350 block, 383 scat rotating assembly. 1)If you line hone the crank mains, is it a simple matter of ordering approproiate bearings to correctly position the crank? 2)How do you set the clearance 'between' rod caps? And side clearance from rod caps to crank counterweight?

Thanks.

Bud.

 

If you line hone block you make crank slightly higher towards cam but only half what you hone out. The only way to do rod side clearance is you can grind rod side faces to make more clearance. This is not something you can really do at home. If the clearance is too much you can move wider rods to help make gap smaller. Make sure rods dont get put in backwards and if pistons are mounted you are limited to which can be moved around. Dont forget to check crank end play and bearing clearance.Hopefully this helps.

 

Well the crank main clearances to cap is matched if the crank is turned down the "standard" sizes (0.010", 0.020", 0.030") by using oversized bearings. Most us novice builders/assemblers use Plasti-Gage to verify all crank bearing tolorances.
But as Tim mentions, the problem with the line honing (or boring) is if the machinist is a beginner or unprofessional and takes too much metal from the block saddles u will have a sloppy timing chain, which in turn produces sloppy timing or even some spark scatter - well at least less than accurate spark timing.
This is bit of an irritant to me as even so called professional performance engine block machinists right here on this forum insist on align hone/boring even when it's not truly nessesary. U can read D. Vizard explains how a crank has plenty of twist under load even when new and straight and with good block machining. Myself i would install crank first and see if it turns freely without line honing/boring - just my 2 cents.

Good luck Bud,
cardo0

 

cardo0 - I have to disagree with you on this one. within the last month we had a poster that was replacing his rear main seal. so while he was at it he pulled off the rear main cap and posted some unusual main baring ware. His block and or crank was out of true.

Lets say that the main barings have .002 clearance when TQ down. Then if either the block or the crank is out by .0021. You are instantly into the baring surface without oil film protection. It is hard to tell when hand rotating a fresh motor if something is just a hair tighter than normal

I won't even assemble a cheap short cut motors. Balanced and blue printed, good forged cranks, with 4 bolt studded blocks is my minimum.

 

Any decent machine shop should be able to give you the correct bearing info for both mains and rods, and align honing the crank bore, re-sizing rod big ends, setting up rod side-play and such should be fairly routine proceedures for them. By all means, if you're putting everything together yourself DO verify their work before final assembly, but unless you're up to giving them direction I'd let them worry about doing the work properly. Just make sure and let them know what all you need done.

Also, unless you run a fixed gear drive a minor align hone shouldn't present any issues of note.

FWIW, I don't do shortcuts when building engines either.

 

I don't align hone unless a block needs it. I have had a bar machined for the major popular blocks. When the mains are torqued, the bar either will or won't successfully drop through the mains. If any of the mains are off by 0.001 the bar will not go through the mains.
Often saves the customer cash.
If the crank journal width is to wide for some reason, and you wish to use that crank, you can have rods made to any thickness you need. Mic your crank journals and see if they are consistant and correct. Mic the large ends of your rods and see if they are also. If you want to have an idea where you are before you assemble, pick two rods, mic them and subtract that figure from the journal width and you'll have an idea of your clearance.

 

Here in the land of Oz, 350 blocks are somewhat rare. Add to that criteria, one that would be suitable for a performance build and it gets much harder. For the final kick-in-the-guts, throw in living in the country. 3 hours from any major city. Believe me, they are far and few between them! Having said that, I had a lead on a 4-bolt block with a standard bore and 10/20 under the timing cover. Problem was the caps had been taken off and/or replaced. I don't mind paying for the machining but I wasn't sure about the extended effects of line honing.

Bud.

 

Bud, if it's that hard to find a good 350, find out what shipping would be and I'll ship one to you. In my core building there is most likely 60 to 70 of them in different casting dates. I may be able to set you up with something in a date on or near your build date. For a reasonable price.
Like was said earlier, the align hone or bore will decrease the distance from crank to cam a little. You can get timning chains to make up for that change. Or just live with it.
If you go that route, get a two bolt block and a set of splayed four bolt caps that angle the outboard bolts. On occasion I've magnafluxed four bolt blocks and found cracks conecting the bolt holes between the factory four bolt holes. Not often, but I think that method removes a fair amount of metal from the mains.

 

I've sent you a PM.

Bud.

 

Between boring or honing sure you will move the center lines together for sure if you cut the caps. Most builder will take about .005 to .008 from the caps, this usually means you will move the crank .0025 to .004. If you need more than that cut probably better to find another block. You also could have a problem with the front seal as the crank has moved and the seal position has not. When a true line bore is done you can re-cut the rear seal and keep it true though but not the front.
I find alot of times I can just hone the block to the high side limit and not really move the center lines, seems alot of blocks from the factory as well as con rods are on the low limits, meaning you can just hone them to the high side. Now honing is good but it has the same problems also as line boring if you cut the caps except you now have the rear seal out of line as well as the front seal, though you won't have that problem just going to the high side.

 

That just scared me off. Think I'll keep looking.

Bud.

 

rod side clearance can be adjusted by welding on the crank journal radii then machining journal. Not economical/practical for typical street motor unless crank is gonna get welded anyway. Seen some 410 sprint race motors with "piston-guided" rods ... rod small end fits closely between piston wrist pin bosses but has huge clearance at crank journals/radii.

 

I don't understand how boring the mains can move the centerline of the crankshaft. I mean, if you bored the mains using the original centerline of the crank as the axis, and used thicker bearings, why would anything change? it sounds to me like someone saying "If you bore the cylinders, it changes the deck height." It just doesn't make sense to me, but alot of seemingly knowledgeable people are either saying it, or agreeing with it. I must be missing some important peice of the puzzle here.


Scott

 

Its because they will shave a slight amount off the main caps and there is no way to shave any off the block. So then the hole squeezes closer towards top of block. So you are moving the theoretical centerline of the crank. When boring cylinders it is possible to move them towards and away from each other but that is another can of worms. Hope this helps.

 

OK, there is obviously something pretty basic that I am just not aware of here. Let's say, for the sake of argument, that you are boring the mains .020" larger. So, .010" is removed from the block, .010 is removed from the cap, bam! a .020 larger hole and the crank is still in the exact same place it used to be. Isn't this why they make oversize bearings? OK, so what is it that I'm missing here.


Scott

 

You cut the caps to reduce the hole size. That moves the center of the main's hole up. the resizing of the hole is from that point. The mains won't offset bore so what ever you cut from the caps moves the hole center toward the block. Some people who hone the mains say they can remove less from the mains on the block taking most from the caps.
Rods recondition by cutting the rods and the caps to reduce the hole. Therefore the center of the hole is approx the same location.
You don't bore the mains anything over. They are bored to factory. The crank is turned under so the over sized bearings fill the void.

 

http://rollmasterusa.com/RollmasterFeatures_2.html
These come in .002 increments for line bored blocks. I used one in my last build. Great timing set and the right way to do it. Line boring is a good option when building a used block. Most blocks have some core shift after repeated heat/cool cycles and a line bore starts you out straight on your new build. Measure everything, twice. Plastiguage is not a substitute for a micrometer or caliper for any build. Using a standard chain on a line bored block is not the solution. Don't take any shortcuts, they always come back to bite you.

 

OK, I understand what you are telling me. What I don't understand is why a machinist would do that. It sounds like the the way to do it would be to machine the caps properly before putting them back on the block. (Maybe a slight little hone once they are back together to make sure they match up real good.) Now, I'm not a machinist, but I am a reasonably smart person, and I am sorry that I sound like such a little kid about this, (You know, "But, why?......But, why?) but it's just my nature that when I see something that I don't understand, I try to understand it. I really appreciate you guys trying to help me out here!


Scott

 

It may help to understand how blocks are cast. Each pair of cylinders (1 & 2 3 & 4 and so on) are cast as a unit. The front of the block and the back of the block. Lifter bores are in with the cylinder casting. Then the final casting puts all those parts together.
Those hole known as freeze plug holes are really the casting holes. This is when core shifting takes place. That is why you see the cam hole off a little more on some blocks.
There is a go no go with regard to that shifting. They are sand castings so those parts are held inplace with the sand cast form.
I have a bar ground to the specs for the major blocks I do. If this bar will go through the mains after they are torqued they are in spec. I don't like to align hone or bore a block that doesn't need it. Some folks do it as a rule.
When they get out of line it is more of a twisting movement than an actual shifting. The bars I had made will not install if the mains are off by about .0007 so if the bar installs and turns the mains are good enough for a build. I find more cranks are out of true than blocks that are out. Cheap after market cranks should be checked or turned to make sure they are OK. Well they all should be for that matter. Often they are sized ok just not true to the center line of the crank.
I'd suggest anyone building their own engine to buy a few good measuring mics and check the work of any machine shop.