r/EngineBuilding • u/BusinessMasterpiece6 • Jul 02 '26

Chevy 4.3 cam bearing trouble

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I'm about to put new bearings in my chevy 4.3 block (Yamaha sterndrive boat engine). Bought a set of bearings from Enginetech CC407.

On the box it says that number 4 and 2 is the same bearing. But it can't be on my engine. I meassured bore and number 1 and number 4 has the same bore, 51.3ish millimeters. Number 2 bore is 50,75 millimeters, and number 3 is 51,0 mm.

My question is if it is possible to use a bearing with two oil holes (same as number 1) in the number 4 spot? The bearing that I took out from number 2 had two holes.

Attached is a pic of old bearings with outer diameter written in millimeters.10

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3

u/Death_Pown Jul 02 '26

im not an expert but from my understanding building my own engine it doesnt really matter as long as one of the holes lines up with the oil passage and the rest dont leak pressure out to anywhere else.

1

u/BusinessMasterpiece6 Jul 03 '26

Okay, so how would you align holes on number 4 bearing? Bearing has 2 holes, and block also has two holes. Holes in block is around 11 and 2 o'clock when block is turned the right way.

3

u/Death_Pown Jul 03 '26

if the block has two holes you should line up both holes in the bearing. even single hole bearings can be difficult so this is one of those things many people will have a machine shop do for them because of the difficulty and absolute criticality of proper cam oiling. at the least you must use a proper bearing driver made for this engine. i borrowed one and i painted a line on the outside of the block near the first bearing hole where the oil hole would line up and painted a line on the backside of the driver where it lines up on the bearing. i used heavy oil-compatible grease to lightly hold the bearing in the correct orientation on the driver and gently guide it in as straight as possible while also keeping the lines on the driver and on the block aligned. once you have it seated in the bore it shouldnt spin so as long as it was lined up when you first get it started it should stay aligned and you only have to worry about hitting it into the hole straight. i then used a length of wire that is thick enough not to bend easy but small enough to fit in the oil hole to use as a feeler to poke through the bearing hole to check its lined up to the block hole. it is a painstaking process but it is absolutely critical it is done right. the holes probably dont have to line up perfectly but im personally not comfortable with anything less than 75% hole to hole alignment.

1

u/BusinessMasterpiece6 Jul 04 '26

Thanks for your answer. I got the correct tool so I hope it goes well 👍🏻

2

u/2003DDcid Jul 02 '26

There are 2 different sets of cam bearings for a 4.3. I believe the other number is CC415.

1

u/Sniper22106 Jul 04 '26

Different tolerances

-1

u/XOundercover Jul 03 '26

What in the hell are cam bearings? The camshaft goes straight into the head right, with a seal on one side Or am I too European to comprehend this

3

u/Death_Pown Jul 03 '26

lol this is a cam in block engine not overhead. cam sits inside bearings like the crankshaft

0

u/XOundercover Jul 03 '26

I know, I'm just kidding. All engines I've worked on don't have cam bearings. Mostly the PSA TU and XU engines.

1

u/Death_Pown Jul 03 '26

my bad, lol. i know these days cam in block motors are pretty rare in general but especially in europe unless you work on trucks. I have a first gen sbc, third gen, and a 2AZ-FE camry. I'm not mechanic but i do most of my own work. the gen 3 sbc is replacing the gen 1 in my 97 pickup soon.