COLLAPSED PISTON

[jeepsr4ever]

Looks like you definately got heat from the top. Are they really early Ross's? I have heard that early Ross pistons yeilded some rather high compression ratios. I wonder if your camshaft isnt dialed in right. I would check the timing gears and see where you are at.

[1980_Cj7]

I remember checking when we were putting the timing cover on. The two round punch marks on the timing gears were lined up with each other, the cam one at 6 o'clock, and the crank at 12 o'clock, and the timing mark was on TDC.

Yes, they are Ross pistons. I don't know about early or late. I can pull up the exact data that I forgot and left at work, but IIR, they were manufactured about a year ago according to the paperwork.

That brownish color on No. 1 piston and the block in the pic above is just the lighting. They are all the same, black.

What are you guys experience with the highest compression ratio that will still run pump gas?

[Blown7]

For some reason I'm beginning to believe that MC may have a good thought process going here, and with your previous posts on your timing troubles Did you set up your cam timing this way or just "line up the timing marks"
Also where your heads reworked? Were the chambers CC'd? You may have a different compression ratio in that cylinder.

BTW I find with some cam/timing chain - sprocket sets that use multiple keyways that you have to use whatever keyway slot combo's that give you what you need, not just slapping the timing set on and calling it good to go.

Jeff

[1980_Cj7]

OK, the Ross pistons have XL408 cast/forged into the underside of the top, and the inspection dates on the paperwork are 1/26/05 and 2/10/05. They have a .145 dish depth and are -23 cc's.

The heads weren't reworked other than new valves, springs, etc. and a valve job. They were milled just enough to true them up. They weren't CC'd that I know of.

Blown, I can't view pics from where I am now, but I'm guessing your pic shows a degree wheel. We didn't set up the cam, the engine builder did. They just put the timing cover on loosely with a couple bolts and no gasket, because, as you know, a lot of the timing cover bolts go thru accessory brackets, water pump, etc. When we pulled it to install the gasket and finish off the assembly, I checked the timing marks, but didn't put a degree wheel on it.

Yes, our timing set had three keyways for advanced, retarded, and standard timing. Before sending the parts to the builder, I did some checking, and I had to open up the divet on the gear as it didn't line up with the hole in the cam journal, so I'm wondering if the keyway/s might have been off too. Now I'm thinking. We got the engine kit from fastengineparts/maddog, and although they advertised a Cloyes timing set, when we got it, it was an S.A.Gear timing set. I called them on it, and they claimed it was much better quality than the Cloyes. It was made in the USA, Los Vegas or somewhere if I recall.

The engine builder was good enuff to offer to come by our place tomorrow night and check things out so we don't have to hassle with getting the Jeep on the trailer with it not running, and haul it around with the engine hanging open. We'll see what he finds when he does some measuring. We'll ask him about the cam timing.

[Holeshot]

Something else to consider is that cyl 5 & 7 plug wires run next to each other & fire in order, so detonation on 7 is always something to beware of & you HAVE to have those two plug wires seperated as much as possible.

The pin end of the rod looks like it got very hot, full-floaters are mandatory in a hipo engine. Does the piston still swivel on the rod well?

Any chance that coolant got in there while running?

Also looks like the two oil ring rails are pretty much lined up, not good practice. If that is an example of the build quality, you need another builder.

I'm betting that detonation due to WAY too much piston to head clearance, plus the error of using pressed pins, plus the possibility of crossfire from 5 to 7 caused this failure. Do you have loud exhaust that would inhibit your ability to hear pinging? How high were you revving it?

Something amiss in the machining, assembly, or execution here.

[1980_Cj7]

The wires are removed now, so I can't check, but I "think" we had them pretty well separated.

The piston is very free on the pin, both rotating/swiveling, and side to side. Can't "feel" any slop in it though.

I think the discoloration on the small end of the rod may be from either the oven they used to install the pins, or grinding evident on the end of the rod that was probably done as part of balancing.

No coolant got in.

I noticed the ring gaps not being offset too and am going to question the builder about it. I'm no engine builder, but even I know the gaps are supposed to be offset, and by a specified amount.

I'm not sure there is excessive piston to head clearance. It's easy to see and check right now though. The pistons come up almost flush wth the top of the block. What should the measurement be and where do we check it? I do have a digital caliper and should be able to get a fairly good measruement on something like that.

We asked about floating the pins, but were told for what we were doing with the engine, there wouldn't be any advantage, and that it would be very expensive to do.

The highest the engine was ever revved was probably 4500 to 5000, and only for a very brief shot.

[AMX69PHATTY]

Whatever happened it's a real bummer to have gone through all the work and espense
and have it go south, especially a fresh thumpin' 401.
Any discoveries on the Connecting Rod Oil Squirting Holes ?
Piston to bore clearance for Forged pistons is looser than Cast.
Per Performance American Style, Forged = .006 to .009, Cast is .001 to .002.
This is the clearance on the diameters.
May I ask the clearance listed on the Ross spec sheet ?
Has the #7 bore and piston from the motor been checked yet ?
What a bummer. Hope you determine what caused it.

[Holeshot]

Another odd thing that may have happened, bearing in mind that you said that your old 258 could have run crcles around the 401, would be that instead of a firing order of 18436572, the dizzy wires got put on 18436752, making the #7 cyl preignite EVERY time & the #5 cyl to fire while the piston was midway on the downstroke of its power cycle. Just grasping for answers...

[1980_Cj7]

Didn't check the oil squirting holes yet. Maybe tonite.

The Ross spec sheet that came with the pistons is calling for .004 the way I'm reading it. There are 2 sets of instructions, "A" if the piston has a step at the corner under the bottom most ring, and "B" if it is radiused. Our piston is radiused, so here's what the "B" instructions say:

Normally aspirated street cars
Bore size 3.475 and under - .003
Bore size 3.476 to 4.499 - .004
Bore size 4.500 and above - .006
Modified type engines, including drags, circle track, and road race - .004 to .005
Turbo engines, small bore - .006
Marine applications add +.002
Nitrous over 250hp V-8 add +.002
Nitrous over 100hp 4 cyl add +.002

There is an interesting note however that engines which have been honed without torque plates will require addtional clearance. I just added another question to my list for the engine builder, "Did they use a torque plate?" If they didn't, and didn't allow the addtional clearance, that might explain the problem. Plus, if they didn't use a plate, the bore would be more likely to be out of round wouldn't it?

My son and I checked and double checked the wires and even had a wiring diagram in front of us showing the correct order, so I'm certain the wires were right. Plus, the engine ran too smoothly to have had them crossed.

Thanks guys for all the help and concern. Believe me we are really bummed out after all the work and money. I'm just hoping and praying this engine can still be salvaged.

[Goose]

I just went back and re-read all your posts and info..If that Galling is on the" top side" (I'm guessing toward the intake manifold) then the odds that this was caused by Detonation/crossed wires or anything to do with the power stroke is small. since that would normally appear on the bottom side of the skirt..(IF you think about it a minute the explosion forces the piston down.) so my guess would be it is a clearance problem or oiling..
Especially when you take into account it happened in 300 miles.

I finally remembered where I had seen that pattern of galling before. In the bad old days when Yamaha in thier infinite wisdom brought out the first watercooled 125 works bikes. we had a problem with "Cold sieze" when you started the bike if you touched the throttle at all. the piston expanded faster than the sleeve and bang! it siezed up! which resulted in pistons that looked very similar to what you have here.. so Im curious to find out what the bore/piston clearance was and is the the bore actually round.