240sx Build Nights, Thursdays 7:30pm

Automotive
#1

After the last Lemons event, our race car was left in only a partially running state, we are now meeting Thursdays at 7:30pm to work on the car, anyone is welcome to attend.

First step was fixing the upper timing chain, the guess was that I got the alignment wrong after swapping the head late in the night, turned out we were definitely a link off on the idler sprocket. Meaning the valves were opening / closing at the wrong time relative to the piston.

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The red marks above were just to verify that the previous alignment was wrong, what matters was setting engine at TDC compression on cylinder 1, taking chain off, then matching the built in black links on the upper timing chain to the timing marks on the sprockets. The mark on the idler sprocket is on the bottom and not visible in picture.

That wasn’t the only problem though, as it still won’t idle, mostly likely next issue is an intake leak as we used rtv instead of a replacement gasket for the intake. So next week will be taking intake manifold off (annoyingly difficult on this car). Will also be replacing thermostat and doing an egr delete (were forced to sawzall egr tube in half to do head swap, and currently an aluminum can + hose clamp is ‘reconnecting’ the tube)

After that will be diagnosing why the starter is nonfunctional (have been doing lots of push starting to test engine so far).

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Board Agenda Item: Future of DMS Racing Group Project
#2

Parts for tomorrow, key lesson from previous head swap, you must remove the bolts and studs on the intake manifold, attempting to slide manifold back over studs will not work

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#3

Since you’re right in there, did you change the chain and look at sprocket wear?

I’ve had the same chain for 250k miles in the Celica, but I do hear they stretch and wear the sprockets – making them more likely to jump timing and mash things up.

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#4

That reminds me of my old Oldsmobile I had. Stupid dicast sprocket sucked & the chain stretched. All that a night after I changed my earl(oil).

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#5

We changed both timing chains and tensioners ~2 races ago (before feb 2015), we are getting a bit too familiar with the ka24de

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#6

We got the gaskets replaced, the most annoying thing is the number of coolant and vacuum lines going all over the place underneath and inbetween the two halves of the intake (several vacuum lines go to the charcoal evap canistor that deals with not venting gas fumes from the gas tank to the atmosphere, and there is a coolant line that goes through the throttle body then back through the idle air control system.

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The vacuum leak became obvious once we removed the top half of the intake, while doing the head swap the two halves of the intake were partially removed and the gasket got messed up, it is right up against the egr there so it wasn’t visible. Turns out the engine wont idle with a vacuum leak this huge.

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We also removed the EGR and welded shut the nut on the exhaust manifold, (which would be illegal on a street car, but this is a track use only vehicle)

Once everything was back together the engine started up and idled great (but only for 30 seconds since was testing it with no coolant, broke one of the coolant lines taking it apart). Next week will be diagnosing and fixing an unresponsive starter.

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#7

I’m not sure that qualifies as a “vacuum leak”. With a hole that size isn’t it more of a “manifold port”?

#8

Got an external digital water temp gauge to install tomorrow. When the coolant boiled off during the race the stock gauge cluster water temp was only about 2/3 between C and H. Also got some extra replacement vacuum hoses, caps, small hose clamps that will be available for anyone to use.

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Will also be looking at the starter, the circuit is very simple(no theft system in this car), with one relay in the way that we can bypass for testing

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#9

Unless it is required in the rules, I would probably figure all the drivers are resonably competent and remove the clutch interlock relay.

#10

those are for learning disabled drivers - just like the cars where you must push on the brake pedal in order to put a slugomatic into gear.

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#11

Got the mount for the digital temp sender put in, didn’t get to installing the actual gauge and wiring it in yet, will probably work on that next week. I bought a lot of silicone tubing for coolant / vacuum lines for the auto area (only needed a couple short sections easier to buy in bulk so now we have various hose sizes if anyone needs some, 2mm, 3mm, 4mm, 6mm, 8mm, 12mm)

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Checked the timing and it was at about 15 degrees btdc, adjusted it to 22 (factory spec), found this article explaining effect of advancing timing

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After charging the battery for awhile (was very dead and not turning over after initial testing showed circuitry was working as expected), the starter repeated the issue of getting “stuck on” once, but it started up perfectly ~5 times in a row after that. So it was likely getting really hot and a low battery causing it to be flaky.

Test driving the car around in the parking lot there is a slightly worrying intermittent knocking noise that is only audible at certain rpm ranges, will require more investigating.

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#12

Also used the exhaust gas detector to be sure that the head gasket on the car now is at least holding for now, after warming car up in the parking lot and depressurizing radiator, filled the chambers up with the test fluid, then holding it against radiator pressed bulb a few times to draw air from in the radiator through the liquid. If there are any combustion gases the blue fluid turns yellow.

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To see what would happen then held the tester behind the tail pipe, this is the color it would be if there were combustion gases in coolant

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This tester is on the auto shelving in a plastic box with most of the other tools for anyone to use if they want to verify they have a bad head gasket or cracked block before going through with expensive repairs.

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#13

Got some wire and plastic conduit to wire in the water temp gauge tomorrow.

#14

Anyone care to listen to this?

I am almost certain now that it is rod knock and this engine is toast. :bread:

Next question is to fundraise the $1,600 for a rebuilt long block from JIS in arlington or to sell the car.

We will drop the oil pan next week to get a closer look

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#15

I would suggest taking a careful look at the bottoms of the bores. It might be worth doing an in house project to install all new crank, rods and Pistons. Probably considerably cheaper than remanufactured.

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#16

I have pulled a motor before & replaced the crank shaft bearings after wiping a main bearing. I still have the piston from it too where it was hitting the head. It was fun for sure.

#17

We certainly could rebuild the engine ourselves, but I don’t think it would be worth it. We have already pulled the engine once and did a partial rebuild, by the time we got new crankshaft, pistons, bearings, seals, had block and head machined, we wouldn’t be saving much money. Plus I’m not interested in jumping through the hoops to make a rebuild a formal class.

#18

Brandon,

How about one evening next week - we (I’m good for any night after 7pm) pull the oil pan like you said and see if the crank is damaged. and go from there…

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#19

I’m a newbie at this depth of maintenance: why would you need machine work done? According to the video you sent, the likely damage areas are the connecting rod & cap, bearing, and the crankshaft surface itself.

#20

for most of the 1980s my father had a 1949 Chevrolet Carryall Suburban … as a daily driver (this itself is a separate story). Starting this vehicle was a skill in itself. One day when I am perhaps 9 or 10, my mother needs to go somewhere and for reasons that escape me, her usual vehicle isn’t available. So she attempts to start the Chevy, which is having none of it since the intricate sequence of starter, clutch, choke, and applying gas the the right moments isn’t happening. After several minutes she gives up and walks back to the house. I give it a go and in short order I discover that the starter motor is all too happy to propel the vehicle short distances. Thankfully, I find this a bit startling so I quit before the starter and/or battery release the magic smoke.

I miss that vehicle - couldn’t really manage highway speeds, but it was relatively unique in the 1980s, would be doubly so now.

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