TheAMCForum.com Homepage
Forum Home Forum Home > The Garage > AMC V8 Engine Repair and Modifications
  New Posts New Posts RSS Feed - fully grooved main bearings
  FAQ FAQ  Forum Search   Events   Register Register  Login Login

Click for TheAMCForum Rules / Click for PDF version of Forum Rules
Your donations help keep this valuable resource free and growing. Thank you.

fully grooved main bearings

 Post Reply Post Reply Page  12>
Author
Message
WARBED View Drop Down
Supporter of TheAMCForum
Supporter of TheAMCForum
Avatar

Joined: Feb/12/2011
Location: Edinburg TX
Status: Offline
Points: 1677
Post Options Post Options   Thanks (0) Thanks(0)   Quote WARBED Quote  Post ReplyReply Direct Link To This Post Topic: fully grooved main bearings
    Posted: May/13/2022 at 5:30pm
Rebuilding my 360 and my 70 390 and so far, I have not found anyone that sells the fully grooved main bearings in any size. anyone one knows of a source. Might end up buying some half grooved and modifying the other half. 
59 American 2dr S/W. 70 390 AMX. 70 232 javelin. Kelvinator fridge ice cold beer storage.
Back to Top
WesternRed View Drop Down
AMC Addicted
AMC Addicted
Avatar

Joined: Aug/03/2010
Location: Australia
Status: Offline
Points: 5782
Post Options Post Options   Thanks (0) Thanks(0)   Quote WesternRed Quote  Post ReplyReply Direct Link To This Post Posted: May/13/2022 at 8:04pm
But 2 sets of bearings and combine if you really want fully grooved.

Let the debate begin on the merits of fully grooved main bearings.
I've finally given up drinking for good...........now I only drink for evil.
Back to Top
WARBED View Drop Down
Supporter of TheAMCForum
Supporter of TheAMCForum
Avatar

Joined: Feb/12/2011
Location: Edinburg TX
Status: Offline
Points: 1677
Post Options Post Options   Thanks (0) Thanks(0)   Quote WARBED Quote  Post ReplyReply Direct Link To This Post Posted: May/13/2022 at 8:17pm
Yea I thought about that but kind of pricey especially when you have a few engines to assemble. I'll probably make a jig on the lathe to machine grooves in the ones I have. half the flow to the rod journals is my main concern especially at higher RPMs. I thought they still made fully grooved and didn't notice the 1/2 grooved description when I purchased them.
59 American 2dr S/W. 70 390 AMX. 70 232 javelin. Kelvinator fridge ice cold beer storage.
Back to Top
jcisworthy View Drop Down
AMC Addicted
AMC Addicted
Avatar

Joined: Jul/23/2009
Location: North Carolina
Status: Offline
Points: 2805
Post Options Post Options   Thanks (1) Thanks(1)   Quote jcisworthy Quote  Post ReplyReply Direct Link To This Post Posted: May/14/2022 at 4:15am
Why do you think you need full groove 
Specializing in dyno services, engine building, and cylinder head porting

rbjracing.com
Phone Number 518-915-3203
Back to Top
WesternRed View Drop Down
AMC Addicted
AMC Addicted
Avatar

Joined: Aug/03/2010
Location: Australia
Status: Offline
Points: 5782
Post Options Post Options   Thanks (0) Thanks(0)   Quote WesternRed Quote  Post ReplyReply Direct Link To This Post Posted: May/14/2022 at 5:02am
I would think if you are building something at the levels that needs fully grooved mains, the cost of a second set of bearings wouldn’t be an issue.

If you are going to make something fancy yourself 2/3 or 3/4 grooved might be the ticket.
I've finally given up drinking for good...........now I only drink for evil.
Back to Top
Trader View Drop Down
AMC Addicted
AMC Addicted


Joined: May/15/2018
Location: Ontario
Status: Offline
Points: 6672
Post Options Post Options   Thanks (1) Thanks(1)   Quote Trader Quote  Post ReplyReply Direct Link To This Post Posted: May/14/2022 at 12:06pm
Just a quote from a book on building race engines:
"Most main bearings are grooved on the upper half only, leaving the full load-carrying capacity available on the ungrooved bottom half. It is important to remember that any groove or journal chamfer introduces an interruption in the hydrodynamic oil wedge causing a partial collapse. This is critical since the wedge’s great­est load-carrying ability is near the center of the bearing and tapers off toward each side due to oil leakage from the bearing. Manufacturers do not recommend extending grooves into the lower bearing inserts. The oil groove in the upper insert provides the oil supply for the rod bearings. Also, the insert with the oil feed hole must go in the block and not in the main bearing cap."
Back to Top
WARBED View Drop Down
Supporter of TheAMCForum
Supporter of TheAMCForum
Avatar

Joined: Feb/12/2011
Location: Edinburg TX
Status: Offline
Points: 1677
Post Options Post Options   Thanks (0) Thanks(0)   Quote WARBED Quote  Post ReplyReply Direct Link To This Post Posted: May/14/2022 at 12:51pm
Thank you. I was wondering why there not grooved anymore. BUT. Yea I know here it comes and not wanting to start a debate, we have all heard it before on the very same subject but there is also another reason actually two, I like fully grooved and want to go that route. I know oil is in between the bearing and main surface so it might not matter but the rod journals receive oil by the groove in the mains bearings so blocking the passage by 50% doesn't seem to be the right answer also I know there has been debate over the squirt hole in the rods to cool the opposing pistons. Is it needed or not?? I have some engines torn apart and this squirt hole is clocked/timed to coincide with the crank revolutions and the alignment of the oil passageways through the crank. so, it actually squirts oil under pressure at the opposing piston. (1 for the engineers) If only half grooved this does not work on some journals and does on others. I know the rod journals are the last thing in the flow chart and need as much flow as there can be. Seems like the rod journals get the most abuse and need as much oil as possible. on all cranks that I have ever machined and that's a few 100 the rods are the ones that need the most machining. I know I talk a lot 
59 American 2dr S/W. 70 390 AMX. 70 232 javelin. Kelvinator fridge ice cold beer storage.
Back to Top
BassBoat View Drop Down
AMC Addicted
AMC Addicted


Joined: Aug/29/2008
Status: Offline
Points: 1706
Post Options Post Options   Thanks (1) Thanks(1)   Quote BassBoat Quote  Post ReplyReply Direct Link To This Post Posted: May/14/2022 at 3:00pm
I used to have a number for a fully grooved main, as you have concluded no longer available.  When I asked my performance machinist to cross drill my crank he commented that cross drilling wasn't done any more, that they just ran fully grooved bearings.  When I explained I couldn't get them, he cross drilled my crank.  Not everybody appreciates the details, and most people get away with half grooved stuff, but for more popular performance engines today, 3/4 groove seems to be the way to go, as Western Red pointed out. 
 
Back to Top
Trader View Drop Down
AMC Addicted
AMC Addicted


Joined: May/15/2018
Location: Ontario
Status: Offline
Points: 6672
Post Options Post Options   Thanks (0) Thanks(0)   Quote Trader Quote  Post ReplyReply Direct Link To This Post Posted: May/14/2022 at 4:27pm
A 3/4 groove would provide more oil for the highest pressure in rotation. Can see this being a good idea. A clocked groove from 10:00 to 4:00 would likely work best, just a thought. A long read, but full grooved bearings are not the ultimate solution:
Back to Top
Jmerican View Drop Down
AMC Addicted
AMC Addicted
Avatar

Joined: Mar/29/2016
Location: Seattle, Wa
Status: Offline
Points: 585
Post Options Post Options   Thanks (0) Thanks(0)   Quote Jmerican Quote  Post ReplyReply Direct Link To This Post Posted: May/14/2022 at 4:53pm
Certainly grooved cranks are a thing, but agreed that the 3/4 bearing, done well, is likely the best as it’s tapered lead-in and lead-out (bad plain bearing pun) would likely keep pressure bleed off to a minimum and provide a stable wedge, timed for high load coming on. And they are out there for example.. Some with less than 270, but more than 180. 

I mean, seriously, fundamentally there are pages and pages of AMC ramble out there on *fixes. Lol. Ain’t backyard engineering fun? 


Back to Top
 Post Reply Post Reply Page  12>
  Share Topic   

Forum Jump Forum Permissions View Drop Down

Forum Software by Web Wiz Forums® version 12.03
Copyright ©2001-2019 Web Wiz Ltd.

This page was generated in 0.109 seconds.
All content of this site Copyright © 2018 TheAMCForum unless otherwise noted, all rights reserved.
PROBLEMS LOGGING IN or REGISTERING:
If you have problems logging in or registering, then please contact a Moderator or