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Old 01-18-2012, 06:41 PM   #1
ted13b
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Default 400 Bored .60 Over?

I see a 400 engine on Craigslist, but it says bored .60 over. I thought you couldn't bore 400's that big because of the cooling passages? Also, any thoughts on building a 400 for Vette use? I'm loking to build a torquey small block to give myy 77 more oomph coming off the line. Are the 77 400 heads any good?
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Old 01-18-2012, 08:09 PM   #2
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.060 is iffy. Most builders won't run one that's over .030 over, .040 tops. You can bore 'em to .060 but may run into cooling issues due to thin cylinder walls.
Pass on it, keep looking for a standard bore block that'll clean up at .030 and have it sonic checked before handing over the cash.
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Old 01-18-2012, 08:12 PM   #3
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To bad you don't hsave your location posted. I know where a good one is.
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Old 01-18-2012, 08:41 PM   #4
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+1 to keep walking

What's your budget, and how much power do you want to make?
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Old 01-18-2012, 11:49 PM   #5
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Originally Posted by L88Plus View Post
.060 is iffy. Most builders won't run one that's over .030 over, .040 tops. You can bore 'em to .060 but may run into cooling issues due to thin cylinder walls.
Pass on it, keep looking for a standard bore block that'll clean up at .030 and have it sonic checked before handing over the cash.
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Old 01-19-2012, 12:45 AM   #6
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It would need to be sonic tested and even at that if it was not plate honed those cylinders are pretty weak they will distort alot once the heads are torqued on.

I would pass on that one and save your money for a good block.
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Old 01-19-2012, 07:06 AM   #7
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Blockman hit it. I'd keep looking. If it's already 0.060 and if it isn't a fresh bore & hone it won't take anymore. There are still some old one's around, but often they won't go 0.030. If it's in your budget, pick up a Little "M" and make anything you want with confidence. Just stay away from the knock off's from China. Just my opinion on them.
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Old 01-19-2012, 08:47 AM   #8
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Blockman hit it. I'd keep looking. If it's already 0.060 and if it isn't a fresh bore & hone it won't take anymore. There are still some old one's around, but often they won't go 0.030. If it's in your budget, pick up a Little "M" and make anything you want with confidence. Just stay away from the knock off's from China. Just my opinion on them.
The Dart SHP block is about 600 dollars cheaper then the Little-M block and is a good choice!!!

I have one of those chinese knock offs in the shop if any one wants a free block!!!
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Old 01-19-2012, 10:30 AM   #9
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unless your building a real horse, save your money and put it in the topend. A stock block thats 30 over is fine for the street. Go with a 383 rotating assembly, scat makes a good cast crank with their assemblies and that will do fine for anything below 7000 rpm.
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Old 01-19-2012, 11:17 AM   #10
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+2 for walk away. I've built dozens and dozens of 400's using factory blocks and without exception, 0.060" will give you overheating problems. 0.040" is the most I've ever been able go without issues.

The sure way to answer this is by sonic testing the cyl wall thickness, but unless you have access to one, that will set you back $50 or so. Keep looking.

PS - you need a 4-bolt block for any serious hp application. The caps ALWAYS walk on a 2-bolt 400 block when you wind them up. If you're going 550 hp or more, you should consider an aftermarket block. The factory caps can't take much more than that.

'77 heads have 1.72" intake valves. They're good for boat anchors.

Last edited by Ben Lurkin; 01-19-2012 at 11:23 AM.
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Old 01-19-2012, 11:49 AM   #11
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PS - you need a 4-bolt block for any serious hp application. The caps ALWAYS walk on a 2-bolt 400 block when you wind them up. If you're going 550 hp or more, you should consider an aftermarket block. The factory caps can't take much more than that.
Never us e a GM 4 bolt 400 block for any performance use. It'll crack the main webbing from the outer main bolts up into the cam journals.

Use a 2 bolt block and have splayed caps installed.
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Old 01-19-2012, 12:04 PM   #12
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Never us e a GM 4 bolt 400 block for any performance use. It'll crack the main webbing from the outer main bolts up into the cam journals.

Use a 2 bolt block and have splayed caps installed.


The 4-bolt 400 main caps are really wimpy on the outer bolts - really a terrible design...but then again, they were station wagon and light truck engines
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Old 01-19-2012, 12:38 PM   #13
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Brings up a couple things. Four bolt mains. I still like two bolt mails unless billet splayed caps are used. Just for the weakening of the upper main saddle reasons. Can't make that point often to folks though. There is more metal there in the two bolt and the weakness is the iron cap instead of the billet steal cap is more an issue. Some builders align hone every build, so if that's the case why not go with billet caps and really strengthen the bottom end. Stud girdle another discussion, I only use with align hone for the same reason torque plates are used for cylinder hone.
Other point, is sonic testing. I find it very difficult to get people to pay for a sonic mapping of their block. I understand cost cutting, but that information is valuable for the boring process. Also to find thin spots from rusting in the water jacket and casting inclusions. I'd like to include it in every build for free, but the damn thing cost me $1,700. It's got to pay for itself. I still use it when I see an issue with a block, but personally I'd map any block I was going to use for myself. It may save an entire build. I've seen an inclusion that was undetectable until the rings had a little wear in the cylinder, and when cooling let coolant into a cylinder and when started made a mess of a bunch of parts.
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Old 01-19-2012, 02:27 PM   #14
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Brings up a couple things. Four bolt mains. I still like two bolt mails unless billet splayed caps are used. Just for the weakening of the upper main saddle reasons. Can't make that point often to folks though. There is more metal there in the two bolt and the weakness is the iron cap instead of the billet steal cap is more an issue. Some builders align hone every build, so if that's the case why not go with billet caps and really strengthen the bottom end. Stud girdle another discussion, I only use with align hone for the same reason torque plates are used for cylinder hone.
Other point, is sonic testing. I find it very difficult to get people to pay for a sonic mapping of their block. I understand cost cutting, but that information is valuable for the boring process. Also to find thin spots from rusting in the water jacket and casting inclusions. I'd like to include it in every build for free, but the damn thing cost me $1,700. It's got to pay for itself. I still use it when I see an issue with a block, but personally I'd map any block I was going to use for myself. It may save an entire build. I've seen an inclusion that was undetectable until the rings had a little wear in the cylinder, and when cooling let coolant into a cylinder and when started made a mess of a bunch of parts.
I have put plenty of billet splayed caps on 400 blocks both 2 bolt and 4 bolt blocks. They may be stronger but really does nothing about the weak webbing in those blocks and even a girdle really does nothing to strenthen the webbing of a block.

They claim on the 4 bolt blocks the caps are nodual iron caps and the 2 bolts are just a standard grey cast cap.

I think over all the years of block machining I have seen more issues with 400 blocks over 350 blocks!!!

Its kind of foolish to spend money on splayed caps and machine work on a 40 year old peice more so you can buy a Dart SHP block for a couple hundred more dollars and have a real block to start with.
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Old 01-19-2012, 03:52 PM   #15
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Nice to buy new blocks but not everybody can or will spend it. They go with what they have or can get with in reason. Plenty of GM blocks racing every weekend all summer. Get freshened up during the winter. At least around here where drag racing in the snow over revs the engine. A few hundred dollars might not sound like much, but when added to the rest of the costs it often runs folks beyond their spendable cash.
It's easy to forget the costs of machining when it's free for the machinist and it's just numbers. I don't think anything about changing my mind for one of my cars after building an engine for it and just do another one, because all I pay is for the parts, and pay wholesale at that. If I had to pay retail and the machine costs it would get my attention too.
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Old 01-19-2012, 04:00 PM   #16
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Never us e a GM 4 bolt 400 block for any performance use. It'll crack the main webbing from the outer main bolts up into the cam journals.

Use a 2 bolt block and have splayed caps installed.
If you put enough stress on it yes; but anything will break. One bolt hole doesn't make a lot of difference in the stress applied to that area and a two bolt will break almost as easily with splayed caps. The factory blocks just don't have a bunch of iron in that area.

I used to drag race four-bolt 400 blocks and never broke one through the webbing. Where I saw them sometimes break was in the cap itsself. Like this (I think this may even be your pic.):

Click the image to open in full size.

A 4-bolt will be fine under 550 hp/7k rpm or so. If you need more than that, get an aftermarket block. All the machining to add splayed caps to a factory block will get you half-way there.
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Old 01-19-2012, 04:08 PM   #17
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A few hundred dollars might not sound like much, but when added to the rest of the costs it often runs folks beyond their spendable cash.

It's easy to forget the costs of machining when it's free for the machinist and it's just numbers.


A "good enough" engine in the car always beats a "perfect" engine that sits on the stand because of going over budget!
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Old 01-19-2012, 04:34 PM   #18
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A "good enough" engine in the car always beats a "perfect" engine that sits on the stand because of going over budget!
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Old 01-19-2012, 08:11 PM   #19
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Billa, very well put!!!
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Old 01-19-2012, 10:30 PM   #20
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Originally Posted by Ben Lurkin View Post
If you put enough stress on it yes; but anything will break. One bolt hole doesn't make a lot of difference in the stress applied to that area and a two bolt will break almost as easily with splayed caps. The factory blocks just don't have a bunch of iron in that area.

I used to drag race four-bolt 400 blocks and never broke one through the webbing. Where I saw them sometimes break was in the cap itsself. Like this (I think this may even be your pic.):



A 4-bolt will be fine under 550 hp/7k rpm or so. If you need more than that, get an aftermarket block. All the machining to add splayed caps to a factory block will get you half-way there.
I have seen that more then once with 2 bolt 400 blocks cause having the main bolt wider apart and its a standard grey cast cap its a weak link.

Last month a guy bolted on a set of heads on his 406 build heard a snap and this what he found.


Last edited by BLOCKMAN; 01-19-2012 at 10:42 PM.
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Old 01-19-2012, 10:30 PM
 
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