[Garry Sr]

What's the advantage? I dono! Lets ask the P-Dude!

[ May 04, 2002, 10:53 AM: Message edited by: Garry Sr ]

[Garry Sr]

What's the advantage? I dono! Lets ask the P-Dude!

[ May 04, 2002, 10:53 AM: Message edited by: Garry Sr ]

[WARPed]

All factory 3.25” main cranks are cross-drilled so there would be no advantage over half grove units.

The original question was thoughts on 3/4 grooved bearings

And I still stand by what I said unless you are heading into the 600+ hp range. But with that said I would install them if the motor were going to be torn down anyway.

[ May 04, 2002, 07:44 AM: Message edited by: WARPed ]

[PONTIAC DUDE]

Call Ohio Crankshaft. Maybe they can help!!

[ May 03, 2002, 12:40 PM: Message edited by: PONTIAC DUDE ]

[WARPed]

Originally posted by PONTIAC DUDE:
Sorry, Warped. Yes there is.

<font size="2" face="Verdana, Helvetica, sans-serif">Master, this is Grasshopper. Teach me the ways of the oil. Or is this one of those things that you would have to kill me after words.

[PONTIAC DUDE]

Sorry. deleted post.

[ May 03, 2002, 12:41 PM: Message edited by: PONTIAC DUDE ]

[ta406pont]

So does this mean that the half grooved bearings that I just used in my 520hp 408 are pretty much junk or what ? Do I have to worry about them spinning and wrecking my new motor ???We already made a few dyno pulls to 6500 with no problems so far...

Thanks alot for any information.... Rob

[PONTIAC DUDE]

.

[ May 03, 2002, 12:25 PM: Message edited by: PONTIAC DUDE ]

[Injunjoe]

Just disassembled my 400 to send it to the machine shop and I noticed that the main bearings are fully grooved, top and bottom. Would there be any advantage to using these stock type bearings in an engine? If 3/4 groove is better would not a full groove be the best?

Joe

[ May 03, 2002, 10:03 AM: Message edited by: Injunjoe ]

[Engo]

The 400 cranks are not cross drilled so the main bearings have to be grooved all around.

[Dave A]

Firsly, listen to whatever P-dude says, sounds like he builds more engines in a month than I'll build in my life.

For those that find it interesting, some more info on the subject:

Grooving a bearing does affect the load-bearing capability of the bearing when the load bearing portion of the bearing is grooved.

As P-dude pointed out, the crank is all over the place during operation, so the direction of the crank load on the bearing changes quite a bit and changes rapidly.

The groove is a 'necessary evil' in some applications to insure oil feed into the load-bearing oil film is sufficient. If the load on the crank was always unidirectional - it did not change all the time, then grooving would not be necessary, but with the extreme amount of activity you get in the crank with a high-powered engine spinning very fast, and the direction of the load fluctuating wildly, it is better to sacrifice some bearing surface and insure adequate oil supply.

On an engine that does not need grooving to insure good oil supply to the load-bearing film, grooving on the lower half will at best do nothing and may actually promote wear.

Since the load most of the time (on a more 'mellow' engine) will be against the lower bearing half, I suspect that's why the upper half is grooved and the lower half is not on some factory bearings. The groove on the upper half does no harm if the load remains confined to the lower half of the bearing.

I do not have firsthand experience measuring the difference, but would suspect that the grooved bearings have little effect on oil pressure; the main effect is oil viscosity and bearing clearance. Grooving may lower the oil pressure by a barely noticeable amount in theory.

[Half-Inch Stud]

Ahem,

Sleeve/Journal bearings are self-feeding, provided there is an oil slick to feed from.

Ungrooved bearing halves are always the loaded side, and get fed from the oil slick presented by the Upper, unloaded side.

INFORMED Folks go to grooved lower halves to promote cooling. First issue is the Grooved Lower ought to be of a lesser groove than the Upper groove. Second issue is too mucha groove leads to less load area.

So, be kind to your crank, and use the groove wisely. Understand what the groove is for, and what it is not for, then the groove will work for you, and treat you right for many years to come.

H.I. Stud

[Injunjoe]

Well does anyone have ny preference concerning my original question, what is the best sacrifice, do I want to insure cooler oil or the increase in bearing surface. I know it is only in the ideal case but the Crank should be riding on a film of oil except during start-up. Does the full groove bearing promote a more even film in the case of fluctuating loads? If anyone has any information either good or bad on the subject I would appreciate it.

[Half-Inch Stud]

The 3/4 groove bearing sounds to me as a risk-free prospect. HAd close discussions with P-Dude over a year ago about this bearing modification, and would recommend these lowers for the 400 and 455 motors that see regular high HP stress.

The ungrooved lowers will survive for years in a motor that has less than or similar to 1HP/CID, and stays cool during the high HP activity. The high RPM activity has the ability to cause dramatically quick journal heating.

Today's Pontiac Engine designers/builders do not want to take the chance of hot journals. Us regular folk keep pounding the spit out of our PMDs with no regard to aging/fatigue of the hard parts. Then add the NOS, Blown, and high RPM folks running the higher stress on the rod journals causes pause to seriously consider grooved mains and cross-drill cranks as the secondary means of cooling the rod journals.

I do not look favorably on the folks running the combination of Deep pan & Dry sump & crank scrapers. Because the Primary journal cooling system is gone and Rod journal temperature rise sharply in all cases.

There are combinations of these taffy-rope reduction efforts (like I run a deep pan with factory windage, and full-groove mains) that keep some sort of Primary journal cooling in effect.

"But do these mods help?": YES.

H.I. Stud

[WARIARGTO]

After all the ongoing "back-ordered" nonsense, it seems Federal Mogul has just discontinued the race series 3/4 grooved bearings line. Not sure how extensive the cuts across the line are, but I guess it's back to Clevite for me...

[ta406pont]

So does any one have any information on the bearings I just used in my new motor a few post's up???

[Garry Sr]

P-Dude, It was just a crankshaft man. There is still plenty of good **** to sell me!

[ May 03, 2002, 10:21 PM: Message edited by: Garry Sr ]

[Garry Sr]

OK, I called Ohio Crankshaft and they told me to call the P-Dude!! Now I'm getting the old run around!!

[Garry Sr]

80pont406, Half groove bearings are fine as long as your crank is cross drilled. Most people have been running them for years, don't sweat it! A few people run 3/4 groove bearings and I was just wondering why.

[ May 04, 2002, 01:22 AM: Message edited by: Garry Sr ]

[Garry Sr]

Dude, I need those secrets. Come clean man. I promise not to tell Rash! P.S. I got a look at the 428 today. The block is hard filled and O-ringed, Turns out that the crank is offset ground and my domes stick up a little to high. Back to the piston shop they go. What do you think about a long stroke 428? Come on man you can tell me. Also using a Mega Brace for lifter bores. Maybe when its done we can race if you give me a couple of cars and the leave. Owe ya no N2o just to make it fare? I'm a greenhorn so you should have this race in the bag! Wait a minute now, you got a pro charger with N2o don't you? Better make it four cars and the leave! [img]tongue.gif[/img] Better yet, I'll just stay home. I can't take the pain of loosing! Might break out in a Rash!!

[ May 04, 2002, 01:15 PM: Message edited by: Garry Sr ]