Triple Carb Blues...

M4vr1k · Post by **M4vr1k** » Mon Jan 01, 2007 9:22 pm

Hey guys. Recently got my car started and going for the first time with the triple Dellortos, Sounds wonderful at idle, beautiful. Took it for a fang around the block, and its bloody awful! Gutless as anything, misfiring, rattly, just generally awful...
The carbs are tuned to perfection, by Murray at Weber Specs, they are all balanced up as well, the cam and ignition timing is all standard, and set 100%
We are out of ideas....anyone else got any gems of wisdom that might help solve this?

240z · Post by **240z** » Mon Jan 01, 2007 10:22 pm

Have you had the car on a dyno if not well worth the money takes all the guess work out.

M4vr1k · Post by **M4vr1k** » Mon Jan 01, 2007 10:54 pm

Nah, havent had it on the dyno yet, But shouldnt really need to, should i? its just a road car after all

ForemanNZ · Post by **ForemanNZ** » Mon Jan 01, 2007 11:22 pm

I have found a dyno invaluable to diagnose a Z32

For you, you would want to get a air/fuel ratio done, as well as engine knock monitoring. Give Robin at Torque Performance a call - he has a dyno setup that has all you need, and his team like nissans. Can't guarantee that he will find the problem, but for the small cost, him and his team will be able to point you in the right direction.

mungyz · Post by **mungyz** » Tue Jan 02, 2007 9:45 am

have you checked to m ake sure you haven't got a manifold leak between the carbs and the head some place? - this will screw up your air fuel ratio really badly and make it run like....... well crap. usually will make it run worse at lower rpm and then improve as the trhottle gets more open, if some ones been trying to tune it like that then it'll run like crap the whole time.

How were the carbs tuned? you may find you will need to change the jets to suit your engine set up, you can only get so far with setting carbs up on the bench then the rest has to be done on the engine.

You may find you need to get the dissy regraphed to suit the new set up (different manifold pressures etc)

How long has the car been off the road? NZ fuel is crap and will go off after only a few mths - this will make any car that is highly strung (high HP for engine size) run fairly badly with detonation etc all creeping in way early compaired to normal.

Check the diaphram hasn't sprung a leak on your dissy ( Im assuming they run one for the advance?)

Hope me dribble helps

Happy new year aye

nzeder · Post by **nzeder** » Tue Jan 02, 2007 10:23 am

M4vr1k wrote:The carbs are tuned to perfection, by Murray at Weber Specs, they are all balanced up as well, the cam and ignition timing is all standard, and set 100%
We are out of ideas....anyone else got any gems of wisdom that might help solve this?

Did Murray tune these on the car? If not then you should have them tuned on the car so they work with your given engine setup - ie cam etc. As stated a visit to a dyno will help as they can put a wide band O2/Lamda thing up the tail pipe and tuned the carbs with a good air/fuel mix. Remember it is carbs we are talking about so they will have a good rev range and might be sh!t else where (no computer to monitor and automatically adjust the air/fuel ratio) - by sh!t I mean not ideal you still should get it to pull hard...hell can't have it both ways ie good up top and down low these are triples and carbs only have a given rev range when they run their best ie 3500rpm-6500rpm will not be too flash at below 3500rpm. So sounds like yours is the other way round good below 3500rpm but crap above. So you might have jet sizing issues, tuning issues or could be timing issues (maybe this is why you popped the lash pad? They usually only fail with big over revs).

So my main advice is this - get the carbs tuned on the car not on the bench which I assume Murray at Weberspecs did - if however Murray tuned them on the car - then I have no idea.

M4vr1k · Post by **M4vr1k** » Tue Jan 02, 2007 4:39 pm

Yeah, they were all set up on the bench, not on the car. Didnt even get the chance to go above 3500 revs...its just so gutless.. Havent got any manifold leaks, thats the first thing we checked. Will speak with Dad later on, and see where we go from here
Cheers guys!

240z · Post by **240z** » Tue Jan 02, 2007 11:38 pm

If you are keen to get the most out of your engine you must go on a dyno as its fairly important with the L series engines to run the correct mixtures to make power.

There is also power in the distributor you dont want to run the vacuum advance line, do it all with the centrifical advance in the distributor you may need to do some mods to get desired max advance. Best to set this on the dyno also.

Murray also set my carbs up years ago and did an excellent job. but as soon as the were bolted on it went on a dyno to get sorted. As all engines are different capacity,cams,head development, exhaust etc almost impossible to set up perfect on the bench.

nzeder · Post by **nzeder** » Tue Jan 02, 2007 11:55 pm

Another note - advice from Ricky - check your fuel pressure dellorto's don't like too much or too little (they are more fussy than webers, other carbs) so it might pay to get a fuel pressure gauge inline and if you are still using the old mechanical fuel pump might pay to consider a good electric unit and good fuel pressure regulator (as you car is a 260z the wiring should be there in the rear already)

These things would be picked up on a dyno

however check the above first to eliminate any fuel supply problems now.

submax · Post by **submax** » Wed Jan 03, 2007 3:09 pm

For what it's worth we had trouble getting my sons 240 to run as well as required an found that the dwell angle was cricital to get max performance.
Cheers Dale

M4vr1k · Post by **M4vr1k** » Sun Jan 07, 2007 2:53 am

Well.
Dont I feel like a plonker.
Turns out the cam timing is out, hence why the car is so flat when under load.....
Will have it back up and running next weekend.

bruce · Post by **bruce** » Sun Jan 07, 2007 11:48 am

well if we all had a $ for every time one of us proceeded off on completely the wrong path sorting tuning woes, we'd all be rich!

Are those Dellortos 40s or 45s? If they are 40s, I have some jet settings somewhere for my old 240 (280 engine, 265 degree cam, around 10:1 compression) that might help - for instance I found that the emulsion tube made quite a bit of difference to the driveability on my road car.

cheers and good luck, once you've sorted your triples you wont go back to SUs in a hurry!

M4vr1k · Post by **M4vr1k** » Sun Jan 07, 2007 7:52 pm

Thanks for the offer bruce, but i reckon once the cam timing is sorted, it will be fine.
Will chuck it on the dyno anyway, just to make sure its all balanced and tuned perfectly

M4vr1k · Post by **M4vr1k** » Fri Feb 02, 2007 12:04 am

Grumble, Grumble, Bitch, Bitch, Moan, Moan.

Have hit yet another bump in the road to getting my Zed back on the road.
Fixed up the cam timing, broke a valve lash pad. Fixed the valve lash pad, only to find that there is no compression in number 4 cylinder....dammit!
Most likely from a bent valve from the lash pad breaking!
Ahh well, not too much longer now.....i hope