4-bolt mains

[Koreth]

I was looking a the internals of the 2.5 I have on the engine stand and I noticed that with the holes from the ballance shaft assembly, it would be rather easy to run 4-bolt mains. You'd still have to drill and tap holes for the #4 main cap, but the biggest problem I see with running 4-bolt mains is that cover thingy on the back of the engine where the flywheel mates to the crankshaft (is that thing called the rear main seal?). It only has enough room to cover the stock 2-bolt main cap. You'd have to fabricate another cover thingy or mod the stock one to cover the new 4-bolt main. Same thing goes for the oil pan, since it mates to the block there.

I realize that on a common block the mains are already pretty damn strong, and that it would probably be easier to run ARP main studs and billet caps if I was really concerned about it. But with some of the power guys with hybrids are making, I am starting to wonder just how much more power can be had with a common block before you get twisting in the mains, like Gary describes at www.thedodgegarge.com, even with unequal lenght axles. This is purely hypothetical, unless someone out there has experce in this situation (making BIG power, craking blocks, etc).

Would anyone like to weigh in on this?

[John B]

I think just bolting the balance shaft carrier back into place would add lots of block rigidity.

[Koreth]

While that is probably true, Is there a reason why 4-bolt billet mains would not be desirable aside from fabrication issues with the rear main seal cover thing (that is what its called, right?)?

[Phreakish]

undesirable? no...

More work than their worth to MOST people? yes.

Good idea with HIGH output engines? definitely.

Give it a try and see... unless the wrong material is chosen (aluminum) there shouldn't be any issues with material difference and expansion rates or fatigue. Should prove stronger, stiffer, and harder.

I've always wanted to build something that would tie all the main caps together, since the bottom of the block seems prone to flexing, just from its simple geometry. Tying the caps together along the length of the block would seem to also help along with the main caps... Especially if the new main bolts were used to do this...

[Koreth]

So, something like a single cap/girdle thingy like the mitsu v6 has?

[MrBelvedere]

you only use 4 bolt caps on the 3 center mains and to use a main gertle it is best to tie it into the oil pan rails because it never will flex

[89acclaim]

You might be interested in this thread bedplate 101
,and this one.
Check Out This Block!!!!!

Daniel Merrill

[Koreth]

Yes, I'd forgotten about that 2.4 bedplate project. That would probably add more rigidity than any set of 4-bolt mains could, and would probably be alot cheaper than having a set of 4-bolt mains made up. If the guys at SMP Performance didn't crack a commonblock until 500-600 hp, then I wonder how much power the bedplate would make a commonblock capable of.

[Phreakish]

my interest would be in the fact that the older 'non commonblock' engines could be made to hold 5-600 hp! Just think, anyone could do a hybrid swap with something like that!

I never saw that before, and never thought of going with something like that... really killer idea. I like it.