Jetting DCNF 1500 SOHC

[Andy128]

Hi Guy,

I am setting of down another path of learning and would like to ask your advise on jets for my 1500cc SOHC engine in a 128 Rally Replica.
Over the last couple of years I have had a couple of attempts at getting my car tuned on a Dyno (Rolling Road).In my limited experience I have found that most of the operators want to either fiddle with the current setup or plug a Laptop into the car (not an option on my old 128!)
I have found a company locally who I think will be alot better this time and actually keep a range of jets in stock.
I have read a post between James Bowen and yourself over and over,

viewtopic.php?f=4&t=2161&p=11276&hilit= ... wen#p11276

also a more recent one

viewtopic.php?f=13&t=2149

The setup I have currently is I think quite similar to James when he was using the DCNF's

Current setup

1500cc
CR 11-1
Ported Head
Valves 40mm Inlet- 35mm Ex
Cam Dur 292
Lobe Centres 106 Deg
Lift 10.8mm
Headers 4-1
1 3/4 x 31 inch long
Carbs 2x DCNF 40 PBS X19 Manifold

Current Jets
Auxilary Venturi 2.5
Air Corrector 160
Emulsion Tubes F24
Main Jets 145
Idle Jets 50
Pump Jet 35
Chokes 32

Having read James post this is the Jets I thought I would start with

Air Corrector 170-180
Emulsion Tubes F24
Main Jets 125
Idle Jets 45
Pump Jet 35
Chokes 34

Can you please have a look and let me know if I am on the right track before I go and buy these parts.

I am unsure about the F24 Emulsion Tubes and the 2.5 Auxilary Venturi's

DSC02037.JPG (57.57 KiB) Viewed 5320 times

DSC02038.JPG (57.89 KiB) Viewed 5320 times

Thankyou for your time and I would appreciate any comments

Regards,
Andy D

[Guy Croft]

OK - try the F24. If lean from 2500 - 7000 maybe bigger mains (maybe 130/135) might be needed with those big valves, depends on the port size really, I'd be on 32-21mm dia inlet ports with that engine. If you have a general over-rich tendency that can't be 'ironed-out' with main jet reduction from, say, 3500 to top end (wherever that is) keep your main and air corr the same as you've as listed and try F21 or F22 that are leaner. I would be very concerned if you went any smaller on air correctors - altering them is the last job for fine tuning the very top end only and I might expect you want bigger (leaner) no more than that.

Make sure you get the ignition timing right - 28 deg +/- 2deg on that engine (@ 5500rpm I think). They run a lot less than the Twincam.

I've never changed an aux venturi in my life!


No problem with anything else that I can see,

G

[Andy128]

Hi Guy,

Thankyou very much for your quick and knowledgable reply.
I will go ahead and get the Jets as you have suggested and post the results from the dyno session.

Regards,
Andy D