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Thread: DIY LTCC or similar system for LT1s

  1. #316
    Fuel Injected! spfautsch's Avatar
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    Quote Originally Posted by vilefly View Post
    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.

    Quote Originally Posted by vilefly View Post
    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.

    Quote Originally Posted by vilefly View Post
    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.

  2. #317
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    Quote Originally Posted by spfautsch View Post
    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.

  3. #318
    Fuel Injected! spfautsch's Avatar
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    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.

  4. #319
    Fuel Injected! vilefly's Avatar
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    Quote Originally Posted by spfautsch View Post
    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.

  5. #320
    Fuel Injected! spfautsch's Avatar
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    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.

  6. #321
    Fuel Injected! vilefly's Avatar
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    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.
    Last edited by vilefly; 2 Weeks Ago at 07:45 PM. Reason: more junk info

  7. #322
    Fuel Injected! vilefly's Avatar
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    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.

  8. #323
    Fuel Injected! spfautsch's Avatar
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    I did that today, but I wouldn't recommend using either of the wheels I have as a pattern.

    Extremely disappointed with the remanned distributor base. I had high hopes of it being worthwhile b/c it was expensive for only a base, was described as a delco-remy and the rebuilder riveted their name to it so I assumed they were proud of their work. They shouldn't be - it was a remmaned aftermarket piece of garbage that I'm probably going to try to return. The trigger wheel had C4105-11 etched on it. The bearing was tight, but sounded like an egg beater when spun like the hub had been pressed in without supporting the center race. The optical sensor was marked J520.

    To add insult to injury, when I put it on to test the low res signal was extremely inconsistent. The controller would lose track of whether it was on or off because it was giving multiple edge triggers. I seriously doubt it would have ran had I installed this in-car and tried starting it.

    Out of curiosity I tried the old optical sensor that was in mine when I bought the car (that was setting a DTC for loss of hi res). I observed the same type of erratic behavior on the hi-res output.

    The only positive that came of it is that the trigger wheel gave slightly better results. I put it in my distributor base because I didn't like the way my "good" AIP sensor fit in the aftermarket base. Timing was still skewed but the difference between cyl 6 and 8 was consistently 3 degrees instead of 4 with the 3001277 wheel. Putting both wheels on the hub and aligning them carefully I was able to observe differences in the size of the low res cutouts, albeit with a magnifying glass. Most were towards the indexed side of the slot, but #8 was on the TDC side.

    I did quite a bit of experimenting with the mechanics of the opti today (mines a gen 2 vented). I found that removing the o-rings from the shaft made it obvious there's some slop between the cam dowel and the hub. Enough that I could consistently make the high res signal change state by wiggling the rotor back and forth. The o-rings damp this slop somewhat, until they get hard. I didn't have a chance to dig out my original cam and check the dowel diameter (think it's supposed to be .250"). But if the aftermarket cam dowel is within tolerance this would illustrate how big of a design flaw this is, and why most of the newer engines have the degree wheels integral to the crank casting.

    I also removed the hub on my old opti to try and find sizes on the bearing. The grease seals on it were marked 6903-RS but it's obviously a custom-order bearing - the outer race has an integral shoulder for the retaining ring. Without this shoulder it would be dimensionally identical to a 6903 bearing (17x30x7) but didn't bother measuring the diameter of the shoulder.

    Without more test subjects to confirm or disprove whether the timing skew I'm observing is common, I'm not terribly happy with the state of things so I'm back to looking for a source for an original degree wheel to test. That, or I dump another 5 bennys and a quarter on a dynaspark.

  9. #324
    Fuel Injected! vilefly's Avatar
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    How about this flanged bearing?
    http://www.vxb.com/F6903ZZ-Flanged-S...-p/f6903zz.htm
    F6903ZZ-2.jpg

    If not, use the designation "NR" after the bearing number to do a search. 6903 NR, and similar, 6903 zznr, ss6903 nr, etc. I have to tend to the "squab", and keep her out of the bathroom before she develops a killer bacterial weapon in there.
    Last edited by vilefly; 1 Week Ago at 07:05 PM. Reason: more info

  10. #325
    Fuel Injected! spfautsch's Avatar
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    I'll have to pull the hub back out and will post pics and dimensions. The shoulder is in the middle of the bearing with steps down to the nominal 33mm race size in front and back, so that probably wouldn't work just from eyeballing it. This is another area where GM really screwed the pooch on design - all in the name of saving a quarter of an inch.

    The hub is a relatively loose press fit to the shaft and I believe even OE used threadlocker to secure it once aligned to TDC. It's fairly easy to remove by holding the hub with something and tapping the shaft out with a punch - no vise or pullers required. Most of the rebuilders drill a 3/32 hole for a roll pin at the mating line before disassembly so they don't have to re-index the hub. I don't want to attempt to remove the hub from the bearing without a replacement bearing, so that will be at the very bottom of my bucket list.

    I'm not feeling like messing around in the garage any more tonight - just finished the 44th oil change (x 10,000 mile interval) and tire rotation on my daily driver, removed the trigger wheel to return the junk distributor base for a refund, and washed the sooty smelling oil off my hands. Going to spend some time relaxing and entertaining my daughter's dog that she swore up and down she was going to take care of. The animal would fetch the tennis ball from 6am to midnight if there was someone willing to throw the damned thing that long.

    The results I had with the other trigger wheel seem to show the a similar pattern of timing skew, trending towards +3 degrees between cyls 1 and 8 and zero around cyl 6. The only explanation I can think of for this other than a junk trigger wheel is that my cam gear is slightly elliptical. Without others reproducing this test on different engines I don't really feel alarmed enough to warrant pulling the timing cover and possibly creating a new oil leak. For all we know at this point, a brand new OE timing set might produce more erratic results. And though we're geographically diverse beyond the pale of vision, I don't see a line forming of LT-1 owners wanting to yank their water pumps to attach a degree wheel and find true mechanical TDC to verify. Ultimately my intentions were to upgrade to an electric water pump so I can run a standard double roller timing set, so maybe that will be my excuse to pull the engine next winter.

  11. #326
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    Why don`t you hit the local scrapeyard. There might be some cheap not working units. Anyway you only want the stock gm wheel.
    New opti is almost impossible to find. Even GM sells only reman units now.

    If we follow common sense you`re timing gear should be a little too tight. Since you hit alot of *5s at idle and stretched chain gives *7s.
    Eleptical wheel will produce too many vibration when spun at high rpm.
    You can compare chain link counts with crank sprocket tooth counts. If they have 2:1 ratio it is possible that half the chain is busted.

  12. #327
    Fuel Injected! Terminal_Crazy's Avatar
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    Quote Originally Posted by kur4o View Post
    Why don`t you hit the local scrapeyard. There might be some cheap not working units. Anyway you only want the stock gm wheel.
    New opti is almost impossible to find. Even GM sells only reman units now.

    If we follow common sense you`re timing gear should be a little too tight. Since you hit alot of *5s at idle and stretched chain gives *7s.
    Eleptical wheel will produce too many vibration when spun at high rpm.
    You can compare chain link counts with crank sprocket tooth counts. If they have 2:1 ratio it is possible that half the chain is busted.
    I have a stock 95 opti I can scan if you want when I get back home.

    The gears have something like 15 and 30 teeth to give a 2:1 ratio but the chain is longer and the links should walk around so they don’t line up regularly.
    Mitch
    '95 Z28 M6 -Just the odd mod.
    '80 350 A3 C3 Corvette - recent addition.

  13. #328
    Fuel Injected! spfautsch's Avatar
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    Quote Originally Posted by kur4o View Post
    Why don`t you hit the local scrapeyard. There might be some cheap not working units. Anyway you only want the stock gm wheel.
    The thought crossed my mind. Generally I go to <big auction site> when I'm looking for scrapyard parts since most yards list stuff there and it saves me the agony of using the telephone and a bunch of driving. I'm not seeing any salvaged optis there. Just one MSD that in the description says it was setting a CMP code so probably needs a new sensor and the MSDs use a proprietary sensor.

    But in addition to wanting the correct wheel I'd like a new bearing, and I'm not hopeful of finding a source for one.

    Quote Originally Posted by kur4o View Post
    If we follow common sense you`re timing gear should be a little too tight. Since you hit alot of *5s at idle and stretched chain gives *7s.
    Eleptical wheel will produce too many vibration when spun at high rpm.
    If the timing gear wasn't perfectly circular or bore where the cam seats in the gear isn't perfectly centered that would cause the chain to be tighter for half a revolution.

    Thinking about this, I've almost worked up the courage to pull the timing cover and see what I find. Maybe I'll put a double roller chain in temporarily and re-test timing. If the cloyes set I put in last year is egg shaped it would really burn me because if memory serves that was a very expensive set.

    Quote Originally Posted by Terminal_Crazy View Post
    I have a stock 95 opti I can scan if you want when I get back home.
    vilefly might appreciate it.

  14. #329
    Fuel Injected! spfautsch's Avatar
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    Found a double roller billet timing set (w/o water pump drive) for a very reasonable price so it's on the way.

    If it improves or eliminates the timing skew I guess I'll take that last step off the cliff and buy an electric water pump.

    Will try to post pics and measurements of opti bearing and base tonight. From extensive reading I'm not feeling very confident an alternative will be possible. I'd really like to remove the hub from the remanned delphi unit to see if there are any part #s visible on it. But I'd also like to be able to return it as it isn't worth what I paid just to gain a better quality trigger wheel.

    BTW vilefly the metal shielded bearing type you posted a pic of would be a problem for vented optis because they need to hold vacuum. The vent system might suck the grease out of that one not to mention letting unmetered air into the intake.

  15. #330
    Fuel Injected! Terminal_Crazy's Avatar
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    Quote Originally Posted by spfautsch View Post
    BTW vilefly the metal shielded bearing type you posted a pic of would be a problem for vented optis because they need to hold vacuum. The vent system might suck the grease out of that one not to mention letting unmetered air into the intake.
    Are the stock ones sealed at the back then ? Otherwise they’d suffer the same. I’ll open mine up when I get back, it’s been a few years now since I was inside.
    Mitch
    '95 Z28 M6 -Just the odd mod.
    '80 350 A3 C3 Corvette - recent addition.

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