NassyVette

Anyone? Whats the difference and what does it refer to?

Thanks :seeya

ddn

The "mains" are where the crankshaft is held and it rotates on. The main caps are the caps that clamp down onto the crank shaft. Some blocks use 2-bolts on the main caps, some use 4. 4 is stronger. 2 is usually enough.

gearheadz

To be more specific, "mains" refer to the two center position journals & caps. The end caps (2) even on a "4-bolt main" block has two bolt caps.



Mark


[Modified by mdsmith, 12:35 AM 1/18/2002]

Shark Racer

The LS1 is a six-bolt main, I do believe...
-Steve

BAD-L88

I have four bolts even on the end caps.


http://photos.yahoo.com/bc/badl88/vw...iew=t&.hires=t


[Modified by BAD-L88, 10:05 PM 1/17/2002]

45ACP

To add to the confusion, some don't even use bolts. They use studs that are screwed into the block permanently onto which high grade nuts are screwed.

Hehe.


[Modified by 45ACP, 5:35 AM 1/18/2002]

NassyVette

:confused:

dladd74roadster

Yellow: The main caps are what hold the crank shaft in the block. As you can see from the pic of the V6, the first cap (in the front of the engine) has one bolt on either side of the crank shaft. Then the next two caps have 2 bolts on either side of the crank shaft. Then the last cap has one on either side. This adds to the strength of the bottom end of the engine. BUT if you are running a mild to hot street engine that is in good shape and preferrably balanced, 4 bolt mains are overkill. Obviously the added strength of these blocks makes them desirable. And someone can correct me if I am wrong but I believe that all L-82 blocks were 4 bolt mains with forged cranks and forged pistons. Again this all added to the strength of the bottom end.

4 bolt mains came in different configurations as well depending on the manufacturer. Chrysler for instance used 4 bolts in the Hemi but two bolts on each main screwed in from the side of the block rather than from the bottom. This produced a very strong bottom end. Hence the reason that a Hemi block can withstand over 5000 hp in top fuel.

As for studs vs. bolts, this is pretty much explanatory. Studs are typically screwed into the block and nuts are used to secure the main caps in high horsepower applications. The reason for this is that you can achieve a more uniform torque across all of the mains using studs. Also, when using studs you can use a windage tray which controls oil slosh during hard acceleration and braking. This keeps the oil in the pan rather than sloshing against the crankshaft robbing you of horsepower.

I hope this helps.


BadL88: I can honestly say that I have NEVER seen a 4 bolt main block that had the front and rear mains that had 4 bolts as well....and I have owned a number of 4 bolt main blocks. Both big and small. I would hold onto that one. Do you know the history behind that block? Casting numbers, original application? I am intrigued.


dl


[Modified by dladd74roadster, 1:15 PM 1/18/2002]

Flareside

Here's a 4-bolt block. As you can see, it has 4 bolts on each cap. A 2 bolt block would not have the outer bolts on each cap.

Dladd, all the caps are 4 bolt :D It's a Merlin.




[Modified by Flareside, 2:23 PM 1/18/2002]

dladd74roadster

Flareside:

lol. I have never owned a Merlin....... :cry .......maybe one day.

dl

P.S. Wonder why they didn't go with the splayed caps.


[Modified by dladd74roadster, 1:54 PM 1/18/2002]

NassyVette

I got it now :) Thanks everyone!

The Dude

Possibly to minimize clearance issues with some oil pans and oil pan gaskets.

Flareside

Yea, I've wondered that myself. Even the Merlin Pro racing blocks don't have splayed bolts (they actually have studs instead of bolts). The Pro blocks can hold a 5.8" stroke crank! :eek: Wanna build a 780? Makes you wonder about the validity of splaying...

Vetterodder

As already posted, 4 bolt mains provide more strength than 2 bolt mains. It's also commonly accepted that forged cranks are stronger than cast ones. My question is: which is stronger? a 2 bolt block with a forged crank or a 4 bolt block with a cast crank?

63Banshee

It means the same as the difference between 10 bolt and 12 bolt rear ends... 2 more pieces to pick up after it breaks. :D

JUST KIDDING GUYS!!!

BAD-L88

It was cast in October '68, 3935439, it is an L-88 motor, "IT"

It was in my car when I got it.