400 SBC Block

Old 07-17-2008, 07:00 PM
  #1  
modracer64
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Default 400 SBC Block

I snagged a virgin 817 casting 400 block to build a 377 for my dirt modified, but when I talked to the machinist about building it for me, he pretty much said he'd rather not build anything using a stock 400 block.

I know compared to a 350 4 bolt main block (which loses the big bore benefit), bowtie block or Little M, the stock 400 is the weakest of the bunch. However, I figured at no more than 550hp and 7500 rpm with a short stroke, long rod, lightweight flat top rotating assembly in a 2500lb car would live for some time. This guy didn't want to touch a build like this PERIOD even with splayed main caps.

What are everyones opinions about using a stock 400 block with stock caps for this application? How long would it live? Will it live at all? What would safe power and rpm limits be before having to really worry about catastrophic block failure.

Thanks Guys,
Darren
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Old 07-17-2008, 07:27 PM
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altune
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I heard with 4 main bolt modification, they can be pretty reliable, My 400 bock was a 2 bolt with stud girdle that lived at 7500 rpm for 3 yrs. and produced a bit more than 600 hp.
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Old 07-17-2008, 07:29 PM
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hink
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Originally Posted by altune
I heard with 4 main bolt modification, they can be pretty reliable, My 400 bock was a 2 bolt with stud girdle that lived at 7500 rpm for 3 yrs. and produced a bit more than 600 hp.
Drag or circle track!!!!!!!!!
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Old 07-17-2008, 07:34 PM
  #4  
hink
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Default Re: 400 SBC Block

Originally Posted by modracer64
I snagged a virgin 817 casting 400 block to build a 377 for my dirt modified, but when I talked to the machinist about building it for me, he pretty much said he'd rather not build anything using a stock 400 block.

I know compared to a 350 4 bolt main block (which loses the big bore benefit), bowtie block or Little M, the stock 400 is the weakest of the bunch. However, I figured at no more than 550hp and 7500 rpm with a short stroke, long rod, lightweight flat top rotating assembly in a 2500lb car would live for some time. This guy didn't want to touch a build like this PERIOD even with splayed main caps.

What are everyones opinions about using a stock 400 block with stock caps for this application? How long would it live? Will it live at all? What would safe power and rpm limits be before having to really worry about catastrophic block failure.

Thanks Guys,
Darren
Over the years we have prepared a lot of 400 blocks and afeter a season of running oly to find a cracks in the decks near the head bolt holes and we have seen cracks in the webbing from the cam tunnel down to the mains. And they are so far out o blue print compared to a good block its not funny.

Dart has the new SHP blocks that can be bored to 4.165 and I beleive we can machine one out, Line honed, decked, blue print bore and plate hone, clearance the lifter bores clean and ship in the U.S. for around 1795.00

We have 4 on order just waiting for them to arrive.
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Old 07-17-2008, 08:05 PM
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us7race
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I had a 379ci destroked 400 and ran it for about 3 years until it finally blew up from too tight mains. I have a 422 now using a stock block with Eagle Billet Splayed Caps shift has ranged from 6500-7000 so far without any issue's. The biggest issue I have read and heard is weak cylinder walls. I added just a small amount of hard blok to mine to the bottom of the freeze plugs maybe a little lower. It never gets over 190 even on 90+ degree race days. I think going with a short stroke helps it live too.
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Old 07-17-2008, 08:58 PM
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dcarr511
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I had a good conversation with a respsected engine builder about using a production 400 SBC w/ a 3.375 stroke for a LSR ( Land Speed Racing ) project and he was 100 % against it !!

He said to use an aftermartket block or forget it ............... ln .02
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Old 07-17-2008, 09:54 PM
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modracer64
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If not for IMCA production block rules, it would be a no brainer to go with an after market block. Unfortunately, that rule prohibits any aftermarket block including bowtie blocks.

From what I'm hearing I can build a 400 production block based 377, but shouldn't expect more than a couple of seasons out of it at most. That sux!

Guess I need to hunt down a good 4 bolt main 350 block and build a good SOLID 383. Anyone have one available?

Thanks for all the replies folks
D
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Old 07-18-2008, 05:16 AM
  #8  
hink
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Originally Posted by modracer64
If not for IMCA production block rules, it would be a no brainer to go with an after market block. Unfortunately, that rule prohibits any aftermarket block including bowtie blocks.

From what I'm hearing I can build a 400 production block based 377, but shouldn't expect more than a couple of seasons out of it at most. That sux!

Guess I need to hunt down a good 4 bolt main 350 block and build a good SOLID 383. Anyone have one available?

Thanks for all the replies folks
D
We have had a lot of calls over the years from some of the IMCA guys who have blown up 400 blocks looking for more its kind of a shyty rule as it should not allow a 400 block as it would save the guys some money in the long run.
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Old 07-18-2008, 06:49 AM
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modracer64
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WOW! was that the understatement of the year LOL.

I do see why they don't allow the aftermarket block though and its because they want to keep guys from building the big motors, thus, forcing the guys who can't afford 2-3 motors per season to use 350 blocks and those who can afford several motors per season to use the weakest SBC block made. I guess their view is if your dumb enough to spend the money to build a big motor with a stock block, shame on you.

If they would just put a displacement rule in, say 410ci or so, then I don't see any reason for the stock block rule AND everyone would have bigger faster longer lasting motors.

JMO
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Old 07-18-2008, 09:28 AM
  #10  
Tod74
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Just a question....Didn't the sprint car guys used to use the factory blocks years ago? I know they are weak but when I was a kid the sprint cars were running 406 -410 ci and I know the top teams had aftermarket blocks but I mean the more local type racers that still ran well. I am speaking of early to mid 80's. Like I said just asking cause I know there are several options NOW for an affordable aftermarket block but what was around back then?
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