OK so the holidays are upon us and many of us have taken are cars off the road and plan on doing some up grades and required maintenance.
I just figures I would start a story of some funny things I have seen people do while rebuilding an engine and thinking they where so smart in their thinking not realizing the problems that they may be making for themselves.
Please share any others here.

Using Slick 50 for an assembly lube...dude that was a bad idea really. Had to rebuild the whole engine. Dudes rings never sealed and destroyed a roller cam from the rollers skipping and sliding over the lobes. Ive seen this happen on more than one occasion just use regular oil and when the say light valve springs use them!

 

I had a buddy with a tunnel ram/nitroused 350 in a Camaro with 4.88's. He was pretty hard on stuff and pretty regularly stacked bearings in it.

His "fix" was to use yellow 3M "gorilla snot" to glue the bearings in place. When I told him he was nuts and that was likely most of his problem...he scoffed. And he kept spinning bearings until he finally paid someone to start building his engines.

JIM

 

Not really an assembly mistake, but I've seen many folks not quite think through the parts combination and realize what parts they are getting.

One of the easiest is that most "replacement" pistons are made "short"...often .020"-.030". They're done that way for rebuild shops who automatically whack the decks as part of the assemby line rebuild so they don't have gasket issues.

So when you assemble them into your "numbers matching" uncut block...the pistons end up .045"-.055" down in the cylidner as opposed to the .020" or so they were from the factory. THEN, everyone uses a .038"-.060" composition gasket because they seal so well while the OEM used .015"-.020" steel shims.

Now with all the tolerance stackups...the OEM 10.25 compression motor was likely around 9.6-9.8 to start with. But...theoretically...if you have a 4.000" bore, a .020" deck and a .015" gasket, a flat top piston with -5cc valve reliefs and a 64cc head...you'll be at 10.28 to 1 compression.

After your engine build...there is a total of .082"-.0115" away from the head as opposed to the OEM stack of .035"-.040" (the OEM's WERE doing it right!).

In this worst case scenario (very common actually) you'll now be somewhere between 8.91-9.34 to one compression.

It's actually even worse because a valve job sinks the valves somewhat into the chamber (even if you use new valves) and you gain head CC's. If they aren't milled to get them back...even more compression goes out the window.

If the "rebuilder" ends up there..he's not worried about it. It's getting a very mild cam and he wants to make sure it will run on any gas.

For us though....we're likely putting a little better cam in it and need all the compression we can get away with. Giving up a full point + of compression is very detrimental to throttle response, engine vacuum and TQ. This is one reason folks can't figure out why their rebuilt engine doesn't run anywhere as good as their buddy's who "has all the same parts" etc etc. It's the details...and the difference you'll feel between 9 and 10.0 to one is REAL.

Plus the tendency for detonation increases with that huge quench area...so then folks pull the timing back...and make it even more of a slug!

A WELL built 327/300 or 350/300 is a really fun engine on the street. With just a little improvement in cylinder head flow and cam they'll run 12's all day long and be super easy to cruise around in.

It's the DETAILS that make a good engine!

JIM

 

Awesome post Jim you are right on the money. Its information like this that most guys don't think about while doing a rebuild that's kind of why I started this post to help others who may be thinking of doing this type of thing themselves.

We have quite a few knowledgeable engine builders here along with some novice ones. Point is to be objective.

 

Camshafts for 454s back in the 1980s were commonly poorly Parkerized on one or more lobes on the off the shelf cams from auto parts stores. I had to replace a cam in a 454 that I rebuilt after only about 1000 miles. The replacement NAPA cam also was losing its profile on one lobe. I sold it to a friend (told him about the cam) whose shade tree mechanic told him the mild engine miss was due to sludge in the engine. (complete rebuild with 4000 miles). He advised putting diesel fuel in the oil to get rid of the sludge. About a week later my friend visited and informed me the engine had "blown up". That's when I heard about the diesel fuel trick. I bought the engine back from him for $200 and took it apart and almost cried at all the damage done to a previously pristine build. Spun main bearings, several broken oil rings, cylinder bores scored, and of course- the cam with one bad lobe that was the ONLY problem.

 

Man...no one wants to share stories.....

Oh well...we can add "hardened seats". There is no need to put them in a set of heads unless for whatever reason the seats are so worn and sunk and you're trying to save them. For the type of driving most folks do, you'll never hurt a set of stock heads with a set of good valves in them.

Also, often, they are installed with little attention paid to the bowl area which ends up destroying air flow and power. I've seen them hanging out into the bowl. It's also a good way to cut out too much meat and ruin a good head casting.

If anything, install larger valves to get back into "good" material without sinking the valve.

JIM

 

Knurling guides. This is a low budget way to tighten the valves. Basically is a screw reamer that makes "threads" in the guide to make diameter smaller...and then you can re-size it to fit. Problem is you've now got half the area supporting the stem and they quickly wear away putting you in worse shape than you were to start with.

Install real liners/guides and be done with it.

JIM

 

Using a "ring groove cleaner". They've been sold for a gazillion years...and have made more oil smokers than you can imagine.

The seal between the lower side of the ring and the piston groove is AT LEAST as vital as the seal between the ring and the cylinder wall. As the piston rises...the ring is pushed down against the ring land to make a seal. This trapped pressure holds the ring out against the wall. If it can't seal to the lower side of the piston groove...the pressure goes under the ring and fails to help hold the piston against the wall.

Be VERY careful with ring grooves!

JIM

 

With a flat tappet cam.....put the lifters in the holes and mark them with a marker on the top edge. Rotate the cam (by hand is fine as long as you hold it in place back against the block). Watch the lifters rise and fall. As they fall you should see them rotate/spin as they go down. If they don't rotate, the cam WILL go flat quickly. Many things can cause them not to spin...but whatever it takes...you need to fix it.

Also measure lifter to bore size. Many cam failures come back to worn lifter bores. Also makes for noisy valvetrain with hydraulics.

JIM

 

Small block Chevy's.

"Most" pistons these days are universal with the same size valve relief for the intake and exhaust. But the better ones still have two different sizes to keep compression higher. If you have two different sized reliefs, pay attention to the which piston goes in which hole and make sure it's oriented properly. On the two end cylinders, the exhaust (smaller) reliefs go to the outside while the two center pistons have the smaller reliefs to the inside. Just look at the head to make sure you've got them aligned to match the valve order in the heads. If you mix them up..you'll likely bend/drop a valve with serious consequences very quickly.

JIM

 

There was the old trick of installing the pistons "backwards" in a smallblock. Was pretty popular way back when. Stock pistons are built with the pin offset to reduce noise. Turning them around sometimes makes a little more noise...but reduces drag/friction and frees up a few HP. LS motors went through this orginally with no offset. People complained of noise sometimes so they later redesigned them.

Many OEM pistons from other MFG's have no pin offset and do just fine.


JIM

 

Be VERY careful also when installing factory domed pistons in big blocks. I can't tell you how many cracked blocks I've seen over the years caused by installing at least one bank with the domes facing wrong way. They seem to be just perfect to crack the block when you go to bolt the head down and the dome contacts the head when torquing. I usually move crank so all pistons are below the deck before putting a head on for the first time to mock things up and make sure nothing hits. I do it with no gasket the first time and slowly roll motor over with head just resting on block ( a bolt just barely in place to hold it from falling off) to make sure it doesn't move when a piston might contact it.

JIM

 

First time I learned about "forgetting" to install the oil pump driveshaft was in Auto Mechanics class in High School. A buddy built a 327 powered Vega wagon and had no oil pressure on start up. Took a while to figure out what he had done and the engine had to come out to get oil pan off. That one stck in my head!

JIM

 

i'll share some stupid things I did when I was young, dumb, and full of....

first thing stupid me and my buddy did in high school we were 16 and knew everything...so we decided on rebuilding the small block chevy in his Camaro. we could borrow tools for the weekend from the auto shop class we were in, but he forgot the torque wrench. he decided we could just wing it with our (my) highly calibrated torque arm. amazing what a little too much torque will do on a rod cap. destroyed bearings, galled crank, would not crank over...and using the wire wheel to clean the pistons was probably not the best idea either...

few years later when I was 18 and rebuilding the 327 in the '68 impala I wrote about in another thread, had the crank turned at the local hot rod shop. assembled the motor (with proper tools this time), but never fully turned the crank 360 degrees, just turned enough to get all the rods in. once it was in the car it turned so far and stopped. would not spin all the way around. took it out, disassembled, could not figure it out.

then I realized the machine shop gave me a 350 crank, not my original 327. saw it sitting in the shop right where I dropped it off...

ALWAYS check EVERYTHING!!

 

Have a friend who is rebuilding his Mitsubishi EVO JDM engine. Engine was supposed to be rebuilt but never seemed right. Then the bottom dropped out of the compression. When we pulled the head every piston had half moon shaped rings worn in the top where the valves had pounded the piston.

 

Either we don't have many folks around here that have actually assembled an engine...or they aren't willing to tell about goofy stuff they've seen.

There's always the forgetting to put the pilot bushing in the end of the crank.

Or, cranks for some OEM engines aren't drilled for a pilot bushing. Heck of a thing to discover when trying to stab the trans!

JIM

 

If you ever did a Ford or a Pontiac and forgot to install the fuel pump eccentric on end of cam before buttoning it all together. No fun to figure it out while trying to determine why the fuel pump doesn't work.

JIM

 

Red rags left in the lifter valley of a big block can get wadded around the cam and split a block. OOps!

JIM

 

Stock big block Chevy pistons (Lo-HP versions) don't have enough radial valve clearance for a 2.19" intake valve. People routinely drop rectangular port heads on them or upgrade the oval ports from 2.06 to 2.19 valves. If you've got any sort of cam at all....it will usually put the edge of the valve very close if not in outright contact with the edge of the valve pocket. Depth will probably be OK...but radially it will be too close. Will probably run...for awhile...but the valve head will snap off soon.

More engines have been killed by missed "radial" clearance than you can imagine.

JIM

 

Doing my first ever engine build this year I learned that one should always mount the oil pressure sensor before priming the engine.

What a mess a pint of oil makes on the shop floor