Never seen a 4-bolt break, once they reach a certain HP level we switch to splayed caps... I don't see much broken stuff other than things built by other machine shops, I like to over-engineer and prevent failures. Yes the 2-bolts are strong because of their wide register, I am not disagreeing on that point but main cap failure are usually due to poor main housing bore sizing and/or alignment.

 

All I can say about my 4 bolt is that the same shop built the 2 year old 2 bolt. At the time I had the 4 bolt built I was warned about main cap failure. It was not splayed...but why splay a 4 bolt (rare) block when a 2 bolt block can handle plenty. I do know that even Mid-America won't touch the internals of Corvette ZF's because very few replacement parts are available. Our Ford dealership also cannot even get the internal parts for Super Duty ZF's or the Focus SVT ZF. Mainly just wanted to pick on you, since you were picking on me.

Zach

 

how do you "splay" a stock 4 bolt main block?

I think we've decided to try this with a "509" 400 block with the 101mm turbo, what the f*** Thanks for the input, if we blow it up, I'll report back..

 

Brady:

I know this is going to sound dumb, but does a "509" 400 casting have the numbers "509" somewhere on the block? I've heard about these blocks. (They're the high nickel content blocks right?) How do you identify one?

 

They say 509 on them. That's the block I have. I wasn't aware of the nickel content...but they have thicker water jackets so they can handle overbore better. Mine is not bored, so my engine cools JUST as well as a 350. I was also not aware of a 509 4-bolt. I have an extra 509 bare block at home, so I'll try to get a picture of the "509" on the block and the location of it.

Brady, you probably know, but you will want to get a crank (and flywheel/dampener) for that engine that is internally balanced as the stock style external balance does not contribute to a long life.

Zach

 

Brady, on a side note, where did you get the chrome Z28 emblems on your car? (In the Mag. article) I have seen RKSport's chrome badges and they are nasty looking with the holes instead of "speed lines."

Zach

 

It can be done but it's not worth the trouble. Laguna is right, the 2-bolt blocks are beefier in the webs, so I'd buy a 2-bolt and splay it.

"Cap breakage" isn't the problem... the 400 usually breaks in the main web or between the cylinders. The first thing you need is a good block. Don't just assume that because you found a "509" that it's good. You'll need someone to sonic check to find a winner. A "good" 400 block can have as much meat in it as a bow-tie.

Back in the 70's, Jack Connely built a number of huge displacement 400's... 440, 454, etc.. Set more than a few drag records with them too. One of Jack's tricks was in finding the "right block" with minimal core shift. He would then plug the coolant holes in the deck surfaces, mill the deck and redrill the the plugs to match those in the head gasket. If the block didn't have coolant holes between cylinders 3-5 & 4-6 (some later blocks) he'd drill and tap for the plug (3/4 NPT) & drill the coolant hole in it. Which is said to help strengthen the block. Adding the center hole helps keep those cylinders from running too hot.

You also have to spend a good deal of time deburing/smoothing the main bulkheads and every nook and cranny of the crankcase area. Jack's blocks even had larger fillets in the bulkheads, courtesy of some serious die grinding I'm sure.

Hey, like you said... build it and see what happens. I'd much rather put a tubo to it than a bunch of nitrous. That's what we did to them many years ago and some held up just fine. With the fine tuning of an EFI setup... there's no telling how much it'll take.

Good luck.

-Mindgame

 

Splaying a 4-bolt is not good as you said because you are taking even more material away from an already thin main webbing by drilling a third hole there.

This is the exact prep that our stock block 400's go through, find a good 2-bolt core to convert to splayed cap, sonic test for wall thickness, core plugs in the deck add ridgidity, we also run bypass coolant lines tapped into the side of the block.

Even after all this work, the stock blocks at 500+ rwhp and 7500rpm are only good for 2-3 seasons before the main webbing cracks, sometimes on disassembly (after the motor ran fine in the last race) the front main webbing falls out with the crank.

As you said, we had to pass on 3 possible cores last month because of cracks on the deck from the steam holes to a headbolt hole.

 

Just makes sense to run a sportsman bowtie don't it?

 

If rules are dictating that he can't then he CAN'T. Or am I missing something here?

Bret,
You're a young guy... I understand. But keep in mind that some of us not-so-young guys were making big power with the 400 back before all the aftermarket blocks came along.

-Mindgame

 

This is some awesome info you guys are putting out. One thing that I've heard mention of, but have never actually seen, is this thing called a "block girdle." This supposedly fits down in the main area of the block and is supposed to add strength there. Has anyone ever seen this? Did it help any? I was thinking it might be another possibility to try with solving the strength problem with this block.

By the way, SStrokerAce: Is OldSStroker your Dad by any chance?

 

What? How many times has this happened? 500rwhp and they're breaking?? come on.. we're going to turn it down with the stock block, but it's still gotta be over 1000.. 7500 rpm is not too cool either, I've buzzed my 380 to 9500.. I'm starting to get worried again..

 

Guilty as charged.

 

MG,

Yeah I know but for the guy who has the choice and wants to save a few bucks it's a far cry to say that a 400 is a "cheap" way to go in terms of prep and selection of cores and then the fact that they just aren't that durable.

As I said before I think it's a dumb rule that costs the racer money.

Bret

 

Oh boy, do I agree with you there Bret. I'll stay off my soap-box on this subject but yeah, just drives the cost of racing through the roof. The hydraulic flat-tappet lifter classes are good examples.

-Mindgame