this could be the reason why my gx coupe didnt run all that good, the head was milled and i took another 1mm off the head, had a 1400 bottom end, 1200 flywheel, twin su carbs and a 290 degree camshaft. i don't want the same problem on the ute, i want to build something that will run good on street without problems. so i guess rather just use the same cam, maybe cut a 1200 flywheel and just do bigger valves on the gx head?

Use a smaller camshaft, will be better on the street. The GX is less than 290, but more than the A14/A15 cams.

something like a 268 or 278?

290 camshaft and SU's are not very good friends. JMAC told me in another thread once that the biggest you wanna go with SU's is 276. I think your cam was the problem.

strange that the cam has a problem with su carbs because there is a guy running a tr85 300 degree cam with su carbs and 1500 bottom end with mazda pistons and the guy is doing 185kmh in 3rd gear with his ute and running in the 15's. the other guy is running the tr68 290 degree and is running 16's witha 15 bottom end with light flywheel. side draughts is not an option, just too much problems and not even to talk about spares around here....

Hmmm, that's strange.
I am just going on what others told me and what I read. I know of a guy that build up a 1600SSS on the Nissan website.
In his build he mentioned he got something like a 288 and it didn't even want to idle and gave problems. A friend who had a race 1600SSS swapped him for a 276 because he also suggested that the cam is too big for the SU's. After installing the 276 he said the car ran fine.

my gx seemed to idle fine once warmed up, otherwise in the mornings choke was the only way.... thank for the advice though, will definitely think twice before getting another 290.

More food for thought, not a Datsun example but will drive the point home. Once upon a time I had an RD350 with wild porting huge carbs and all the other go fast goodies. To get the bike off a light you needed to rev it to at least 4000 RPMS or you'd drown the plugs, not to mention the bike chugging and bucking.........back to our 1200.

You can't put a race cam or near race in a street car as the motor isn't expected to be idling or running below 4K, the closer you get to this spec the less friendly the car becomes. SU carbs relay on vacuum to lift the slides, the race cam behaves much different then a street cam in this aspect.......hence SU's are not happy. The further a engine is nothing more than a giant air pump so the head, cam, carbs, exhaust etc. need to be done as a set.

If you take a GX engine clean up the ports, get a good exhaust system you'll probably up the horsepower a solid 10%, maybe a little more. Now 90-100 BHP sounds kinda weak but our cars are light and will run loads of revs so you can run a lower rear gear. Finally the other aspect I always bring up is gearing, remember the standard Datsun box will drop 2000-3000 RPM's between gears so a peaky motor is not the thing to have. The most radical I would go is probably a notch above the GX cam.............yeah you can get more power but day to day hotted up street motors tend to wear on you're nerves.

All my .02 of course
Tom