Thanks for that Lou! Pretty awesome journey for You and Your Slanty, certainly can't say You left anything on the table with that one!!!
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| How tough is a Slant 6? https://www.slantsix.org/forum/viewtopic.php?t=67140 |
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| Author: | Dart270 [ Mon Mar 13, 2023 2:08 pm ] |
| Post subject: | How tough is a Slant 6? |
Yesterday I did a post-mortem on the 68 Dart engine (shortblock), which is the first Slant 6 I built, back in 1989. This has been the longest running of my Slants and has had the largest number of different modifications. It has been a rolling, revving experimental testbed for more than 2/3 of my life... What has this engine experienced? 1) Right around 200,000 miles, almost all on the street and many of those miles with hard/regular beatings 2) Somewhere between 600 and 1000 drag passes 3) Hauling possessions like a pickup truck (up to 1800 lbs of load in the car a few times, going over the Rockies, also pulled trailers/boats) 4) Ran it out of oil at least 5 times, maybe as many as 15 times (leaking gauge port/hose, hole in oilpan, etc). 5) Went 130 MPH a few times on empty roads 6) Carbureted (mostly) from 1989 until 2003, then port EFI since then. Tried at least 4 different intakes, 8 different carbs, TBI, then finally port/batch EFI 7) 5 different cylinder heads with compression ranging from 8.8:1 to 11.0:1 8) 4 different camshafts, from mild/stock up to the MP 0.490" cam 9) Turbocharged since 2011 with boost ranging from 6 to 15 psi (1 blown head gasket before I did water/meth injection, and drove it 130 miles home on 4 cylinders). Approx 40k miles with boost. 10) Best ET 12.75 @ 108 MPH, slowest ET in the high 18s 11) Highest revs around 5600 RPM, but usually kept it under about 5300 12) I had a few water/meth injection failures over the last 2-3 years and heard detonation at least twice on the track What was in the shortblock: (just under $1000 in 1989 dollars) 1) Stock-type 3.430" Silv-O-Lite pistons with moly top ring 2) 0.010" under stock crank with M77 bearings, with tight clearances (around 0.001") ... before I knew any better 3) New MP rod bolts 4) Stock rods balanced but crank and pistons not balanced 5) Melling high volume oil pump, circa 1989, with shims for a bit extra oil pressure 6) Double roller Cloyes chain with MP 0.436" cam (best for turbo, other cams used over the years) 7) Custom built deep/baffled pan (0.8" lower than stock) and extended pickup, installed in 2000. 8) Cleanup mill on deck and deck height of 0.185" What did it look like inside? 1) 5 of the 6 pistons had broken off piston skirts (one or both, about an inch from the end of the pointy bit) 1-2 of these skirts were inside the oil pickup, which was probably why my oil pressure dropped some in the recent past. 2) 2 of the 6 pistons had broken top rings (just in half, not multiple pieces) 3) ONE of the pistons had a 0.5 mm split all the way from the top ring land to the bottom of the piston. This one had a stuck oil ring, which is probably why it was burning so much oil recently, especially when cold. Can't believe this didn't let go completely! 4) All rods and crank look just fine to the eye. Easy to rotate the assembly over before disassembling it. I would probably not even polish the crank if it mikes OK. 5) 3-4 of the rod bearings had very smooth copper showing on maybe 1/4-1/3 of the area of one shell (upper?). 6) All main bearings had some scuffing, but no copper and no big grooves 7) Not much oil residue on the inside of the engine. Some black film, but not thick or chunky. A testament to modern oils. Let's just say I got my money's worth out of this one! RIP, my friend. The block, crank, rods will come alive again, I'm sure. I'll try to post some pics, but you know how I am... Lou |
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| Author: | Greg Ondayko [ Mon Mar 13, 2023 3:13 pm ] |
| Post subject: | Re: How tough is a Slant 6? |
Nice report. Peace of mind to have replaced it. |
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| Author: | EC_CO [ Mon Mar 13, 2023 5:44 pm ] |
| Post subject: | Re: How tough is a Slant 6? |
I have a buddy in SoCal with a '70 Challenger /6 (built within 2 days of my Barracuda, same LA plant, 1st week of e-body production) that he bought in '73 ... he has put over 500K miles on his, still original paint, but rebuilt the motor a couple times ... impressive IMO. |
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| Author: | DadTruck [ Mon Mar 13, 2023 7:26 pm ] |
| Post subject: | Re: How tough is a Slant 6? |
Lou, Same oil pump drive gear in use over the life of that motor and all 4 cams? How did the oil pump gear look for wear? Did the motor have a windage tray? What motor oil and grade was typically ran? Oil change frequency? Do you run a stand pipe on the filter base or in the filter? Or no stand pipe at all? I can see the detonation causing the broken top rings, but what do you attribute the broken piston skits to? Nice write up. Thanks |
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| Author: | Killer6 [ Mon Mar 13, 2023 9:46 pm ] |
| Post subject: | Re: How tough is a Slant 6? |
Thanks for that Lou! Pretty awesome journey for You and Your Slanty, certainly can't say You left anything on the table with that one!!!
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| Author: | Will [ Tue Mar 14, 2023 4:00 am ] |
| Post subject: | Re: How tough is a Slant 6? |
Very Cool! Will |
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| Author: | Dart270 [ Tue Mar 14, 2023 5:35 am ] |
| Post subject: | Re: How tough is a Slant 6? |
Thanks for the comments, folks! Answer to questions from John: - Same pump and drive gear for all cams and configurations. It looks slightly worn, but I would use it again. I may pop the cover off and look inside and maybe flatten the cover before reinstalling it. EVERY cam I used was made before 1995 (Crane new, 2XMP new) or was on a regrind stock core. - No standpipe ever and mostly cheapie oil filters (fram, whatever, although switched to Wix and better ones in last 10-15 yrs). I probably had a few that hand standpipes, but did not worry/think about that. - Changed oil about every 3000-6000 miles. Early on, I mostly used Castrol or Valvoline (no pennzoil wax, thank you). Since turbo I have mostly switched to synthetic oil. I started out as a "thicker is better" guy so ran 20W50 and 10W40 for the first ~50k miles. Lately, I have run 5W30 or 10W30, sometimes combined with some 15W40 truck oil. A few times I ran the "euro" 0W40 oil. - I ran an MP windage tray (kit from the 80s w/340 main bolts) for about the first ~80-100k miles (can't recall) until I built the new baffled pan. After that, I figured it was such a small HP increase so why bother. Think I sold the tray to someone on ss.org. - I am guessing that stress from high boost combined with detonation and the high mileage did the damage to the pistons too. The skirts might have broken because the pistons started to wear and get rock in the bores, and then they could work back and forth and break off? There was no damage last time I had the pan off (10-15 yrs and 40-50k ago - pre boost). My guess is that the regular oil changes and careful assembly/reassembly (at all stages) helped longevity. Careful/conservative tuneup on the turbo is also imperative. You can see why I don't give a rats patoot about standpipes or used oil pump gears. I have run all my other main engines (64 Dart - 2 engines and many cams, 66 Valiant, others) with no standpipe oil pumps and no oil issues... I forgot to mention that I ran the engine for maybe 2-4k miles in Madison, WI with no air cleaner (tall carb/adapter, impatient high schooler, screw the air cleaner). That was in the first 10-20k of service. Lou |
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| Author: | DadTruck [ Tue Mar 14, 2023 8:15 pm ] |
| Post subject: | Re: How tough is a Slant 6? |
Lou, Thanks, great info. I agree with your assessment on standpipes. I have a standpipe in the pump on the 83 D150 that gets mainly daily driver usage. I do not have a standpipe on the pump or in the filter for the oil pump in the 68 Barracuda. For performance engines maximum oil flow at high rpm and high loads is the prime objective. |
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