[Tony Lamb]

My UK model 260Z is running 240Z carbs, nismo race 1 header and a 2.5 inch system. It's quite nippy when it gets going, but initial pull-away is very poor. If I accelerate hard from low revs the car will bog down and not want to know until the revs build up to 2000 or so. This means that - for purely theoretical purposes of course - I wouldn't dream of trying to beat anything faster than a pedal bicycle away from the traffic lights.

Any ideas why? Could it be the oil in the carbs? Like I say, if I'm doing 40 or 50 and give it some gas she'll pull very well, but from stationary or very low speed she's a slug. I'm aware that the exhaust set-up I have favours high-rpm running (sounds like it for sure!), but it shouldn't slow her that much surely??

Any ideas welcome folks

 

[yo2001]

vacumn advance? my car can enough vacumn and it's real sluggish 'til 2000rpm

 

[kjones]

I'd start by rechecking the carbs and insure they are adjusted properly.
You mention some modifications to the head... Does it have the stock cam? Has the head been shaved? The reason I ask is that if the head has been shaved and there is more than .020 of slap in your timing chain it will retard your cam timing by about 4 degrees. Putting the cam in the number 2 hole might help if this is what was done to the engine. Of coarse, this is purely speculation because you haven't given us enough information to properly diagnose the problem.

 

[Tony Lamb]

Sorry. To the best of my knowledge, the head and cam are stock. The only mods I've done are the carbs and header. I know there is a little wear in the chain, but I'm told it isn't enough to be a problem. I'm running quite a lot of advance already though - we had lots of trouble getting the engine to run properly. Compression is good by the way.

The only really puzzling hitch was that I couldn't get the dizzy/oil pump drive shaft to align itself exactly the way it's shown in the book. Where the shaft lug has to line up with the dizzy bolt holes, you know? Whatever I try it's about 3-5 degrees out. Strange. Everything else checks out ok now.

Does this help?

 

[kjones]

Some Ideas

I'd start by re-checking the carbs... You need to get the airflow setup correctly with a unisyn flow guage and then adjust the mixtures... How have you done the carb adjustment in the past? Did you dissassemble them? Which needles do they have? Are the floats adjusted properly? Have you tested to insure that your fuel pump is putting out enough volume? Are there ANY vaccuum leaks (including the throttle shafts)?

I'd guess that your problem is fuel related, but again without knowing all that was done it's hard to guess...

Your problems with the distributor are probably another "partial" cause of the problem... although you can usually get the timing pretty close if you know what you're doing even with the distributor installed incorrectly. Are you sure you have all the spark plug wires installed correctly with the correct firing order?

 

[Tony Lamb]

Re: Some Ideas

Well, I didn't do the carb setup but the guy who did is pretty well clued-up on these things. The carbs have been taken apart, cleaned and had all-new filters, jets, needles etc (dunno which jets though I'm sorry to say). Floats are ok too I think. The fuel pump is brand new and so far as I can tell is working fine - it certainly was better than the old one when I tried it by hand!

Vacuum leaks is an interesting one. I'm sometimes aware of a very faint whistling which sounds like air getting in, but it's tiny and I haven't been able to find it. It could just be the K&N's. All the manifolds and gaskets are properly sealed and tightened. It could be the carb bushings for the throttles but I was told they were ok (I asked the chap who reconditioned the carbs the very same quesion).

She's fine when the revs build up though. The problem is only initial pickup from very low speed. If I was doing 70 and wanted to get to 100 then she'd go like an express train no worries! I can pull away from lights steadily, but if I gave it 3000 rpm and dumped the clutch she'd cough and splutter like mad... a bit embarrassing for a Z!

And yes, the firing order is fine. New leads, new dizzy cap, new plugs, new coil, new resistor etc etc!

**** car!!