Doug996InKC

Over the weekend, I made some more progress on my 3.4L to 3.8L rebuild, by installing the valvetrain components and performing the cam timing. Can someone help verify the final intake cams' "notches" are correct? I'm second guessing myself because both intake cam notches are facing the cam cover. Here are the steps I took:

Bank 1 (Cyl 1-3)
1. lock crank at cylinder 1 & 4 TDC, visually verified both piston 1 and 4 are "at the top" by viewing through spark plug hole (one of those will be the TDC overlap, the other TDC compression)
2. assemble new chain onto intake and exhaust cams based on cams' divets (assured 6 links between, meaning 1 & 7 "on" above divets, all per Jake's rebuild course book)
3. install assembly assuring intake cam notch facing up
4. perform all the other steps

Bank 2 (Cyl 4-6)
5. rotate crank 360 degrees
6. same as #2 above
7. install assuring intake cam notch facing down
8. same as #4 above
9. rotate crank 360 4 times

Observations
Intake notch facing cam cover for both banks (correct?)

(On a side note, you may notice from the photos that the exhaust sprocket for bank 1 looks to be "off" a tooth (bolts aren't in the center). However, when I rotated the sprocket, the bolts ended up closer to the right side of the opening, never in the middle. I remember during disassembly, the same, so I suppose everything okay? I don't recall the cam deviations before disassembly, but I do remember the bolts lined up similarly as they do now.)


bank 1, intake cam notch facing cam cover


bank 2, intake cam notch facing cam cover

Ahsai

I believe so but the ultimate test is just rotate the crank and feel compression on each cylinder one by one. They should provide compression in the firing order 1-6-2-4-3-5. This test will catch and reveal the "forget to turn the crank 360 degrees" mistake. I use a TDC whistle tool attached to the spark plug hole but you probably can even feel the compressed air by hand.

Ahsai

Oh, another way is the cam timing tool should only be able to fit one bank at a time. Rotate the crank 360 and the tool should then fit the other bank.

Doug996InKC

Confirmed! Thanks for the suggestion. I also found some notes regarding the position/direction of the smaller portion of the exhaust cam "half moon" ("small segment" in Bentley Manual vernacular). Here are some photos of the exhaust cam ends for each bank, with the smaller segment marked in blue.

State X
Bank 1 (Cyl 1-3): "small segment" faces the head cover, the timing tool fits, and this is the bank that should be timed
Bank 2 (Cyl 4-6): "small segment" faces the engine block, the timing tool does not fit

Rotate Crank 360 Degrees (Transition to State Y)
Bank 1 (Cyl 1-3): "small segment" faces the engine block, the timing tool does not fit
Bank 2 (Cyl 4-6): "small segment" faces the head cover, the timing tool fits, and this is the bank that should be timed

Photos below represent "State X".


bank 1, small segment faces head cover, time this bank


bank 2, small segment faces engine block, do NOT time this bank

Ahsai

Yup. Make sure you rotate the crank many more times, recheck timing and make sure the timing doesn't change a bit.

1ricardo

Hello,

I sent you a PM, I wonder if this notches facing both the cam covers are correct? I just assemble my engine and the cam notches end up bpth facing the cam covers and now I'm doubting myself
I'm 99.99% sure that I rotate the engine 360 after timing the bank 1 and then I timed bank 2
BUT, if I made bank one and install the cam assembly on the head with the notch facing the cam cover ( and by the way the divet on the sprocket and this notch are aligned ) and then I rotate the engine 360 degrees, the notch on bank 1 should be facing the block ( since its a 2:1 ratio between crankshaft and cam shaft ) no i'm installing bank 2 cam with again the divet/notch up ( facing the cam covers)
They should end up 180 degrees apart from each other ( when bank 1 face the cam cover bank 2 face the block and vice versa)
The small and half moons on the exhaust cams are 180 apart from each other, the timing tool does NOT fit both cams at the same time.
I does fit bank one, then I rotate the engine 360 and now the tool does fit the bank 2
What am I missing here?

Thanks for the help

Doug996InKC

I'm no expert, and it's been a while since I performed this procedure. But, from what you describe, I believe you have set the timing correctly. I find it confusing using the terms "tabs", "divets", and "notches", because they may have different meanings in different countries and languages. However, there's no mistaking the "half moon" concept. Please re-read post #4 where I describe the "states". (As a software engineer I sometimes involuntarily compose written communication as if I were coding.) To be absolutely sure, you could take Ahsai's advice, and confirm piston power stroke ordering using the whistle technique.