Hi everyone, I've got a 74 cutlass with the 455 that i'm putting main bearings in. Working on the number 5 main right now. The old bearing both halves had two grooves running all the way around them. On the new bearing only one half has one groove and the other half is smooth. Other than that they're identical. The new bearings came from NAPA. Is this a problem? Thanks.

 

#5 bearing ^should be grooved on both halves

 

I don't want to disagree all the way but I have seen many sets with the lower half of the bearing in question having no groove. It gives more support to this critical end of the crank. I'm sure some of the racers will chime in on this.

 

I've recently researched this for a customer. The two shell groove design has been discontinued by the aftermarket manufacturers for many years. The single shell works just fine.

 

grooved bearings discontinued...really?

 

Really? Did you read what I wrote?

 

i have bought about 6 sets over the past few years and as recently as this past few months and both shells on all (except #1)have been grooved so all my bearings are several years old?

 

these are brand new...

anyway i like the grooves for oil delivery and i like all the journals drilled thru

 

I recently installed new .020 bearings in my 400 and all of the halves except one had grooves. My machinist said to put the solid piece in the bottom of the front journal.

 

Sorry, I did not read the initial question correctly - it is the #1 position that has had many aftermarket suppliers go to only having one shell grooved - not #5.

 

I don't think I have ever seen a grooved bottom half for #1

You cannot place the ungrooved half anywhere but #1 due to the tang placement

#2 = #4 evidently
#3 is thrust and very different; #5 wider and unique
#1 has the centered-tang lower half.

 

The number one main bottom half is smooth. all the rest have a single grooved top and the bottoms have a single groove that runs about 1/4 of the way down each side, including #5. pogo69, the bearings in your pic look like what I took out. My question is can I install what I have or do I need to get the dual grooved ones. Thanks

 

yes...your #1 bearing is grooved on one 1/2 and smooth on the other 1/2

 

just make sure you install the smooth bearing in the cap and not in the block

 

Geez guys!
Here are the facts. Clevite main bearings are full groove except for the lower half of #1 as mentioned.
Napa brand, aka Federal Mogul is a half grooved bearing. As described all grooved halves go in the block, non grooved in the caps.
Thanks.

 

Do both styles work equally well or is one style preferred over the other style ?

 

The grooves are there to allow oil to be transferred to the rod bearings. It could be that at very high rpm plain lower bearings might not allow sufficient oil to the rods, but both Clevite and Federal Mogul are reputable manufacturers, for normal use they will be fine.


Roger.

 

Actually you have it backwards. The slower the crank turns the less opportunity for oiling. And remember Olds cranks are cross drilled on 1, 2 and 4 main journals. That enhances oiling on its own. However that type of crank is now scarce, most aren't doing that anymore.
And ask a BBC builder what they prefer, the half grooved bearings, or full grooved ones. They'll tell you the half grooved.
I'm switching from the Clevites to the Federal Mogul half grooved race bearing for the next couple of builds. That, coupled with the new spring for the HV Melling pump should provide extra oil pressure.

 

My machinist suggested the FM race bearing set 5 years ago.

 

Then I guess I'm a slow learner!!!!!

 

If you come across any of the old childs &,albert indium bearings they are top notch

 

No disrespect, I want to learn more. But please expand a little for me. I have read your posts and checked some of your references, I want to be a willing student, but I will question things I don't fully understand although I've only visited Missouri a few times.


Roger.

 

No problem.
The first thing is to remember there's a film of oil all around the bearing and journal all the time so oil can flow into and thru the oil holes in the crank at any time.
Secondly when the oil holes "line up", they'll do so for a longer period each time when the crank speed is lower, not when it's faster.
However as the crank speeds increase so does inertia/centrifugal force pushing the oil into the rod journal and consequently the bearings.

The full groove mains don't really enhance anything. In fact they offer less support and area for oil film on the lower half, where you need it most.

Hope this helps.

 

The cap half #1 bearing has a tang with a different offset- I recall it being centered and not off to one side like all the other locations. So, you really just cannot mess that up unless you force pcs together that are obviously incompatible in which case why are you building an engine?

 

thats true one is centered more