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Discussion Starter · #1 ·
Please help decode block. It's a 396/402 from what i know. Here's casting #3969854 and t0521clb. Thanks.
 

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Discussion Starter · #3 ·
Lol

Damn big Dave I spent two days trying to find that info online.

Should've just posted it here from the get go. Right on thanks a lot.

So is it still considered a 396?
 

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Lol

Damn big Dave I spent two days trying to find that info online.

Should've just posted it here from the get go. Right on thanks a lot.

So is it still considered a 396?
Yes it is. They retained the 396 moniker on the Chevelle and the Camaro SS because it had a lot of street cred that GM wanted to cash in on. In the Nova, Impala and light trucks it was called a 402 even though it is basically the same displacement as the 400SBC that was introduced in 1970. The made up the 402 name because 402 is bigger than 400 maybe? Anyway the 402 is a big block and a 400 is a small block, but both displace just slightly more than 400 cubes.

Big Dave
 

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Discussion Starter · #5 · (Edited)
I've heard the same but I've also read that after 70 it was no longer called or considered a 396, just a 402.

But like you just said maybe it still was for the camaros and chevelles.

And were all "real" 396's 4 bolt main?
 

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There were precious few four bolt main 396 motors made and of those few that were made most have long ago been sent to the orient as scrap metal after sacrificing their all in a drag race (mostly on the street late in the evening on a weekend night upholding the honor of Chevrolet).

It is easy to tell if your motor is a four bolt from a two bolt since both engines started out with the same block. Only additional machining and the addition of the four bolt caps separate them.

If you look above the oil filter and towards the front of the motor you will see a 3/8 inch pipe plug hole in the block. If you have a four bolt main block it will have another larger 1/2 inch pipe plug hole directly above the oil filter.



These holes were machined for the oil cooler used as standard equipment in the Corvette (an option on the Camaro and the Chevelle). Without the oil cooler the front hole is reduced down to an 1/8th inch pipe plug with an adapter to give you a second tap for oil pressure.

Big Dave
 

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Of course today unless it's all original who knows, a gazillion blocks have been converted(very simple to do)to 4 bolt, picked up a core a couple of years ago at yard sale for $100, it was a 2 bolt block out of a Chevelle wagon that got destroyed in a wreck, took it home and pulled the pan and surprise, a standard steel crank 7/16 rods and forged pistons, so these days ya never know..
 

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I've heard the same but I've also read that after 70 it was no longer called or considered a 396, just a 402.

But like you just said maybe it still was for the camaros and chevelles.

And were all "real" 396's 4 bolt main?

The CLB coded big block (402/300hp) was used in the Chevelle, Monte Carlo, Camaro and Passengers cars in 1971...this code was carried over to 1972 but the HP rating was now only 240hp. After 1972 the only big block used was the 454..it was still available in certain models until 1975.

Even though Chevy started using the 402CID engines in 1970, the popular and iconic branding of the 396 engine size continued...in some models the 402 was actually branded as a "400"...adding some confusion with the 400cid small block which was introduced in 1970. There are many theories that have been presented over the years as to why Chevy went to the 402...some claim it helped with emissions...others say it was because the ban on 400cid engines in mid-size cars had been lifted...and so on. Bottom line, they were basically .30 over 396 engines...the block came in 2 bolt and 4 bolt in 1970 and only 2 bolt for 71 & 72. Though CE replacements were still available in the 4 bolt configuration.

While it is true the 4 bolt setup was the domain of the L78...there were a few early 4 bolt blocks utilized in the 396/360hp Chevelles in 1966..but, they are rare....Colvin references this in his 65-69 numbers book.

wilma
 

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If this 396/402 had been installed in a one ton truck it would have had a four bolt main block as well as a 5140 alloy steel crank. The true "Truck" block 396 was a tall deck; and was found in either a school bus or a medium duty truck (dump truck or wrecker of the era).

All tall deck blocks are four bolt main blocks, and they all use high nickel content alloy to pour the blocks, but you generally don't want one in a car (especially not a Nova nor a Camaro that has very limited amounts of room under the hood for a big block to begin with). A tall deck really complicates getting headers to fit. A tall beck raises the stock exhaust ports by 0.400 inches, and if you have a set of aftermarket AFR heads on top of your tall deck block then your exhaust ports are an inch further up and out which means you are looking at custom headers (because AFR raises the exhaust ports on their rectangular port heads 0.640 inches).

There are few four bolt main blocks regardless of displacement (396-402-427-454) most were two bolt because a two bolt will hold up to 650 horsepower easily, and there hasn't been but two big block motors that have been factory rated at over 600 horsepower. Four bolt mains are a racing thing, or in the case of the Corvette, a matter of prestige for the Doctors and bankers that buy a Corvette to compensate for missing their youth by spending their adolescence studying instead of street racing. Four bolt mains have the same advantage to them as does their Rolex compared to the $36 dollar digital Timex divers watch that you or I might buy because it is sweat proof (not that a Doctor or a banker ever works up a sweat at work which is why they can get by with a Rolex).

Big Dave
 

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Discussion Starter · #11 ·
Great info fellas thanks.

I've decided not to get that block. Looking for a 396 with a build date between 66-69.
 

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Discussion Starter · #12 ·
Im going to look at a 396 off of a 66-67 chevelle tmrw # 3855961.

Correct me if wrong but those came with 325 HP right?
 

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Great info fellas thanks.

I've decided not to get that block. Looking for a 396 with a build date between 66-69.
That is a pretty wide spread on the dates for a numbers matching car. Most numbers matching cars have a block and heads casting date within four to five weeks of the car's actual build week as found on the trim tag. That is unless there was a labor strike that car production year; then it could be off by as much as six months, because the factory stock piled motors ahead of the strike to build cars with SCAB labor and the supervisors actually getting dirty also working the line assembling cars.

Another factor to consider is that in the 1965 and 1966 year 396 and 427 big block has an oil groove cut into the cam itself. In 1967 and up production years they cut the groove into the cam journal behind the bearing. It means that with a 1967 and up BBC you have to exercise a little more effort in getting all three oil feed holes to line up with the holes in the cam bearing, but that is usually a problem for your machinist; unless you want to install your own cam bearings. This also means that when you buy an aftermarket cam you have to tell the cam grinder to carve the oiling groove into the cam or you will not get any oil at all (mains and the lifter galleries will be dry). So without that $75 dollar groove you can loose your whole motor.

After the 454 was introduced in late 1969 (not as a production motor in a car, but as an over the counter service part) almost all 1969 and later blocks have the relief grooves to clear the 454 rod bolts already cast into the bottom of the block. That was about the last significant change order that I can think of as far as blocks go so 1969-'73 blocks are all about the same. In 1974 the 454 was still offered in the Corvette but after the 1973 gas crisis hardly anyone bought one. So most 1974 through 1990 Mark IV blocks are all out of three quarter or one ton trucks. This is fine for the block but after 1973 all production BBC heads are what is less than affectionately known as a peanut port head.

If you are shopping for a BBC engine to build I would yank one of those and recycle the heads. A 396 decal looks just as at home on top of the air cleaner of a 454 as it does on top of a 402 or a 396. From a quick look from the outside without putting it up on a lift, it is hard to tell the difference.

Big Dave
 

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Im going to look at a 396 off of a 66-67 chevelle tmrw # 3855961.

Correct me if wrong but those came with 325 HP right?
Chevelles and Camaros came with a 325 horse 396, a 350 horse 396, or the 375 horse 396 motor as an option. The 325 and the 350 had a hydraulic cam and passenger heads, with the 375 being the only 396 motor to use the rectangular port heads and a solid flat tappet cam. By the way Hi-Perf rectangular port factory heads are WAY TOO BIG for a 396 displacement. Wait until you are pushing 496 or more cubes before you even consider anything bigger than the PASS heads that came on the 325 and 350 horse motor.

Just as a "Fer Instance" the factory engineers installed an oval port (230 cc intakes) head on the ZZ502-502 horsepower with 2.30 intake valves and 1.88 exhaust valves opened by a hydraulic roller cam. Just about every one I know thinks that the 500 cube line in the sand is the limit for the bigger heads, a lot of 540 motors still make serious power with the PASS oval port heads when ported a reworked to accept the biggest valve you can stuff in the chamber (to go bigger you have to move the valve centerline which involves moving the port as well so that only happens on new cast aluminum aftermarket heads designed and cast to run the bigger valves).

Big Dave
 

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Discussion Starter · #15 ·
Yea Im aware of the grooves on the 67's.

As for the HP ratings how would one find that out? I assumed that casting # meant 325 horse?
 

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325 and the 350 differed in the piston's static compression and in the specs on the cam otherwise it was the same engine. Both used the same block. Big Blocks like ignition timing (an indication of an inefficient head), and compression. EPA says they can have neither, so they were effectively gutted in the early seventies.

Big Dave
 

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Im going to look at a 396 off of a 66-67 chevelle tmrw # 3855961.

Correct me if wrong but those came with 325 HP right?
That block was used for the 65-66 passenger cars w/325hp...and the 66 Chevelle with either 325hp or 360hp. This was basically the first production big block for the low horsepower applications. A different block came into use late in the 66 model year (#3902406) it replaced the #961 block.

You need to check the deck stamp on the pass. side front to determine the exact application for the block you are considering...there will be a two letter code w/assembly date....that will tell you what car it came in and the horsepower rating. There is also a casting date on the right lower side of the block...that may be helpful if the pad has been decked.

The main difference between the 325hp version and the 350/360hp was the camshaft. They both used the same cylinder heads and had the same compression ratio of 10.25 to 1. The early low horse motors all had a forged crank...later versions had a cast nodular iron crankshaft.

***here is the most important part about buying an engine block that is out of the car...you can't see the critical issues with your eye...you need to have it checked professionally...I wouldn't buy it unless the proper "pre-flight" can be done...if the seller objects...walk away! If the seller agrees you will still need to discuss who pays to have it "checked"...I always offer to split the cost if it reasonable...but, it shouldn't all be placed on you. Folks who sell engine parts on a regular basis will normally have these things done before offering items for sale.

If you are considering an engine block to build from be sure you have magged and checked for any problems...you also need to know if it has been bored out at some point in the past... if so, you need to be sure there is still adequate cylinder wall thickness. This is done by having a sonic measuring test of all the cylinders. A competent machine shop can perform these services for you.

There are lots of BB motors around...take your time and make a good choice the first time.

Wilma

***I wasn't sure if you were buying a bare block or a complete engine...if it is the latter...be sure to check all the parts you are considering. If the motor is all together this becomes a little harder.
 

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Discussion Starter · #18 ·
right on tom thanks.

ok so i took a look at the block. It looked good but the only thing that through me off was that one side said hi perf pass and the other side said hi perf truck. Any one know whats up with that.
? I assumed these blocks were only used on cars.
 

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Most Chevy big block motors had the words Hi-Perf or Hi-Perf Pass or Truck on the casting. It will typically be found in the bell housing area..or in the timing chain area in the front. The generally accepted theory is that these stampings denote a passenger car or light duty truck application...Chevy also made "tall deck" BB motors, which would have a different casting mark...Many cylinder heads had similar wording...all of this really means very little. Some truck applications had blocks with higher nickel or tin content...usually noted by the numerals "10"..or 10-10.

For your purposes the only thing that really matters is the pad stamp...that will tell you what vehicle the motor came in...though I really don't see what difference it makes. It is either a 2 bolt or 4 bolt...all the rest is conversation....beyond that, the items I previous listed about the integrity of the block are what you need to verify before pulling the trigger.

Hope that helps...wilma
 

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The molds that the blocks are poured into are basically all the same with the exception of the truck block (it is a half inch taller). They change out the casting number and the date and shift code every time they pour a different block, but ignore those casting identifiers after they have changed it as all of the blocks in that production run poured during that shift are going to be the same. The only casting that constantly changes is the clock code which is automatic. It is an actual wind up analog clock has an hour hand that moves as the shift progresses. Hi-Perf and PASS are supposed to be there; I am not so certain about the Truck block ID casting mark being included in a passenger car block run.

It doesn't hurt anything as the only reason it is cast into the block is so that the person that inspects the block to verify it is a good casting and that most of the sand has indeed been beaten and prodded out of the water jackets. After he knows he has a good casting he will take a crayon and swipe over the casting mark on the block that corresponds to the build order that it was made for.

The next operation is the machining of the block. The first machinist to touch the raw casting drops the block onto a milling machine to dress up the lugs on the side of the block. This is done before the horizontal milling machine using the square lugs on the side of the block to locate it carves out the main cap registers that the main caps sit in. It is then moved again to a vertical mill where according to the crayon marks highlighting the casting mark Hi-Perf, Truck or PASS; he will drill and tap the holes to bolt on the main caps. Once the block has the main caps on it can be line bored and honed.

All following machining operations will take place based upon the centerline of the crank or the machined face of the locating lugs cast into the block; depending upon how critical the machining operation is. These blocks were machined long before the days of seven axis CNC mills and they passed from work station to work station requiring constant set-ups. Because the block has to be repeatedly set up every time another machining operation occurs errors frequently show up in the machining process (such as lifter bores not perpendicular to the cam tunnel centerline, or locating dowel pins and bolt holes that attach the bell housing not being concentric with the cranks centerline.

GM kept a huge quantity of records on everything they did for quality control (the only leverage they had over the unions). Every time you touched the part from raw casting to being bolted onto the car GM knew who had touched it and what they had done to it. (they were equally fussy with outside vendors, and the parts that they supplied). Unfortunately just like the build sheet all of these records went into the trash as soon as the warranty period expired. This limited liability in law suits ("What car? Did we build a car?") and relieved the quantity of paper records stored in their warehouses.

A lot of the confusing marks that feed urban legends cause people make up stories about what they see but can not explain. (kind of like our ancestors having fire gods and water gods and myths of monsters explaining dinosaur bones).I find reading internal engineering change orders and memos to sales managers that former employees kept and have posted on line, or from dumpster diving fans of a certain GM product who lived in Detroit much more enlightening.

Big Dave
 
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