DHLA 40’s and QED 420nCams

[mark030358]

Hi all,
I have never felt that the jetting given by QED was anything like optimal and could be improved on.

So has anyone on here had experience of re-jetting the carbs with these cams?

Thanks
Mark

[nmauduit]

imho if one wants optimal jetting for his modified engine (say Q420 cams) there is only one way to be sure: lots of testing on a dyno or rolling road of this very engine in the desired configuration.

[elans3]

I agree with the above, it's the only way to get a decent result. Plus, it would be no good someone who had done the same giving you their jet sizes, as every engine is different.

[checkrail]

Out of interest this the spec of my S130 bought from Paul Matty 4 years ago rebuilt by Laurie Barton, it has QED 420 cams and DHLA 31 40's
choke 33 main jet 130 air corrector 170 emulsion tube F16 idle 50F8

regards John

[TBG]

I have posted this before but it may help you in the right direction. All very frustrating to do! D

PS also on QED 420s with 40s and a big valve head.

[mark030358]

I have posted this before but it may help you in the right direction. All very frustrating to do! D

PS also on QED 420s with 40s and a big valve head.

Spot jetting.jpg

Thanks you all for your replies. I’ll order up some parts and see how it goes,

Cheers
Mark

[types26/36]

These jet numbers being quoted are for DCOE Weber carbs and not for DHLA Dellorto carbs, the jets are not interchangable between the carbs.

[mark030358]

Good spot Brian, thanks.

Anyone else with recommendations?

Thanks
Mark

[Dellortofan]

I think an air fuel ratio meter may be ideal. Every engine is different with its own requirements.
You will need that 18mm bung for the O2 sensor way upstream of tailpipe.
It will pay for itself with the RR charges now —plus where's the ecu mate for remap questions!
If you want to remove it then put a block off bung in and sell it for some return.
I've seen some cars (poss with low oil pressure /bottom end wear) destroyed by unsympathetic dyno operating. They may have lasted another 50,000m if used on tarmac...
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