COLLAPSED PISTON

Holeshot

You are using some sort of spark box, like MSD, correct? Makes reading the plugs harder. I'd say that the engine was extremely rich & the gas could have been washing the oil off of the walls. That, coupled with tight clearances & everything being new & not having polished itself to a broken-in condition, could be contributors. Never did hear whether the rings were file-fit & what the ring gaps were set at, but It seems that the "builder" missed the boat on the piston clearance, & setting the ring gap is a tedious & time consuming task that he may have skipped (?). Ask him what ring gap clearances he used & what he used to file the rings.

If we were to look for a lubrication problem as the cause of this, where would we start?

How about the engine builder's fee & whatever he used whilst you were grabbing 'yer ankles :oops:

That's totally a joke and I'm sorry, I just couldn't resist. :razz:

1980_Cj7

No, we are not using a spark box. We are using the stock ignition with the exception of a Ford TFI coil. Wouldn't the plugs be all carboned up if it was running rich enuff to wash down the cylinders? We will check with the builder about the ring gap. I did look at the ends of the rings to see if they were shiney from rubbing together due to insufficient gap. They were not. I have several books, "BJ Builds an AMC", "American Performance", etc. BJ didn't use a torque plate on the engine he built in the book. The builder we had check out our dimensions said he never uses one on any engines he builds. Don't get me wrong, I'm not saying it isn't better to use one, I'm just wondering how hard it's going to be to find a builder around here who has a torque plate for AMC's. Also, is there any way to check the cam degreeing with the heads off and the pistons out?

Blown7

1980_Cj7 wrote
Also, is there any way to check the cam degreeing with the heads off and the pistons out?

Not really, just throw number 1 piston back in. You need to find Top Dead center on the number one piston to determine where TDC is, to set the degree wheel. The heads can be off . You use the intake lifter from number 1 cylinder. You probably don't even need the rings on the piston to get close enough.

Jeff

1980_Cj7

I know the cam will need to come out to rehone the cylinders, and be set up all over again, but I'd just like to know if it was set up right the first time before we tear it apart.

1980_Cj7

Still wondering what happened to our engine. Was looking at the rod bearings and oil squirter holes in the rods. How does the oil get to the holes? There are no holes or grooves or anything in our Clevite bearings. Came across this post while researching http://www.bulltear.com/forums/viewtopic.php?t=3215

AMX69PHATTY

On the ends opposite the locating tangs, there should be half circle cutouts on the end of each rod bearing where the two halves meet that makes a hole about 1/8" diameter that allows oil to escape and feed the squirt holes.

82Waggy

You need .005 - .006 minimum piston to wall clearance with forged pistons. You need to finish hone with a torque plate. With forged pistons you need to let the engine warm up fully before stepping on it.

My machinest laughed when I showed him the page in BJ's book that said he did not use a torque plate - GET ONE! - and promptly discounted the rest of BJ's book after that, as did I.

BHJ sells torque plates. http://www.bhjinc.com/1products/0-landing.htm

1980_Cj7

AMX69PHATTY wrote
On the ends opposite the locating tangs,
there should be half circle cutouts on the end of each rod bearing
where the two halves meet that makes a hole about 1/8" diameter
that allows oil to escape and feed the squirt holes.

That's what I thought! There are no holes, grooves, notches, or anything. The bearings are solid the whole way. I can't see any way any oil could have gotten to the squirter holes.

And we always let the engine warm up before going anywhere.

AMX69PHATTY

AH HAH ! EUREKA ! Finally a "discovery" =D> I don't know about Blown7 and the Carillo Rods with no oil squirt holes, but would think the rod bearings lacking oil holes definitely contributed to the problem. Why would AMC have put them in there if not needed ? Sorry Blown7, I haven't built that many motors. That's wild that your Carillo rods lack an oil squiter hole. Maybe they're not all that neccissary, but I'd get rod bearings with holes. :-|

82Waggy

Lack of squirter holes may have been a contributing factor, but your p/w clearance of .004 is still too tight, especially for a bore that was not finish honed with a torque plate.

1980_Cj7

AMX69PHATTY wrote
AH HAH ! EUREKA ! Finally a "discovery" =D>

I don't know about Blown7 and the Carillo Rods with no oil squirt holes, but
would think the rod bearings lacking oil holes definitely contributed to the problem.
Why would AMC have put them in there if not needed ?
Sorry Blown7, I haven't built that many motors.
That's wild that your Carillo rods lack an oil squiter hole.
Maybe they're not all that neccissary, but I'd get rod bearings with holes.

:-|

I have been talking to a Keith Black technician, and he said the pattern of wear we experienced is caused by lubrication problems. Maybe we're finally on to something here. I am going to be talking to the folks at Maddog and Clevite about the bearings, and also to the people at Ross about why pistons for a 401 AMC engine did not have the proper compression height. I will also be asking the engine builder why he didn't catch both of these problems.

Holeshot

I am going to be talking to the folks at Maddog

Well, right THERE is your problem!!!!!

They don't know SPIT about AMC engines, just selling parts!!!!

You probably got all uppers or lowers or seconds, something stupid like that.

Blown7

1980_Cj7 wrote
AMX69PHATTY wrote
AH HAH ! EUREKA ! Finally a "discovery" =D>

I don't know about Blown7 and the Carillo Rods with no oil squirt holes, but
would think the rod bearings lacking oil holes definitely contributed to the problem.
Why would AMC have put them in there if not needed ?
Sorry Blown7, I haven't built that many motors.
That's wild that your Carillo rods lack an oil squiter hole.
Maybe they're not all that neccissary, but I'd get rod bearings with holes.

:-|

I have been talking to a Keith Black technician, and he said the pattern of wear we experienced is caused by lubrication problems. Maybe we're finally on to something here. I am going to be talking to the folks at Maddog and Clevite about the bearings, and also to the people at Ross about why pistons for a 401 AMC engine did not have the proper compression height. I will also be asking the engine builder why he didn't catch both of these problems.

Oiling holes not necessary if you have enough piston to cylinder clearance. Think about it, alot of comparisions from AMC's to SBC here but anyhow SBC don't have a oiling hole.
Read this old post http://www.bulltear.com/forums/viewtopic.php?t=4121

Jeff

Blown7

Ok I have a few minutes this am to get into depth on why the squirter hole isn't necessary if the engine is done correctly. First here are some rods from another engine showing comparision to Carillo rods http://www.club4ag.com/faq%20and%20tech_pages/Connecting%20ROD.html
Next is a compulation of various ways a piston can scuff
http://www.acl.com.au/web/acl00056.nsf/a7d23b8ace0d7e31ca2560d3001fb663/a889f2115e9d9f944a2563c60024554e?OpenDocument

Primarily the squirter hole is to lube the wrist pin and very indirectly the cylinder wall. The function of the oil control ring is to scrape oil up to the compression rings for dynamic sealing.
The primary lubrication of the cylinder walls is by splash, the oil leaving the sides of rod bearings varies as the square or cube of the clearance, so a diff. of say .0005" could mean a big diff. in oil throw.

. Now we know the crankshaft is spinning throwing oil all around the bottom end of the engine and alot of oil is hitting the cylinder wall (if it wasn't that little squirter hole wouldn't be enough no matter how you sliced it. Especially considering it only squirts once every 360 degrees of connecting rod throw rotation.)
When the oil leaves the main bearing it courses up thru the drill hole to the connecting rod throw, lubricating the conn rod bearing,thenit leaves the bearing at the sides of the bearing between the rod side and the conn rod throw. Now this oil is flung constantly in a 360 degree radius all around the bottom end including the cylinder walls. The squirter hole is offset in the conn rod and when it aligns with the conn rod throw oil hole from the main it is pointed at the wrist pin not at the wall.
With this being said the what was the cause of your particular problem?
This is just my opinions.
First your piston to bore clearance was not enough.
Second What type of rings where installed? If you had high tension rings that would scrape excessive oil up to the compression rings thus not leaving behind enough oil to lube the piston.
Third where your connecting rods checked for straightness? and for enough clearance fron the big end to the crank throw (side clearance of the rod to the flange?) This allows enough oil bleedby.
Forth what and how was the inital cylinder lube applied before initial startup?
Fifth your initial timing was off considerably, very bad.
You had alot of things against you here on this buildup and to say that definatively one item was the downfall of this buildup is not true. I can't remember if you had full float pins or not but next time get them if the wrist pin froze in the piston it would also allow the piston to not float correctly in the bore and cause the problem also in conjunction with the squirter hole being blocked.
As one last thought my Carillo rods are thru drilled from the conn rod bearing to the full floating wrist pin. Best bang for the buck for keeping the wrist pin oiled.

Jeff

1980_Cj7

Thanks for your thoughts and experience Jeff. Rings are Hastings chromoly. Pins are not floated, but all are free both side to side and rotationally. If you look at the first picture of the No. 7 piston I posted, it looks like the pin was getting plenty of oil. Engine lube was whatever builder used for assembly. We added a container of assembly lube that I got at the Chevy dealer's to the Castrol 10W40 oil when we filled and primed the engine. Don't know if the rods were checked for straightness or clearance. I will check. Yes, I agree, the timing was screwy on this thing. I am going to check the cam timing before I tear it apart. Would checking the movement of the lifter work to check the cam, since the heads are off?

AMX69PHATTY

Thanks Blown7 :oops:

1980_Cj7

I asked Ross why the pistons we got didn't have the proper compression height for our engine. Here's the reply I got: You are talking about a engine that is over 30 years old! Now if an engine builder gives me an exact block deck height I will zero deck the compression height if requested. I generally like .005-.010 down depending on side clearance because it will rock to zero. It is because of now knowing how much if any a block has been decked over the years that our standard deck clearance is .017. Now if I had zero decked the piston and your block was decked .015 and it stuck out of the hole would you have been happy? Most profession engine builders will get the pistons .010 down and square the block after.

Blown7

I think now your understanding what building a "true high performance engine" means, the term "Blueprinting" is a misnomer it actually entails just checking every dimension against the manufacturers specifications and allowing the necessary tolerances to make the engine perform correctly. You cannot just buy a bunch of things and hope they fit, or expect the engine builder to know these things, it's up to you to do the homework. When you buy custom pistons you have to know the exact dimensions and deck height is one of them. Get the JE pistons custom order form and look at all the dimensions JE needs to build a piston FOR YOUR ENGINE.http://www.jepistons.com/pdf/custompistons-orderform.pdf

I think it's time to check the cam timimg before disassembly and yes just use the lifter on number 1 like this

Also notice the o ringed block for higher compression, and I marked every piston for the ring gap location. STP and engine oil makes a great build lube. Forget the Hastings rings and go with Speed pro rings.
Jeff

Scott H

RE: Get yourself some Muriatic acid to eat the aluminum off the cylinder walls, THEN Sunnen hone them enough to get .009" clearance with the new forged pistons, or don't open up the bore & use KB hypereutectic pistons. If you use Sodium hydroxide (LYE, active ingredient of DRANO) it will disolve the aluminum without eating the cylinder bore. HCL (muriatic) will disolve the iron bore almost as agressively as it disolves aluminum. Note that both are dangerous to your skin and lung tissue so do it with proper ventilation and protective eyewear and rubber gloves. Depending upon forging alloy used, 4032 alloy can be run snugger than 2618 alloy but IMO 0.004" is too tight. I would go with 0.007".

1980_Cj7

Yep, we're learnin'. This is our first time at having an engine built. We didn't do it ourselves because we are smart enuff to know what we don't know. We took it to an engine builder because we thought they knew what we didn't. The engine is nowhere near the level of performance stuff you're into Jeff. The only thing not stock is the pistons and cam. We just wanted to get a little more than stock performance out of it since we needed to rebuild it anyway. So, would you guys who are more experienced at this stuff mind giving us some recommendations for this second time around? The engine will be in a CJ7 used for serious rock crawling and also driven on the street. We'd like to get as much power out of it as possible of course, but want it to run on pump gas. Having to use 94 octane is no problem. So, what would you recommend as far as pistons? Cast, hypereutectic, forged? (I understand the part about knowing the bore and deck dimensions before ordering.) What kind of clearance for whatever pistons you recommend? (I know it varies depending on the type of piston.) How about compression ratio to work with the pump gas? How about intake and carb? (We know fuel injection is the best, but the budget definitely won't allow that at this time, especially after having to do this twice in 300 miles.) We had an Edelbrock Performer intake and Performer 750 carb on it, but have access to an Air Gap too. Anything else we're forgetting? Oh yeah, to save you digging back thru the posts, the cam is a Clevite 284 hydraulic (218/218@.050, .488/.488 lift, 105/115 separation). Thanks for the help.

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