DIY LTCC or similar system for LT1s

[spfautsch]

The first part when you are idling is rich on *5s.

It sure is - I keep forgetting about the "hacker" view settings. I'll have to add a user setting to eehack so that's the default view.

Strangely, I see very few count errors in the microcontroller's log data. Nothing remotely close to the number of 5s I'm seeing just skimming through the .eedata log.

My last logs with new chain and almost new crank sprocket with the same opti bring very consistent *6s at idle with coolant temperatures ranging from freezing cold to really hot.Only a moderate drop to *5s is seen at heavy acceleration above 3000 rpm and single *4s at 6000 rpm.

Is this with stock valvetrain or do you have mods? I don't know if my roller rockers could be contributing any, but I have ~170lbs seat pressure and ~380lbs open springs.

I don`t know how arduino converts the ADC channel in hex, so I suggest, to log some raw data in hex from the ADC channel and see how voltage changes with 1 increment in hex. Than you can figure some easy conversion.

I already have the conversions worked out - the only difficulty I will have is calculating the dwell skew for different voltage ranges. I'm going to try to work that out now. The ADC in the mcu returns 0-1023 (0x0-0x3ff), which is far more resolution than required. I'm also using a voltage divider network to keep the ADC input within a range of 0-5v.

The 96 roadmaster optispark that came in earlier this week looked original. Mitsubitsi pickup and all. The optical wheel had 10475417 on it.

Thanks - I'm relatively sure that's the Delco Remy part. Curious, is that a low mileage roadmaster? Ironically I saw a beige wagon with the wood "inlay" this morning on my way to work. My wife would shoot me, but I'd just love to have a b-body wagon.

[vilefly]

I think the roadmaster has about 140K miles on it. Supposedly, the distributor was replaced by firestone, but it looks OEM-new to me. It came to me when it still had a misfire with new wires on it......burnt wires. This roadmaster has a pretty rough interior. Panels missing, and such. I found mine in perfect shape in a small town in nebraska. I find it best to shop in small towns instead of big cities with boombox-obsessed punks.

[spfautsch]

I think the roadmaster has about 140K miles on it.

That's sort of at the ragged edge of my definition of "low miles" for a 22 year old car. I bought my y-body with 152k on it, and I'm pretty sure up until four days ago when I broke down and ordered new ones, it was still running the original double platinum plugs.

Supposedly, the distributor was replaced by firestone, but it looks OEM-new to me. It came to me when it still had a misfire with new wires on it......burnt wires.

That's probably the other big drawback of the opti. It's a major B itch to route the wires decently without pulling the damned engine.

I found mine in perfect shape in a small town in nebraska. I find it best to shop in small towns instead of big cities with boombox-obsessed punks.

That's where I live (smalltown, MO). A classmate of mine bought one as scrap last summer. I knew the original owners - he was a former Buick dealer. Sold me my first car actually. They'd both passed away and his son had to get rid of a 94 wagon and a couple 80s models. Think he gave $400 for all three, and they were all in impeccable condition considering their age. They'd been garaged most of the last 20 years save for grocery runs. Managed to get them all re-titled. Sold the 94 for a handsome profit.

I think I have the voltage detection "cleaned up" - at the very least there should be zero floating point math taking place anywhere in the firmware unless something has slipped past my eye. Created a new table to lookup the raw adc values. All that's left before I can test is to:

* have new flywheel weight matched to old one
* determine if transmission suffered any damage from running w/ nuked DMF
* finish building more permanent type of controller circuit board
* wait for replacement opti base to arrive
* wait for connectors for coil harness to controller to arrive from China
* install engine
* clean up vehicle wiring harness
* install new u-joints in driveshaft before re-installing exhaust

So I suppose I better get cracking with the wrenches.

[kur4o]

Is this with stock valvetrain or do you have mods? I don't know if my roller rockers could be contributing any, but I have ~170lbs seat pressure and ~380lbs open springs.

Stock type timing gear. The mods are 846 gm camshaft and crane double springs.
The springs are a little too stiff than my preferences. The old comp cam 502 had severe wear on lobes with the same springs and the stock gm chain stretched alot. So cast cam with crane performance lifters and springs with high seat pressure leads to premature wear. You should closely monitor you valvetrain for wear.

[spfautsch]

Lobe wear on a roller cam sounds like problems with the lifters not rolling smoothly. Did you maybe put cam assembly lube on the lobes? Roller cams are supposed to be installed with the lobes dry and the lifter rollers soaked in plain motor oil (no friction modifiers).

The stock square toothed gears are going to be problematic with any aggressive spring load. The factory springs were only 85lbs at seat if memory serves. My lawnmower has stiffer valve springs.

[vilefly]

Lobe wear on a roller cam sounds like problems with the lifters not rolling smoothly. Did you maybe put cam assembly lube on the lobes? Roller cams are supposed to be installed with the lobes dry and the lifter rollers soaked in plain motor oil (no friction modifiers).

The stock square toothed gears are going to be problematic with any aggressive spring load. The factory springs were only 85lbs at seat if memory serves. My lawnmower has stiffer valve springs.

I have been finding that the biggest problem with premature cam wear is too low rpm in final gear causing too little splash lubrication. This has happened before when the 305 engines came out with overdrive transmissions. Under full load conditions, they would operate below 1800 rpm, and show up at the shop with flat camshafts, despite being stock. Now, the same thing is happening with the gm 4.8L engines.(especially in vans) They have damaged cam bearings from too low an oil pressure under full load. Occasionally, I will see it on a 5.3L also. The annoying part is that the oil pressure loss does not show on the oil pressure gauge till it is plugged with bearing material, and you have to either replace the cam bearings (and hope they are not spun) or change the block. This is one of my gripes about the LS motors.

Of course, in the aftermarket area, mismatched springs and cams are common.

[spfautsch]

Got the shipping confirmation on my distributor base and it should be delivered tomorrow. Hoping to have better news then.

Were the rollers flatspotted on these 305s, or are you talking about flat tappet engines? I've personally never seen a roller cam wear, but I'd have to imagine the only way it could is if the rollers were trashed.

I have to wonder how many of those failing LS engine are being filled with oil that's only suitable to use for starting a fire.

I'm going to be pulling the intake to re-seal the ends with better RTV than I used last time, so I might just put a dial indicator on the lifters and see if I've lost anything off the lobes.

[vilefly]

Well, good oil is always important, but the flat tappet-hydraulic cams in the 305 engines still failed, even when that super-dilligent old man who never misses a change drove it. I now have finally lived long enough to see roller tappets fail for various reasons. In some cabs and police cars, I have seen them fail for ........excessive idling with the a/c on (donut cops). The oil was stressed and the splash lubrication was minimal. I honestly thought I would never see them fail, myself. Looks like a perfect design.....but one cannot underestimate the destructive abilities of humans.

As to the LS motors.....run synthetic or die. The oil is now used to cool the piston with jets of oil from the lower connecting rod end, and this piston is very cheaply cast with a carbon-magnet type alloy we call hypereutectic. Naw. That's not hard on the oil at all....heh. The cyl-shutdown tech has an extra discharge port that tend to aireate the oil, and has been revised for that very problem......revised, not recalled. The PCV valve is eliminated in favor of running straight vacuum to the driver's valve cover, and the restriction is in the oil baffling in there. The sealer that holds the baffle in place decays eventually, and the motor ends up sucking raw oil into the intake, causing a perceived spark knock/oil consumption problem. So you have to replace the whole valve cover to correct this. Hence, my theory on limited life automotive vehicles. I figure they are targeting at 5yrs until a major failure.

[vilefly]

Oh, I forgot. Did you intend to scan in your optical wheel? I think it would be a great idea, since it would allow us to copy it and check it for trueness with a CAD program. I am currently trying to draft one up using emachineshop.com 's free cad program. I intend to make another mountable wheel that would let one generate an LS crank/cam signals directly with no conversion. The great part is that the cad program lets you do estimates of the cost of a production run. It would be awesome to just drop in a wheel, and use any engine management system you like.

I have been known to scan in carburetor gaskets at actual size, and reproduce that which could no longer be bought. If I was feeling fancy, I would even load up the gasket paper directly in the printer. Works like a charm. Great also for making TBI to carb adapters from scratch, too. I had to remember to print out with the "actual size" option selected.