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eat a beaver, save a tree
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Discussion Starter · #1 ·
i just bought a 406 (.030" 400 Chevy) bare block. it had been hot tanked, bored .030", decked to 9.005", new cam bearings, new freeze plugs, & billet steel CV products splayed main caps. after i get it home i noticed the 3 splayed caps fit perfect on the side that has the notch for the bearing notch (in the main bore), but on the other side the bore of the cap is about .015" bigger than the bore in the block. i asked him about it after i got home with it & he said he noticed it too. he said that he asked the machinist that did the work to the block about it, & the machinist said he did it to help keep the bearing from spinning under high horse power. myself, i've never heard of such a thing, so thats why i'm here asking you good people.
 

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Make sure theyre not on backwards or caps mixed up. Sounds like a pieced together job with some old caps to me.

A .015 lip thats not right. thats a sure way to wind up with a spun bearing.
Now you got to be wondering just how bad did he screw up the block? If he cut too deep the whole works will be junk.
 

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block

I hate to give you the bad news but you are going to have to fix that..... What happened is when the guy cut the register to fit the splayed caps he forgot to allow half on each side for the finish line bore. Aftermarket caps are made with a rough bore in them. Some caps are real close to the finish size. Like they only have .015 on them to finish. I have not used the cv products caps but would guess they are real close to the finish size. If you don't get the rough bore eactly centered on the block then when you finish the line bore they won't clean up........... And you are asking how do i know this????? I actually messed a block up once because i did this exact thing... I had to re-work it to get it right...

Keith
 

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eat a beaver, save a tree
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Discussion Starter · #4 ·
k-star, your right. i took it today to my new engine builder & he's gonna fix it for $175. it's .007" big on the cap side. i'll have $700 in it when it done. so i don't think i did to bad.
 

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bolts

Something else i just thought of. If you put this engine together your self look at the outter bolts on the splayed caps. they will usually break into the water jacket. This does not hurt anything but you will need to put a small amount of sealer on the bolt to prevent water sepage into the pan....

Keith
 

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eat a beaver, save a tree
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Discussion Starter · #6 ·
what type of sealer would you recommend on the outer bolts?
i have to say, the splayed 4 bolt block looks a lot stronger than a stock 400 4 bolt block. is the main webbing thicker on a 2 bolt?
 

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406 ss monte said:
what type of sealer would you recommend on the outer bolts?
i have to say, the splayed 4 bolt block looks a lot stronger than a stock 400 4 bolt block. is the main webbing thicker on a 2 bolt?
I am a little confused. Do you have a 4 bolt main block with splayed outer bolts? Did it start out 4 bolt?

The 2 bolt blocks had the strongest web area. The 4 bolt blocks were weaker.

A 2 bolt block with splayed outer bolts added is a lot stronger than a stock 4 bolt block with splayed bolts.

One thing worth mentioning to everyone reading this post is that when you add main studs you may have to align bore also. ARP recommends this when you switch to their main studs.
 

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Discussion Starter · #8 ·
i was just commenting on how much better looking the splayed block looks than the factory 4 bolt main 400. it was a 2 bolt converted to a splayed 4 bolt main.
 

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If you have an area of one of your cap that is .007" too large, you might consider making the machinist who screwed up your block buy a new set of caps so you can start over.


.007" is quite a bit (especially since it's just on one side of the cap. Your machinist will have to whack quite a bit off of the caps to get it to clean up.

Find out if they use align-honing or align-boring. (or both).

In a situation like this, I would prefer to use a quality align-boring machine, so it can be set up once, and cut once. A skilled machinist can get this job done without removing much material from the block side of the main bore. This will minimize the amount your crank is "sunk" into the block. If it's severe, you can run into piston to deck problems and loose timing chains.

Make sure you get a quality job done.

400 blocks are hard to find.

Brian
 

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eat a beaver, save a tree
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Discussion Starter · #10 ·
i bought the block already done, if my machinist had done it i would make him repair it. i bought it & didn't notice it until i got home with it. i've got the block at Vick Hill's Racing getting it done right. it's going to be line bored, then honed. after this i'll have $700 in it total, which still isn't to bad (i don't think).
 

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sealer

I use arp tefflon on those outer bolts... Check the holes first to see if the go into the water jacket....

The 2 bolt 4 bolt debate has been beat to death on ever forum i visit. The 2 bolts with the splayed caps are a stronger set up in my opinion. I have a friend/customer that ran a gm 4 bolt block hitting it with 400 plus shot of spray and the engine was in his car for 3 seasons in a 8.40 et car .... So just when you think something will not work there is always someone to prove you wrong. Oh yea it was a gm steel crank in that engine also!!!!

Keith
 

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I'm not clear where this gap of yours is, but I had Milidon splayed caps machined onto my early 350 2-bolt block. The instructions with the caps specified there is to be a .001" to .003" gap under each outer cap shoulder, designed to stop bearing walk at high RPM. My machinist was familiar with the requirement and agreed fully. The line boring and honing was, of course, done after the machining with the caps torqued. If your gap is one sided it's wrong and if it's .015" you do have a serious issue to address.

As far as sealer goes, check each angle bolt hole to see if it broke through the bottom and use the appropriate sealer, like silicone if it's into the jacket. Otherwise use motor oil or ARP lube. Note that with the ARP bolts and lube the torque spec is probably different than stock bolt with oil recommendations.

Good luck, Larry
 
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