Cam Bearings for a 3.4

[mongo]

I considerd that as well but from an engineering stand point I am surprised they would locate an oil hole there as I would not think the increase in oil would outweigh the loss of support caused by the oil hole....

[geoffinbc]

I think if I were having problems with the timing gear or chain that was due to oiling issues I would drill a .030" hole through the thrust surface on the block directly into the oil galley going from the cam to the crank. Then you would have full pressure oil on the thrust surface. However if you have having serious problems it is most likely due to the thrust surface and gear being out of alignment. But again with sustained high speed operation extra oil will go a long way in lubricating and cooling the timing set.

When I rebuilt my engine and used the SBC bearings I did not bother with the second hole in the front bearing. The extra width of the bearing provides more support anyway and as long as you have good oil supply there will not be any issue. The rear bearing supports the load of the oil pump / distributor gear just fine. I just believe it is down to personal preference. However if I was running a monster roller cam I might try and improve oiling to all of the bearings and not just the front one.

[mongo]

I am not having any trouble... I just don't want to! I am trying to build a high reliability motor (with a little extra power) so oil delivery is a top concern for me. Since the 3.4 block won't support roller cams, I will be probably be going with a conservative cam like a Comp cams 262.

[mongo]

Just when you thought it was all over...

I told my machinist to toss the first bearing, then use 2/3/4/5 from the SBC set as 1/2/3/4 in the 3.4 block and don't forget to drill the second hole in the first bearing. He said "why?" I explained that it was necessary due to the cam chain stress and he said that was not possible. He said he never drills the second hole in this situation as the hole removes surface area and the oil pressure cannot POSSIBLY be strong enough to make a difference. Following his logic, the only reason the second hole exists is to cause enough oil seepage at the front bearing to hit the oil slinger/cam sprocket and oil the chain. If I drill a galley plug for this, the second hole in the bearing should not be necessary and is actually a bad thing.

Opinions?

[3400-95-Modified]

Tell him to stuff it up his ass and do as you are telling him... LOL

It's like that stock, your already increasing the surface area of the bearing greatly over stock as well... so whats the little hole going to do besides provide the same amount of oil pressure and extra oiling for the front/chain as a stock motor would be doing?

If it was NOT like this from the factory and factory replacement bearings did NOT have 2 holes then ok I could see the arguemnt, but OEM and OEM replacement bearings have the two holes up front for the extra oiling. Besides, how many 60* motors has he put SBC bearings in that he "never drills the second hole in this situation"?

[geoffinbc]

Like I said I never drilled the second hole. I believe your machinist is right. But if you want to copy the factory then just ask him to copy the old No.1 bearing.

[3400-95-Modified]

Right about what? That drilling the hole removes surface area? Or that the pressure doesn't matter?

There are two arguments here... One of which is obvious, yes drilling a hole removes surface area, that’s a no brainer, BUT your already increasing how much is there by doing the SBC bearings to begin with... so that is not an issue... now the pressure one, well yeah ok maybe I can see the pressure not being a huge helping factor in extending the life of the bearing by supporting it more, BUT I do however see the point that having two holes doubles the amount of oil that is not only lubricating the bearing itself, but also the block cam thrust plate, and the timing set... There are a few more items out front that need the oil, so why starve it?

[mongo]

I have to agree that logic dictates the second hole is not imperative to the bearing but for the oiling of the timing components. I think the Sealed Power bearings took this one step further when they milled a groove from the second hole to direct the oil to timing set. To me, all of this indicates that the seepage from the front bearing is the main (and possibly sole) source of oil for the timing components. Now I just have to decide if I am going to drill one of the galley plugs or modify the front bearing....

[geoffinbc]

Drilling the galley plug would be fine. Put a .030" hole in it and you will have oiling to the back of the timing set. For High RPM use I would do it. For a street motor I would simply leave the bearing as is with one hole.

The Chevy Power Manual does not say to drill the extra hole when installing SBC bearings.

[mongo]

The GM parts direct instructions for the front bearing also omit mention of a need for a second hole. This again indicates the hole is unnecessary for the cam. Looks like I will be drilling a galley plug. Given the timing chain discussions going on in other threads, I am REALLY wanting to ensure that the timing set gets oil.

[geoffinbc]

Ask your machinist about drilling directly through the thrust surface into the oil galley that feeds the crank. This modification will supply oil directly to the thrust surface. Almost the same as drilling the galley plug but slightly better. Drill a .030" hole and de burr it. Endurance racing guys do this on small blocks for sustained high rpm use. But again It is not necessary on the street but wont hurt.

[mongo]

After a long series of delays (my machinst's boring machine not working, the secondary machinist going on vacation, me going on vacation) my block is just about to come home when.....

I just got a call from my machinist. He is having trouble getting the SBC cam bearings installed in my block. He beleives they are completely incompatible (96 Corvette with a 350). Looks like I may have to go ahead and order the OEM bearings for my block (95 Camaro 3.4). Any opinions on what may be going on?

[geoffinbc]

You bought LT1 bearings. You need Gen I SBC bearings

[mongo]

Arrgh! Can you name a recent Chevy that would have the correct motor! I don't know when the Gen 1 SBC motors were made.

[neo71665]

gen one SBs are anything made from 1955-mid 90s. The standard old reliable V8, since you want something exact, um 1993 ck1500 fullsize pickup.