# Rebuilt shortblock will not turn on stand



## goatsnvairs (Sep 12, 2014)

Hmmm, I'm rebuilding a '73 455 for my '67 GTO. I'm using the original reconditioned rods, .030 over speedpro pistons, and a graphtite rear main.

Anyway, I plastigauged the crank bearings, within spec. I thought when I just had the crank torqued down it was a bit harder to turn then I expected.

Then I started adding the rods. Noticed the bearing clearance was on the tight side (crank is std/std), so I ordered some .001 extra clearance bearings. Then the rods had decent clearance, towards the mid / wider.

Anyway, as I put in the pistons and torqued the rods the engine got to the point where it was nearly impossible to turn it using a wrench on the crank where the balancer attaches. So, if all the bearings measure within spec, what the hell is going on?


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## PontiacJim (Dec 29, 2012)

goatsnvairs said:


> Hmmm, I'm rebuilding a '73 455 for my '67 GTO. I'm using the original reconditioned rods, .030 over speedpro pistons, and a graphtite rear main.
> 
> Anyway, I plastigauged the crank bearings, within spec. I thought when I just had the crank torqued down it was a bit harder to turn then I expected.
> 
> ...


Many thoughts come to mind. You did not provide a lot of info, so don't take offense at any of this as I am trying to cover a lot of bases and you may have already done all this - just sayin':thumbsup:

Did you have the block align-bored by chance? The Pontiac mains have a specific crush on the bearings and often times if it is align-bored, the "average" rebuild shop doesn't take the time to measure each main cap for the specific crush required. 

I assume you had the crank mic'd because you said "standard/standard" on the bearings. Not too often you get that lucky and don't need to turn then .010/010. Did you mic the crank or a machine shop? Did you have the crank journals polished? 

Did you have the crank checked for straightness? I had one that had lost a bearing, got real hot, and actually warped the crank it got so hot. Figure yours is not mine, but, a crank can warp. I purchased a new Eagle 455 crank.

Thrust bearing. Do you have the correct end play? If you don't it could be binding. Need to check this.

Do your bearings have a generous radius on the side up against the crank? The crank has a radius on each side and if the bearing edge is more straight than cut to compensate for this radius, it could be binding just enough.

Same goes for the rod bearings. Off the top of my head, one side has the radius which goes up against the crank while the opposite side (where the 2 connecting rods rest side by side) is straight. 

Rod side clearance. Is it correct and within spec using a feeler gauge?

I also am not too comfortable when you mentioned "reconditioned" rods. If one of these is out of round, when you torque it down it will bind. The best way to ensure you have the correct clearances is to mic the crank journal, then mic the inside of the rod after it has been properly torqued down in a fixture to ensure it is straight, and subtract the two numbers. Plasti-gauge is OK, but does not give you the accuracy you will get from a mic reading - and plasti-gauge is only measuring the crush from top to bottom when you could have an issue at some other point on the rod/crank journal which you are finding when you turn it over. (Make sure you keep your RPM's down with factory cast rods)

Next thing is your pistons. If they are not correctly sized to each bore, they can be binding. A good machine shop will not finish hone your bores until they have pistons in hand. You can't bore a cyl .030" over and then slap in your pistons because you purchased .030" over pistons. Depending on the manufacturer and the type of metal used in the piston, the manufacturer has a specific clearance required for their piston. If your machinist bored the cyl .030" over and the piston called for an overbore of .031" to meet the required piston to wall clearance, you would have a piston that is too "tight" in its bore. Each piston/bore has to be measured and fitted. You could have a piston(s) binding in the bore.

Did you check the ring gap and make sure it was within spec? If you broke a ring while installing it into the bore, this could be a problem spot.

I don't know if this is the correct way, but what I do is install the crank first, and spin it over. I put some oil on the bearings so it will spin. As I recall, you do the plasti-gauge dry. If it spins over good/easily, then a piston and rod at a time. I do this for each rod/piston - lightly oil the bearing and bore as you don't want to install them dry. You will get resistance as you add each piston/rod assembly, but it should still turn fairly free and easy. If you get any binding or the resistance seems excessive, stop right there and take a closer look before moving on. You need to find/fix the problem.

Give us some more feedback and let us know what you have done and perhaps more info can be provided that will help get that Pontiac running.atriot:


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## goatsnvairs (Sep 12, 2014)

Thanks for the thoughts. First let me state the simple stuff. The block, crank, rods are all of the same original 1973 455 out of a Grand Prix. Re the crank, I mic'd it and it showed std size. The machine shop found the same, and just polished it (mains and rods). The block wasn't align bored because all the caps, block, crank were original.

The machine shop bored the block, and they had all the pistons to measure proper bore. They also did the rod reconditioning. Understanding this is not a "Pontiac specific" machine shop I'm wondering if maybe the pistons were put on the rods backwards or something, so I'm looking for some sort of reference document to tell me if the notch is this way the oil hole should be that way, etc.

Re the crank straightness, all the original bearings I pulled out looked very good (hence the std/std and polish only). Re bearing radius I need to disassemble and check I suppose. I would not expect a factory crank and OE type (Speed Pro) bearings would have this interference, maybe I'm just too trusting.

I guess to sum it up I didn't expect that putting a motor back together that has all the original main components would give me this much trouble.....

I did break one ring putting a piston in but mainly because the compressor I have is really at it's open limit and I think I grabbed it bad. Machine shop also had rings to check but I will also check.


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## goatsnvairs (Sep 12, 2014)

*Found it....*

Gees, when you rebuild a Pontiac motor once every 25 years this is what happens, you miss the obvious.

The machine shop numbered the rods backwards (even numbers on drivers side, odd numbers on pass side,) and piston notches facing accordingly. And when I went to put them in, piston notch facing forward, odd numbers on drivers side, it essentially meant the connecting rod chamfers that are supposed to face the crank were facing each other. This took up all the gaps and created the tightness.

It hit me when I told the guy "those were original rods, and they were not stamped with cyl numbers, but when I got them back they were...." He said "yeah, I told the kid to number them for you". So I asked "did he put the odd numbers on the drivers side?"

"Hmmm.....I bet he did it backwards.

Hmm, I bet he did. Waiting for my wife to send me a pic of one so I can send it to him......

2 hours later: Yup, piston notch forward, bearing locks facing down. Wrong.


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## PontiacJim (Dec 29, 2012)

goatsnvairs said:


> Gees, when you rebuild a Pontiac motor once every 25 years this is what happens, you miss the obvious.
> 
> The machine shop numbered the rods backwards (even numbers on drivers side, odd numbers on pass side,) and piston notches facing accordingly. And when I went to put them in, piston notch facing forward, odd numbers on drivers side, it essentially meant the connecting rod chamfers that are supposed to face the crank were facing each other. This took up all the gaps and created the tightness.
> 
> ...


Glad you found it and it was a minor mix-up. It's all about the chamfers! LOL Like anything, you just have to go step-by-step and study the details and it will usually find you. I always have apprehensions when any machine shop has a "helper" and the owner is not the guy working on/assembling your parts or engine personally. Big sigh of relief.:thumbsup:


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## goatsnvairs (Sep 12, 2014)

PontiacJim said:


> Glad you found it and it was a minor mix-up. It's all about the chamfers! LOL Like anything, you just have to go step-by-step and study the details and it will usually find you. I always have apprehensions when any machine shop has a "helper" and the owner is not the guy working on/assembling your parts or engine personally. Big sigh of relief.:thumbsup:


Biiiiiig sigh of relief. I could not figure out what the heck was happening! I got the parts back and have 6/8 pistons back in and it still turns nice. Whew! Scrapped the original rod bearings because they had some slight scarring where they were up against the crank. Showed it to the machine shop guy who said "you can probably polish that with one of those green 3m pads and use them". It took that to mean "I acknowledge I screwed up but I'm not going to replace your bearings". I ordered a new set, waiting on the last 2.


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## PontiacJim (Dec 29, 2012)

goatsnvairs said:


> Biiiiiig sigh of relief. I could not figure out what the heck was happening! I got the parts back and have 6/8 pistons back in and it still turns nice. Whew! Scrapped the original rod bearings because they had some slight scarring where they were up against the crank. Showed it to the machine shop guy who said "you can probably polish that with one of those green 3m pads and use them". It took that to mean "I acknowledge I screwed up but I'm not going to replace your bearings". I ordered a new set, waiting on the last 2.


I love a good learning curve. :lol: I have come to realize that a true rebuild or restoration needs to be factored by an additional 1/4 of the actual parts purchased to cover those parts that don't seem to fit right due to others, need to be modified in some way, or because you screwed up and have to buy the parts again with the new knowledge gained on how it _really_ goes together(and of course experience gained is priceless, right?). If your factored expenses don't come in at 1/4 over total purchase prices, then you are golden and did something right. HOWEVER, don't celebrate just yet because that savings will surely be used up at some other point in your project build! -Murphy's Law :thumbsup:


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## goatsnvairs (Sep 12, 2014)

Yes, I've found the same thing. When I tallied up my receipts for my Corsa resto last year (always a shock) I found a few things I bought twice 'cause I screwed it up the first time. But hey, that thing runs great so no harm done!

Got the rest of my parts, will finish short block this weekend and post some pics under the 64-74 resto forum. I have a thread going titled "First Time I've Posted About My Resto...."


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## Medic Abroad (Jul 7, 2015)

I'm still running the 400 from the '69 Tempest hardtop I bought in '84 for $150. My roommate couldn't get it running, I put a timing chain in it and it ran for 2500 miles before 7 of 8 pistons self-destructed. It was my first rebuild and I forgot to label the rods and caps. I spent about two months taking the lower end apart and swapping rods and caps before I got it to turn worth a dam. I was too broke to by new rods and too embarrassed to go back to the machine shop to ask for help (I was only 20.) 

The motor is in a '68 Tempest convertible I bought 2 years later for $2000 and has been purring like a kitten ever since. 

My assembly technique has improved in the last 20 or so years and I learn something new every time, and pay a little more attention to details. Sorry you had to suffer from someone else’s screw-up.


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## geeteeohguy (Feb 2, 2008)

Medic, great story. One of the best engines I ever had was a $150 junkyard special out of a '67 Cat. It was a 400 2bbl with 061 heads. With tripower and in my '66 GTO with a 4 speed, it was darn near unbeatable. My first rebuilt engine was a '65 389 that I assembled in 1981, at 20 years old. I didn't realize that there were a thing called oil galley plugs, and that there were THREE of them. (The one in the back of the block got fixed after about 500 miles of loud-lifter driving after I found a schematic). That same engine is still running strong, never even had to adjust the valves, with about 50-60k miles on it, in my '65 GTO, 34 years later. Hell, the asbestos rope rear seal doesn't even leak. Sometimes we get _lucky_.


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## Bensjammin66 (May 12, 2009)

The guys are covering the bases pretty well on your issue but one thought comes to mind right away. Dump the stock rods and at least get some Eagles in there while its apart. Stock Pontiac rods leave much to be desired even fitted with ARP hardware. Eagles are relatively cheap insurance. $450 shipped i believe.


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