Loss of power after high speed run

[Murph]

Fuel lines are fine. I checked the fuel bowls and there's no gunk in them. The carbs were compleltly cleaned and kitted 3 months ago. My mechanic said they were in pretty good condition.

[Alfadog]

Did you check the fuel lines or just the fuel bowls? Disconnect the fuel line before the fuel filter, and have a look.

All the gunk can restrict fuel flow, causing something a bit like your problem to happen...

[Murph]

Still have to do that yet. Still doesn't explain it choking up at idle.

[dspillman]

Dato,

Don't forget linkage check to assure even opening of both carbs.....visual check should rule it out ....uneven airflow,linkage issue or bent valve.

Long shot,but plug brake booster line at crossover to rule out leaky check valve,line or brake booster. just thoughts.:cross-eye

david

[Murph]

Linkages are good, carbs open together. Previously I'd pulled the brake booster line and plugged the hole, and it seems to run exactly the same.

I'd say at this stage I'll be chasing up blockages in the fuel line/fuel pickup and valve adjustment.

Thanks for all the suggestions everyone, greatly appreciated.

[dspillman]

I mentioned the brake booster,I wasted 2 weekends racing while chasing imaginary gremlins...when all the time it was the booster going bad"leaking"...only affected engine above 5500 RPMs....

Good luck.

[Murph]

I'll have another look at it tomorrow just to be sure. Mind you there aint much point reving my motor over 5k.

[240Z4me]

I just had a similar problem with my 73 240Z. The car was running great, then after a high speed freeway run, it start to surge and idle very poorly and sickly sounding. I replaced both fuel filters, nothing. The adjusted carbs(dual webers) nothing. Finally replaced the cap and rotor, and have not had a problem since. Even though they did not look worn or damaged, they were the cause.

[Murph]

Cap looks ok atm, but you never know. I've just adjusted the valves and only have to put the rocker cover back on, then I'll take it for a spin, see how it goes.

[Murph]

I've just put it back together and WOW! The motor is so quite and smooth! I've always commented on the amount of mechanical noise from the engine and it's always had a tick from the top end.....now no more tick, and it's virtually silent! Generally runs a bit smoother and a little stronger. Idle is still a bit lumpy, but not too bad. Gotta do a 20min drive tonight, see how she goes.

Thanks for all the help everyone!

[240Z4me]

I am also getting a tick from the top end, I guess it is time to attempt my first valve adjustment. Any tips?

[Murph]

Be careful when you undo the lock nuts if they're tight! One of the ones on cyl 6 was pretty damn tight and when it did go I smashed the knuckle of my index finger into the top edge of the block, which made a nice 1cm long gash to the bone. This is bad.

Anyhow, do them cold as it will take a while your first time. Just give it go, not too hard at all, you'll get the feel for it pretty quickly.