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66 Chevelle SS396 & 66 Chevelle 327 Convertible.
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Discussion Starter · #1 ·
I am quite inexperienced in this area. My Hollander exchange book has me a little confused. It seems to indicate that you can exchange any 65 to early 69 396/325 or 350-360 block with any late 69 396 (402) or 70 400 (402) block as long you also exchange the pistons at the same time. Does this mean that late 69 402 or 70 402 with its pistons will work with 65-69 heads?

However it seem to indicate that the 71 & 72 BB 400(402) cannot be exchanged with either.

My chevy by the numbers seems to indicate the same block 3969854 from late 69 to sometime in the 72 model year (maybe oct, nov, or dec of 71). So what makes the 71-71 block not exhangable.
 

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Hi Jim,the only real difference in the bbc/396 from when it 1st came out in 64 thru 71 was 2 things.

Only the 65 & 66 bbc's required a groved rear cam bearing & journal for proper oiling of top end/cam ,lifters,rockers,valvetrain in general .

But GM redesigned the 67 and later bbc's so they would not require the groved rear cam bearing & journal anymore for proper valvetrain oiling anymore.

In late 69 gm decided to do a .030 over bore on the 396 out to 402 even though gm kept the 396 namplate they were actually 402 cuid from factory. But some LS3's 402 bbc in 70 that were 330hp were called 400's which was confuisng with the new 400sbc flaoting arround at that time.

But as far as heads/cranks/pistons go they were all interchangeable from 396/402/427 in 65-69 for427 & 396/402 thru 71 and even after that. But the 454 was externally ballanced,that used a different crank with longer stroke ,harmonic ballencer,and flywheel/flexplate.

As for the heads what you have to watch out for is using the correct pistons for the heads being run (open vs cloase chamber,thats whats important there ,not the yr of the block.

I hope this info gives you some answers but there is alot more info/history to bbc's then i stated here,i was just touching the surface/getting the ball rolling on it.

Scott
 

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66 Chevelle SS396 & 66 Chevelle 327 Convertible.
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7,195 Posts
Discussion Starter · #3 ·
Thanks Scott. I was looking at buying and putting a pair of 1966 207 heads (Closed Chamber) on a 1970 3969854Block, that I was told was a 402 350HP block. Was told the pistons from the block would not work with the 66 heads. But they would work if I did some work on the chambers of the heads. Is this true? Or are you also saying that I could use pistons that were designed for 1966?
 

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Something else to watch for: the older heads will not accomodate a water sender, nor will they allow for bolt on a/c bracket (the one that goes by the exhaust manifold).
 

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I think he means 2702 heads. I have several sets from several different 66 396 motors. They seem to be very common.
 

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for the purposes of swapping heads, the block doesn't matter- but the pistons do.
those 1966 heads will bolt right on a stock late 80's 454 short block, but the compression would be extremely high and the pistons might actually hit the head.
 
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