Main cap walk

[78Eliminator]

Drag cars that get into tire shake are Hell on mains.
That is a statement that is worth repeating. Think of what a drag car does to a motor as opposed to a prop that burns out and then hooks up more down the pass and starts to really work 1/4 track and beyond.

[LakesOnly]

What causes it? Amidst all the possible causes mentioned, nobody mentioned one of the biggest causes: detonation.
Dowels can certainly help by way of improving structural integrity, as can other bolt-ons, etc. But main cap walk is more-so the cap lifting off the block, and the caps already have registers machined into the block for proper alignment so the dowels are not the best answer...just an improvment of sorts. Due to the primary physical action of cap walk (lifting)...is why there are splayed outer bolts and cross-bolted mains. They are the best upgrades.
Ultimately, the best way to prevent main cap is to maintain a motor at optimum tune and not use componentry beyond its means.
LO

[cstraub]

2 Bolt main with studs in the 600HP range will walk. Other factors like compression, rpm level, bobweight, and detenation will influence the "WHEN".
"Lakes" Check your e-mail and let me know......

[Badburn]

Detonation. 99 percent of the time that is the cause. As stated above, wheelhop, or anytime the crankshaft wants to rotate, but cant. The pistons are pushing down, if the crank resists too much it will get pushed downward along with the main caps.
-with detonation, the fuel mixture gets lit before the piston reaches tdc and it pushes the crank and main caps downward.

[058]

Detonation. 99 percent of the time that is the cause. As stated above, wheelhop, or anytime the crankshaft wants to rotate, but cant. The pistons are pushing down, if the crank resists too much it will get pushed downward along with the main caps.
-with detonation, the fuel mixture gets lit before the piston reaches tdc and it pushes the crank and main caps downward.Not true....detonation is when 2 or more flame fronts collide inside the combustion chamber. All properly timed engines will ignite the fuel before TDC.

[396_WAYS_TO_SPIT]

I thought you planned to build a large cubic inch deal. Stroker as I remember.
"If we spun the jet to 7800 it would be inefficient"
Now what I know about jets would not fill a thimble. But I would treat a jet as a pump....and I would think one would want to build the motor with breathing and structural to run 7000 plus rpm....and then taylor the size of the impeller to let the motor get to that rpm.
Those were the intentions BUT financial situations are preventing the build. So in turn, I will build a 496 that will be alot softer on the wallet for the time being. THe large cubic inch is still on the list but has to be put off for a few months. I would like to finish the boat and have a little fun at the lake for the summer. It really sucks riding in someone's boat other than your own.
To get the rpm's past 7000 in a jet you would have to cut the impeller down quite alot. In turn you would suffer severely on holeshot. Thats what the 1/4 mile guys do. Not to mention that they are running 300lb layups. my hull is medium duty @ 525lbs and is a lake boat. I will have to have somewhat of a holeshot

[dmontzsta]

To get the rpm's past 7000 in a jet you would have to cut the impeller down quite alot. In turn you would suffer severely on holeshot. Thats what the 1/4 mile guys do. Not to mention that they are running 300lb layups. my hull is medium duty @ 525lbs and is a lake boat. I will have to have somewhat of a holeshot
Yet another reason to buy a V-DRIVE! That way you can maximize your motors potential, dont hold it back!

[BrendellaJet]

Yet another reason to buy a V-DRIVE! That way you can maximize your motors potential, dont hold it back!
Building a motor that makes power at 7500-8000 is not hard. Building one that makes that same power at 6000 rpm is.
Not to mention keeping the revs down is not as hard on parts.

[Fiat48]

Those were the intentions BUT financial situations are preventing the build. So in turn, I will build a 496 that will be alot softer on the wallet for the time being. THe large cubic inch is still on the list but has to be put off for a few months. I would like to finish the boat and have a little fun at the lake for the summer. It really sucks riding in someone's boat other than your own.
To get the rpm's past 7000 in a jet you would have to cut the impeller down quite alot. In turn you would suffer severely on holeshot. Thats what the 1/4 mile guys do. Not to mention that they are running 300lb layups. my hull is medium duty @ 525lbs and is a lake boat. I will have to have somewhat of a holeshot
But we are still talking more stroke so I would put a girdle on anything with an arm in it.

[Badburn]

Not true....detonation is when 2 or more flame fronts collide inside the combustion chamber. All properly timed engines will ignite the fuel before TDC.
Actually about 34 or so degrees before TDC, you can change the words around if you want, but the fact remains- if the charge ignites too soon, it's gonna put some serious downforce on the rising piston, rod and crank. This will cause the main caps to walk.