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Author Topic: Inline-four crankshaft  (Read 98447 times)
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Jack Gifford
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« Reply #345 on: March 10, 2017, 12:59:09 AM »

It will be awhile until I have more info. Cranking compression is way low, so it's got to come all apart for examination. sad
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« Reply #346 on: March 10, 2017, 08:18:54 AM »

Generally it is unusual for methanol to detonate but if the tune up is off enough it will and violently. Do the plugs show anything- aluminum balls, black specs, broken insulators etc? Getting the part throttle tune correct is tough on engines like yours where there is no real experience to rely on. Hope your dyno tune guy can be helpful. You mentioned engine software. You are using mechanical FI are you not? Is this a program that helps judging the tune in some way rather than controlling the engine?  Fingers crossed the damage is not bad.
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Jack Iliff
 G/BGS-250.235 1987
 G/GC- 169.741  2009
 G/GMS-178.835 2010
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« Reply #347 on: March 10, 2017, 01:34:48 PM »

Check valve clearance first.  I've seen "booms" cause the shims/keepers to dislodge.
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Jack Gifford
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« Reply #348 on: March 11, 2017, 01:06:33 AM »

The only hopeful sign is the lack of any aluminum specks on the plugs. Yes, the insulator was broken off #1 plug- I didn't think much of it at first, figured the plug wire got yanked by a piece of debris. But looking at the valvetrain, the only thing not right is zero lash on #1 exhaust valve. So the explosion may have begun in #1 cylinder, possibly as severe detonation. And maybe enough percussive force to tulip the valve .020"?

Hindsight, as they say, is easy. I should have been more alert to the brief running not sounding right- instead of the unsteady loping of a somewhat 'fat' no-load alky engine, it was very steady and "flat" sounding.
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« Reply #349 on: March 11, 2017, 10:13:04 AM »

Jack, is there any way that enough fuel could be injected to cause a hydraulic lock in a cylinder?  In other words, the combustion chamber would have been completely full of alcohol and there would be no way to compress it.
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jacksoni
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« Reply #350 on: March 11, 2017, 01:52:10 PM »

To me (have seen it unfortunately) a broken insulator is diagnostic of bad detonation. Will need to check ring lands for compression (not to mention holes in pistons and .....) Though hydrolock is good thought, short of the innards coming out of an injector so it flowed wide open I don't see how that could happen with a running engine. Usually is fuel (or water) in a cylinder that locks when trying to start it. Bent rods the most common result as well as possible other damage. Pieces of piston could have hit the valve, bending it or tulip/stuck open. Let us know Jack. Hoping things not too bad.
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Jack Iliff
 G/BGS-250.235 1987
 G/GC- 169.741  2009
 G/GMS-178.835 2010
Jack Gifford
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« Reply #351 on: March 12, 2017, 01:34:28 AM »

"Torched" spot by #1 exhaust- mostly in head but also small divot in block just outboard of sleeve flange. ("Scab" on head created by molten aluminum pushed away from chamber). Hole in gasket at the same spot, so I assume that either molten aluminum or copper acted as glowplug to initiate the 'bang'. Although the main culprit was the way-lean mixture, I'm also puzzling over why that one spot was the only victim. Could simply have been a porous spot in the 55 year old castings. The ends of the steel wire O-ring were located right there also- probably should have positioned the ends other than adjacent to the exhausts. Still need to pull pistons/rods to look for collapsed ring lands or whatever.


* torched11.jpg (113.92 KB, 800x600 - viewed 137 times.)

* torched22.jpg (98.92 KB, 800x600 - viewed 134 times.)
« Last Edit: March 12, 2017, 01:41:00 AM by Jack Gifford » Logged

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« Reply #352 on: March 24, 2017, 12:42:22 AM »

Slowly getting answers to most everything. First clue- removing the head, I was watching that both dowel pins stayed in the block rather than falling out on the floor. The rear dowel remained in the block, but the front one was nowhere to be seen. I figured it probably lifted from the block and dropped out. But after stripping to the bare block and searching the whole floor it still isn't found. Looking closer at the torched spot on the copper gasket, it appears the gasket was outboard from center on #1 cylinder, with barely any copper clamped by the head/block inboard of the O-ring, leaving some copper (only .022" thick) with no good cooling path. I have a spare gasket which is a perfect match to the used one (machined their bores simultaneously); placing the spare gasket on dowels on the head confirms that I must have assembled it with no front dowel pin... embarassed embarassed embarassed embarassed

Under "good news"-  pistons/rods/crank/sleeves are fine; ring lands still measure .002" side clearance on all rings. All rings are good except top ring in #1 lost a bit of moly.

Repair of the head is underway. I prefer not to TIG weld it (would require keeping the whole head over 300 degrees F for a while), since EVERY surface would need to be re-machined true. So I milled out the damaged area to a rectangular relief (about 1"x1.5"x.250") and pressed in a precisely sized piece of 6061T6. I drilled/tapped for two aluminum flathead screws to guarantee that the piece won't move during later machining (in the assembled engine it will be firmly clamped between block/gasket and head). Both bronze valve seats need to be replaced in that cylinder (press fit was no long satisfactory), and that exhaust valve will be replaced. Also found a couple of intake valve with slight runout to be replaced- probably occurred during valvetrain spin-testing, after which I didn't strip the head to check everything.

Also taking advantage of it being apart to improve (?) some things. Bottom end oil flow volume wasn't as much as I like, so I'll increase the side clearance of the rods' big ends- and perhaps increase main bearing clearances .001"; maybe also rod bearings after I finish cleaning up and inspecting them.
Spent quite some time fussing with the O-rings to make their ends flat where they meet. I had never worried much about it, but it appears that crude "snipped" wire ends may have contributed to this incident.
« Last Edit: March 24, 2017, 12:52:20 AM by Jack Gifford » Logged

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« Reply #353 on: March 24, 2017, 08:16:36 AM »

Glad some answers are there and things can be fixed and that the rotating assembly is pretty much OK.

What is your evidence that lower end oil flow was low? Since rod side clearance is usually much larger ( 0.010" for instance) than the bearing clearance ( maybe 0.0025") the side clearance has no impact on oil flow/pressure as I understand. Slightly increasing the bearing clearances my help your flow. I know there are differences of opinion about bearing clearance depending on use, rpm's, power level etc, etc. As long as oiling system can keep up with it and considering how much you are leaning on this thing (10k rpms and who knows how much power) a somewhat larger than average clearance may be helpful.

A comment from Darin Morgan of Reher Morrison racing engines:

If your having bearing problems with 05-30W synthetic oils your problems are not with the oil as much as they are the clearances and the machine work. Bearing misalignment or worse yet, to tight a clearance will hurt you every time. A good line honed main and properly trued and honed rod housing bores seem like a given but they seldom are. They need to be addressed, checked out and honed by a professional that knows what he is doing. You need to have .003 on the rods and .0035 on the mains or your playing with fire. We run .003+ on the rods at all times never less than that, ever. We run .0035 to .00375 on the mains and never less than that, ever. On engines with higher loads the clearances go up never down. Pin bores can have up to .00225 for clearance on some engines with high vacuum in the crank case and good oil control in the pan. The better the oil control and vacuum in the pan, the less oil the wrist pins get! We run 0055 (not a misprint) weight and it about the thickness of water. we run .0035 on the rods and upwards to.004 on the mains in the PS engines and the mains last all year long. Our 1300 horsepower Super Series engines have .003 rods and .0035 mains and run for 600 runs down the track! The record so far is 675 runs by Scotty Richardson.

(1) Get a good, professional machinist to line hone the mains and hone the rods properly.
(2) Make sure you have proper oiling. If your pressure fluctuates during the run,, you have problems.
(3) .003 rods and .0035 mains for clearance
(4) Use a good synthetic 05-30w oil like Mobil-1 or Castrol syntec
(5) In my personal opinion you need to stop using any oil from Amsoil. That is not a racing oil even if they say it is.

And one from Larry Meaux, also I think one of the smartest guys around (Pipemax fame)

"
Darin, all i can say is "I'm glad you Posted this first"

like your results , for the last 20+ years i've run nothing but
.0035" to .004" rod and main bearing clearances
on every Engine i've built, even my old Chevy Suburban Dragster Trailer Tow vehicle's SBC 406 cid has .0035"
never had 1 rod/main bearing failure yet in 20 years, not one !
Bearings look new -to- almost brand new after full season or more,
and most of time i never replace the main bearings, just new Rod Bearings instead on rebuilds.

all the Engine Builders i deal with run .003 to .004" Rod/Main clearances,
and most just tell Customers they have .002" to .0025"
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Jack Iliff
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 G/GC- 169.741  2009
 G/GMS-178.835 2010
Jack Gifford
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« Reply #354 on: March 25, 2017, 12:11:15 AM »

Thanks for the comments.
Only having run it a few seconds at a time didn't provide a lot of opportunity to observe oil flow volume. But the last run for about 20 seconds allowed me to glance at the scavenge line dumping back into the oil tank. It was a smaller stream than I'm used to seeing at about 3,000 RPM.
Race engine builders have found that opening rod side clearances up to almost .020" continues to flow more oil. I think i'm at .011" now- need to look at notes.
Also need to look at what my rod & main bearings clearances are. I'm pretty sure they are a little less than what's recommended by Darin Morgan and Larry Meaux. I always ran at least .004" clearances in my blown V8, sometimes .005". This engine behaves like clearances are too small- spinning on the starter instantly runs oil pressure up to 50-60 PSI, and after it stops turning it takes a good 10 seconds or so for pressure to bleed down to anywhere  near zero.
« Last Edit: March 25, 2017, 12:13:37 AM by Jack Gifford » Logged

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« Reply #355 on: April 06, 2017, 12:46:14 AM »

Just discovered a MAJOR screw-up. I meant to use jets in the hat around the range of Hilborn #24, but the #24 jets I bought are apparently per Enderle sizing- the equivalent of Hilborn #9! shocked
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« Reply #356 on: April 06, 2017, 07:25:12 AM »

Ouch!!- but at least you found a reason.
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Jack Iliff
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 G/GMS-178.835 2010
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« Reply #357 on: May 15, 2017, 06:27:23 AM »

Hey Jack- how are you coming with any further diagnosis and the repair of your engine? Progress?
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Jack Iliff
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 G/GMS-178.835 2010
Jack Gifford
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« Reply #358 on: May 16, 2017, 12:43:54 AM »

Pretty much found explanations for everything. Re-construction is progressing slowly. Still working with the head- a number of valve seats lost their press fit, and some surfaces "moved around". Shortblock is back together. Blower manifold rebuilt- now with a burst panel and four(!) popoff valves, and injector bolt pattern machined into it to allow running naturally-aspirated for awhile during initial running.
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« Reply #359 on: August 12, 2017, 10:24:12 PM »

After much delay, I finally fired it up today, with my son's help- mostly to observe. Only ran about 30 seconds but didn't see/hear anything out-of-line. I'm surprised how healthy it sounds unblown- very good throttle response. I'll proceed to check compression, leakdown, etc. before running it longer (to get up to temperature and check coolant flow, etc.), before bolting the blower back onto it.
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