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I'm giving up, i need some input


ChrisZ

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After the re build of my motor i have been spending some time adjusting the engine and just cant get it running smooth, i have been reading searching and reading, but still i cant figure this out.

The motor is a L24 with L26/28 crank, flat top pistons, late E88 head, C-cam round tops (3 screw) SM needles and Pertronix

It also have headder and of course my new exhaust http://www.classiczcars.com/forums/showthread.php?t=34025

At the first start up i set the timing to 5 degrees according to the FSM, turned down the mixture nuts 2.5 turn and synced the carbs, the car sputters, backfires or after fires, depending on how much i turn down the adjustment nuts, float hight is set at the front carb, mainly because i got to bend it out of adjustment when looking for dirt in the bowls.

I have also tried to adjust the ignition with a vacuum gauge for best vacuum when it fires, eather has been sprayed every possible way i could think off, no changes.

Valves has been adjusted but only cold.

Timing advance seems to work as well, when i suck in the vacuum hose the advance will turn and stay there until i relese the vacuum, if i turn the distributor shaft and let it go it will turn back as there is a spring helping it, so i believe it works as it should.

The car runs very rich at idle, i mean very very rich, it doesn't smell it stinks of gas, then when i turn the mixture nuts up to lean it, it will then pop/backfire as running to lean, i can't really figure out WTF is going on.

After having put on my dual exhaust i have noticed something interesting, while holding my hand in front of the outlet there is a big difference in how much preassure there is at the end of the exhaust, the uppe one isn't blowing /pushing half as much as the lower one ? it must indicate that there is something wrong at the rear end of the motor witch the upper one connects to.

Please help, all input is appreciated.

Chris

Please guys what am i missing here ??.......

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Your difference in exhaust pressure from the back 3 pistons, combined with fuel stink would make me first check that I was getting spark at those 3 pistons, and that the plug wires were on the right plugs. Next thing I'd check is if the rear carb needle is moving up/down properly and that it sits in its seat perfectly. If it doesn't sit down properly at idle, that could cause the fuel stink and poor idle, because its letting too much fuel through. Are the back plugs wet with fuel? You mentioned those SM needles, which means someone must have had the needles out to put those in. Maybe they weren't put in just right? Finally, is the choke returning after you shut it off. If not, that'd contribute to the problem.

The fuel stink may be unrelated to the poor running, and just be a bad float bowl gasket, since you've recently had them opened up. I've got that problem on mine right now. Under certain conditions, I get a tiny fuel leak through the float bowl gasket. Doesn't affect how it runs, but it sure stinks when it happens, though. I've got new gaskets, just haven't put them on yet....

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My thoughts are similar. It sounds like the rear carb isn't working to me. As mentioned, check the rear carb piston to make certain it moves freely. You mention the float height at the front carb, what about the rear? Has that been checked?

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The float hight havent been cheked at the rear, mainly because the car ran with those carbs before i re build the motor and got to fiddle with it, i'm pretty sure that the plug wires is in the right firing order but i will check and confirm, while at it i will also have a look at the plugs.

The SM needles is some i got hold of and installed, the shoulder is equal with the buttom of the piston, i swapped because the other needles that was in the carbs looked to have a home grind and who will trust that, the float bowl gasket was put on with some non hardning sealant, the fuel smell is from the exhaust.

I will take off the dome pistons tomorrow and clean them again, when the dome are taken off the piston falls freely to the seat, when i have them out i will do the 1 Mississippi, 2 Mississippi, 3 Mississippi test if ya know what i mean, they could of cause have been swapped.

i will also check the wires, it must be possible to test it with a test lamp.

Thanks for your replies, any other with some input on this.

Chris

Edited by ChrisZ
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Maybe i should add that a compression test showed that it have from 185 to 195 psi on all cylinders, i'm comftable with the difference because the rings haven't been broken in yet.

Chris

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Oh, one thing more, the motor have a "whistling" sound, but not constant, it just kind of "whistle" once in a while, do anyone know what that is ??....

Edited by ChrisZ
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Oh, one thing more, the motor have a "whistling" sound, but not constant, it just kind of "whistle" once ni a while, do anyone know what that is ??....

Possibly a vacuum leak. Squirt a little carb cleaner around where the intaks manifold connects to the head. If you've got a leak you'll know as soon as you hit it.

Steve

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Since you recently completed a rebuild you should double check that the assembly went as required. Start with the timing. Put your engine at TDC and make sure the distributor shaft is in the right position. Then check your cam timing.

Do this before you tear apart your carbs. Since your car ran fine before with the carbs the way they are I'd leave them alone and make sure everything else is ok.

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Chris,

Steve and Ed both offer good suggestions on things to check.... When you do the spary around cheking for leaks, sparay all the mounting surfaces between the carbs and the head.

Now, if and when you do pull the carb domes and pistons checking for whatever your checking for, grab a flashlight and look down in the fuel nozzles and see where the fuel level is in relation to the top of the nozzle. The static fuel level, if the floats are correct should be about a 1/16" below the top of the nozzle. This should be done shortly after the engine has been run. If gas is pooled up on top of the nozzles that will give a rich condition, if the level is farther down the tube that will give you a lean condition. I would guess, all things being equal this should be done with the nozzles at 2 1/2 turns down for full up top.

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Since you recently completed a rebuild you should double check that the assembly went as required. Start with the timing. Put your engine at TDC and make sure the distributor shaft is in the right position. Then check your cam timing.

Do this before you tear apart your carbs. Since your car ran fine before with the carbs the way they are I'd leave them alone and make sure everything else is ok.

Ed you have a point there, but it all have been checked, the cam timing is right on the spot, the camshaft location notch lines perfect up with the oblong grove on the location plate, when #1 hole is used, i have been thinking of trying to move to hole #2 just to see if it makes a difference.

When i assembled that motor i did it with the FSM at my side, nothing have been skipped, most of the time i used assembling vent with measuring clerance and so on.

Steve, thats also what i think, but i have sprayed every possible place with starting fluid (eather) also around the brake booster, still nothing, i will give it a 2nd try, there is also that "whistling" sound, i need to use a hose listening where it comes from, being that sound isn't constant it gets more irritating.

Bruce, i will check.

Thanks so far guys

Chris

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Update, today i pulled the carbs and intake, cleaned it all up and re assembled it, when putting it all together i used some Locktite, just a thin layer on every connection surface, it is a non hardning and oil /gas resistant sealant.

I also inspected the carbs, everything looks good except of the float at the rear carb, it was to high, i re adjusted the float, cleaned up the carbs with acetone and put it together, i also checked the "fall of the pistons in the domes" they went down in 3 seconds on both.

I put it all together and adjusted the nuts down 2.5 turn, started up the car and began adjusting and balancing, i got it pretty well balanced, to check the mixture i lifted the dome piston ½ an inch, front carb ran pretty good at idle 3 turns down, rear carb ran to lean but i finally got it to run when the front was out of function, balanced it all again, set the high idle and adjusted the flow, when i rev the motor it revs fine, might not be good enough but still better than before, i went for a drive around the block and noticed a big difference, it pulled much better, when i got to a main road i floored it and then there was some hesitation, it just didn't rev good enough, then when i got back home the car didn't idle good enough, now it just die instead of idle, pulling the choke doesent help a bit, how can this be ?

Bruce is the float high the same in the rear as in the front, i remember reading some place that there is a difference i just can't remember if it was the 3 or 4 screw carbs.

Ed, will it make a difference if i adjust the cam to location #2 on the cam gear ?

Anyway, positive progress but not good enough.

Chris

Edited by ChrisZ
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The # 2 location the cam gear is to compensate for a timing chain that is old and stretched out. Refer to your FSM. There are diagrams that show where your timing marks should be. To me it doesn't sound like your timing is off too much. I think your on the right track and are slowly getting to a solution.

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Well Ed so do i, there are two things i'm focusing on now.

#1 valve adjustment, there are marks on the rockers surface that is curving down where the cam is hitting it, so when adjusting the valves i can't compensate for those marks and that will make the adjustment to sloppy, am i correct if i say the ratio on the rockere is 1.5 to 1, meaning that if i multiply the thickness of the feeler gauge by 1.5 and measure at the lash pads it should be all the same.

#2 either the battery is shot or the altenator / relay is, i have read someplace that it can cause that the spark plugs isn't getting enough voltage and that will affect performance, just got a new battery today,(needed one anyway the other was not mine), im going to install that tomorrow and measure the output from the altenator.

Rear float hight on the 3 screws can some verify if it is the same as the front or different.

Chris

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Update, problem solved, first i pulled one plug wire at time in order to see if it would make a difference, nothing, then i used my timing light to se if it would work on all wires, there was no flashing on #5 cylinder, 6 new plugs gapped ad installed and now it pulls HARD

Time to re adjust the carbs and get raedy for a long trip tomorrow :D

Chris

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Thanks Adam, i just got home from a 2 x 120 miles cruise (90mph) it was fun and i got to know of some more small "need to fix bugs"

While i have you Adam, can i then get you to have a look at the wiring colors at the coil and ballast resistor and then tell me the color codes?, i really need to know.

Chris

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Thanks Adam, i just got home from a 2 x 120 miles cruise (90mph) it was fun and i got to know of some more small "need to fix bugs"

While i have you Adam, can i then get you to have a look at the wiring colors at the coil and ballast resistor and then tell me the color codes?, i really need to know.

Chris

Sorry Chris, I swapped out the original dizzy and added an MSD 6AL and Blaster coil some time ago. In the process I ran some new wiring and wrapped it all up so it is no longer visible. If I recall correctly, the original wiring was as follows:

BW from IGN SW (start) to Coil +

B from Coil - to dizzy

GW from Ballast to Tach

BW from IGN SW "run" to Ballast

Condensor to Coil +

This is from memory so I could be wrong on this. I recommend double checking a wiring diagram to confirm. You can also check the before/after pics I took of the 280ZX dizzy and B210 coil swap. There may be some pics where you can see the original wiring with the ancient Lucas coil and the replacement from a 79? B210.

Edited by =Enigma=
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Thanks Adam, i will take a look, problem is that my tach isn't working and i don't recall having a GW wire out there.

Do you know if you have a 3 or 4 wire tach ?

Chris

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Do you know if you have a 3 or 4 wire tach ?

Chris

Based solely on the Instrument Harness diagram in the 1973 FSM, it's a 4 wire. The shown are B, G, BW, GW at the connector for the tach. I haven't had to go under the dash yet thank God so I can't verify this.

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