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How many of you 400 guys are running a .060 over bore?
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thesoundandthefury
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PostPosted: Sat Sep 02, 2006 1:34 pm    Post subject: How many of you 400 guys are running a .060 over bore? Reply with quote

The idea I have in mind is to install a 3.48" stroke crank in my 400 block, and punch it .060 out to make a 383.

Here's why I like the idea:

- Less side-loading on the cylinder walls
- Lower frictional losses
- Lower piston speed
- Less stress on the main webs
- A 4.185 bore seems like it would unshroud the valves better than a 4.030 bore (stroked 350)
- there's an inexhaustible wealth of information out there about 383's and the different heads/cam combo's being used and how much power can be made, etc.


If I understand all the stuff I've studied on this, a 400 destroked to a 383 should be able to make just as much HP and TQ as a 350 stroked to a 383.

Does anybody happen to know off-hand what the minimum cylinder wall thickness must be to still be "safe?"

I'm interested in hearing any and all input from people who have gone .060 over on their 400 blocks.....the good, the bad, and the ugly.

TIA
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bill jones
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Location: Salt Lake City Utah
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PostPosted: Sat Sep 02, 2006 2:09 pm    Post subject: Reply with quote

-several major problems with that idea.
---------------------------------------
-inside the water jackets there is a full length notch under every headbolt hole--that runs the full length top to bottom.
-These notches are way too thin to start with.
--------------------------------------
-You need to look at your head gasket choices to see if you can actually find a gasket bore that will fit over the large bore and the associated chamfer usually needed at the top of the bore so that you can get the piston rings started in to the bore.
---------------------------------------------
-you might have a problem even getting some piston manufacturer to build you 60 over pistons---and you'd need to make sure you can get piston rings.
------------------------------------------
-Personally I'd rather have a standard bore block and keep the bore at .020".
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artinla
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Joined: 09 May 2006
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1971 Chevrolet Nova

PostPosted: Sat Sep 02, 2006 2:24 pm    Post subject: Reply with quote

I have run several .060 over 400's without incident but I was careful to check for core shift. .060 is really pushing the limit of the 400, and if you aren't very careful you will end up with a split bore. I don't really see the head gaskets as a big issue.

The combination that you are considering is appealing because it is a big bore shorter stroke/long rod combination. I won't go into the myriad of reasons why that is desirable, but it is. You hit on many of them in your original post. The .060 is the only hitch, I would feel better about giving you a thumbs up if it were .040 or less.

Art
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Big Dave
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PostPosted: Sat Sep 02, 2006 2:54 pm    Post subject: Reply with quote

Chevy production block is limited to 0.030" overbore. Aftermarket and early Bowtie blocks will go 0.060" over without a problem.

The additional 0.030" bore size will not be justified economically; in terms of it's contribution to overall engine displacement, compared to what you can obtain by a slight increase in the length of the stroke. I made this same mistake with a BBC by punching out a standard deck height block to 582 cid.

I spent more for those extra 10 cubic inches than they were worth. In that the thinner bores created sealing problems for the rings. I was looking for a thousand horse on the engine and it fell short, which if I had simply gone up a notch on the stroke I would have saved money, and had a more potent motor. In other words I could make what I make now with a 572, and bought myself a lot of other parts with the money I blew on the overbore.

But I wanted the biggest cubic inch displacement that I could scratch out of the block just for bragging rights and it cost more than I got back. Hope this saves you from making the same mistake.

Big Dave


Last edited by Big Dave on Sat Sep 02, 2006 3:46 pm; edited 1 time in total
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96capriceMGR
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PostPosted: Sat Sep 02, 2006 3:43 pm    Post subject: Reply with quote

Big Dave wrote:

But I wanted the biggest cubic inch displacement that I could scratch out of the block just for bragging rights and it cost more than I got back. Hope this saves you from masking the same mistake.

Big Dave


I wish more folks were this honest. We have all screwedup and we all get to go faster if everyone helps the next guy avoid repeating the mistake he already made himself.
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artinla
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PostPosted: Sat Sep 02, 2006 9:57 pm    Post subject: Reply with quote

I agree. Even though I got away with .060, I know that it was the exception and not the rule. I know a lot of guys that will just throw away a block that needs to go .060, that is why I was running them! Wink
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af2
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1933 Willys Coupe

PostPosted: Sun Sep 03, 2006 12:04 am    Post subject: Reply with quote

96capriceMGR wrote:
Big Dave wrote:

But I wanted the biggest cubic inch displacement that I could scratch out of the block just for bragging rights and it cost more than I got back. Hope this saves you from masking the same mistake.

Big Dave


I wish more folks were this honest. We have all screwedup and we all get to go faster if everyone helps the next guy avoid repeating the mistake he already made himself.


This is no B.S. The machine shop that I deal with just got finished with a .030 400 and torque plate honed it to the final size. They removed the plate and the block had cracked from the bore to the head bolt. You didn't need a magnifying glass to see the destruction. A total waste!!!!!!!!
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artinla
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PostPosted: Sun Sep 03, 2006 6:58 am    Post subject: Reply with quote

Damn Adam, you have the best luck with parts!

Very Happy
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Paul P
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PostPosted: Sun Sep 03, 2006 7:17 am    Post subject: Reply with quote

Bore it .060 and run it. You can visually see if it is shifted bad by looking at the holes for the lifter bores. It is not a sonic check but if the lifter holes are in the middle of the casting for them it is a good bet that it will be OK. Sonic check it to be absolutely sure.

Shocked Wow Adam you have some hard luck I agree with artinla. I have some parts I could sell you with a tail light guarantee. Laughing
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Big Dave
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PostPosted: Sun Sep 03, 2006 9:27 am    Post subject: Reply with quote

Well I wouldn't trash a block for a cracked cylinder. Back a long time a go in a world without aftermarket blocks I used to bore for water and then sleeve a block whenever I found water. Never have to worry about core shift with eight sleeves. Of course it cost more than an aftermarket block and isn't as strong as the aftermarket blocks that are now available but I have always wanted an unfair advantage and having the biggest motor at a race usually helps. I never could figure out how to get small block Chevy valve covers to fit on a 409 so I had to bore out 327, and 283 blocks to try and get there with a stroker crank.


Big Dave
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af2
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PostPosted: Sun Sep 03, 2006 10:59 am    Post subject: Reply with quote

Paul P wrote:
Bore it .060 and run it.

Shocked Wow Adam you have some hard luck I agree with artinla. I have some parts I could sell you with a tail light guarantee. Laughing


Hey Art and Paul luckily it wasn't my block. Laughing I bought my heads used from an a hole off Ebay that had to know they were trash. I should have had them pressure tested right when I got them. Live and learn. Shocked
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thesoundandthefury
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PostPosted: Sun Sep 03, 2006 3:20 pm    Post subject: Reply with quote

Wow, thanks for all the responses guys. There's some good info here.

Big Dave, I appreciate your honesty regarding ego's, and I couldn't agree more. In my case, I wish it were as simple an issue as keeping my own ego in check, but unfortunately it's a little more complicated than that. I bought this block based on a lie. I purchased it from a guy who, at the time, I considered a good friend and somebody who's word I could take at face value. He admitted that the engine had been hurt, (spun a rod bearing which in turn caused a piston to gouge one of the cylinder walls), but he also told me that it was an unbored virgin block. So here I was operating under the notion that down the road I could just have the cylinder bored .020 or .030 over to clean up the gouge and she'd be good to go.

Turns out, I was wrong.

The block is already .030 over. Now it's time for me to eat crow and admit that the predicament I'm currently in is based on my own ignorance about how to tell if a block is good or not. At this point, I really don't want to throw this thing away because I've put quite a bit of effort into it as evidenced here.

Quote:
Back a long time a go in a world without aftermarket blocks I used to bore for water and then sleeve a block whenever I found water. Never have to worry about core shift with eight sleeves.


Could you explain this a little more in detail? It sounds like it might possibly be a solution to my problem. I'm wondering if it's possible to do this with a thick enough sleeve that you could have a .060 over bore but still have the same cylinder wall thickness as a stock bore?
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artinla
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PostPosted: Sun Sep 03, 2006 4:40 pm    Post subject: Reply with quote

It is possible, but the last sleeving I had done cost me $100 per hole.

If you can get away with 1 hole, then you would be OK, but if several need sleeving... scrap it.

Would the block go at .040 if you sleeved the one hole? If so, that is what I would do. Forget .060 unless it is absolutely necessary.

BTW, that is a nice looking polish job on the block. Must have taken many hours to do.

Don't ever worry about being ignorant on any subject. Nobody knows it all except Big Dave Very Happy. There are no stupid questions, only stupid people afraid to ask questions. I have bought many parts that turned out to be lemons... and many times it was things that I knew to check for and just didn't.

One thing for sure, you came to the right place to ask. These guys know their stuff and I have saved plenty of $$ and a lot of grief by following the good advice found here.

Art
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thesoundandthefury
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PostPosted: Tue Sep 05, 2006 1:09 pm    Post subject: Reply with quote

Anybody here think a .010 overbore would clean this up?


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clay
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1972 Chevrolet Nova

PostPosted: Tue Sep 05, 2006 5:46 pm    Post subject: Reply with quote

I hope the pics make it look worse than it is, because it looks like sleeve material by them. That gouge looks like 0.060 might not clean it up by the pics but Hanz or Bill Jones would be better than me at judging it. Clay
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