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1. The rods are machined round. If you mix up caps they are no longer round. If they are not numbered they need to be resized.

2. The bearings are offset in the rods toward the middle of the journal. The radius at the edge of the journal will lock the motor if the bearing touches it.

When I build a V8 I install one bank at a time. The rods should slide front to back on the journals easily. Once the other bank is in they should have proper side clearance.
 

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Cracked rods

You can't resize stock cracked rods. They are throw-away if they are out of spec. The standard way to resize rods is to cut the mating faces of the caps, torque the rod bolts to spec, and re-machine the rod journals to size. This can't be done with cracked rods because of the cap and rod mating face issue. The only way to do it would be to machine the rod journals oversize and get oversize bearings but I'm not aware of anyone selling anything like that. If you put the wrong caps on the wrong rods and torqued them you probably damaged the mating faces where even if you now put the right cap/rod assemblies together they won't fit right. The cracked rod concept eliminates the need for shouldered bolts (like stock 302/351/etc) or dowels and cap screw bolts (like aftermarket). The "broken" face alligns the cap and rod back to the original machined position. If you need another set of rods let me know.
 

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fastford351 said:
Stock rods or aftermarket? Stock rods are cracked (you mean "machined" don't you?) from the factory so the rod and cap only allign one way. Definitely an issue if you have the wrong caps on the wrong rods. Aftermarket are also rod/cap specific and need to be installed correctly but they are machined and doweled. With the wrong caps on the rods you don't have round rod journals. Also, which crank (position maybe?)? The rods are installed a certian way to offset the bearings to cnear the radius on the crank pin (outer edges of the crank pin). If the rods are installed backwards the outer edgs of the rod bearings can interfere with the radiuses and lock the engine up. This will also cause no clearance between the rods.
Other than my issue with use of the word "cracked" and position maybe, good post I think.

If the rods AND caps are numbered on the flats (most are and if not, get a stamp set and do it before tear down), using the number for that cylinder position, and reassymbled in same location and relationship, that is "the way" to do it.
 

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Cracked rods

No, I meant exactly what the post said.... Stock Modular rods are made of powdered metal and are machined to size then cracked to leave a set of "peaks and valleys" on the mating surfaces so they only go on one way and locate the rod and cap exactly as they were machined.... Take one apart and you'll understand this.... If you put them together incorrectly you'll break off or distort some of the peaks and valleys and the caps won't line up right anymore.... Aftermarket rods are machined flat, stock rods are not. If you're basing your opinion on experience with 302's then forget what you know... Modulars are not the same.
 

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fastford351,
the poster asking the questions, the one with the problem, quick35th, .... well, he shows a 92 as his car and a 5.0 (302) as his motor. I have looked through his posts here, he doesn't specifically say what he's working on. In other threads he talks about a 306 based on a 5.0 that he's almost finished, and this is the 5.0 & 5.8 forum. I just figured it was a 5.0 that he was working on.

If not, my appolgies.
 

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Well that's a good point. this is in the 5.0 forum too. lol

Obviously the term cracked only applies to the 4.6's rods.
 

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Oops

Somehow I wound up in the 302/351 forum, thought I was in the Modular forum.... 302 rods are machined as you said, not cracked.... My bad...
 

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Don't sweat it, while I knew what I was saying was correct for a 302, and while I was pretty sure he was talking about a 302 ...
... I wasn't aware that the 4.6 were as you described as I had never been into one that deep, so I learned something about 4.6s that I didn't know.

take care......
 

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Discussion Starter · #30 ·
Yesturday proved to be somewhat warm compared to how the last few weeks have been so I took advantage of it and tore down the motor. I got the pistons in the correct order and matched the correct rods with their caps. After I installed each one I made sure the crank would still turn and after all eight it turns! Granted its tough as a mother to turn but thats how its supposed to be. All this rest of the week is supposed to be warm as well so we'll see how much work I get done.

Well today I've run into another problem :( After torquing the heads back down to spec I cant for the life of me get the crank to turn. I was going to figure out the correct length pushrod that I will need for my combo and realized that I cant get it to turn. I have a low profile nascar style jack and I am using its handle on the end of the 1/2" ratchet on the crank bolt. All I seem to be able to do is lift my body weight into the air which in turn tries to tip the engine stand over on its side.

The pistons are high compression so is what I am experiencing normal or what? Should I just have someone heavier than me stand on the engine stand so it wont fall over? I am afraid that I might strip the crank bolt since I have to give it this much effort.

Shane

PS, this came in the mail today :D

 

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Rotating assembly

You shouldn't have the spark plugs in while trying to turn it over but even then it should move..... If the pistons are domes then maybe you have a piston to chamber issue. Rotate it backwards and see if it turns. If so pull the head off, clay the piston, bolt the head back down and see if there is interference..... A longer pipe or more weight is definitely not the answer to your issue. If there isn't a piston interference issue then the torque of the head bolts/studs may be deforming the cylinder out of round and locking the piston in the bore(I doubt it but I guess it's possible). I'd guess it's a piston clearance issue.
 

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Discussion Starter · #32 ·
No spark plugs are in, no rockers are installed except for one and a pushrod length checker tool. Pistons are set for somewhere around 10.1.1 to 10.5.1 compression.

This is what my pistons look like in my short block:



Could my lifters be binding against the cam causing it not to turn? Is there something that I am over looking when dropping my hydraulic flat tappet lifters into the holes?

Shane
 

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Turn over issues

I guess take it back a step at a time.... Remove the rocker and pushrod and see if it turns. I've never seen a lifter issue other than in rusted lifter bores... If it still doesn't turn pull off the timing chain and see if it turns then... If you're checking it without a head gasket and the head deck surface has been milled to where the piston sticks out of the top of the bore it won't turn over... I'd start back tracking until you get it to turn and you'll know what it was.....
 

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stupid question but you havent been assembling this thing dry have you?
 

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I'm certainly no expert on this but I have done this assembly. The crank shouldn't be all that hard to turn with no heads on it. Even with heads on it wasn't that bad though I'm a bit bigger than the average guy so that may discount my experience.

In any event, it shouldn't be that hard to turn over. Sounds like something is definitely wrong there.
 

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randy, you're not large, you're the jolly green giant! ;)
 

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Discussion Starter · #38 ·
stupid question but you havent been assembling this thing dry have you?
Journals all had a big blob of assembly lube on them. I probably should have smeared it all around but I figured by turning the crank by hand would move the assembly lube around.

Randy,

I know you are extremely busy with the new born and building a new house but if you have any time to spare you should come out and take a look at this thing for me.

Shane
 

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fixed it for ya,
 

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shane did you oil the cylinders as well?
 
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