jalexquijano

Took my 240z for a spin on saturday and got into heavy traffic. RPM mantained at 1,100 in light traffic but once i started going bumper to bumper, the rpm started to lower to 800 rpm and the raised back to 1100. The car carries Datsun L24 motor with crank and rods from a L26, special oversized 84mm flat top black coated pistons from D.L. Potter Engineering with E88 Head and Far 311 New Race Cam and 2 original SU Hitachi round top carburetors rebuilt reason why it has a rough idle.

According to one of the members this is what i really have in my car pursuant to the mentioned cam and pistons:

"a L26 crank makes my motor 79 mm stroke instead of the stock 73.7 mm
stock bore is 83 mm for the L24 and the L26 motors
my block has been bored out 1 mm to compensate for wear
that makes my motor a 2.627 liter motor
your E88 head from 1972 will give you about 8.7 to 1 compression
FAR performance went out of business in 2002 so I have no cam specs
311 could be their advertised cam duration
if it is the same as BRE 311-------

BRE 240Z 311/C-1 cam: At 0.001" lift: In open 33 deg Bef TDC In close 66 deg Aft BDC Ex open 66 deg Bef BDC Ex close 33 deg Aft TDC IN Lift at TDC 0.108" Total Lift 0.463"

At 0.050" lift: In open 14 deg Bef TDC In close 45 deg Aft BDC Ex open 45 deg Bef BDC Ex close 12 deg Aft TDC

IN Lift at TDC 0.108" IN Lift Total 0.463"

EX Lift at TDC 0.097" EX Lift Total 0.469"

I did remove the EGR system as the servo diaphgram was broken:

[ATTACH][/ATTACH]


HOW DO I SOLVE THIS IDLE PROBLEM? ANYONE? Should i spray contact cleaner around all the hoses and tubes to see where the leak really is?

7d82adz

do u drive your 240 on a regular basis? low quality fuel or contaminated fuel has a hard time burning correctly in any motor..

with trouble shooting always check basics first, fuel, fuel quality, fuel pressure, ignition, timing, airfilter, etc..

are the carbs synced properly?

theramz

Had the same problem. Turns out it was the linkage sticking. If your idle goes up and down while just sitting it is vacuum or fuel/carb related.
If you still have the antibackfire pod on it then you should check to see if vacuum is bumping up the idle.

jalexquijano

I removed all the EGR system from the car. Installed new carburetors and a complete Schneider 274F camshaft kit. The problem still continues.

jalexquijano

WHich linkage?? I removed all the EGR System and have cancelled the antibackfire pod!

If i am stuck under traffic or leave the engine on for 7 to 10 minutes the car starts decreasing its idle from 1000 RPM to 950 or 900 RPM. The problem gets worse if turn the headlights on bearing in mind that i have the Dave Irwin headlight mod which connects the headlights directly to the battery through a relay switch. The idle lowers from 1000 RPM to 900 RPM and after 5 to 7 minutes could lower to 600 RPM.

I was advised that if i replaced my Bosch 60 amp alternator with a 125 amp alternator this situation could be solved:


http://www.datsunstore.com/high-outp...nator-p-1.HTML


Before proceeding with this purchase i would like to be secure this will really help. I would be installing a Sanden 508 compressor with Vintage Gen II Mini evaporator kit once the idle becomes stable.

theramz

Check your vacuum advance with a vac pump. If you don't have one disconnect the hose to the dizzy while it's running, plug the hose and observe idle speed. Make sure you breaker plate moves and returns with your fingers. If you have a timing light check for advance when you open the throttle quickly. It should advance immediately until the mech advance takes over.

FrappNasty

It sounds like a charge issue. The alternator may be out putting well enough at higher RPM, but at idle you get no charge, at idle your ignition may be running on battery power. I have seen this before, and it can be a easy check, with the car at operating temp and running at idle and check at the battery for voltage. You should see around 13-14ish volts. I'm running a 60amp unit and have no issues.