I am soon going to be putting a pair of 40 DCNF Carbs onto my 1981 X1/9 and would like to get some opinions.
There is a thread on this site discussing the the DCNF jetting for a race X, however mine is a road car and I thought it would be good to try getting some more specific info.
My current setup;
1600 Tipo engine, which I inherited from the previous owner as a rebuilt short block and a box of parts. Apart from the extra capacity the driver for using this engine was the larger valves and extra head bolts that keep the oil in the engine. This is how I received it;
- pistons and conrods weight matched.
- Head skimmed to raise the compression to 9.75:1
- Valves have been de-shrouded
- mild porting
- Lightened flywheel
I then had a spare cam reground to a fast road spec and the cambox machined to suit the new baseline;
0.412" Lift
IVO 15deg
IVC 47deg
EVO 53deg
EVC 9deg
Centerlines; Inlet = 106deg ATDC, Exhaust = 112deg BTDC
I put it all together and it is running pretty well on the standard carb, now that I have put a pointless distributer on it. The engine pulls cleanly and very smoothly throughout the rev range, but feels a bit restricted at the top end. The car is a reliable runner now and I have sorted the few niggles, so it is time for the DCNF's to go on.
The carbs I have have had the chokes machined out to 33mm, and of the main jetting only the emulsion tubes are worth using as the mains and air have been soldered and drilled what looks like a number of times. The idle jets are at 50, pump jets at 45, emulsion tubes F24
So what I think I should be running is;
Mains = 125
Emulsion Tube = F24
Air Correction = 200
Idle = 50
Pump = 45
These correspond pretty well with the jetting from the race X post, although Guy suggested 170-180 Air Correctors.
I have ordered 120/125/130 mains and 170/180/190 Air Correctors, and should be able to get it on a rolling road around Christmas....
The next discussion point is the exhaust, which is standard headers/downpipes into two freeflow boxes;
- Exhaust.jpg (54.01 KiB) Viewed 1970 times
Please bear in mind that this is a roadcar, I am not after peak performance, but I don't really want to make any easily correctable mistakes.
Thanks
Dylan