Your donations help keep this valuable resource free and growing. Thank you.
|
fully grooved main bearings |
Post Reply | Page 12> |
Author | |
WARBED
Supporter of TheAMCForum Joined: Feb/12/2011 Location: Edinburg TX Status: Offline Points: 1677 |
Post Options
Thanks(0)
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.
|
|
WesternRed
AMC Addicted Joined: Aug/03/2010 Location: Australia Status: Offline Points: 5782 |
Post Options
Thanks(0)
|
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.
|
|
WARBED
Supporter of TheAMCForum Joined: Feb/12/2011 Location: Edinburg TX Status: Offline Points: 1677 |
Post Options
Thanks(0)
|
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.
|
|
jcisworthy
AMC Addicted Joined: Jul/23/2009 Location: North Carolina Status: Offline Points: 2805 |
Post Options
Thanks(1)
|
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 |
|
WesternRed
AMC Addicted Joined: Aug/03/2010 Location: Australia Status: Offline Points: 5782 |
Post Options
Thanks(0)
|
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.
|
|
Trader
AMC Addicted Joined: May/15/2018 Location: Ontario Status: Offline Points: 6672 |
Post Options
Thanks(1)
|
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."
|
|
WARBED
Supporter of TheAMCForum Joined: Feb/12/2011 Location: Edinburg TX Status: Offline Points: 1677 |
Post Options
Thanks(0)
|
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.
|
|
BassBoat
AMC Addicted Joined: Aug/29/2008 Status: Offline Points: 1706 |
Post Options
Thanks(1)
|
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.
|
|
Trader
AMC Addicted Joined: May/15/2018 Location: Ontario Status: Offline Points: 6672 |
Post Options
Thanks(0)
|
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:
|
|
Jmerican
AMC Addicted Joined: Mar/29/2016 Location: Seattle, Wa Status: Offline Points: 585 |
Post Options
Thanks(0)
|
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? |
|
Post Reply | Page 12> |
Tweet
|
Forum Jump | Forum Permissions You cannot post new topics in this forum You cannot reply to topics in this forum You cannot delete your posts in this forum You cannot edit your posts in this forum You cannot create polls in this forum You cannot vote in polls in this forum |