Ive got a simple question. Ive heard both negative and postitive things about splayed main caps. Ive heard they actually make for a stronger bottom end than standard 4-bolts, but Ive also heard that they distort blocks. Anyone had any experience with these? Thanks!

 

Splayed are more stable than the stock 4 bolt configuration.

The stock 4 bolt arrangement just causes part of the webbing across the cylinders to be removed to make room for the bolts. The problem is they're pretty close together which leaves the area between them at risk.

Splayed aren't sitting next to the other "inner" bolts, and there's more material between them, so it's less likely to snap.

I've never heard of anyone breaking the webbing on a stock 4 bolt unless it was from overheating.

 

I split a main cap. wasnt pretty.

but then most people dont install them backwards

 

Ouch, I bet you will never make that mistake again!

formularpm,
Standard 4 bolts are pretty strong, unless you are looking to build something that is stroked and really going to scream in the upper RPMs. Splaying would be a waste of money.
It is my understanding that if you are going to splay a block, it is best to start with an original 2 bolt block and have it modified for the splayed 4 bolt caps. These are supposed to be a whole lot stronger than a factory 4 bolt.

 

The 400 blocks are certainly that way.... the early blocks, that got 4-bolt caps, didn't have as much metal around the webbing as the later blocks, that they only installed 2-bolt caps onto. So in the case of 400s, the best combo is a later block, 2-bolt, with aftermarket 4-bolt splayed caps.

350 blocks are mostly the same between 2- and 4-bolt versions. They took the same block, and just installed whichever caps on it. So a 010 casting for instance has no more or less metal depending on which caps the factory happened to put on that particular individual. It's a good bit easier to install most of the splayed caps if there's not already a hole where you have to drill, though.

 

Splayed outer bolts also 'pull' from the sides of the block instead of the webbing, which gives added strength.

 

So no one has ever heard of splayed caps distorting a block?

 

No, I never heard of the spayed caps distorting a block. Unless the drilling and tapping was done by hand without guides or something weird like that.
If anything, splayed caps are overkill for all but the most severe-duty motors.
But I have to say, if I had the coin, I'd do it just for peace of mind.

Best
S-D

 

Any time you add bolts to a block, or have something bolted to the block, you "distort" it. Believe it or not, cast iron does flex.

For instance, when you have a block bored and honed, the block should be honed with torque plates. They simulate the heads being on the block so the bolts can "pull" the metal where it needs to be, that way the cylinder is round when it's honed. The machinist should also bolt the caps on the main journals for the same reason.

1st scenerio...... If the machinist hones a block with nothing attached, then after he's done, puts all the bolts in (like heads and main caps) the cylinders will distort and become out-of-round. BAD!!! :nono:

2nd scenerio..... If the machinist uses a torque plate (which he should) then hone the cylinders, the cylinders are round. When the plates and main caps are removed, the cylinders actually "distort" and become out-of-round. But when the heads and caps are put back on, the cylinders go back to being round. GOOD!!

So to an extent, yes. Adding 2 more bolts to the center caps (6 bolts total) will "distort" the cylinders. It would be a good idea to install them BEFORE the block is machined for the reasons I mentioned earlier.

If you've already had the machine work done, then talk to your machinist about what you want to do. He should be able to answer all your questions, and should be able to help you. If not, find a new machinist. He isn't very experienced.

 

what kind of application is this?

you'd be surprised the amount of power a 2bolt main studded would take

 

The plan is a budget-oriented 383. I want 450-500hp, and the max rpm shouldnt be over 6500. I was also considering a 150 shot, so thats why Im thinking about the splayed caps, Ive got a 2 bolt block now.

 

Isnt there a arrow on the top of the cap that should point towards the front of the motor??? I'm asking because I will be putting mine back together real soon...looks like an arrow to me???

 

AJ_92RS,
I agree with your distortion argument. But he isn't talking about adding 2 bolts to a 4 bolt block. He is asking about just a 4 bolt splayed block.

 

Uhhhh AJ,
I just re-read your post. You meant adding 6 bolts total, not 6 bolts per cap. I appologize. That was my bad.

 

6-bolt mains? Like the LS1?

Any time the main caps are changed, the case assembly needs to be align-bored (or at a minimum, align honed). This not only sizes the caps but should relieve some stress from different bolting patterns.

Look at the GM Rocket blocks, or Sportsman, or CNC-prepped, or Dart or Donnovan aftermarket blocks, and they will have at least 4-bolt splayed main caps down the center three, and some even use 4-bolt caps at the front end or both ends. If you're planning on any more than 500HP on a small block, it's a really good idea.

 

a 2 bolt block that is studded and prepared correctly can hold 500-600hp without a problem imo. Little risky, a 4 bolt would be better but i wouldn't spend the money on the splayed caps. Honestly i'd just stud what you have and run it. You would really be honestly surprised how much it lived.

Of the 5 or so years i've been playing with cars the one thing that i have found, on the internet at least, is people over building their bottom ends. The money is better spent elsewhere imo. The most important thing in the bottom end is who does the balancing, the bearing clearances and the rod bolts.

just my .02

 

If only...