[hurryinhoosier62]

You said this is a 389,correct. It should have oil spurt hole in the parting
surface of the connecting rod. These spurt holes must be pointed toward
the cam. If not, the rod is installed backwards.

[slowbird]

I dont think anyone is saying he put the bearing on the rods wrong as that would be impossible (almost) but he can put the rods on the pistons wrong. My machinist did that and he was a Pontiac guy. I was 20 at the time and didnt know that there was a right and wrong way. When I put the engine together I notice that it was not turning over the away it should. So I took it all apart again and that is when I notice that the rods have a bevel to them that should go to the outside of the crank. With it backwards the bearing ends up riding on the corner radius of the rod jounral.

[TCSGTO]

I bought a set of 455 .030 TRW's & con rods for $50 once. Engine was rebuilt by a very good performance shop with an excellent rep but knocked a few minutes into break-in. The frustrated guy who sold me the pistons/rods blaimed the heavy TRW's & cast rods so he bought new Ross' & Eagle rods and had the engine redone.
The rods were installed backward,chamfer side in. 66geeto,please don't forget to let us know what the final diagnosis is.

[Will]

66geeto,

Accusation vs. helpful info?

I am attempting to outline what could have gone wrong - the things you should keep your eyes open for during the engine teardown.

First issue is -were the rods even rebuilt? If not, they are suspect. Even rods that led an easy life in granny's station wagon often are out of round when inspected after over 100K miles, and the stock rod bolts are notoriously weak. Not an accusation, but a statement of fact.

Second issue is whether the rods were installed in the correct orientation. Not the bearings (as you pointed out, installing the bearings backwards would be stupidly hard to do), but the rods themselves. The reliefs for the bearing tangs go towards the inside of the engine, or towards the cam as Mr. Pbody said, on a Pontiac, but on a Chevy they go towards the outside, towards the pan rail. It's a common mistake for a Chevy builder to install Pontiac rods using the Chevy orientation and that will cause big problems. I don't know this engine builder from Adam. I hope that he is a very standup guy and if he did put the rods in backwards that he'd realize his error and do you right for it. But, if you didn't know what to look for and he wasn't ethical, he might feed you a line of bull and leave you stuck with a blown engine. This is what I'm trying to help you avoid.

I'm sorry if my attempts to educate are not helpful to you.

[lunaticeh]

Seeing as you say this engine sat for a while before being fully assembled and fired, did you remember to prime the engine before firing? Depending on what the builder used for assembly lube, it might be possible that not much of it was left. When I worked for a local machinist, if a customer came to pick up an engine that had sat for an exteneded period of time, short or long block, the pan was usually taken off again, caps pulled, re-lubed and re-torqued. After numerous cases of blown up engines, the owner purchased a dyno and now a short break in on the dyno is mandatory for all engines that leave the shop. Suprisingly the number of blown up ones coming back has dramtically dropped. Like some people have said, you might not ever know the answer as to why this thing cratered and the reasons are endless. If it hasen't been torn down yet I wouldn't be guessing at a problem. Wait till it stares you in the face, then see where you and your machinsist have to go from there. Good luck...

[INJUNTOM]

another thing that i've seen "Chevy guys" do is get the #2 rod behind the #1 rod in the lineup like a chevy....

most every engine out there has the #1 cylinder as the furthest one forward, and the head on the #1 side of the block sits farther forward than the other head - not so on a Pontiac. #2 is furthest forward.

the only other one i can think of right now is an old International.

[TheMonkey]

Any update on the tear-down?

[jamesgennock]

I have a completely rebuilt 400 for my 70 GTO that has been sitting for two years. It will be going back to get disassembled and reassembled!

[elohssa]

I made the mistake of installing the rods the wrong way on a 455 I was building up once, but it became painfully obvious there was something wrong while the engine was still on the stand because it was nearly impossible to turn over by hand! Cant see how you could get to the firing stage with it being that tight.

[Half-Inch Stud]

elohssa makes a superb observation.

Soooooo, must be a bad pin-press process. Like using a draw-arm Arbor, drifting a dirty pin, distorting the slug, or....

Just maybe the piston expanded into locking-up onto the CYL wall.

[Pitch 400]

On putting the rods on the pistons the wrong way, I think that HO Racing said back in the 80's to put the pistons in backwards to reduce side loading on the walls since Pontiac pistons have a 1/16" offset. A while back I was helping a guy doing a break-in on a Ferd motor that had set a long time too. We primed the motor and on start-up it took out the bearings.

[chiphead]

Thats what I was worried about when I realized this engine had sat up. Any surface rust or flash corrosion on journals can grind or grab the bearing inserts. Should show up as scoring or debris damage to one or two journals, but the others (not rusted) ones would be fine. If the bearing grabbed the journal and spun, the rod would overheat, seize the crankpin and twist apart. The rod big end and journal will show massive heat, and a maybe break just above the big end. If the rod beam broke, its a bad rod. If the caps were loose, you might see a beat-on flatspot on the journal and a teardropped rod cap.

[66geeto]

oil pump shaft looks like a candy cane and the rod is broken. Bottom half of the rod brok pretty short and clean but it did punch the bottome of the cylinder a couple of times causeing quite a bit of damage. My skirts on my pistons come out of the cylinder sleeves at bdc. so i am assuming the block is screwed. The guide that holds the oil pump shaft (cast part of the block that is inbetween the distributor and the oil pump.) has cracked off and only has half of the guide there. So i assume this block is toast. I really planned on putting up some pics but I looked for my camera for like 3 hours and couldn't find it. I will post some pics with my sisters but she isn't home. Later guys and thanks for all the help. (Ordering eagle rods today!)

[TheMonkey]

so what was the reason for the grenade?

[GtoBrian]

What good is "ordering up eagle rods today" if your block is toast?

[66geeto]

gotta rebuild, do you want me to sit and sulk or what...........I'm not gonna sit in it and make engine sounds. I have a few blocks and i will look for a few more of those too, before i find the one i want.

[convgto]

66, had my 389 oil pump shaft break off aswell, and they welded it back up and sleeved #7, only because its my numbers matching motor, i am also having it pressue checked and every other kind of check. Let us know what caused your engine to go. Ken

[hal101]

(oil pump shaft looks like a candy cane)

do you mean it is twisted

[chiphead]

What did the bearings look like? Did all bearings show signs of oil starvation, or just the rod that broke? Was this a hardened pump driveshaft? Did the rod big-end break, or did just the rod beam break?

If several bearings show signs of oil starvation, the oil pump driveshaft went first. If only the one rod and bearing shows signs of damage, that rod went first.

[66geeto]

still waiting for my little sis to send me some pics in my email. I'll post as soon as i get them, sorry for the wait. No apparent reason for this to happen. Oil pump drive shaft seems to have lost a tang off of the oil pump side and then, rather than falling into the bottom of the pan it was hit by the crank and bent. The bend then came in front of the rod as it passed and snapped the rod. Had oil pressure the whole time so this happened in a very few revolutions.


I'll post pics once i get them. Block is probably salvagable. Can hone the cylinder but we have to weld the guide back in place somehow, but he didn't seem too worried about that.