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Old 06-24-2013, 06:09 AM
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chevy balancing questions

hey there guys,

i kinda have two builds going on here and i'm still new to all this. both are 1 pc rear main seal SBCs.

one is a hot 350 with a redline intended to be somewhere over 7krpm and 450-ish hp. questions on this later.

other one is a mild L98 rebuild going in a 3rdgen F. i have this crank http://www.summitracing.com/parts/nal-14088526 and was gonna use stock L98 pistons and rods. bores on the block will check out fine with just a hone according to machinist. am i gonna run into issues with no balancing on this one? this one should be done soon.

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Old 06-24-2013, 07:01 AM
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Quote:
Originally Posted by janus View Post
hey there guys,

i kinda have two builds going on here and i'm still new to all this. both are 1 pc rear main seal SBCs.

one is a hot 350 with a redline intended to be somewhere over 7krpm and 450-ish hp. questions on this later.

other one is a mild L98 rebuild going in a 3rdgen F. i have this crank http://www.summitracing.com/parts/nal-14088526 and was gonna use stock L98 pistons and rods. bores on the block will check out fine with just a hone according to machinist. am i gonna run into issues with no balancing on this one? this one should be done soon.
Obviously, dynamic balancing is preferred. But if the budget is so tight that this isn't possible, you can at least static balance the rods and match the pistons to the lightest one.

Install new ARP bolts and resize the rods prior to static balancing.
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Old 06-24-2013, 07:46 AM
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ok so for budget dictating build, static should be fair enough..?
dynamic balancing as you're referring to is the balancing of the crank to a specific bobweight i guess.
arp bolts even on a stock performance build?
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Old 06-24-2013, 07:57 AM
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Quote:
Originally Posted by janus View Post
ok so for budget dictating build, static should be fair enough..?
dynamic balancing as you're referring to is the balancing of the crank to a specific bobweight i guess.
arp bolts even on a stock performance build?
Static is better than nothing but obviously not as good as spin (dynamic) balancing w/a specific measured bobweight, etc.

Yes, ARP bolts even on a stock rebuild. Reason is, you don't (or do you?) know if the engine had ever been over revved to the point that a bolt(s) might have been stretched to their deformation point, rendering them useless for holding a set torque value. Or if the engine had ever been apart, if the rod bolts had been over torqued. Not to mention OEM hardware- even if perfect- is not as good as ARP. And the rod bolts are arguably the hardest worked fastener in the entire engine.

Now, there have been countless engines rebuilt using the OEM rod bolts. But for as small of a cost as new hardware is, I always change them out. If the budget is so tight that this isn't possible, then go w/the OEM fasteners and hope for the best or wait until you can save a few bucks to buy them.
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Old 06-24-2013, 08:05 AM
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I never re-use rod bolts. New OEM from your chevy dealer (not amazon or eBay) is about as low as I'd go. I don't understand pinching pennies by skimping on fasteners and bearings.

If you're just using a 'dingleberry' hone, I'd use an iron ring, not a moly coated one. If you're having it machined in a shop, ask your machinist what ring he prefers for the surface finish he is going to provide
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Old 06-24-2013, 08:11 AM
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Originally Posted by AutoGear View Post
If you're just using a 'dingleberry' hone, I'd use an iron ring, not a moly coated one. If you're having it machined in a shop, ask your machinist what ring he prefers for the surface finish he is going to provide
Good advice. Conversely, if you've already decided on the type of rings you're going to use, be sure to talk it over w/the machinist to get the correct hone finish to compliment the rings.
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Old 06-24-2013, 08:20 AM
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good points on honing and ring type, thanks. i'll leave both up to the machine shop tho.

so static balancing it's gonna be then.
while this is not the originally intended topic any more... but as for the rods, you also mentioned resizing. just measure the diameters and see if they check out ok with the stock hardware? or do you basically resize only with new bolt hardware. i get what you're saying about not knowing the condition of the rod bolts... but it's not my engine/decision kinda.

honestly the stock type rebuild is for a friend who knows jack sh1t (even less than I do lol) about engines but yet e.g. claimed the bores wouldn't need honing or boring although they were obviously junk. i offered to swap blocks with mine since i wanted to bore for other pistons anyways.. he accepted but without even really saying thanks for the offer.

i was gonna let the machine shop take a look at the rods/pistons and then decide. every decision or recommendation i do for that "friend" ends up in a discussion with me defending my recommendation and him not having a clue and being a cheap jack*ss.. getting tired of that

thanks for any and all input guys!
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Old 06-24-2013, 10:28 AM
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If you install new rod bolts, the rods MUST be resized. It is an interference fit, so they must be pressed in and out. The interference fit causes the metal to expand, thus you need to resize.

Once the old bolts are out, the flat surfaces between the rod and cap are milled down a few thousands of an inch.
Then the new bolts are inserted, caps are installed, and then torqued down.
Then the journals are bored back into round with the assembled rod.
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Old 06-24-2013, 10:57 AM
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Quote:
Originally Posted by janus View Post
...but as for the rods, you also mentioned resizing. just measure the diameters and see if they check out ok with the stock hardware? or do you basically resize only with new bolt hardware. i get what you're saying about not knowing the condition of the rod bolts... but it's not my engine/decision kinda.
If this is a dirt cheap deal, and the engine was in running order before being torn down, AND the crank and bearings looked good, you could chance reusing the rods as-is I suppose. It's not something I would do personally, nor would I recommend anyone else do it- but if that's your marching orders, it's on the one giving those orders should it all go bad.

It's just not wise to not at least check the rods for size. Most engines that have a lot of miles on them will have big ends that are out of spec. If that's the case, adding the ARP bolts before resizing is a no-brainer, IMO. Otherwise, reuse the rods and bolts and tell him it's not guaranteed.
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Old 06-24-2013, 11:01 AM
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ah right, that was the deal about resizing with new bolts... forgot about the interference fit since the manley rods i'm gonna use on that hi-perf build are 'sleeved' and have the 12pt arp bolts. thx
so i'll let the machinist check those stockers out and decide i guess.. is it completely unlikely those rod big end will still be the right dimensions?

just saw your reply cobalt... yeah i'll let them check em out. but with aftermarket rods this cheap i always felt a bit like it's kinda not worth it to press old pistons on/off, install new arp bolts and do big end resizing no?
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Old 06-24-2013, 11:07 AM
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Quote:
Originally Posted by janus View Post
ah right, that was the deal about resizing with new bolts... forgot about the interference fit since the manley rods i'm gonna use on that hi-perf build are 'sleeved' and have the 12pt arp bolts. thx
so i'll let the machinist check those stockers out and decide i guess.. is it completely unlikely those rod big end will still be the right dimensions?
You may have a few good and a few bad, or all bad. Usually not all good.

Have you priced a set of recon rods w/good bolts, ready to assemble?

ARP Wave Loc bolts are superior IMO to knurled bolts.

Re the crank you linked to- why it? I mean, if you're building this engine w/the old pistons (hopefully you'll be using new rings and taking care of the ridge at the tops of the cylinders) and rods, etc. you surely don't need a nodular crank. Is there something wrong w/the old crank? 'Cause if it spun a rod bearing, that rod will at the very least need sizing. If it tore up a main bearing, you should consider at least checking the main saddles.

Reusing the original crank will also negate balancing issues- although the OEM balance jobs aren't the best. But I'd wager it'll be a ot closer than the new crank and static balancing the rods and pistons.
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Old 06-24-2013, 12:09 PM
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Heh, good question there cobalt. Well now that you asked you'll get the full length story :p
Once upon a time, i got me a stock L98 short block and a nice, barely, broken in rotating assembly that my builder was offering me for cheap. That's the nod crank, 6 in manley rods and forged diamond racing pistons. Let's just say i got it for about what the crank cost new. Block seemed to be in good used condition but was planning to overbore +020 for those pistons anyways.
Meanwhile, my "friend" spun a rod bearing on his stock L98 and just wants a stock-ish rebuild, but his bores are also shot. Looks like a classic oil change fail block to me.. So i offered to change blocks, and also my old stock rot assy. Comes out my block's original crank also had a rod bearing fail at some point and is cut 40 on one rod journal and 10 on the mains.. So he can't really use that either or that's what i thought because 40 cut is already a tad much no? also cutting a crank here is about 200 euros, that's more than the cost of a new cast eagle or scat crank. BUT then again after shipping and customs, he's getting close to what i'd be willing to sell my nodular crank for.. so i was now thinking he could use my nodular cast crank and i'd get something forged for my HiPo 350 build?
Well at any rate at least we now have 16, minus one or two, stock rods/pistons to choose from

So to reissue we got now:
Block #1 which is mine with good bores, which is now destined to be used for the stock-type rebuild with just basic block prep
Block #2 which had the rod spun recently and has shot bores.. gonna overbore this one 0.020 and more serious block prep for the HiPo build
Crank #1 stock L98 crank of #1 block.. apparently with main and rod journals cut 0.010 and one failed rod journal earlier, cut to 0.040
Crank #2 with the spun rod journal, haven't looked at this too close yet
Crank #3 is the nodular crank. No idea if this was dyn. balanced back then, my builder doesn't care for balancing a whole lot out of some stupid reason
16 pcs L98 rods/pistons
8 pcs nice manley rods and diamond racing 4.020 pistons

hope everything's clear as mud now ^^

Last edited by janus; 06-24-2013 at 12:38 PM.
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Old 06-24-2013, 12:47 PM
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I built one engine without dynamic balancing in my life.
what does it cost you for balancing where you live?
iN Your opinion,what are the advantages to balancing an engine?
The 450 HP engine,???what parts and machine work do you have planned there and why?
hints;balanced,align hone/deck/square,,,,give me reasons to skip any of these procedures
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Old 06-24-2013, 01:39 PM
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the no balancing idea was just for the low-perf/stockish rebuild to save costs.
i have yet to find a local shop for balancing a v8 rotating assembly.. no luck so far. for the few builds he wants balanced, the engine builder i got the parts from sends his stuff to the UK but as said he's quite reckless about balance in my eyes.
no way to skip on mentioned machine work on the HiPo build...

i was just thinking about using the nodular crank in the stockish rebuild since both stock cranks are kinda toast... what's the max you can cut these to anyways?
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Old 06-24-2013, 06:40 PM
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Stock large journal SBC cranks 2.100" can be ground to .060" under with readily available bearings. Next step after .060" is small journal crank size. 2.00" then these go to .040" undersize. Then Honda rod size... and so on..
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