Help in selecting rod & main bearings
 

Pontiac Guys a question: what brand and style bearing would you use for this build AND 1/2 groove or full grove and why... thanks

1967 Firebird (engine is from a 71 GTO)
Street Car, 400ci +035 with Weisco Pistons 2 valve relief +2.60
Standard rod w/ ARP bolts
Crank Nodular cut 10/10
Comp EX256H cam and kit (keeping it just a hair above stock)
#96 Heads all redone with a tiny bit of chamber cleaning and hardened seats
STOCK TH400 and converter
3:08 Posi

If I run this at all it would be maybe twice a year at the NMCA West Street class.:usa2:

Federal Mogul 4040M 3/4 groove mains. Clevite rod bearings. full groove is old school and developed before the engineers fully understood the need for a good oil wedge to support the crank. I once took a P350 apart that had full groove mains and you could see the abnormal journal wear that lined up with the full groove.

Some constructive criticism- I would ditch the stock rods in favor of cheap forgings. By the time you install aftermarket bolts and have the big ends resized, its the same cost as stronger rods.

XE256 is a decent cam for a P350, but not a 400. I had that cam in the same 350. XE cams have valvetrain noise in my experience with 2 different XE grinds. I'd use a slightly larger cam like a Summit 2800, a 067 copy or something with about 215 duration with 112LSA. The XE grinds are on a 110LSA so the power peaks then ends early. Those 96 heads will put the compression in the mid to high 8s, so you'll have to mill them if you want any serious power.

Never have seen that in the engines I've built. I have seen FM bearings have wide variations in thickness due to the fact they're made in Mexico. If you're concerned about full groove bearings, use Mahle Clevite p/n MS-483G (mains, grooved only on the top shell) and CB-758HN (rods). I agree with replacing the stock rods with QUALITY 5140 replacements. Stay away from TRW/Speed Pro forged pistons. They're quite heavy when compared to Icon or SRP forgings.

I am going to use full groove bearings by "King". These were recommended to and sold to me by Ace when he had PPR. I don't see why a full groove bearing wouldn't work. I am under the impression from a few different sources that King bearings are of the highest quality and I will just proceed with the belief that their engineers aren't wrong.

Bearing can be of the highest quality but if you have insufficient bearing support for the crank weight and rpm, the bearing will overheat and fail. You need a minimum surface area for any given bearing speed to support the firing and inertial loads from the engine.

That being said, a 455 running to only 5500-5800 rpm will have a high success of living a LONG TIME.

Tom Vaught

Tom,

In my specific case I have the following; A .030" over 400 block, obviously a 3" crank journal, Very light rods(700g), pistons are 543g, so my bob weight is 2003g. I'm figuring this engine can live many years on the STREET occasionally hitting 6000rpm using the King MB5526AM and CR815CP bearings.

Clevite, P series, full grove, is ok on the non cross drilled 400 factory crank.

1/2 grove on the 3.25 cranks that are cross drilled.

A decent read. Check out the discussion further down;

Basically, 180 or 1/2 grooves give better loading without starving the rods.

http://www.vandervell.co.uk/images/s...gPerforman.pdf

I would get either 1/2 groove or 3/4 groove bearings. I don't run full groove bearings, unless that's all that's available. I've seen cranks wear the main journals pretty bad with full groove bearings. They're a no/no in my book.

I've used King bearings in diesel applications. They hold up well.

OK, I went an ordered the connecting rods so thats a worry gone. Now as for the Bearings I'm leaning to a 1/2 grove...