Jakes64

I have a big block in my 66 vert. Built and installed in 2007 by previous owner. Block casting #3869942. According to my research this could have 2 bolt mains or 4 bolt mains. Is there a way to tell which I have without having to pull the pan? Found some pics showing different size oil pressure pickup holes over the oil filter boss as an indicator. Big hole = 4 bolt, smaller hole = 2 bolt. Is this right? Is there any other way to tell?

Thanks for the help.

Nowhere Man

What is stamped on the stamp pad

65 Pro Vette

All the 4 bolt blocks have 2 oil presser fittings, one large one smaller about 1in apart. (the ones I have) The 2 bolt blocks have one .

AZDoug

To clarify teh post above:

Above the oil filter boss, if you have two holes, about 1/2" pipe thread, that have threaded plugs in both of them, it would be a 4 bolt. The plugs would probably be made to remove with allen wrenches.

Doug

rongold

Here is a picture of the oil filter area of a 4 bolt block. The left hole is for the oil pressure gauge (with a reducer fitting), the center hole is for an oil cooler, and the hole slightly to the right and above the center hole is for the clutch cross shaft pivot ball. ONLY the 4 bolt blocks have that large center hole--the 2 bolt blocks have only the other 2 holes.

kenba

I believe it was for a oil cooler line.

Jakes64

OK, should have included more info on first post. Block is 3869942. NOM-BB, engine was built and installed by previous owner in 2007. Stamp pad is blank.

Following pics I found in another post showing the area above the oil filter boss. These blocks were not ID'd with block codes but are BB's
.





First pic is ID'd as a 2 bolt. Middle hole is smaller than middle hole in the second pic which is ID'd as a 4 bolt. Far left hole has a pipe plug installed in both blocks but is partially hidden in the top photo. Top photo also shows the oil pressure feed installed in the middle hole. Someone said the far right hole is for the end of the clutch Z shaft but on the top pic the clutch shaft is to the left of the pipe plugged hole just above the freeze plug
???

1. Is this a correct way to tell the difference between 2 bolt and 4 bolt?
2. Is there any other external differences that will help identify which block I have?

59BlueSilver

Is this true also for a sbc 350?

JohnZ

Yes. The photos in posts #5 and #6 and your second photo show typical 4-bolt machining; your first photo shows typical 2-bolt-machining. The block is identified by the casting number and the type of machining you find above the oil filter.

This only applies to big-blocks; there's no way to identify a 4-bolt 350 without dropping the oil pan.

Jakes64

Thank you again JohnZ for your, as always, knowledgable input.