KillerBjt Posted March 25, 2007 Share Posted March 25, 2007 I have a 240z with the orginal L24 and tripple PHH44's, a Isky cam with 480 lift/280 duration, hardened valve seats, lightened flywheel, E-31 head, and a 2.5inch exhuast to a 3inch flowmaster muffler. The current jet sizes are Main Air-210, Main fuel-140, and Idle-57.5. I was wondering what any of you recomdend doing, should i rejet it or what? And if i do rejet it what do you think the range of jets i should buy is? Quote Link to comment Share on other sites More sharing options...
KillerBjt Posted March 25, 2007 Author Share Posted March 25, 2007 Oh and heres a picture of the setup, and i cant really rev past 5000RPM, just doesnt have anymore go after that. If anyone can help please let me know what you think.... Quote Link to comment Share on other sites More sharing options...
JMortensen Posted March 25, 2007 Share Posted March 25, 2007 If you want to tune the carbs in closer the easiest way in my opinion is to install a narrowband O2 sensor in the exhaust and use a multimeter to read it. Should be around .8V for max power. I don't think its the jetting that is causing it not to go past 5000 rpm. Sounds like an ignition problem to me. What's the timing set at? Points or electronic ignition? How old are the plugs/wires/cap/rotor? How about the coil? Quote Link to comment Share on other sites More sharing options...
KillerBjt Posted March 25, 2007 Author Share Posted March 25, 2007 Im not sure how old the wires/cap/rotor/coil are but the spark plugs are pretty new and its a electronic ignition, i have no idea what kind of electronic ignition since ive never heard anyone talk about it on any of the Z sites. Im pretty sure at idle which is about 1000rpm it is 17degrees BTDC. i have no idea other than that, but the distributor is at its max retarding setting so i would need help figuring out how to fix that is i need to set the timing lower. Edit: btw heres a picture of my distributor Quote Link to comment Share on other sites More sharing options...
X64v Posted March 25, 2007 Share Posted March 25, 2007 That's a Pertronix Ignitor. Uses a little magnet over the hex on the dizzy shaft, and just fires the coil like the points did, nothing special. If you're using a 240 dizzy (looks like it) then unless it's been recurved, 17 degrees at idle is way too much advance, because it'll climb to around 41 degrees full advance. You should be down around 10 degrees of advance at idle. There is a bolt in a slotted hole that holds that plate onto the dizzy. if you loosen it, you can move the plate that has the retard/advance scale on it, therefore letting you back off your timing to whatever. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted March 25, 2007 Share Posted March 25, 2007 The jetting seems about right so I really don't think that's the issue. As x64v mentioned, this looks like a 240 distributor, so initial timing should be around 10 degrees. Where I'm going to disagree with him is on the distributor adjustment. On the 240 there is a pointer attached to the timing cover and marks are cut into the balancer. The deepest mark is 0 degrees, then there are marks at 5 degree intervals past that one. So you want two marks past the big one. You only have a limited amount of adjustment, but there are actually two adjusters on the distributor. One has a 10mm lockdown bolt and is very obvious. The other is a smaller 8mm bolt, and I didn't even know it existed until someone showed it to me. It's on the opposite side of the distributor from the first one. If both of those still don't allow you to adjust the timing enough, then you might have to pull the distributor shaft and reposition it. If you search you should find info on that, but basically it requires pulling the oil pump out of the bottom of the timing cover, moving the shaft, then reinstalling the oil pump. One more thing for you is you might want to try and verify that your timing marks haven't moved. Lots of old Datsun harmonic balancers come apart and then the outer ring with the marks can rotate over the inner ring that is actually bolted to the crankshaft. You can get a good idea of whether or not it is right by pulling the #1 spark plug and putting something long like a welding rod or a pen into the spark plug hole then turning the crank until it hits 0 degrees on the balancer and see if that's as high as the piston actually gets. If the balancer is right I'd start by replacing the coil, wires, and cap and rotor. It definitely sounds like an ignition thing to me. Quote Link to comment Share on other sites More sharing options...
KillerBjt Posted March 25, 2007 Author Share Posted March 25, 2007 Alright ill give those things a try, thanks for all the help and info. Man i love this site, everyone is so nice and helpful. Ill post agian if all that doesnt work. Quote Link to comment Share on other sites More sharing options...
KillerBjt Posted March 25, 2007 Author Share Posted March 25, 2007 Well i just started up the car to tweak the spark timing and well i heard a click click click coming from the cylinder head, and ive heard this sound a few times listening to videos people posted on here and what most of you have said is that the valves floated and hit the piston, which means now i have to rebuild the head, or atleast that one cylinder. So i might as well take this oppertunity to rebuild the engine and transmission since ive been meaning to do it anyway. So who in the bay area wants to help me pull and rebuild a engine and tranny? hahahah Quote Link to comment Share on other sites More sharing options...
X64v Posted March 26, 2007 Share Posted March 26, 2007 One has a 10mm lockdown bolt and is very obvious. The other is a smaller 8mm bolt, and I didn't even know it existed until someone showed it to me. It's on the opposite side of the distributor from the first one. That's what I was refering to. "That plate" is the one with a retard/advance scale on it with markings, but no numbers, that's held on with the 8mm bolt. I should have worded it a little better. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted March 26, 2007 Share Posted March 26, 2007 Well i just started up the car to tweak the spark timing and well i heard a click click click coming from the cylinder head, and ive heard this sound a few times listening to videos people posted on here and what most of you have said is that the valves floated and hit the piston, which means now i have to rebuild the head, or atleast that one cylinder. So i might as well take this oppertunity to rebuild the engine and transmission since ive been meaning to do it anyway. So who in the bay area wants to help me pull and rebuild a engine and tranny? hahahah Why don't you pull the valve cover and try to adjust the valves and see if your sound goes away. Valves hitting pistons is not very common in my experience. Quote Link to comment Share on other sites More sharing options...
srgunz Posted March 26, 2007 Share Posted March 26, 2007 I agree with Jon. Why not check valve adjustment and then run a compression test. Tearing a motor apart for a click click is just nuts without further testing. Quote Link to comment Share on other sites More sharing options...
KillerBjt Posted March 26, 2007 Author Share Posted March 26, 2007 Alright ill adjust the valves and run a compression test, but it'll be a week or so before i can do it, dont have the necessary tools do do it at home but in a week or two i can do it in my auto class at college. Quote Link to comment Share on other sites More sharing options...
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