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Discussion Starter #1
Are the 1969 396 main caps the same as 75 454 main caps? If they are different, how so?
Thanks
 

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Main caps are fitted to each block. They shouldn't be exchanged with out a very good reason then the block must be align bored.
 

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Discussion Starter #3
Thanks, oger. I'm thinking of converting my 2 bolt 512 block to a 4 bolt. I would definately get it align bored. I assume I can get proper fit bearings, once it's been bored/honed. Any other cautions I should be aware of?
 

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It is virtually impossible to take the caps from one block and install them on another, especially the rear main with the thrust surfaces. Once theya re machined to fit one block, they usually will not fit on another, even with align boring. You would be better getting a set of aftermarket caps. You can talk to your machine shop about it.

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Bill Koustenis
Owner
Advanced Automotive Machine
Waldorf Md
1971 Chevelle "Heavy Chevy" original owner
 

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Listen to Bill, he is right. I had a 350 bolck repaired with a rear main cap from another block and it never was right again. Is the 454 block scrap? If it isn't, why not use it? You could use your 396 crank in it with some 427 pistons and have a 427!

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'69 RS/SS396 pro street
427/4spd/9"
Byars Performance
High Performance Drive Train Parts And Service
www.lubedealer.com/biggearhead
 

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Some of the serious race guys will change everything but the rear cap on a big block to 4 bolt. I really don't see why most big blocks have no trouble with the 2 bolt caps. Just put studs in them and go at it.
 

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Discussion Starter #7
My 512 is a 427/2 bolt from a 69 Impala. I am building a Yenko Camaro Clone, and when I did my engine, I left the 2 bolt mains and cast crank, and 7" balancer.
I know the setup I have is adequate for the car (9.7 CR, 232 duration @ .050 and .540 lift-if I remember correctly)
But I'm having "restoration remorse"..... I wish I had rebuilt it more like the L72 engine. That's why I was thinking of changing it.

I bought a set of 4 bolt caps for $ 45, but sounds like I wasted my money. Can I use the center caps and either get an aftermarket rear cap, or do as oger says and reuse the original rear cap? Just a curiosity, does the rear seal become a problem when you use non-original caps?

Also, Big Gear Head, I know the dimensions on the crank are identical for 396 and 427, but CBN says the 427 has a wider counterbalance to make up for the larger diameter pistons. Can you use the 396 crank in a 427 without balance problems? If I do all this major surgery, I would definately get the rotating assembly balanced.

I know this is a lot of questions, but as you can see, I am no motor expert. I appreciate your advice.
 

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Bill, can he cut the bottoms of the three, (or is it four), four bolt caps and then rebore/hone, but just leave the rear one alone and not be out all that much money???

As stated, just leave the rear cap alone...

I just installed studs for less hassle b/c of this. pdq67
 

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I used a '70 375HP 396 crank with LS6 rods in a bow tie block to build my 427. The machine shop actually had to remove material from the crank to ballance it. I don't see why you couldn't use the other 4 main caps and leave the rear cap alone.

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'69 RS/SS396 pro street
427/4spd/9"
Byars Performance
High Performance Drive Train Parts And Service
www.lubedealer.com/biggearhead
 
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