I am looking into purchasing a date matched 396 for my 1966 Chevelle SS and was wondering if the 396 360 HP engine is a 2 bolt main or a 4 bolt main? I know there are two blocks for a 66 396, 961 and 962 but I am not sure which one is the 4 bolt main or maybe both are. Also, did the 360 HP engine utilize a Holley carb?

Thanks!

According to Chevrolet by the Numbers, the 961 engine was used for "all" 360 hp versions and was only available in a 2 bolt version. Then to confuse matters, a note also says that the 962, all 4 bolt blocks, went into "some, if not all" 360 hp cars. Most likely, most got the 961, while some got the 962. Maybe somebody else has accurate numbers on the split.

It appears that the 360 hp 4 speed cars came with Holley carb. list #3419 or 3409 if an A.I.R. car. Automatics came with list #3420 or 3608 if an A.I.R. car.

David

I have a 66, EF code, 961, date code L 65, 2 bolt block. From my research the 962 block was the 427, 4 bolt block while the 961 was the 396, 2 bolt block. could be wrong just my .02 from the research for my block.

I have a 66 962 4 bolt block that was 360hp. There are also some 961 4 bolts. But I would think they would be rare. 66 360 hp could be either 2 or 4 bolt.

Mine was a 2 bolt but even back in 66 there were rumors that some went through as 4bolts.

From my research the 962 block was the 427, 4 bolt block while the 961 was the 396, 2 bolt block.

I had an EG coded 962 4-bolt 396 block,

I think the 427 4-bolt was the 942

I was told there were even 961 4-bolt motors for some L78s (EG coded)...

according to mortec the 961 could be a 2 bolt 427 in 66. Jason.

Why would they use either block instead of going with one or the other in the first place? I just cant see this as something random but it almost sounds like it in a way.

The short version is that if they were in a position to stop the engine line AND they had something handy that was at least as capable as the bare block they "needed' substitutions were made. Way back then not a lot of the motors were opened up and analized to death as faras the casting numbers like they are being opened up and numbers checked today. The "incorrectness" of some of the factory substitutions could easily have gone unnoticed. Just like cars that came with 12 Bolts but "should not have had 12bolts". If the inventory control system had a 12 bolt and the assembky line would have stopped to wait for a 10 bolt.....you guessed it in went a 12 bolt.

I suppose that a lot of folks will get all stoked up about such a wild accusation but how many cars arrived from the factory with rear gears other than what the customer ordered or options that were not supposed to be in the car. The dealer just talked the customer into paying for the upgrade or the dealer kissed off the added cost of the "wrong" part to keep the customer happy. Back in those days there we no Big Brother Industry Watchers lokin into every carto make sure that all the EPA controls or that all the correct options were on the car.

Some of the Corvette Urban Lore says that there are "special" Corvette blocks that will bore farther than the same block casting number cast for use in an Impala or a Chevelle. More jibberish I think. Might indeed be that some blocks will bore further than others but the idea of a thick walled 9XX 4 bolt block just for Corvettes and the exact casting number in a thin walled version headed for a Chevelle? Not likely. Corvette guys seem to actually want to believe this kind of stuff...makes them feel better payng big dollars for Corvette only parts I guess.

Some of this "specification certification" gets kinda far afield and I am getting far afield with this discussion.

In closing I would bet there are (were) 4 bolt 360 HP 66 Chevelles out there...just seems too unklikely that the factory got the bill of material (2 bot versus 4 bolt in 360HP) right every single time.

Great information, thanks all of you for your responses!!!

My '66 SS396-360 came with 2-bolt mains, a small Holley on a cast iron intake, wide-ratio 4-speed, and 3.73 gears. It just flatout hauled ass and I beat on it for years.

Wish I could have it back!

Randy

I have to agree that some 360 horse versions in '66 were 4-bolt mains while most were 2-bolt.

I seem to remember reading a dealer memo via the old 'Chevelle Trivia' that Tom Wilson used to post. It advised against using the replacement 4-bolt long block assembly to replace the 4-bolt block 360-horse engine because by that point the 4-bolt block was only used with the 375-horse version. On that fitted long block assembly, piston clearance would be an issue with the closed, oval port heads combined with the domed pistons.

WRT the early 396s, namely the '65 versions, they had the ability to be bored out to 427s. 7 liters is a key displacement in racing (427 c.i.d.) and there was noise being made at the time of a 6.5 liter limit in NASCAR, which is 396 c.i.d. For 1966 the 427 was a reality and the 6.5 litre displament limit did not materialize, and so the 396 blocks were cast with revised water jackets, reducing the weight and iron content. That also meant that it was very iffy to bore a revised casting 396 out too much.

I just found a EJ coded four bolt 396 chevelle shortblock if you know anybody who wants one....standard and complete...late 65 dated...

my 66 396 with date stamped 2 66 on the rod bearings was an EGH stamp. came with the holley intake and carb. Two bolt main.

Im to understand that the early 396's were indeed a thicker wall, alowing the MFG to bore it into a 427, I recall reading that on mortec.

1966 - 961 block with 396 or 427, this must be the early 396's.

with the freeze plugs removed. I "cant" get a pencil to fit between the clyinder bores.