Boosted12 Posted October 21, 2013 Share Posted October 21, 2013 Hello all, I'm a long time lurker here and am having issues with my fresh (600miles) rebuild. The engine is an 83 L28ET, using MS1 V3.0 with spark control, Holset HE351 turbo, mild turbo regrind cam, forged pistons (~8.5 to 1 CR). I did a WOT throttle run to redline testing a higher boost setting while datalogging, near redline (6k in my case) the car sputtered, missed, and backfired badly. I got off the throttle, coasted to a stop, engine is dead. Cranked it back up, only ran while applying throttle. Still backfiring and sputtering, I pulled over and got the car towed home. Removed spark plugs, verified even compression in all cylinders ~120PSI. Verified static timing, verified fuel pressure, plugs are clean and not fouled. I had a helper start the car and hold the throttle while I watched with a timing gun - the car is now firing 1 at ~33 deg BTDC. I then checked the distributor shaft - it looks slightly off, but not a huge discrepancy. I then rotated the dizzy to "account" for the extra timing and get it back to 20 deg BTDC. Car idles without throttle input now, but is still running like a pig, stutters, doesn't want to rev, etc. I decided to not risk any possible damage and starting documenting everything. Valve cover is now off, I've attached pics of the cam position and the hash mark, the harmonic damper's position relative to TDC, and also a pic of the distributor rotor and the shaft tang below. After plenty of searching, the only thing I can come up with is the oil pump drive gear has slipped several degrees, but that doesn't account for why the car still runs bad even after i artificially fixed the timing by retarding the distributor position. My next step is brand new fresh plugs, perhaps a new fuel filter to eliminate that possibility (car is getting 35 PSI at idle, but who knows might not have enough to run more?) Any ideas guys? And I apologize in advance if I've overlooked anything obvious... I'm naturally very worried and easily may have skipped over something. Also, please let me know if you need me to take pictures of anything else. Thanks! Quote Link to comment Share on other sites More sharing options...
jeffp Posted October 22, 2013 Share Posted October 22, 2013 my experience with this was almost as bad as your experience, except I drove 100miles and was buying dyno time at JWT in San Diego. Sure enough, the gear spun on a pull much like yours. So the solution is this: 1) make Damn sure the pump is not binding the shaft. Use ONLY a Nissan pump gasket. 2) remove the dist shaft, and reclock the position of the drive to the distributor. Be percise, as 1/2 a tooth off will make the distributor adjustment afterwords a little screwey. If you are as fortunate as I was, the timing on the distributor was not quite enough for the slots on the distributor. 3) drill out the gear and shaft with a 1/8" drill, and buy a 1/8" reamer to clean out the hole after you drilled it. Keep everything square and perpendicular and on center when you drill the hole. 4) buy a 1/8" precision ground and hardened pin. Press the pin into the hole you drilled and reamed. Hopefully it will be literally a squeaky tight fit. Leave about 1/16" longer pin on each side of the gear. Use a dremel if needed to cut the pin to the correct length on each side of the gear. 5) using a good ball peen hammer, set the gear, specifically the pin, on a hard piece of metal, a good mill vice works excellent. Start tapping one end of the pin, and you will be able to mushroom over both ends of the pin. No more gear slip problems. Now in addition to the repair of the gear andrive , I also recommend installing the bronze oil pump drive gear in the crank shaft, and if you want, talk to John Coffee about the mods he did to the drive. Myself, trying to tighten up the slop in the drive gears, set the cover up to stop the up and down motion of the drive gear in the cover and minimize that movement of the drive gears. The reason being is that the shaft movement up and down equated to about 2 degrees of tolerance in the timing. Now how would that be under boost @ 600hp @ 7K RPM. Marbles get into the engine and bad things start happening to the ring lands right Tony LOL. Hope that answers your question. Quote Link to comment Share on other sites More sharing options...
Tony D Posted October 22, 2013 Share Posted October 22, 2013 "Man, my engines smoking like crazy, I'm going to put a catch can on it." Have you done a compression check? ********************* Might want to check compression after an event like that, or so a leak down test... Quote Link to comment Share on other sites More sharing options...
Boosted12 Posted October 22, 2013 Author Share Posted October 22, 2013 Tony - Yes, I've verified compression at ~120PSI for all 6 cylinders, which is normal for this engine so far. Jeff - Thanks for the confirmation - I was going to pull the pump drive/gear and pin it anyhow, but your advice makes me doubly sure. This headache and your valid concern in regards to the timing possibly wavering under high boost makes me want to convert to a crank angle sensor a la EDIS... Maybe that's in the cards after pinning the pump drive. IF I do convert to CAS, would you still recommend a new crank drive gear for the oil pump, or will the slight slop be ok, as the pump will be driven regardless? Thanks! Quote Link to comment Share on other sites More sharing options...
Tony D Posted October 22, 2013 Share Posted October 22, 2013 Boost has nothing to do with it, it's force reversals in the oil pump drive train that overload the friction fit the gear has on the shaft.....It happens on high RPM N/A motors as well. Crank fire ignition is always a reference standard, and recommended! Quote Link to comment Share on other sites More sharing options...
johnc Posted October 22, 2013 Share Posted October 22, 2013 Jeff's recommendations are a basic mod for any performance L6. On my NA 3L I also had a problem with the tangs on the oil pump drive snapping off. I did a little filing on the shaft tang and wrapped a strip of .015" brass aroung the shaft tang to act as a cushion and that solved the problem. Quote Link to comment Share on other sites More sharing options...
Boosted12 Posted October 22, 2013 Author Share Posted October 22, 2013 John, Where on the shaft? The actual input to the pump, or at one of the locating areas where it goes through the timing cover? I don't plan on going above 6k RPM, and I only expect to make ~350WHP maximum. I do plan on buying a new shaft and pinning it, would you recommend a new crank drive gear as well? I was able to visually inspect mine, it doesnt seem deformed. Quote Link to comment Share on other sites More sharing options...
johnc Posted October 23, 2013 Share Posted October 23, 2013 Where on the shaft for what? Quote Link to comment Share on other sites More sharing options...
Lazeum Posted October 23, 2013 Share Posted October 23, 2013 FWIW, this is what Braap has made to the shaft I run in my L28. Quote Link to comment Share on other sites More sharing options...
Xnke Posted October 24, 2013 Share Posted October 24, 2013 I would be looking at the oil pump as the main culprit for spinning that gear...takes a lot more to turn that pump than it does the dizzy, under normal conditions Quote Link to comment Share on other sites More sharing options...
Boosted12 Posted October 25, 2013 Author Share Posted October 25, 2013 Xnke - I had sort of the same idea... I'm replacing all components related to this to be on the safe side. We'll see the result when I get the car started back up. John - I was asking where on the shaft you applied that strip of brass. I'm having trouble visualizing where you put it. Quote Link to comment Share on other sites More sharing options...
Gollum Posted October 29, 2013 Share Posted October 29, 2013 Considering you're running wasted spark and not sequential spark, I'd get a crank trigger on that sucker! EDIS isn't a bad option, but really all you need is the ignitors, as MS can control the rest. Floating around the msextra forums I've seen quite a few different methods to tackling the same mountain. But this has certainly happened to more than a few people, and you've gotten some good advice already as to how to keep it from happening in the future. Quote Link to comment Share on other sites More sharing options...
Tony D Posted November 2, 2013 Share Posted November 2, 2013 It's not the oil pump, they ALL do this. It's force reversals on a constant load. Yes, the oil pump is the load culprit. But it's load stays constant. A Drop Throttle or like JeffP experienced a 'lean surge' where power flows become equivalent to someone tromping on and off the pedal will give you the force reversals that overload the friction fit and slip the gear at temperature. As John mentioned, adding that brass shim stock acts like a 'cushion' to prevent the reversals from doing something dramatic. Like in his case: shearing off the drive tang of the oil pump. To visualize where it is, just look how it's driven with a screwdriver going into a slot on the pump. You gotta put the cushion between the screwdriver and the slot where it's applying force. Make the tang smaller by 0.007", make the slot wider by 0.008" and you can wrap a 0.015" shim around that screwdriver and still fit it in the slot. I don't know how much slop he had EXACTLY, which may be all there is to it---removing slop prevents the backlash and acceleration that can occur during force reversals. In JeffP's case it happened right at 5,500 rpm and sounded like a conventional rev limiter. Nothing big, up 'rev limiter', hmmmmm, run it up again 'rev limiter'....Hmmmm, more scratching of heads. Run it up a third time, 'rev limiter--DIED'... Pulled the dizzy cap after checking timing and the rotor was 180 out. Jim Wolf says "Well, we know you didn't drive it here like that!" So under the car he went, retimed the works...dead on. Ran it up "rev limiter" quickly checked the timing an it had slipped 7 degrees... "Well, we're done for today." THEN he drove it 120 miles back to his house. Smoking.... Not really funny, but it was not anything spectacular. The car just sounded like it hit a rev limiter. No backfiring nothing. Eventually we understood at 5525 the injectors go from two pulses to one, and because of obstructed screens in the inlets the injectors just made it run dead lean like flicking a switch. Never heard the marbles. Never heard a ping. 5 Pistons with sunken rings. Forged pistons with sunken rings. Consider yourself LUCKY! Personally I'd never do anything off the dissy drive again. Put an LD drive gear and welch plug in there and EDIS or Flywheel Time it.... Never off the Dissy again! Quote Link to comment Share on other sites More sharing options...
johnc Posted November 2, 2013 Share Posted November 2, 2013 Tony answered for me. In my case it was a lift throttle at the start finish line at Willow. Took the checquer, lift off the gas at 6900 rpm, looked at the gauges, and saw oil pressure drop to zero. Clutch in, hit the kill switch, coast to a stop between 1 and 2, wait for the tow truck. The NAPA in Lancaster had a pump and we were racing again in 2.5 hours. Figured out the issue when I got back to the shop and made the mods I mentioned. Quote Link to comment Share on other sites More sharing options...
Tony D Posted November 2, 2013 Share Posted November 2, 2013 The only unknown is the slop left in the drive tang. Generally oiling clearance is 0.003", but with consumable brass in there to prevent galling and fretting of steel-on-steel contact on the drive points, you might be able to get by with less clearance. Personally I'd measure clearance after leaving the parts in an oil bath heater at 265F for a heat soak period.... but that's just me. It's the only way to get a 'running clearance' without doing some theoretic calculations that end up having to be checked this way (or running it) anyway. Quote Link to comment Share on other sites More sharing options...
Boosted12 Posted November 4, 2013 Author Share Posted November 4, 2013 Great, thanks for the screwdriver analogy. Makes much more sense now. I guess I have my answer now as far as timing goes.... next upgrade I'll be going with a CAS for sure. Quote Link to comment Share on other sites More sharing options...
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