Help needed from the experts - Impala Tech
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post #1 of 9 (permalink) Old 05-30-2018, 09:10 PM Thread Starter
 
 
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Help needed from the experts

New User Here....

I have a friend that has a 1966 Impala SS Coupe with a 396 in it and I am thinking about buying it. He claims it has the rare 420hp/396 Mark IV engine but it looks like this engine option was only offered in 1965 correct? Lastly how do I go about identifying what 396 is in this car and whether it's a numbers matching example?

Any help is greatly appreciated.

Thomas
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post #2 of 9 (permalink) Old 05-30-2018, 09:25 PM
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Welcome to the Team Thomas!

It will have a partial VIN stamped on the block application pad. All big blocks were stamped, because they were frequently stolen.

The difference in horse power is a marketing reaction. When the 1965 375 horse solid cammed big head port engine came out it was rated at 420 in the Corvette. It was rated at a higher RPM than the same 396 engine was rated in a Chevelle.

Problem GM had; and why the horsepower rated numbers changed, even though all of the parts remained the same, was that the insurance companies rebelled saying they didn't want to insure any car with over 400 horsepower. Lower the RPM and the horsepower falls off even though if you reved it higher it would make more power than it was rated.


The Big Chevy never got a solid cammed 396 engine which makes yours a very rare option indeed. There was a 425 horse 427 which had a solid cam used in the 427 SS: but that was a rare special option available in 1967-'69. I remind you the SS in the Impala was a trim style, not a performance option. So you could order a SS Impala with a 230 six cylinder and a PowerGlide to go with your bucket seats and SS decals.

Big Dave
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post #3 of 9 (permalink) Old 05-31-2018, 12:43 AM Thread Starter
 
 
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Thanks Big Dave !!

Is the engine application pad on the lower right or left side of the motor as you stand in front of the car? Is there anyway to tell if its the standard L35 325 HP 396 as opposed to the Mark IV L78 which was rated at 420 HP?

Haggarty's lists the 8-cyl. 396cid/325hp 4bbl L35 "for 1966" and the 8-cyl. 396cid/425hp 4bbl L78 "for 1965" so maybe its the L35 engine?

History of the 1965-1970 Chevrolet Impala

New for the 1965 Impala lineup was another special package, this one created for the four-door hardtop. Called the Caprice Custom Sedan option, this deal included a stiffened frame, revised suspension, black accents front and rear, and special trim and wheelcovers. The Caprice nameplate adorned a complete new model line beginning in 1966.

Still available for all Chevys, the famed 409 V-8 appeared briefly for one last run before being superseded midyear by the division's new Mk IV big-block V-8, a 396-cid beast that made 425 horses in top form in 1965. Beneath Caprice hoods, the optional 396 was rated at 325 horsepower. Both the 396 and its 427-cube Mk IV running mate were available for the 1966 Impala SS. A specially packaged SS 427 Impala debuted in 1967 and carried on alone after the base Super Sport was discontinued in 1968. Chevy offered its last full-sized SS 427 in 1969. The original Impala run ended in 1985.

Thomas
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post #4 of 9 (permalink) Old 05-31-2018, 02:00 AM
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325 horse has a cast iron intake manifold topped by a Rochester QuadraJet (new for 1965 introduced with the BBC and the TH400 transmission). The 375 horse 396 had an aluminum high rise (cast by Winters) and topped with a Holley 780 cfm 4150 series carb.

The 325 horse had painted stamped steel valve covers but they have probably been replaced with the 375 horse chromed ones by now, as virtually every one does it.

Big Dave
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post #5 of 9 (permalink) Old 06-01-2018, 10:38 AM Thread Starter
 
 
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Thanks Again Dave..

One last question..

For the 66 Impala to be consider "numbers matching" does this only include Cowl Tag/Vin Number and the Engine? Is the transmission also stamped like Mopars?

Thomas
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post #6 of 9 (permalink) Old 06-01-2018, 12:21 PM
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Originally Posted by Thomas_Toys View Post
Thanks Again Dave..

One last question..

For the 66 Impala to be consider "numbers matching" does this only include Cowl Tag/Vin Number and the Engine? Is the transmission also stamped like Mopars?

Thomas
Under federal treaty between the US and that liberal group that live north of the border all cars all cars were to be stamped with a partial VIN after 1965. The manufactures said if they had to stamp cars they would all go out of business from the added labor expense. They there fore asked for, and received a two year extension to keep from complying. The treaty was written to fight autotheft. Cars that had a factory rated motors above 300 horsepower were marked with the partial VIN from 1963 and up. This was because Corvettes and cars with a big block were in demand so car thieves targeted them.

In addition to the motor the tranny and rear end were also stamped; if it was a four speed, or a TH400 (but not the PG), or it had a 12 bolt rear (or a "P" case if made before 1965). New cars have every part (including the head lights, window glass, and even the air bag) marked with a partial VIN.

Thieves still steal cars but it is a lot easier to prove a part is stolen now which is why most are stolen and shipped out of the US.

Big Dave
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post #7 of 9 (permalink) Old 06-01-2018, 01:18 PM Thread Starter
 
 
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Thanks Dave !!
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post #8 of 9 (permalink) Old 06-03-2018, 02:52 PM
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Quote:
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Welcome to the Team Thomas!

There was a 425 horse 427 which had a solid cam used in the 427 SS: but that was a rare special option available in 1967-'69.

Big Dave
Actually Dave that started in 1966 in the B bodies. I'm not sure if there were any 1967 B bodies with it, but it resurfaced in the B body for 1968-1969.
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post #9 of 9 (permalink) Old 06-13-2018, 02:36 PM
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Quote:
Originally Posted by Thomas_Toys View Post
New User Here....

I have a friend that has a 1966 Impala SS Coupe with a 396 in it and I am thinking about buying it. He claims it has the rare 420hp/396 Mark IV engine but it looks like this engine option was only offered in 1965 correct? Lastly how do I go about identifying what 396 is in this car and whether it's a numbers matching example?

Any help is greatly appreciated.

Thomas

To answer your question directly, the assembly code on the block pad will have the assembly date as numbers, unless it has an I in place of a 1, and a 2 letter code that will identity what model car the engine was installed in and what transmission the car had. To know if it is the "born with" engine, the partial vin on that pad needs to match the vin tag on the door pillar. Some transmissions had the partial vin, especially a 4 speed or TH400.

'62 Impala SS 409 TH350
'66 Chevelle SS 496 M20
'70 Chevelle SS 396 M20
'67 Camaro ss/rs 350 PG
'38 Chev coupe street rod
'54 Chev 210 2 door
'69 Chev C10
'89 Chev R3500 roll back
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