Fatal Mistakes....

[ItsA68]

what are some common fatal mistakes when assembling an engine? When I say fatal, I mean things that you could do while assembling the motor that would cause it to become unsuable without major repairs....not talking about things that would leave some power on the table. Think about common and not so common mistakes that you have seen that have resulted in disaster.

like:

poor cleaning job on block and parts with dirt in the motor...
crank/rod/cam interferance

What else?

[allblowdup]

put rear camshft plug in to far. It holds the cam ahead and screws up the mesh on the dist gear plus it eat the casm plug at the back puttiing all that into the engine.

[bevans]

Well, the stupidest thing I ever did building a motor was not check ALL the piston to valve clearances, and not notice that one intake valve had been replaced and was .050" farther into the chamber than the other three. Since I only had .060" of clearance, the motor lasted just long enough to get tuned on the dyno, into the car, 6 hour drive to the race track, and 10 minutes in the first session.

Twice. First time I also had a bad heat treat on the cam and I thought that was the only problem...

My bad - but it was my motor so no customer to grovel to...

Brian

[Keith Morganstein]

Here's a few "greatest hits" from working 30 years in shops.

One of the worst and I've seen it more than once, is installing the main bearings up-side down.

almost as bad was no upper half bearings (bearing roll on a truck where the mechanic had a "high powered lunch")

oil galley plugs missing

adjustable distributor collar set wrong so pump drive doesn't turn

wrong size bearings, caps backwards, rod bolts not torqued

smashed oil pick-up (from mechanic setting the engine on floor with no oil pan)

failure to prime the oil pump

rocker ball pivots upside-down.

head gaskets on wrong or wrong application

Have found a variety of things in lower radiator hoses. Shipping plugs, rags, hardware and even a snap-on scew driver (turned that in for a new one)

one valve keepr left out.

certain types of valve lash adjusters left loose will drop a valve in a hurry.

[ADR]

One my favorites is a crank grinder that can't/won't cut a thrust surface properly or won't put the proper corner rad on his stone. You can really get some junk work from a crank grinder.

Machine shops with micrometers and measuring equipement that is not set to the same standards as your own....so when you call out specific sizes...well you see where this going.

Next favorite....ring gaps on hypereutectic pistons.

[MDT]

One of the first motors I built was when I was still in high school--When you dont pay attention to which way the rear main seal goes, you can get a decent oil leak.

[mtkawboy]

I walked in on a buddies 327/340 shortblock rebuild and he had all 8 pistons in with the dome facing the wrong way. Ive seen 428 FE fords with the cam plug put in like a freeze plug. When you tighten the cam retainer it pushes it out enough for one giant oil leak and a ton of work in a Mustang with headers as soon as it fires. Ive seen flywheels balanced by drilling the clutch disc side. Ive seen a 12 year old kid pour a coffee can full of sand in a brand new 428 CJ race engine with no intake on it.

[ADR]

I watched a guy assemble a SBC that was fresh out of the hone tank and had never been washed. There were hone drippings all over the place, yet he and his brother the "pro mechanic" were pounding things together.

I tried as nice as possible to tell them that it HAD to be cleaned and he looked at me....took a can of brake clean and sprayed the valley and rubbed it with a paper towel and tossed the towel in the corner, leaving paper towel shreds all over the valley casting.... I didn't say another word.

The engine was back out of the car in less than 200 miles.
Sometimes you cant help people.
Dale

[Masher Manufacturing]

Crank thrust washers with the steel side facing the crank. ( some motors have TW seperate from the main bearings and usually just on the block side ) Or both TW left out or first one installed then falling out because the crank was pushed.

While not strictly a engine failure, not lubing the pilot bearing.

[Procision-Auto]

Weld the oil pump pick up

Strokers - check the rod clearance

Thread lock and thread sealer $6.95 and it's good insurance.

[scottyz]

I watched the guy that worked beside me port his intake ports on his fresh 350 iroc heads while on the motor. He looked at me and said " you dont know shiit" after i said "WTF are you doin?" I couldnt believe it as none of the other mechanics in the shop. AND this was after the old heads were pulled off to find a mess of rust in every cylinder. We told him to have the engine machined and start from scratch. "You dont know shiit" was what we were told. The car ran actually. Smoked like a tire fire. Apparently it could beat sport bikes. Until it met numerous winter beaters throughout our shop. The guy quit. Literally. It was ugly. Some people just know it all I guess.

[C Stevens]

Replacing the starter on a marine reverse rotation OR back mount bellhousing with a standard automotive rebuilt unit. (engine turns backward)

[ClassicComp]

Heres only 3 for now
Not checking or setting the thrust clearance.

Not double checking the oil pump,connecting rod torque or main cap torque before bolting the oil pan on.

Not checking for oil pressure be lighting off an engine build.
I saw a kid stick an engine in a minute or so just because he was in a hurry and forgot to fill the pan with oil .

[Ron Golden]

Helped 2 friends after they tried to install the thrust bearing in the rear main of a SBF.

FE engine with 123 psi oil pressure at idle.

In my 40+ years of playing with engines I've learned quite a bit by making, and correction others, mistakes.

I think we all go brain-dead at times...it just seems to happen more often of late.

[stock z/28]

Hi,

About the worst engine killer I know of are rotary Scotch Brite pads on a die grinder. The abrasive eats just about everything after it embeds in the brgs.

On a humors note I had customer use red Loctite behind the rod and main brgs on a Small Block. By the next day it was locked solid after the Loctite expanded.

One of the funniest things I have seen was-- I did all the machine work and assembled the short block on a 350 that was being installed in a 86-87 monte carl0 replacing the 305. The heads were the older ex pattern and lacked the "third" bolt hole. My customer worked in a shop with a cnc pattern cutter so rather than buying the adapter to use the stock ex manifold he made it. After he installed the engine he worked on it for several days trying to fix a backfire through the carb. He jerked it out and brought it back claiming I had the timing chain wrong. As we were unloading it I removed the exhaust manifolds and noticed he had forgotten to cut the ports in the ex plates, it was just a solid plate. Oh well he saved about 25.00.