2 bolt or 4 bolt big block
Thread Starter
Burning Brakes
Joined: Mar 2014
Posts: 904
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From: Crestline CA
2 bolt or 4 bolt big block
So, I know they made 2 and 4 bolt version of the 396/427/454 blocks with the same casting numbers but is there any way short of pulling the pan to tell? I seem to remember reading in performance book put out by chevrolet that all early 4 bolt blocks were drilled and tapped for a oil cooler above the oil filter boss, any truth to that? Also, when did chevy stop putting steel cranks in the vette big blocks?
Race Director
Joined: Apr 2011
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From: North of Toronto - Ontario
Short of pulling the pan....
All 4-bolt blocks were tapped for the oil coolers, but some 2-bolt blocks were also tapped so that's not always a good tell.
IIRC I read somewhere that if it had the oil-cooler holes AND the HI-PER PASS casting AND the tapped holes on the sides of the front cam boss it was probably a 4 bolt block
As to the steel crank, I believe the the lower 396 and 427 had cast cranks (no vette?) and that late 72 was the transition year from forged to cast for the 454's, my 72 LS-5 still had a forged crank but some report that they have a cast crank in 72. I believe all 73 and 74 were cast.
M
All 4-bolt blocks were tapped for the oil coolers, but some 2-bolt blocks were also tapped so that's not always a good tell.
IIRC I read somewhere that if it had the oil-cooler holes AND the HI-PER PASS casting AND the tapped holes on the sides of the front cam boss it was probably a 4 bolt block
As to the steel crank, I believe the the lower 396 and 427 had cast cranks (no vette?) and that late 72 was the transition year from forged to cast for the 454's, my 72 LS-5 still had a forged crank but some report that they have a cast crank in 72. I believe all 73 and 74 were cast.
M
Racer
Joined: Feb 2002
Posts: 378
Likes: 19
It's been awhile, but I think:
The L36 2 bolt blk 427/390's had steel cranks. Passenger car, other than Corvettes, had cast cranks, (as what Mooser posted).
The rectangular port head HP 427's not only have steel cranks, but have cross-drilled oil passages.
The L88's/ZL1's had the above + (sp)"tufftrite" journals.
The old HP series 396-454 book is a good rerference for what had what, like which versions had 7/16 rod bolts and what had the 7/16 boron steel rod bolts.
The L36 2 bolt blk 427/390's had steel cranks. Passenger car, other than Corvettes, had cast cranks, (as what Mooser posted).
The rectangular port head HP 427's not only have steel cranks, but have cross-drilled oil passages.
The L88's/ZL1's had the above + (sp)"tufftrite" journals.
The old HP series 396-454 book is a good rerference for what had what, like which versions had 7/16 rod bolts and what had the 7/16 boron steel rod bolts.
Safety Car
Joined: Oct 2007
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From: Austin Texas
Corvette of the Year Winner 2017
2016 C3 of Year Finalist
just for reference;
69-73 Z 2/8 350 came with same motor as corvette, same 4 bolt block,
same forged crank, and pistons, same Heads, with the Aluminum finned valve covers.
69-73 Z 2/8 350 came with same motor as corvette, same 4 bolt block,
same forged crank, and pistons, same Heads, with the Aluminum finned valve covers.
Last edited by 69Vett; May 21, 2014 at 09:46 AM.
Melting Slicks
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From: Tolland CT
Race Director
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From: North of Toronto - Ontario
Team Owner
Joined: Jul 2004
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From: Redondo Beach, California
My 70 454 is now in an engine stand. A good Memorial Day weekend adventure to drop the oil pan and have a look. The 454 is not numbers matching for the 70. When I posted the block ID numbers a couple of years ago, I got a response that the block was from a 69 Impala SS 427 BB.
(FYI: The 427 and 454 engines had a common block..the only difference as far as displacement goes, is that the 454 cranks had a slightly greater stroke and were not internally balanced.) Next opportunity I'll walk out to the garage and see if the external oil cooler fittings are there.
(FYI: The 427 and 454 engines had a common block..the only difference as far as displacement goes, is that the 454 cranks had a slightly greater stroke and were not internally balanced.) Next opportunity I'll walk out to the garage and see if the external oil cooler fittings are there.
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Drifting
Joined: Jun 2010
Posts: 1,781
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From: Oxford Ohio
Last four on the casting number of those who were either is 5961. Having sonic tested many of them, they will normally bore to standard bore 427. I have one on the boring bar today that will soon be standard bore 427. Kind of depends on the wear. Or if the boring bar will offset bore.
Same for the Ford 390. Some will bore to standard bore 428 depending on the wear. The mirror 105 under the timing cover usually will go std. 428.
Same for the Ford 390. Some will bore to standard bore 428 depending on the wear. The mirror 105 under the timing cover usually will go std. 428.
Melting Slicks
Joined: Apr 2006
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From: Airdrie Alberta
IIRC I read somewhere that if it had the oil-cooler holes AND the HI-PER PASS casting AND the tapped holes on the sides of the front cam boss it was probably a 4 bolt block
Not concerned, i'm using ARP Crank studs, rod & head bolts, won't be above 5,500 so should stay glued together
Drifting
Joined: Jan 2011
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From: Hamilton Virginia
I know its not a corvette motor, but according to the numbers on a 454 I got from an RV, it was supposed to be a 4 bolt block. Well when I pulled the oil pan to change the gasket, it had 4 bolt caps but the block was never drilled for 4 bolts. Never did find out whether it was missed at the factory, or they ran out of 2 bolt caps and used 4 bolt caps instead.
Race Director
Joined: Apr 2011
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From: North of Toronto - Ontario
396 Oil Pad
427 4 bolt main
427 2 bolt main