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Ivan
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I have Dellorto 45's on my '74 JH.  I get a hesitation/coughing at about 3,000 RPM that goes away at about 4,000 RPM.  As I have done some reading, I think this could be an emulsion tube problem.  I am in So. Cal. for the week and I understand that there is someone in the area who is the guru at Dellorto's and emulsion tubes in particular.  Could someone point me in the right direction. 

Greg, great job on the new BB.  I will be sending you my dues as soon as I get back to Phoenix.

Greg Fletcher
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The 7772.5 emulsion tube is one thing that's pretty much a constant on the JH Dellortos. That's not neccessarily your problem though, you may have additional issues to consider as well.

Ivan
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In reading John's article regarding his experience after installing his Del's, it resembles mine exactly.  I just remember reading that there is someone, I thought his name was Gerry or Jerry at a local supplier who knew Dellorto's really well.  The engine runs great up to or near 1500 RPM, I said 3000 before but it is actually 1500 and then clears up at 3000 RPM.

I have a Petronix ignition and all plugs appear good and burning properly.  The timing is correct as far as I can tell.  Since there is no really good mechanics for JH's in Phoenix (unless someone knows something I don't) I have to try to get the JH running properly again so that I can enjoy it and get the impetus to make it more driveable.

I also noticed that the original (I think) fuel pump continues to run (click) fast as after starting the engine as it does before the engine starts.  I don't think this is correct?  It does not appear to have an effect on the running of the engine though.

I appreciate any help and would love the opportunity to find some of the parts here in So. Cal.

Judson Manning
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I spent a year re-jetting the "Correctly Jetted" carbs I got from Dave Bean.  I have a nice pile of jets if anyone is interested in a swap!  One of the things i did was  change from 36mm to 34mm chokes.  My bottom-end performance and throttle response greatly improved, however, the car ran out of steam by 5500 rpm. 

The problem you are describing sounds like the transition from the 'slow-running jets' to the 'main' jets.  I suspect you've got some form of imbalance between choke size,  pump (~45), idle (~55) and main jets (~135) that needs to be smoothed out.

Also, your distributor advance tops out at 3000rpm.  Put a timing light on it, you may find that your distributor's timing for 1500-3000rpm isn't optimal.

As I've already mentioned, the only way I solved my problem was to change jets, take a ride, and then change them again until I found what worked best.  I'd also recommend investing in either an 02 sensor or an Exhaust Gas Temperature gauge to assist you in your quest.

good luck

Brian Kelly
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Hello Ivan,

I had the same situation.  Your trouble is probably in the idle circuit (the main kicks in around 3000rpm).  In my case I solved the problem by going with richer idle holders and then using leaner idle jets.  The idle holders that were in the carbs (dhla45’s) were 7850.1 and the jets were #60.  I went to 7850.7’s and #56 jets.  The leaner holders were allowing too much air into the mix (with idle holders the cross drilled holes allow air into the mix so smaller holes leads to richer mix). 

 

I’ve bought a lot of Dellorto parts from a supplier in Italy.  His prices are very reasonable and delivery takes 2 weeks.  Email him with what you want he’ll get you a price – Paypal, and the NEW parts are on their way.  It takes some time but he’s got it all.  I’ve ordered an assortment of jets to “play” with. 

 
He's at:


italian.carburetors@tiscali.it

 

Also I've found the Morgan Carbtune balancing tool is a must if you like to “play” with your carbs.

 

Hope this helps,

Brian Kelly

Jensen Healey
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Just remember, the factory couldn't do what you're trying to do!

 

Kurt



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