Is a 66 67 vintage 396 a keeper? - Impala Tech
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post #1 of 27 (permalink) Old 09-18-2013, 10:25 PM Thread Starter
 
 
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Is a 66 67 vintage 396 a keeper?

I just bought a 1967 Impala SS. It's build sheet calls for a 275hp 327, but sitting in its engine bay is a casting number 3855961 big block this checks as a 66-67 396. The 396 runs but has enough blow by that it should be refreshed.

I am wondering - since I am looking at engine work either way should I sell off the 396 to fund a small block build or build the 396?

Is such a 396 valuable to someone with say an SS396? or is it just another big block laying around.

I hope this isn't considered as an ad for the 396 - I really need input as to the costs and values involved - I am a long way from "selling" if I ever do
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post #2 of 27 (permalink) Old 09-19-2013, 03:02 AM
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Two issues with a 1966 396. First is that it requires a grooved cam. If you buy a replacement aftermarket cam with either hydraulic or solid roller lifters (don't even think about a flat tappet cam) you have to add $50 to have the rear journal grooved or the top end will not get any oil. The block was redesigned in 1966 to make it into a thin wall casting (the 1965 and half of 1966 396 blocks can be safely bored out to accept 409 size pistons at 4.3125 inches because Chevy hadn't decided what stroke they preferred to use by time it went into production).

This is a very important distinction (the 1965-'66 thick core blocks are very rare) as most gave their lives racing, or were recycled by people who past over the small bore 396 in favor of the 4.250 inch bore 427 when it came out in 1966 (not realizing the bore potential of the first Mark IV blocks cast). By the early part of 1966 the newer thin wall castings had come out with a new casting number to reflect the change to the cylinder wall thickness. It was revised again later in the year to reflect the use of a grooved cam bearing and changes in the machining process to feed oil to the lifter galleries.

Your block is most likely the thin wall casting due to it's age (the 1967 production year). which leaves you with a 4.094 inch bore boat anchor. You can build a SBC 400 that has the same bore and stroke (near enough anyway) and will make more power for less money. Even if you are down in power output from a max effort 396 the SBC will still beat it because it has 280 fewer ponds to drag around.

A 396 is a mistake. A 454 is a good start, but to make power with big block heads you have to build a big, big block. Most build a 496 out of a stroked 454 bored 60 over. It looks just like the 396 you have now and costs about the same to build as your 396 will to rebuild (only difference is the price of the 4.250 inch stroke crank). Slap on some 396 decals and you can not tell them apart until you line them up side by side. Then the difference is obvious.

You can put 396 decals on a SBC 400 and argue that the only difference between the two motors (besides the 280 pounds of cast iron) is that the 396 has a 3.76 inch stroke crank and the 400 has a 3.750 inch stroke, resulting in the two cubic inches difference in displacement between the 402 big block and the 400 cube small block. Starting in 1970 the 396 received a 0.030 inch over bore at the factory to increase the bore size to 4.125 inches, but retained the 396's decals because of the street cred the big block had achieved at that time (in the B-body car line they called both the big block 402 and the small block 400 a 400 to confuse car owners).

Big Dave
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post #3 of 27 (permalink) Old 09-19-2013, 07:50 AM
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If your not into high HP motors and spending large amounts of money. I would rebuild the big block. If it was already installed with all the pulleys and brackets , Id just go with what you have.
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post #4 of 27 (permalink) Old 09-19-2013, 08:20 AM
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Like to see a copy of the build sheet for our files.

Paul

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post #5 of 27 (permalink) Old 09-19-2013, 09:50 AM
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There are some guys out there who will know for sure, but my guess is that block does not require a grooved cam But even if it did, $50 is incidental in the big picture. Again I find myself fully agreeing with Larry on this.

Mike

1965 Impala SS 396
1967 SS427
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post #6 of 27 (permalink) Old 09-19-2013, 07:14 PM Thread Starter
 
 
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Thanks all for the input so far - I like having some like minded guys (or gals if it applies) around to bounce ideas off of.

Paul if you pm me an address I'll try to get a copy of the build sheet on the way to you.

I'm still on the fence, but I do live only two blocks from a locally legendary SBC builder - Cassell Engines.

Maybe I'll start looking for a 454

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post #7 of 27 (permalink) Old 09-19-2013, 10:14 PM
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3855961 is a 65-66 396. It will have the grove for the rear cam bearing.
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post #8 of 27 (permalink) Old 09-22-2013, 07:18 PM Thread Starter
 
 
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Quote:
Originally Posted by dadstoy View Post
If your not into high HP motors and spending large amounts of money. I would rebuild the big block. If it was already installed with all the pulleys and brackets , Id just go with what you have.
If I rebuild the 396 to basically stock specs and run it with a stock (maybe a shift kit) TH400 and 3.55 gears would it be able to get out of it's own way?

IOW could it run alongside a stock 1995 Mus$%ng GT auto - my minimum level of desired performance (never mind cornering)?
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post #9 of 27 (permalink) Old 09-22-2013, 08:06 PM
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You are talking about a 3,785 pound car (mass) based upon the curb weight of a BBC 1967 Impala, and at best on a good day you can get about 360 horsepower out of a 396 (horsepower is a measure of force). According to our old pal Newton, he was able to predict quarter mile ET's back before the automobile was even invented by this little formula "F=ma". It is still used to predict Elapsed Times in all of the simulation programs that rely on drag racing a car.

All you have to do is figure out what your buddies Mustang weighs (that information can be found on-line if you look up the shipping weight from Detroit) and then plug in his horsepower (that will depend upon whether he has a 289, a 302, a Boss 302 a 351W or a 351C under the hood as all of these motors have the factory rated horsepower posted as well as common hop up combinations are making) then solve for "a" or the rate of acceleration.

My money is on the mustang because odds are it is going to be a lot lighter with about the same level of power.

Now if you want to make it interesting build a bigger bore big block than a 396. I don't know of anyone who is competitive with anything smaller than a 540 cid BBC as there is a lot of cast iron up front, and a SBC makes a lot more power per cube because of having much more efficient heads.

This assumes you want to race heads up. If you don't mind being spotted a few seconds head start you could bracket race the big B-body and probably be very competitive, as it will be much more consistent than the Mustang ever will be, even if it is a lot slower. I used to drive the owner of the local drag strip crazy as I raced my little 194 cubic inch Chevy II against his Hemi powered 'Cuda and beat him every week because it ran dead on 18.94 and never varied from that time. I got a six and half second head start and he would either break out every week or I would beat him to the stripe. Drove him nuts spending all that money on a factory hot rod only to loose to a stone stock six banger week after week.

Big Dave
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post #10 of 27 (permalink) Old 09-23-2013, 06:53 AM
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Modern cars have the big advantage of electronic fuel injection. That means that they get the best of many categories. If you are talking about a flat out drag race it is going to be expensive to beat the Mustang GT. But if what you really want is seat-of-the-pants performance, then the mild 396 would be cheaper to build than a small block and a lot cooler. The 396 with the oval heads and the proper cam will make a bunch of low end torque that you can feel at a much lower RPM than the small block. Since you have an acceptable block, use it.

Mike

1965 Impala SS 396
1967 SS427
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post #11 of 27 (permalink) Old 10-04-2013, 07:51 PM Thread Starter
 
 
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An update

I may have found a 454 block (1974 from a motor home - 4 bolt!) and 2 336781 heads .

They are at the engine builder being checked.

If they are OK - I am considering a 496 rotating kit for it - but I am torn: should I use the aftermarket cast crank, better than stock I beam rods w/arp 7/16 bolts and Hyper pistons or spring almost a grand more for the 4130 crank, H beam rods, and forged pistons?

Also I am eye balling a Lunati Vodoo hyd flat tappet cam (10110703) with 268/276 advertised duration and .542/.554 lift

or should I go with a bigger cam (a roller then) to get the lope and midrange giddy up I want on the street?

The car is heavy, and it will never see the track or even a "serious" street race - most likely the occasional parking lot burn out and a very rare "beat down" laid on an uppity ford at the stop light.
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post #12 of 27 (permalink) Old 10-05-2013, 03:38 PM
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Cast crank and stock rods with ARP 7/16 rod bolts is fine for your application. Put the extra money into a good set of heads. A 496 is pushing the magic break even point for larger rectangular port heads on the street (though no one uses rectangular port heads as the corners are all dead air with no flow, so a slightly smaller Oval port will out perform the older rectangular heads and being made of aluminum saves you 84 pounds (noticeable when leaning over a fender to install a cast iron BB head).

Finally unless you are willing to spend $8.90 a quart for Brad Penn, or Joe Gibb's Racing motor oil you can not use a flat tappet cam because motor oil (with the exception of those two refiners) will not have enough DZZP in it to protect your flat lifters from excessive wear. You have to have a roller cam with modern motor oil.

Big Dave
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post #13 of 27 (permalink) Old 10-05-2013, 11:43 PM
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I didn't read every word of every reply above, but I dropped in a '67 396/325 with a 375 Horse Cam, Solid Lifters, Edelbrock Hi-Rise, 750 Holley Dual Feed with Hooker Headers along with an M-21 Muncie 4-Speed in my '62 Impala. The engine ran great and sure was plenty fast.

Even though I'm basically a Small Block fan, that 396 was one of the best engines I ever had.

Bill
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post #14 of 27 (permalink) Old 10-06-2013, 02:32 PM
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If you liked the 396 then you would have loved a 454 with the same changes made to it. The L-78 375 horse 396 cam was good, but the L-88 427 cams is even better. Same duration numbers, but with even more lift. It used a very aggressive cam lobe that used to eat lifters.

Which is why I learned a long time ago that roller cams are a lot cheaper than any flat tappet cam you can buy. Solid rollers are the only way to go in a big block because the valve train is so heavy to start with the added weight of a hydraulic roller tappet really complicates your control of the valve train above five grand.

With a solid roller you can run a rev kit in addition to stiffer springs that will allow your big block to rev just as high and fast as a small block. You have got to love those 11,000 RPM shifts they are making now with 500 cubic inch big blocks in pro stock. Just last year it was a 10500 RPM shift but every one is pushing harder to stay competitive.

Big Dave
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post #15 of 27 (permalink) Old 10-09-2013, 11:39 PM Thread Starter
 
 
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Well, today I settled on specs with the engine builder - 1/4 in 4130 stroker with .060 overbore forged pistons (10:1 CR) & H beam Rods (496 Cubes). .262/.268 hydraulic roller cam, roller rockers, good springs, 10 degree locks etc. Ported and polished 336781 heads with 2.19 intakes and 1.88 exhausts by Manley with adjustable guides.

Built with 150 - 250 nitrous in mind for the future

My engine builder has basically the same engine (but 427 cubes) in his 67 impala and it runs 12.6 to 12.8 all day long (10.50's on 250 spray) it dyno's at 465 - 475 RWHP - he thinks I will have about 90 - 110 more HP than his and should be able to drop into the low 12's NA and perhaps 10 flat if I hit it with 250 spray.

Oh, baby!
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post #16 of 27 (permalink) Old 10-18-2013, 02:57 PM
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Rick, welcome from Spokane!
Seems like you will have quite the setup and I shouldn't have any trouble finding you on the streets next summer. Maybe I missed it, but can you point me in the direction of finding some pics of your car?

Love the 67's! (Almost as much as the 65's ;-)
-Nick

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post #17 of 27 (permalink) Old 10-18-2013, 08:32 PM Thread Starter
 
 
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Hi Nick

Yea, you won't miss the RED 67 SS496 Impala and you should be able to hear it coming.

I will be putting more pictures on my bloggy thingy - link in my signature.

What color is your 65?
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post #18 of 27 (permalink) Old 10-18-2013, 08:39 PM
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Awesome!
My 65 is white. I don't have a grumbling big block, but it doesn't look like a honda civic either.



-Nick

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Classic Nation car pictures.

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post #19 of 27 (permalink) Old 10-20-2013, 01:59 AM Thread Starter
 
 
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I love the stance of your Impala - What size wheels/tires are you running? is the suspension lowered? If so how did you do it?

Sorry for all the questions - but I do like the look
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post #20 of 27 (permalink) Old 10-22-2013, 01:01 PM
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Quote:
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I love the stance of your Impala - What size wheels/tires are you running? is the suspension lowered? If so how did you do it?

Sorry for all the questions - but I do like the look
Thanks. Wheels are 18/20 with 235/35/18's up front and 255/35/20 in back. In this pic, I have 2" dropped spindles up front and 3" lowering springs in the rear.

Since this, I have decided on air ride, and I have the rear completed, as well as the tank and plumbing. Now I just need to install the front bags and I will be all set!

-Nick

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post #21 of 27 (permalink) Old 10-31-2013, 08:24 AM
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Quote:
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Awesome!
My 65 is white. I don't have a grumbling big block, but it doesn't look like a honda civic either.



-Nick
That's a sweet ride.
Great stance n wheels.
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post #22 of 27 (permalink) Old 11-01-2013, 04:53 PM
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Quote:
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That's a sweet ride.
Great stance n wheels.
Thanks man!

OCD Customs
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Classic Nation car pictures.

1965 Impala SS
6.2L LSX with 4L80E, 3.73 Gears, Disc Brakes, Air Ride
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post #23 of 27 (permalink) Old 12-03-2013, 01:33 AM Thread Starter
 
 
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Getting my 496 tomorrow



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post #24 of 27 (permalink) Old 12-05-2013, 10:44 AM
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Those 781's flow very well, especially with the larger valves. The company I work for builds a 496 with those heads, a flat tappet cam and they make 480 hp and near 600 ft lbs of torque.

I just swapped a set of 781's on my '70 Caprice's 454. I lost a full point of compression over the oval port closed chamber heads, 10.25 to 9.25, but actually gained some power. Mine still have the stock 2.072 valves in them too.

1965 Impala SS, 383, 4 spd
1970 Caprice LS-4 454, TH400
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post #25 of 27 (permalink) Old 12-06-2013, 01:40 PM Thread Starter
 
 
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Quote:
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Those 781's flow very well, especially with the larger valves. The company I work for builds a 496 with those heads, a flat tappet cam and they make 480 hp and near 600 ft lbs of torque.

I just swapped a set of 781's on my '70 Caprice's 454. I lost a full point of compression over the oval port closed chamber heads, 10.25 to 9.25, but actually gained some power. Mine still have the stock 2.072 valves in them too.
I expect them to be plenty for a hot street machine.

My engine builder (Jeff Cassell) says the comp ratio of mine is 10.25 and he expects it will move my 67 pretty well (tee hee).

I will lose a fair amount of power through the TH 400 - but the torque multiplication at launch should be good on the street.

We will see
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