WARNING: Splayed Main Caps Kit.
The "splayed main caps" are another sales gimmick by those pushing a slew of over priced and not too worthwhile 6.5 diesel products to avoid.
Splayed main caps are not usually a "gimmick" but in our professional opinion when used on the GM 6.2/6.5 Diesels they are a gimmick... Just because product or concept that is valid on one engine does not make it a cure all or fix for others, and this is the case here. Like changing rocker arm ratio on one engine type can show power gains, do that on another type and you can loose power, float valves or even break something. Simply put, copying a concept that is successful on another engine type does not make it a good idea, it appears the success of splayed main caps on another engine type is used as a means to try to market the "gimmick".
Now we explain why the splayed caps are a NOT such a good idea on the GM 6.5 Diesel. Our founder Jim has been building High-Performance engines since 1978, before he was old enough to get a drivers learner's permit, the shop where Jim learned was a real turbo specialist call "Turbo People" so you could say he has a LOT of experience when it come to splayed main caps, because he has personally used them on countless Chevy Gas V8's.
On those we start out with a 2-bolt main block which actually has more meat to them than the 4-bolt blocks, then the block is machined to accept the splayed caps. The splayed caps can help to reduce some crank flex crank and usually do NOT strengthen the block, in fact material removal may weaken a block in those areas but on the Chevy Gas V8s it is not typically a concern as the blocks are not a prone to weakness unlike the 6.2/6.5 Diesel Blocks, in fact many of the oil squirter blocks in 96+ were thinner and some of the weakest!
Even on the appropriate engines they
were designed for Splayed Main Caps are a basically a waste of money unless you
are pushing 600hp/800tq+ even then its hard to
justify the expense, many do it for the "peace of mind" effect or bragging right
to say "it's got 4-bolt mains". We've run and seen many Chevy V8s with
twin-turbos and N2O, etc., run well in to 1000+TQ on stock 2-bolt mains. Hot
Rod, Car Craft and many other magazines have written numerous articles and build
ups on hi-po motors with huge power output running stock 2-bolt mains and they
have lasted. Back to the 6.2/6.5, it is a block that is
already weak and has been known to crack so machining it and removing material
from an already weak link is not wise. Also the 6.5
block is already a 4-bolt main design, so to do the splayed caps you are
drilling 2 MORE HOLES in to the block in places not intended for holes and near
other holes, NOT good!. NOTE: on the Chevy
V8s it is mainly recommend to add splayed caps ONLY to 2-bolt blocks!
Why do cranks break and blocks crack on the 6.2/6.5?
Glad you asked :) Typically
because of crankshaft flex usually due to an imbalance or excess vibrations, the
harmonic balancer/torsional dampener on these engines is a weak link and should
be checked at each oil change, inspect the rubber ring it should be intact and
not have and pieces missing, large cracks and should be uniform in fit, if you
notice any areas are migrating or bulging out or you see any problems etc. then
REPLACE the harmonic balancer/torsional dampener. Another reason for problems is
improper installation of the harmonic balancer/torsional dampener, be sure to
use the proper removal and replacement tools, even if you have to rent them,-
gear pullers and hammering it back on is not wise on a part that is already a
Additionally, we have noticed that the number of guys running the gear-drive timing set for the 6.5 being pushed and promoted hard by the unethical forums seems to have a much higher incidence of crankshaft breakage and block cracking, this is most likely due to the removal of the cushioning effect the stock timing chain has, the harmonics and vibrations of the valvetrain are more directly transferred to the crankshaft. Now add to that the already weak link harmonic balancer/torsional dampener, or one with a deteriorating rubber ring, or one that is improperly installed and you can most certainly expect problems. Keep an eye on the balancer/dampener and do NOT install a gear drive timing set, and it is not likely you will need to worry about crank or block breakage problems.
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