does anyone have a a15 with a big cam coz i do and i find it coughs and splutters below 3000rpm but then ity runs real nice all the way to 7500-8000, i'm running a gx head with the twin su set up as well, has anyone else experienced this and if so, does anyone have any ideas coz i don't want to get rid of the cam, the idle is too good but i want to try and make it a bit more drivable down low just try and get rid of the spluttering below 3000

u sure its the cam? maybe its the points? mine did the same thing and occasionally died, i then fixed the points and it rund great now. Or youre timing can be really far advanced so it runs good on top end but now on bottom.

nah it only runs about 10-11 degrees timing and the dwell angle is around 45-50 degrees my guess is maybe the crap gxtwin su set up i tried valve clearancess at different gaps timing from 7 degrees all theway to about 18 degrees different dwell angles and so on maybe it is just the cam but i am hoping i can get around it but i have a standard a15 i coukd just use aswell

what about the carbs, ive got similar problems with my motor for the same reason, huge cam, but the main reason it cant be fixed is cause the chokes in the cabies are too large (34mm need 30mm) and jetting it right is impossible, i haven got the chokes yet cause ive got no cash, but you should be able to get your motor to run right with diffrent jetting because the carbs were designed for the car.

The problem you are experiencing could be many possibilities. First thing after checking the electrical side of the engine, would be the carbies. SU type carbies are fiddly little animals. Being a constant velocity type carb, they love operating flat out. From my experience, they are not so crash hot at low rpm, not as responsive as a pair of webers.

1. I would try and identify what profile needles your carbs have. The taper of the needle influences the feul delivery.
The second link i quoted to a SU carb site has a needle calculator from memory.

2. Check that the dampening plunger is not restricted in its movement. Is there to much or not enough oil in the dampeners.

3. Are both carbs synchronised?

4. Is there air leaking through the throttle butterfly shaft. this is a common wear prob, with this type of carb.

5. Float levels?

Try these articles, they may help

http://www.sonic.net/~kyle/su.html

http://www.jetlink.net/~okayfine/su/sutech.html

Short of all that maybe the cam you are using is too big. The cam may be better suited to higher compression and high octane fuel.

Good luck. and im sure you will let us know the outcome.

I just put 2and 2 together
Have you had a chance to find the prob yet?
The other 1200 at GD had same problem aswell, he took his to pistons auto in bayswater and they fixed it up just before the event, he has twin 40mm webbers on his thing

yeah i probly need to put some flat tops in and raise compression a bit but i have no money so i just rev the tits off my car and hope i don't get busted speeding

Dude i think you misunderstood, the place that tuned it for him was called "pistons" he didnt have any internal work done, sorry didnt make that clear, basically they jetted it a lot better for him, i dont think he even had to change the chokes in his

With my real hot L18 with 300 degree @0.05" and .65 total valvelift cam which with 45mm webers & 36 chokes starts make real power from about 6500rpm idles quite nicely at 1000 rpm and runs very smoothly 1000-3000rpm but only with about 35 degree ignition advance. Any less and that engine dies when you hit the gas pedal. Actually best results come with 40 degree advance at 2000rpm, but that engine starts to ping at 6500rpm when it goes to power zone, so wihout computer based ignition max advance have to limit to about 35deg, with 25 deg initial advance and all mechanical advance coming before 2000rpm.

Also with wild cam that vacuum advancer have to removed as it's usually makes ignition unstable at low rpm when accelerating, resulting engine stuttering and poor running.

That L18 of mine won't produce much power under 4000rpm, it feels like having A10 under the hood and it also dies if push gas pedal too much at low rpms, but it still runs very fine, no problems at all with cruising in town at 1500-2500 rpm.