rods that don,t destroy your budget

grumpyvette

grumpyvette

Administrator
Staff member
25C 70 said:
Rebuilding a 70 l34. From what I've read it is more cost effective to buy new rods than re-bolt and re-size the originals. My question is what manufacturer is preferred and what bolt size 3/8 or 7/16. thanks.
Click to expand...

pis004-1.jpg

I know from long experience that the stock connecting rods, and pressed in pins that are pictured above are fully adequate for a stock rebuild ,but I would never personally re-use stock connecting rods without upgrading the rods with a careful polish resizing and bead blast, then,upgrading to ARP wave-lock rod bolts, but that is fairly expensive in most guys eyes, and in my mind is a total waste of time, as I vastly prefer far stronger 7/16" ARP rod bolt SCAT rods with the full floating pistons,pins and 4340 forged rods that allow easy self assembly and reassembly during the often repeated clearance checking procedures.
the reason is simple, by the time you pay to have the much stronger ARP rod bolts installed on stock rods and have them polished to remove stress risers the average machine shop parts and labor cost equals or exceeds the cost of the far stronger SCAT aftermarket rods.
http://www.superchevy.com/how-to/74038- ... ting-rods/
yes much of that labor could be done at home if you have the correct tools and know whats required,
http://www.summitracing.com/parts/arp-134-6403
arp-134-6403.jpg

http://www.tennesseespeedsport.com/Scat-26135-CHEVY-I-Beam-Rods.html
sca-25700_w.jpg

http://www.summitracing.com/parts/sca-2 ... /overview/
http://www.summitracing.com/parts/sca-26000716

http://www.summitracing.com/parts/sca-6600021

sca-6700_w.jpg

IVE used these connecting rods,with 7/16" ARP rod bolts, in most SBC 383-406 builds with complete success, but as mentioned always CHECK clearances
sca-25700_w.jpg

http://www.summitracing.com/parts/sca-26135

http://www.summitracing.com/parts/sca-26385716

and these with 7/16" ARP rod bolts,rods in most BBC builds with zero problems, I can,t imaging why anyone would use 3/8" rod bolts as they are a MINIMUM or 20% weaker due to the smaller cross sectional area, this larger 7/16" rod bolt,adds little weight for the significant strength upgrade

read this
viewtopic.php?f=53&t=510

viewtopic.php?f=53&t=1168&p=41255&hilit=polish+rods#p41255

http://www.tennesseespeedsport.com/Scat-25700716-CHEVY-I-Beam-Rods.html
ibeam-07.jpg


far stronger than stock, SCAT rods with 7/16" ARP bolts (easily 200% over stock rods) cost less than having smaller diam 3/8" ARP rod bolts installed in the weaker stock rods then having the stock rods resized and polished for stress relief

matters.jpg

READ THE LINKS
I-BeamvsH-Beam.jpg

http://www.superchevy.com/how-to/74038-polish-connecting-rods/

http://www.hotrod.com/how-to/engine/ctrp-1012-race-engine-rebuild-tips/

http://www.hotrod.com/how-to/engine...building-factory-aftermarket-connecting-rods/

http://www.jensensenginetech.com/5-05_tech_tip.html

http://www.enginebuildermag.com/2007/04/performance-connecting-rods/

http://www.chevydiy.com/crankshafts-connecting-rods-pistons-guide-chevy-big-blocks/
 
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alot of people overlook rod bolts but grumpy has a legit point... the crank is spinning, and most pistons have a hefty pin in them, but the weight of the inertia of the piston as it has to change directions in the cylinder puts great stress on the rod bolt. even if you have an inherently light piston the stresses are incredible.. theres no reason to skimp on rod bolts, but theres great reason not to
 
I got asked if its really worth the time and cash to use forged cranks, 4340 forged connecting rods with 7/16" diam. L19 or ARP connecting rod bolts
well, posted below here what happens when a connecting rod snaps off at high rpms ,
and yes it can happen if you float the valve train or break a valve spring etc.
but assuming you build the engine correctly and keep the rpm levels fairly reasonable,
the strength of the better quality components tends to GREATLY reduce your chances of expensive crap like this occurring,
simply because the better, name brand forged parts tend to bend a bit rather that come apart as shrapnel, and don,t stretch nearly as easily or develop stress cracks nearly as often as the reconditioned stock components, then I have to ask if the $240-$600 you might have saved , building your aveage performance 350-383 SBC while using cheaper rods and pistons vs refurbish stock parts looks like a real BARGAIN any longer

pistonde1.jpg

pistonde.jpg

you can,t just swap in a different set of pistons or connecting rods,yes you might occasionally find a lower cost set of used rods and pistons at a bargain price,
the pistons must be the correct bore size and the rods and pistons must be balanced to the crank counter weights,connecting rods can be converted to full float pin design but the cost is usually not worth it as better & strong rods can be had at a reasonable price.. and most pistons designed for pressed in pins are rarely top quality and most are not forged
to balance the rotating assembly , plus theres side clearance , bearing size, quench distance and a dozen other potential issues

READ THESE THREAD's
and don,t skip the sub linked info
http://garage.grumpysperformance.com/index.php?threads/engine-balancing.3900/

http://garage.grumpysperformance.com/index.php?threads/engine-balancing.3900/#post-57940

http://garage.grumpysperformance.co...t-don-t-destroy-your-budget.10958/#post-48174

http://garage.grumpysperformance.co...g-and-installing-connecting-rods-pistons.247/

http://garage.grumpysperformance.co...ng-rods-from-pressed-to-full-float-pins.6909/

http://garage.grumpysperformance.co...ng-piston-pin-height-compression-height.5064/

http://garage.grumpysperformance.co...tion-of-crank-durring-short-blk-assembly.852/

http://garage.grumpysperformance.com/index.php?threads/balance-damper-question.10462/

http://garage.grumpysperformance.co...ng-and-basic-piston-ring-info-youll-need.509/

http://garage.grumpysperformance.com/index.php?threads/piston-to-bore-clearance.4630/

http://garage.grumpysperformance.co...tion-of-crank-durring-short-blk-assembly.852/

http://garage.grumpysperformance.co...guess-on-clearances-and-journal-surface.9955/

http://garage.grumpysperformance.com/index.php?threads/obtaining-desired-clearances.4324/

http://garage.grumpysperformance.com/index.php?threads/engine-block-cylinder-wall-thickness.976/

 
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