg (Downloaded 108 times)

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