Well, this started up in another advanced post and I didn't want to stray from its original topic. Can we get a discussion going about options for increasing a blocks integrity beyond the basics of 4-bolt mains? I'd like to hit a couple specfic topics:
Girdles: what's available? I've heard a few things about a girdle inbetween the oil pan and bottom of block.

Front and Back Main Caps: Most kits for stronger Main caps only provide the inner 3 caps. I understand that a larger amount of load is dispersed here, but wouldn't more rigid end caps?

Clearancing for Strokers: Does this subtract from the block's integrity?

Bracing: Is there anywhere where some sort of bracing or extra material could be added to add support to the block? Examples: anywhere in the lifter valley, on the outside of the block, oil gallies or in the other unutilized space in the block.

Studding: not the horse-type. By using studs vs. bolts for the oil pan, heads, intake etc. can you add some rigidity?

Block Filler: Is it useable and how much does it help on a street motor? In know some have added half or even 1 inch into the bottom of their LTx water passages.

Spinach: How about developing an oil w/ spinach in it to accquire a "Popeye" effect???LOL, joking that time.

Carbon Impregnation: Can it be done to an existing block at a reasonable cost? I know some of the extremely high powered 4-cylinder guys are playing w/ this. My Structures and properties of Materials professor calls it, "Crunchy on the outside, Chewy in the middle."

Just want to know what the options are here to increase the bearing life, cylinder wall integrity, etc. on a 800+hp street car.
While we're at it, how much stronger overall, not necessarily just from being 4-bolt mained is the LT4 block compared to the LT1? I was told there is added material in the main webbing etc.

 

My block is partially filled. Dunno how much it helps. The LT4 block is the same casting. Only difference is the main caps.

Rich Krause

 

George Baxter ran his stock 4-bolt straight main block with over 1,100 hp for over 2 years if memory serves me.

 

BTW: mine has straight (not splayed) 4-bolt caps. I guess I am a "mini-Baxter" with a heavy, powerful convertible.

Rich Krause

 

I'd like to hear about the pros/cons of cryogenically freezing the block for added strength.

I haven't heard a lot about it being done on the board, but have heard of a few imports doing this to help strengthen their blocks.

 

I've heard of a few guys over on TB.com freezing their blocks, but it seemed to not have any effect and cost them a bunch of money.

I'm not sure that a girdle would be reasonable since the main caps are not inline with the oil pan rails. Here's one for the LC2:

http://www.rjcracing.com/RJC_Buick_P...ne_girdle.html

But it, unlike the LT1, has its main caps tucked up inside the block. The LT1's caps protrude out the bottom.

Just go with all the best forged or billet parts you can find and hope it stays together. Like mentioned above, Baxter went to 1100+hp with a supercharger, which in itself puts a lot of stress on the internals. A turbo would certainly allow for a few more ponies to be safely had.

 

 

If you look at the Donovan aluminum blocks they have the bracing in the lifter valley. Most likely a necessity with an alum. block. You don't see anything as far as that goes with the Rocket, Dart or SB2 iron blocks. Nothing really noticable about the top-side of the good blocks either and some of the circle track alum jobs are even lightened along the sides.
What you do see with the good iron blocks is a bit more meat at the main bulkheads in comparison to say a 010 block. The corners of the block are usually the first places to go when you start really pushing the power and I think the block filler is a step in the right direction there. If you lose bore stability, you lose ring seal and once you lose ring seal the engine is a stone. That's why some of these high output race engines make more power in a beefier block with no other changes.
On the filler.... I wouldn't run more than 1/2 full on a street engine or you may run into some cooling problems. The thrust side would bea good place for filler and a little tipping would move the filler in that area easily.

Other than that, I'd just go to a good block and figure out the rest. For most power levels, it's really a moot point cause the stocker is up to the task. Just my 2 centavos.

-Mindgame

 

On a related note, lately, I’ve been surprised to see bunch of LT1 blocks used for more serious applications machined for 4 bolt billet caps, but with straight outer bolts (actually studs).

Any thoughts on this? I haven’t been able to get a really good answer why someone would bother going aftermarket, getting the machine work done and then go with straight outer bolts. The only answer I’ve gotten is that some claim that splayed bolts distort the cylinders. I don’t buy that since sure, they probably do distort the bottoms of the cylinder walls but you would bore and hone the cylinders afterwards with them installed anyway, which should make this irrelevant.

 

As it has been explained to me, anyone feel free to jump in and back this up, the only reason for splayed bolts is that there is more material on most applications to tap into going splayed vs. straight in. In most cases there just isn't enough material to tap it straight. To the person's knowledge who told me this (he's a machinist) there is no strength advantage to going splayed as long as there is enough material to anchor into in the same plane as the original bolts.

 

Maybe I have no idea what I am talking about, but it would appear in my mind that, by spreading out the stress load into multiple planes, more of the block would be holding it than otherwise, or is this just restating what LT1Brutus just said about lenght?

jon

 

Yes, that's the reasoning behind it. If you have more meat around the bolt, the cap/bolt/assembly/foundation is gonna be stronger.
Splayed=more beef.

-Mindgame

 

OK, fine, you've repeated what I was thinking/believe/hinting at...

Now can someone tell me why seemingly knowledgeable people are spending time/money to put billet caps in with straight outer bolts (and we're talking machining 2 bolt blocks for them, not just replacing 4 bolt caps with billet ones and line boring them)? It even looks like straight caps are more expensive (I'm guessing because more people make billet splayed caps...) making this make less sense to me.

 

Some blocks have more than enough meat to do this. Without going into I, J, K vector nonsense, a bolt is the strongest in the vertical direction. Putting the bolt at an angle, you are loading a shear stress onto it that it is less capable of handling. With splayed caps instead of the area of the surface of it's threads displacing the force onto the blocks threads, the "thread end" of the bolt is just acting as an anchor and all of the stress is on the diameter of the bolt.
Mindgame? comments? Do you concur? I'm going out on a limb here using ideas from my Physics I, Statics, Dynamics, and Strc. Prop. of Materials courses, but dont' know that this is the actual case. A steel "rod" (the bolt) has much higher tensile strength than it has a bending moment, correct?

 

A "bending moment"..... ah yes, I have one of those every morning right after getting out of bed...... a little crack here and a snap there.... ahhh.

Sorry, couldn't resist that one Brutis.

You're talking to the wrong guy about statics, dynamics and all that jazz. I'm a programmer who likes racing cars and playing with engines. I'm still pretty good with math and can still do a fair bit of calculus but I'm far from the materials or mechanical engineer.
I do think theres a bit too much emphasis put on the "bolt" here. If you look at a sbc block, OEM and aftermarket, you'll see they have "registers" for the mains..... some even use dowels. When you use a good aplyed main cap from Oliver, Pro Gram etc, they are machined to fit into these registers very precisely. I'd think that plays a significant part in keeping stress off the bolt itself.... besides, standard practice is to use studs on the inboard bolts.

On the splay thing..... if you look at the bottom of a block (looking down on the mains) you see that the sidewalls of the block are at an angle going out away from the crank center. Seems logical to me that you'd want your "splayed" bolts to run at the same or a very similar angle. That would assure that the bolt has the most material around it (360*). That to me would make for a much stronger cap/bolt assembly. I'd assume that that's why all the aftermarket blocks use them. I've always used them on my race engines and have never really given it as much thought as I am now but the GM engineers seem to agree that the splay is the best way to go...... hence the Bow-tie block's 20* splayed bolts on the center caps.

Just my opinion.

-Mindgame