FE vs. BBC rod journal

[67xr7cat]

So seems the FE weak point is the rod journal, big on diameter and too narrow. The BBC is the solution to this load bearing issue, but at what point does it matter.

Seems like back in the day in 1963 Fords solution was a full grooved main bearing, a grooved main crank journal, a 100psi relief valve in the pump, and an 80psi pressure relief at back of the block to help make sure oil got to all the rods.  Seems these days all this is not considered the best way. BBC rod journals seems can work with 1/2 groove main bearings and can run .0022" rod clearance, instead of the .0025"+ guys say need with the FE journal. 

So what point does it matter, what RPM, what HP?

Reason I ask is I have one of those old '63 427's am about to build that old school way, but wondering at what point want to update this.  If I was going with a stroker would be moot as they all are BBC rod journal, but I'd like to keep this a stock stroke.  Thanks, Steve

[blykins]

Are we talking about using factory rods or aftermarket rods with FE rod journals? 

Using aftermarket rods helps things tremendously because the rods are more rigid.   

[67xr7cat]

Aftermarket rods

[My427stang]

Brent will likely chime in with more, but unless you have an aftermarket crank built, or modify a steel crank (which isn't cheap), just stick with what you have.  Bearing speed and choices are better, and rod choices are FAR better with the BBC rods, but it takes width machining too, not just journal size, the journal size is the easy part for the machinist.

Now if you were buying an aftermarket steel crank, and had it made that way, you could get a little longer rod, lighter piston, but if sticking with an FE crank,just make sure everything is balanced, oiled well, and straight and true with the lightest components the budget allows.

[blykins]

Aftermarket rods

I feel that the aftermarket rod closes up the gap quite a bit, but I don't think I can give you an exact number as to when you need to change from an FE journal size to the BBC journal size.  I have quite a few 550-600 hp engines with FE rod journals and a few that I've taken to 7500 rpm, but they are not factory rod combos.  Generally, they will have Molnar rods and I prefer using coated bearings in a lot of my engines. 

Doing a 427 high riser right now with a factory crank and Molnar rods.  I expect it to be around 600 hp and be in the 6500-7000 rpm range. 

I don't think you'll have any problems with your build and a factory crank.

[gdaddy01]

is the high riser going to have stock style rods ? can you get after market rods that fit stock cranks ?

[Nightmist66]

I can't bring myself to put a stroker kit in my junk, so I'm still running the stock journal. I have a stock 2U crank with Scat 6.490" H beams. I am using King full groove mains. I have taken a little more caution and some undercover work to the crank and bearings to try to make it live. I am turning it 7500 since cam peak should be 200rpm or so under that. Pulls strong to there, so that's where I'm running it for now. I only have just under 200 miles on this combo, but it has been some hard miles. Hoping to get to the track real soon.

[e philpott]

is the high riser going to have stock style rods ? can you get after market rods that fit stock cranks ?

Sure can . I've been running Eagle  H Beam's in my 416 since 2000 and it hits 7K about every time I take it out and still running strong

[67xr7cat]

Hi,

Thank you to all for the comments. Since I don't think this will see more than 6,500 RPM guess will be good with the Ford rod journal and proper prep. As said I have an HP oil pump, bought a new rear pressure relief valve and spring from pump builder and the factory crankshaft is fully grooved on the mains. Not sure this all is needed, but certainly helps with oil supply.  Also will be using a Canton 7 qt. T pan.

So leads to a few questions:

Full groove or 1/2 grooved main bearings?
What clearance to run for the main and rod bearings?
Is it worth getting the bearings coated?
If get the bearings coated do you use uncoated or coated measurements for bearing clearances? 

Thanks, Steve
 

[blykins]

Hi,

Thank you to all for the comments. Since I don't think this will see more than 6,500 RPM guess will be good with the Ford rod journal and proper prep. As said I have an HP oil pump, bought a new rear pressure relief valve and spring from pump builder and the factory crankshaft is fully grooved on the mains. Not sure this all is needed, but certainly helps with oil supply.  Also will be using a Canton 7 qt. T pan.

So leads to a few questions:

Full groove or 1/2 grooved main bearings?
What clearance to run for the main and rod bearings?
Is it worth getting the bearings coated?
If get the bearings coated do you use uncoated or coated measurements for bearing clearances? 

Thanks, Steve

You can take several routes with the bearings there.   Here's what works for me:

1.  If you use standard 1/2-3/4 groove bearings like a 125M FM bearing, I would set the clearances at .0030-.0032 on the mains and .0030 on the rods.
2.  If you use coated 1/2-3/4 groove bearings like a 125M FM bearing, I would have Calico coat them and set the mains at about .0027-.0028 and the rods at about .0025"
3.  If you use full groove main bearings like a King, I would only use them coated and I would set the mains a little lower, between .0022-.0025.

I keep coated bearings on the shelf as most of my engines use them.   

You always check clearances with the coating. 

[MeanGene]

Maybe it's time to try some coated bearings- I think I have a likely candidate. 454, 64 block, Adney Brown old school welded/stroked 391 crank, Crower rods, and factory lightened (milled underneath) domed Arias pistons. Done many in the basic .025/.030 combo with good results, and this one should be pretty good for strength. Have some good heads, cams & induction to get it into 7-7.5K range. Maybe I should do some good measuring and get a set from you- have you done any with the Crowers?

You can take several routes with the bearings there.   Here's what works for me:

1.  If you use standard 1/2-3/4 groove bearings like a 125M FM bearing, I would set the clearances at .0030-.0032 on the mains and .0030 on the rods.
2.  If you use coated 1/2-3/4 groove bearings like a 125M FM bearing, I would have Calico coat them and set the mains at about .0027-.0028 and the rods at about .0025"
3.  If you use full groove main bearings like a King, I would only use them coated and I would set the mains a little lower, between .0022-.0025.

I keep coated bearings on the shelf as most of my engines use them.   

You always check clearances with the coating. 

[blykins]

Maybe it's time to try some coated bearings- I think I have a likely candidate. 454, 64 block, Adney Brown old school welded/stroked 391 crank, Crower rods, and factory lightened (milled underneath) domed Arias pistons. Done many in the basic .025/.030 combo with good results, and this one should be pretty good for strength. Have some good heads, cams & induction to get it into 7-7.5K range. Maybe I should do some good measuring and get a set from you- have you done any with the Crowers?

You can take several routes with the bearings there.   Here's what works for me:

1.  If you use standard 1/2-3/4 groove bearings like a 125M FM bearing, I would set the clearances at .0030-.0032 on the mains and .0030 on the rods.
2.  If you use coated 1/2-3/4 groove bearings like a 125M FM bearing, I would have Calico coat them and set the mains at about .0027-.0028 and the rods at about .0025"
3.  If you use full groove main bearings like a King, I would only use them coated and I would set the mains a little lower, between .0022-.0025.

I keep coated bearings on the shelf as most of my engines use them.   

You always check clearances with the coating. 

No sir, I haven't used the Crower rods.

[turbohunter]

I’d like to get into the reasons for clearance targets and and bearing types as I’m overthinking everything these days.
Brent you state that you would go .003 on an uncoated FM 125 style bearing and a little tighter (.0025) on coated. Does the uncoated bearing need the extra clearance/oil pad?

[blykins]

Talking about bearing clearances is something that most builders may vary a hair on but we are generally all in the same ballpark.  Keep in mind that we all have years/decades of experience and our experience is based on stuff that has bit us in the hindend at one point or another.  So at some point, we had to fix something we did wrong, and it sticks in our heads. 

The bearing clearances that I listed up above are what work for me. 

But to answer your question, a bearing coating is hard.  It's made for high performance scenarios, where there is a chance that the oil film may be breached.  The coating takes up a little clearance (generally about .00025" per shell).   

Remember that oil clearances vary by journal diameter.  An FE has a fairly large main journal diameter (in comparison to other engines) so the clearance has to be adjusted so that you do get an adequate supporting oil film.   Since the layers of an uncoated bearing may not be as hard, I like to see a little more room for that supporting oil film. 

Also keep in mind that there are clearances I "like" to see and clearances that I will accept.   We all have to step back and realize that we are working in TEN THOUSANDTHS OF AN INCH, which means if I see .0028" instead of .0030", then I'm rolling. 

[turbohunter]

Ok cool
It occurred to me that I have a bearing clearance target I want, but the only reason is, “well that’s what everyone does”.
I’d like to know why I’m shooting for that target.