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: Big Blocks: 454 vs 427


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gunnersix8
12-12-2004, 11:19 AM
I have always had small blocks, and still do, currently, but I know someone offering a good deal on a 454 big block, very nice. I know that the original engine available in my 68 was a 427, and they seem to be very much more sought after than 454's, but is there any disadvantages to the 454? It obviously won't be emissions applicable but those are not a concern to me. Its about power per buck spent! (And the bonus for the big block on the vette's coolness rating)

CorvetteInfo
12-12-2004, 01:54 PM
'70 LS5 (390hp)**
'71 LS5 (365HP)**/LS6 (425hp)
'72 LS5 (270hp/due to rating change)**
'73 LS4 (275hp)**
'74 LS4 (270hp)**

The 454's came in 2 (**) and 4 bolt main configuration.

Block Numbers:

'70/'71's: 3963512
This block is identical to 3935440 ('68/'69 396c.i.), except for cylinder wall and water jacket revisions and used as a 427 and 454 block simultaneously during '69/'70.

This block has huge reliefs cast into the block for crank clearance (introduced in '69 as a 427, in anticipation of the '70 454). Standard high tower distributor boss and casting date on the side of the block until the redesign (11/17/69) to a much shorter tower and casting date moved to the rear of bellhousing flange.

'72-'74's: 3999289
This block is identical to 3963512 ('70/'71), except for minor interior and exterior casting and machining changes. Only available in 2 bolt** main. Heavy truck useage until '78. Short tower distributor boss located in the lifter galley. Casting date found at the rear of the block on top of the bellhousing flange, near the casting number.

454's have externally balanced crankshafts. The 4 bolt blocks are drilled to provide for external oil coolers.

[Corvette By The Numbers, A. Colvin]

C'ya
D

CorvetteInfo
12-12-2004, 02:09 PM
Originally posted by gunnersix8
... on a 454 big block.... I know that the original engine available in my 68 was a 427, and they seem to be very much more sought after than 454's, but is there any disadvantages to the 454? ...
There is a disadvantage in changing a numbers matching Corvette to a non-matching car.

As for the 454 itself, the 2 bolt main blocks are considered a low performance block.

The BB '68, 427 uses the same bore (4.251") as the 427. The 427 stroke accounts for the CI difference (3.76" vs. 4"). The '66-'69 427's are actually bored out 396 (internally balance) blocks.

If the available 454 block is a 4 bolt main, and your car is NOT a numbers matching, I'd consider setting the block up to 427ci. configuration and match to the stock '68 engine (coolness rating). If you are looking for raw power, just build the 454.

JAT
D

CowboyBob
12-14-2004, 10:10 AM
Speaking strictly from the experience of driving a new 390hp 427 (in a '69) and runnin' it against '70 454s, I whooped'em all. It struck me that the stroked 427 (which is what I was told the 454 was) in the '70s on up just didn't have the "heart", i.e., low end torque to match up to the 427's pull.
:nuts:

raidmagic
12-14-2004, 08:38 PM
Originally posted by c5d


As for the 454 itself, the 2 bolt main blocks are considered a low performance block.



If the available 454 block is a 4 bolt main, and your car is NOT a numbers matching, I'd consider setting the block up to 427ci. configuration and match to the stock '68 engine (coolness rating). If you are looking for raw power, just build the 454.

JAT
D

You set the 4 bolt apart from a 2 bolt. Is that because of the strength or proper block for the car? If your not turning the motor over 4000-4500 rpms would that strength matter? The reason for my questions is I just built a 454 for my Camaro and it is 2 bolt. Did I screw up here?

CorvetteInfo
12-14-2004, 10:05 PM
Originally posted by raidmagic
You set the 4 bolt apart from a 2 bolt. Is that because of the strength or proper block for the car? If your not turning the motor over 4000-4500 rpms would that strength matter? The reason for my questions is I just built a 454 for my Camaro and it is 2 bolt. Did I screw up here?
All of the above...

First issue is that I owned a '68 Corvette with a 427, 2 bolt 390hp motor. This has been my least favorite engine to date.

Then, if I was going to replicate a 427, I'd certainly NOT build the 390hp configuration. The 400/430/435hp's are all 4 bolt mains (for added strength of course). The higher HP would be much better initial bang for the buck/effort, and bring a better rate of return on sale.

Finally, when I restore, I replicate the engine internally as well as externally. Just my quirk.

As for your particular Camaro, I'd doubt that a 2 bolt block would screw it up. But if you were going after a bulletproof block, you should/could have used splayed caps, that strengthen and fit either 2 or 4 bolt blocks:

http://www.milodon.com/new%20images/11050-11210.GIF
[http://www.milodon.com/maincaps/pg57.htm]

C'ya
D

raidmagic
12-15-2004, 04:47 PM
Thanks for the info. I gave soem thought to the splayed caps but I didn't think the RPM range would warrant the expense. I guess If I tear it up I'll just do it right the next time.:D

hiperf 427
12-16-2004, 02:42 PM
2-Bolt main blocks with aftermarket main cap bolts should be good to 550hp. Install aftermarket main studs and that takes you to around 600. The bottom end on a big block is waaaay over-engineered. Unless you're spinning it to the moon, run it hard and enjoy it, it'll handle it.

Fred Mann
12-16-2004, 04:42 PM
Originally posted by hiperf 427
2-Bolt main blocks with aftermarket main cap bolts should be good to 550hp. Install aftermarket main studs and that takes you to around 600. The bottom end on a big block is waaaay over-engineered. Unless you're spinning it to the moon, run it hard and enjoy it, it'll handle it.

In support of the above from hiperf 427, note that 427/390s and 427/400s, both 2 bolt main engines, were redlined at 5,800 rpm from the factory.

CorvetteInfo
12-16-2004, 07:15 PM
Originally posted by Fred Mann
... note that .... 427/400s ... 2 bolt main engines, were redlined at 5,800 rpm from the factory.
Please cite a reference in support of the 427/400hp being a 2 bolt main block.

I believe the acknowledged expert opinion is Corvette by the Numbers, 1955-1982, A. Colvin.

Every reference in his book indicates the 390hp stands alone as a 2 bolt main, 427 block. 400 (& above) are all listed as 4 bolt mains. That also supports my long held understanding.

But if there's something we've both missed, I'd certainly like to know about it.

TIA
D

70 LS1
12-17-2004, 03:13 PM
Wow, I don't think any of you even answered Gunner's question. The engines are pretty much the same. Go with whatever makes you happy. And I am not talking about stock specs here. I would reccommend not building to stock specs. That is 1960s technology.

Advantages of a 427:
You can rev a well built 427 higher than a 454 due to the shorter stroke.
Power output can be made the same as any 454 just in a higher RPM band.
Corvettes look cooler with 427 on the hood.
Internally balanced.

Advantages of a 454:
A 454 is going to be cheaper to build up and easier to find.
No matter what size, a big block is always cooler than a small block.

CorvetteInfo
12-17-2004, 03:28 PM
Originally posted by 70 LS1
... I would reccommend not building to stock specs. That is 1960s technology.
...
What "spec's" do you reccommend?
Originally posted by 70 LS1
... No matter what size, a big block is always cooler than a small block.
A guy named Duntov would disagree with that... not to mention a few others...

To each his own.

JAT
D

moore_rb
12-17-2004, 04:01 PM
Originally posted by 70 LS1

No matter what size, a big block is always cooler than a small block.

If by Cooler you mean heavier and more expensive, then we are in total agreement. :thumbsup:

I used to love tromping Big Block cars with my 68 vert and it's teeny-weeny mouse motor....

IMO, Big blocks seem cooler because they are punchier due to the Big-Block's torque, but punchier does not make a car quicker, or faster; and torque only generates inertia in the powertrain's moving parts. Once inertial momentum overcomes the static mass of the parts, Horspower is the only way to increase RPMs, and only HP to weight ratio is what makes a car quicker and/or faster....

Weight reduction is a lot easier with a small block than a big block which weighs almost twice as much.....

You need the extra torque and cubic inches just to get the extra weight moving.... :smack

If having a 427 emblem on the hood is important, then what better way is there than to start with a lightweight Milodon racing 427 cubic inch SMALL block?

Fred Mann
12-17-2004, 06:00 PM
Originally posted by c5d
Please cite a reference in support of the 427/400hp being a 2 bolt main block.

I believe the acknowledged expert opinion is Corvette by the Numbers, 1955-1982, A. Colvin.

Every reference in his book indicates the 390hp stands alone as a 2 bolt main, 427 block. 400 (& above) are all listed as 4 bolt mains. That also supports my long held understanding.

But if there's something we've both missed, I'd certainly like to know about it.

TIA
D

I'm no expert, but my understanding is that the 427/400 is an L36 with tri-power. In the same way that a L71 is a tri-power version of an L72. I'm not sure what it is that would link the oval port, cast crank, cast piston 400Hp with the higher output rectangular port, forged crank, forged piston L71/L72/L89 engines. In quite a few articles and/or books I have (The Best of Corvette News) and on the internet (The C3 Registry), it is common to see an engine listing showing the 390 HP as "L36" and the 400HP as "L36/L68". These two engines are grouped together in Chevrolet's own terms as "High Performance", while the rectangular port jobs are "Special High Performance", with the exception of the L88 which is "Heavy Duty". Even in the Service Manual Specifications, just about everything is the same between these 2 engines with distinct differences between the L36 and L68 as a grouping and the rectangular port engines. This is just my gut feeling and 30 years of being a Vette Nut.

In "Chevrolet Big Block Parts Interchange Manual", by Ed Staffel Jr., the L36 is described as "2 bolt block". Under the 400 L68 is says "same as L36 except " carbs and aluminum intake. In "Vette Vues Fact Book of the 1968-1972 Stingray", by M.F. Dobbins, it says on page 9 on the 400HP 427 "The internal specifications were the same as the 390HP".

I would think someone on this forum owns one of these cars and can say one way or the other. I e-mailed a guy today that had a 427/400Hp engine for sale on an NCRS website. The description said it was a "IM" engine out of a 68 vette, but the block could also be used for a 390HP, but that the VIN for the car showed it was a 400HP car. When I asked if the block was a 2 or 4 bolt main, the reply that came back just said "2". So that's all I know (or thought I knew) on this subject.

CorvetteInfo
12-17-2004, 06:21 PM
Originally posted by Fred Mann
... In "Chevrolet Big Block Parts Interchange Manual", by Ed Staffel Jr., the L36 is described as "2 bolt block". ..
No argument there.
Originally posted by Fred Mann
... Under the 400 L68 is says "same as L36 except " carbs and aluminum intake. . ..
My only defense is that Staffel's book is about "Parts Interchangeability". Listing the parts that are the same or different (intercahngeable) is not descriptive/indicative of the block.
Originally posted by Fred Mann
...In "Vette Vues Fact Book of the 1968-1972 Stingray", by M.F. Dobbins, it says on page 9 on the 400HP 427 "The internal specifications were the same as the 390HP". ..
Same argument, the "internals" could very well exclude the block's "externals".
Originally posted by Fred Mann
...I would think someone on this forum owns one of these cars and can say one way or the other. I e-mailed a guy today that had a 427/400Hp engine for sale on an NCRS website. The description said it was a "IM" engine out of a 68 vette, but the block could also be used for a 390HP, but that the VIN for the car showed it was a 400HP car. When I asked if the block was a 2 or 4 bolt main, the reply that came back just said "2". So that's all I know (or thought I knew) on this subject.
Now this is interesting. If this is a true, factory original, '68, "IM" 427/400, 2 bolt, then the "bible" is wrong.

Time to go digging.

C'ya back here,
D

Fred Mann
12-17-2004, 07:24 PM
Originally posted by c5d
No argument there.

My only defense is that Staffel's book is about "Parts Interchangeability". Listing the parts that are the same or different (intercahngeable) is not descriptive/indicative of the block.

Same argument, the "internals" could very well exclude the block's "externals".

Now this is interesting. If this is a true, factory original, '68, "IM" 427/400, 2 bolt, then the "bible" is wrong.

Time to go digging.

C'ya back here,
D

First off, nobody is on trial. We are talking about 30 plus year old stuff here.

The section of Staffel's book that I'm refering to is on page 5 of a 100 plus page book. The purpose of the chart is just to give a basic statement of what the different engines are. There is no discussion of interchangability there.

If a main bearing cap bolt is an "external", what is an "internal"? I'm not sure I'm following you. Don't you have the logic and nomenclature reversed here? The full quote is "67-69 427/400hp Corvette same as L36 except three 2-barrel Holley carbs on oval port aluminum intake". The meaning of this seems pretty straight forward.

CorvetteInfo
12-17-2004, 07:42 PM
Originally posted by Fred Mann
First off, nobody is on trial...
Exactly, so why get defensive???

As far as I'm concerned, this is a quest for correct information, ONLY.
Originally posted by Fred Mann
... If a main bearing cap bolt is an "external", what is an "internal"? I'm not sure I'm following you. ...
You left off the qualifier, "parts" or "specifications". Are the main caps an "internal part" that one "interchanges", or a fixed "external" casting?

Bottom line is the "Bible" states specifically, "2 Bolt Main". Your references, although they may imply 2 bolt main (and may be correct), apparently do not specifically state that and are contradictory. So the question remains unresolved from my point of view.
Originally posted by Fred Mann
... Don't you have the logic and nomenclature reversed here? The full quote is "67-69 427/400hp Corvette same as L36 except three 2-barrel Holley carbs on oval port aluminum intake". The meaning of this seems pretty straight forward.
Yes, but that is contradictory with other established references. So the issue remains. Why is one book any more correct than the other? Every book I've ever read had an error in it somewhere.

Regardless, I will have the answer shortly.

C'ya
D

Fred Mann
12-17-2004, 10:23 PM
[QUOTE]Originally posted by c5d
[B]Exactly, so why get defensive???

I refer you to your own post above..."My only defense is..".

Fred Mann
12-18-2004, 01:01 PM
Reference "Sports Car Color History - Corvette String Ray 1963-1967", by Mike Mueller.

"RPO L68 replaced the L36 427's four-barrel with those three Holleys, resulting in a power increase from 390 to 400hp. While most powertrain RPO numbers referred to an engine as a whole, L68 represented the tri-carb set-up alone, which was only natural since everything else about the 390 and 400hp 427s was pretty much identical. Window stickers on a 400hp 1967 Corvette showed both RPOs: L36, priced at $200.15, combined with L68, which tacked on another $105.35,.."

If the phrase "pretty much identical" bothers anyone, one of my books shows a listing for an L36/L68 only cam, separate from the L36 cam.

The above quote explains the grouping of L36 and L68 designation together ("L36/L68") to describe the 400hp engine. This is similar to the L71/L89 situation.

The above is another case where it doesn't say that the L36/L68 is equipped with 2 bolt mains in exactly those words. Does it then mean the contrary? Of the 46 Corvette and BBC books I have in my library, there isn't one reference to the L36/L68 as having 4 bolt mains. Maybe I have all the wrong books. I have looked on the Internet too.

In researching this subject over the last day or so, I have found many inconsistencies in the published literature. I thought, and still think, that the best way to go is to have someone who owns one of these 400hp cars give us the real word. The one owner that I did contact (someone I don't know) was selling a freshly rebuilt 400hp engine and stated it was a 2 bolt. When I thanked the guy for responding to my question, I wrote that he had just confirmed my thinking that the L68 was a tri-power version of the L36. His unsolicited response was "Exactly". Maybe he is full of it. Just like me.

Enough of this subject, lets talk about something that's much more straight forward and that we can all agree on....like Blonds vs. Redheads vs. Brunettes or small blocks vs. big blocks.

gunnersix8
12-18-2004, 10:23 PM
Umm...Big Blocks and Brunettes?