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.
KJMac
tufcj wroteCall MadDog's 800 number, ask for extension 113 and ask to talk to D.W. He's their AMC guy.
Looks like the block was bored without enough piston/wall clearance. Looks like the piston expanded and galled itself on the cylinder wall. There should have been a spec sheet that came with the pistons that should have had the piston diameter specs, and the necessary clearances. Your machinist should have worked from that to determine final bore diameter, not just a standard .030" over stock.
I have Ross pistons from Mad Dog in my 69 390. They are a high quality piece.
Bob
tufcj
The piston to cylinder wall clearance was set up too tight!!!
82Waggy
Yup, I think it was too tight myself - maybe some dirt.
Most non-AMC builders do not have a torque plate. I had to custom order one from BHJ for my two projects.
I also have considerable experience with the cold seizure issue on small engines and your piston does look just like that problem. Skirts start to stick first as the piston head stays cooler from the intake charge.
Most people also do not realize that you need to let a forged piston engine warm up good before you lay on the power - otherwise the block does not expand as quickly as the piston.
It also looks like you were running rich to have that much soot build up already.
1980_Cj7
Yes, agreed that we were running rich. We were working on carb tuning and plug heat ranges, with Fuzz as a matter of fact, trying to get that straightened out, when we had to quit due to the knock showing up.
Hmmm, maybe I'm on to something here. I wonder if Fuzz sabotaged our engine so we wouldn't blow his doors off??? No, wait a minute, that couldn't be...he ain't go no doors! Some ricer already must have blown them off.
Goose
Well I hope ya get it figure out.. and poke the holes looser(Sorry couldnt resist) cause as we all know theres chevys and fords and even a few mopars out there but none of them sound like an AMC doin what its best at..(Sorry here you have to imagine a Trosley drawn AMX and a CJ smokin off into the sunset goin "WAAAAAAAH"
(To anyone who doesnt know who George Trosley is that last deal wont make a bit of sense).
1980_Cj7
Yes, ours did sound REALLY good, the short time it was running. Even Fuzz commented on how good it sounded, and I consider that a real compliment coming from him.
AMX69PHATTY
Yep, a torque plate insures cylinder roundness.
When the head bolts are torqued they cause some distortion in the cylinder walls.
So cylinders honed round without a torque plate can be out of round when heads are installed.
Using a torque plate on the block while honing prevents this by introducing
the same stresses in the block as will be there when the heads are torqued down.
I've been told machine shops hate AMC Blocks because they wear out there boring tools
due to the fact that AMC blocks have high nickel content and are very hard.
1980_Cj7
I have heard the same thing about the AMC blocks being hard and wearing real good. I hope it is true and our No. 7 cylinder isn't ruined.
I just came in from checking, and the oil holes in the rod caps are all to the inside.
Holeshot
why don't you take the rings off another piston & stick it in it's bore & see how much clearance ya have so we can all take another breath?????
1980_Cj7
Goose wroteI 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.
Good point. And yes, the wear is on the top or intake side.
Should be getting some measurements tonite.
1980_Cj7
OK, the engine builder made a house call tonite. Just before he arrived, we pulled piston No. 1. It was starting to show signs of wear in the same place as No. 7. The builder was really stumped. Said he never saw anything like this before. He said the wear is always on the bottom side of the cylinder, and at the very ends of the piston skirts. He said the pistons are tapered, and showed us that the pistons measure .004 bigger diameter at the ends of the skirts, than they do in the middle. He demonstrated this on the piston that wasn't worn.
He measured the cylinders, and said they are in spec at .004 over the piston size. Luckily the cylinders, even the worst one, No. 7, didn't measure out of round, even where the piston was rubbing.
He said he didn't use a torque plate, but that with engines this heavy it wasn't necessary. He claimed you only really need them on thin-walled engines like 302's.
So, while he was here, we pulled the other two pistons, and guess what, they were worn just like No. 7, but hadn't progressed as far. So, we thought there might be a pattern to the wear, getting worse the farther back the engine you went. That didn't hold out though, the order of best to worst was 1, 5, 3, 7.
The builder looked at everything, head, valves, lifters, pistons, rods, bearings, etc., and said that everything looked fine and normal except for it running rich and being carboned up. I mentioned that some of you noticed the discoloration on the small end of the rod. He looked at it and said that was normal and was from their rod oven, and that if it was from overheating, the pin would show discoloration too.
So, he, and we, are basically stumped. He recommended we pull the other side apart and see what we find there. I asked if he thought Ross might be able to provide some insight, and he said we should send them pics of the pistons and see what they think. Said we might even want to send them some pistons to check out.
The pistons do have offset pins by the way, but with the way the valve pockets are cut, it would appear they can only go in one way. Or, could they be switched from side to side??? I have to think about that one a little.
I'll get some more pics of the wear on all 4 pistons and post it, but right now I'm too disgusted to look at it any more tonite. The only good news is that the block is salvageable...at least so far. We haven't looked at the other half yet. There no sense putting anything back together though until we figure out what caused it, and what to do to keep it from happening again right away.
The builder didn't have anything along to measure the deck height. I tried my best to measure it with my digital caliper, and was getting less than .045. What effect would that have, other than valve and piston interference, which there is no indication of. The builder mentioned something about quench, and less deck height giving more power and allowing more timing advance, if I understood him right.
