What type of bearings to use?

[DanM]

What brand of bearings should I be looking at using for my 351W? Federal Mogul/SpeedPro ones? Clevite? Something else?

Keep in mind that it's a mild street build only.

Also - as far as main bearings go - there are different versions listed for 69-76, or 77+. My block came from an 86 car, but the casting is D4AE ... which do I need?

[blykins]

I like the Clevite stuff.....

Keep in mind that even though it's for a street build, everything depends on the bottom end of the engine.....so don't scrounge on this part.

I would at least use the H series of the Clevite bearings. It's a little more expensive...but like I said it's worth it. The difference between the P series and the H series is huge....Especially if you're using a bore mic to mic the mains....you will see the difference.

As for what year bearings.....your block is a 74 model block. The mains should be 2.9999".

Do yourself a favor, spend about $120 on a good bore mic that reads to the half thou. Don't use that crappy dentalfloss stuff (plastigage) on an engine build. It will come in handy...especially if you're gonna blueprint the engine.

[Excaliber]

After you have used your really fancy mic's and measured to the half thousandth, use the crappy dental floss to confirm your "math". Unless of course your totally convinced YOUR math is good.


Strangely enough most proffessional race car teams DON'T take for granted the "math", the final check is "dental floss". Only way to be sure.

Following Blykins advice I DO drive it like I stole it, buy the good bearings and do the same!

[blykins]

...

[brainsboy]

You should not use H-series bearings unless you have too.


To understand why you have to understand the differences in bearings. Bearings are not round, they have eccentric walls, meaning that the thickest part is in the middle, from there the bearing tapers off smaller in each direction. Depending on the type of motor you have you will need different bearings. All clevite bearings are a tri metal design the difference is in the amount of taper or oval which is called eccentricity. The clevite regular bearings start with a part number "p". Dont confuse these with there race bearing the "P series". The P series has the greatest amount of eccentricity and have a high crush and overlay so that they last longer under higher loads. For performance and longevity this is your best choice in most street/strip cars. The H series has a medium eccentricity. These were originaly designed for nascar but used in most other racing now. H series also have a larger chamfer so they clear the crankshaft fillets. These are your best choice if you plan on runing alot of high rpms, or your only choice using some aftermarket crankshafts due to side clearance.

All these bearings will fit and for the most part work fine. The difference can not be seen by the eye, so it leads to alot of debating on which is the best. I would say your best choice in your situation would be for a Clevite P series. Im not sure why one person said there is a big difference between H & P as both will measure the same in the center and the taper is only .0005 difference between them. The P series is one of there oldest series and still used in millions of cars.

[scottj]

Why would he want the greatest amount of eccentricity in a low rpm, low load street build?

Scott

[brainsboy]

In a modified motor the materials used are stronger and often lighter. They turn higher rpms and have more loads placed on them so they need to be stronger. When you tighten a rod bearing cap you have the section between the cap and rod which is a weak point, this weak point creates distortions. These are called static distortions. When the motor is running, you have the weight of the rods, the type of material used, rpm range which creates dynamic distortions. When you deal with racing, not street cars you have lighter pistons, lighter rods, and stronger parts, the distortions seen in race parts is not as great as in a stock vehical. Remember bearings are not round, all bearings are oval in design, A stock rod is going to need more eccentricity then a rod strong enough to handle 2000hp, because the force needed to created distortion is greater in a stronger rod.

[scottj]

Originally posted by brainsboy


You should not use H-series bearings unless you have too.

"have to" means if you have a large fillet crank you have to run the H-series. If you have a stock, small fillet crank use the P-series.
Also, the P-series has a little more lead than the H and is a little more forgiving.
The difference in eccentricity doesn't factor in to the decision in the least for a mild street engine.

Scott

[brainsboy]

Originally posted by scottj


"have to" means if you have a large fillet crank you have to run the H-series. If you have a stock, small fillet crank use the P-series.
Also, the P-series has a little more lead than the H and is a little more forgiving.
The difference in eccentricity doesn't factor in to the decision in the least for a mild street engine.

Scott

The P series have a small thin overlay added which the H series dont have. Eccentricity is very important to even street cars, If it didnt factor in, bearings would be round not oval in design.

[scottj]

[quote]Originally posted by brainsboy


Eccentricity is very important to even street cars, If it didnt factor in, bearings would be round not oval in design. [/QUOTE

Ben,

I never said eccentricity didn't factor in to bearing design. I said, "The DIFFERENCE IN ECCENTRICITY doesn't factor in to the decision in the least for a mild street engine."

[cobrashoch]

Hi Scott - been a while,,,,,,,,,,,,,,
RE: bearings - The general rule of thumb I've allways went with was------ hard crank, soft bearings--------soft crank , hard bearings.
You can run hard/hard or soft/soft combos but you will have to clearance the bottom end too loose for my tastes.
A combo that seems to be popular right now is a Scat or Eagle crank (soft) together with Clevite 77's. (hard,hard)
I just stuck a set of stock rod bearings (over and unders, 2.2 Chev) on my Bryant forged crank this summer.
Lessin' someone tells and explains to me a better way that's where I plan to stay for a while too.
cobrashock

[cobrashoch]

Brainsboy - Bearing eccentricity is about oil control on the crankshaft , nothing more. True, it is determined by bearing design and materials. But with todays bearings it's pretty much a given. Wasn't always that way though.
I have the true and neat story that expains where all of that business came from, and how it evolved. It all started back in the 50's with a drag racer named Jake King,,,,,,,,,,,,,,,,,,,,,,,
cobrashock

[brainsboy]

Brainsboy - Bearing eccentricity is about oil control on the crankshaft , nothing more.

Well Let me show you an artical from Clevite themselfs, that I got my information from. It explains the eccentricity and its purpose beyond oil control
_____________________________________________

We are frequently asked "How can I tell which Clevite 77® High Performance Bearing to use?" With all of the options currently available in the Clevite 77 Engine Bearing line that's a reasonable question to ask. Before answering, let us explain why we offer so many.

Background

All bearings are an interference fit in their housing; this relates to something we call crush. Crush results from each half shell bearing being made a few thousandths more than a true half circle. When two bearing shells are placed together their outside diameter is slightly larger than the ID of the housing they fit into. When the housing cap is torqued the bearings are compressed, like a spring, resulting in a radial contact pressure between the bearings and the housing. Another way of looking at it is that the housing is squeezing inward on the bearings and the bearings are pushing back outward against the housing. This is called "Housing Bore Distortion" or just "Bore Distortion". With these factors in mind it's easy to understand why housings made of different materials like aluminum versus iron or steel will have different amounts of "Bore Distortion".

Compensating for differing amounts of bore distortion isn't as simple as just making an adjustment in the bearing clearance when the engine is assembled. The reason is that most housings (connecting rods and engine blocks) have irregular shapes surrounding the bearing. Rods, for example, have a beam at the top, notches for bolts heads or nuts. Some have ribs over the cap while others don't and of course, the parting line between the rod and cap is a weak point. The result is that bore distortions are seldom uniform in all directions. Some housings go out of round with the greatest dimension in the horizontal direction, while others grow more in the vertical. Still others may bulge where there's a notch for bolt head clearance. All of these bore distortion characteristics relate to the static loads between the bearings and housing when the engine is not running. Still another consideration is what happens under the dynamic conditions of a running engine where loads are constantly changing in magnitude and direction. Engine loads placed on the bearings and their housing will result in still further changes in housing bore geometry.

Original equipment bearings are tailored to compensate for the combined static and dynamic distortions which occur in the housings. Specialty high performance parts like connecting rods and aluminum blocks are made for lighter weight and to withstand the higher loads and speeds of high performance engines. They seldom ever duplicate the bore distortion characteristics of the original equipment parts. Taking these facts into account, it should come as no surprise that standard passenger car bearings are not suitable for engines modified extensively to produce higher horsepower and speeds. This not only explains why we have special bearings for high performance applications, but also why we offer several choices.

With so many different specialty high performance connecting rods and blocks available, it's impossible for the bearing manufacturer to know the characteristics of every piece. Even if we did, the choices of related parts which influence such things as rotating and reciprocating weights and balancing, all affect bearing loads and consequently, dynamic bore distortions.

top


Bearing Design

So, just how are bearings tailored to compensate for bore distortions? To understand this important design concern we must first determine what the most desirable shape for a bearing ID is. If everything remained constant like loading, speeds and housing geometry, a perfectly round bearing could be made to work very well. For example, electric motor bushings run almost indefinitely under these conditions. In an engine where we have the variables described above, it has been determined that a slightly oval bearing ID with the minimum diameter oriented in line with the maximum load is the most desirable. To produce this type of profile bearings are made with what we call an eccentric wall. In nearly all cases the bearing wall is thickest at 90 degrees to the parting line and tapers off from that point toward each parting line by some specified amount.

The amount of change, called eccentricity, is tailored to suite the bore displacement characteristics of the housing. A housing which experiences its greatest distortion in the horizontal direction (across the parting line) provides the desired oval shape so the bearing requires a minimum amount of eccentricity. Bearing is needed to compensate for this and produce the desired maximum ovality in the horizontal direction.

Connecting rods are subjected to high inertia loads at the top of the exhaust stroke when the weight of the piston, rings, wrist pin and top end of the rod are all pulling on the rod cap. This loading tries to stretch the rod and pulls the big end out of round causing it to close in across the parting line. In this case, bearing wall eccentricity provides extra clearance to let the rod flex without having the bearings contact the shaft. Besides low, medium and high eccentricity, Clevite 77® High Performance Bearings are offered with numerous additional features to make them compatible with related parts and suitable for the loads and speeds of competition engines.

All bearings stamped "Clevite 77®" are constructed of Tri-Metal™ cast copper lead. These bearings have a steel back for support, a cast copper lead lining to withstand the loads of engine operation and an electroplated babbitt overlay on the running surface to provide bearing surface qualities. The Clevite 77® marking alone does not necessarily mean the bearing is optimum for high performance. We make Clevite 77® Engine Bearings for passenger cars too. All high performance bearings are cataloged separately in the "high performance applications" section of the Clevite 77® Engine Bearing Catalog.

Bearing Series

"P-Series"

These are not to be confused with the standard passenger car and light truck parts for the same applications which also have a "P" suffix letter. These high performance parts have unique core part numbers different from the standard parts for the same application.

P-series parts are the oldest series of Clevite 77® High Performance Bearings. The rod bearings in this series typically have the greatest amount of eccentricity. Most rod bearings are available either with or without dowel holes for use in aluminum rods. Most P-series main sets are full grooved to maximize oil flow to the rod bearings. Both rods and mains have high crush for maximum retention and a reduced overlay thickness to prevent overlay fatigue sometimes referred to as hen tracking. Rod bearings use a hardened steel back for added strength and resistance to fretting. Extra clearance rod bearings are available for .001" additional clearance and select fitting.

Use the P-series rods where extremely high RPM's cause severe rod bore close in. This is typically indicated by nearly full parting line to parting line shaft contact with bearings having less eccentricity. Use P-series mains where higher eccentricity is desired to narrow bearing contact patterns and to provide increased oiling to rod bearings. Rod bearing oil starvation is typically indicated by polishing and smearing of the bearing surface possibly accompanied by discoloration predominantly concentrated at the axial center of the bearings.

"H-Series"

These bearings are identified by a letter "H" in the part number suffix. Part numbering is based on the same core number as the standard passenger car parts for the same application. These bearings were developed primarily for use in NASCAR type racing but are suitable for all types of competition engines.

H-series bearings have a medium level of eccentricity, high crush and rod bearings have a hardened steel back and thin overlay. These bearings also have enlarged chamfers for greater crankshaft fillet clearance and are made without flash plating for better seating. Bearings with .001" extra clearance are available for standard size shafts and carry the suffix "HX" (X = extra clearance). Rod bearings are available with or without dowel holes (HD = with, H = without), main bearings are available with standard 180 degree upper half grooving and with full 360 degrees grooving (H = 180 degrees, HG = 360 degrees).

Use H-series bearings with crankshafts that have oversize fillets and where engines run in the medium to high RPM range. H-Series bearings should be used if contact patterns obtained with P-series parts are too narrow. Contact pattern should ideally cover 2/3 to 3/4 of the bearing surface.

[cobrashoch]

Brainsboy - Interesting response. And I didn't even tell you what I know and you claim to refute it.
BTW - I was a chief mechanic for for several years for, what the hell, who cares anyway?
I think this type of response is amusing though. What you are confusing is the technical merits of a subject (and what you think you know) with how a car runs and the experience of the builder and the results. Two very different things.
Good luck on your endevers, and my advice to the original post stands. Even on 5000 horsepower engines that I know a bit about.
cobrashock

[brainsboy]

I guess I missed somthing here, I just posted a quote from Clevite...
Im not sure why you got so rude, defensive, and sarcastic... oh and dont want to forget amused.. I guess when you dont agree with Top mechanics on something it hurts there ego

I feel your response was sophmoric and childish. If you have something constructive to post, We all would like to hear your point of view, prove clevite wrong. There is no need for the no body wants to listen to me and no one loves me sympathy ploy... We were just having a friendly debate.... Grow up Chief


Ben

[cobrashoch]

Brainsboy-I grew up child, a long, long time ago. And I'm for sure not out to prove anything to anyone let alone you. Your reply WAS provocitive, and convesant, whether you knew it or not. I'll not reply to this post any more and give you the right of last reply.
If you choose to do so it will indeed say somthing about you and why you are on this board.

DanM - Sorry to take over your thread. I'll try to make it up to you.
Cobrashock

[G.R.]

Doesn't take much to get one's panties in a wad here lately.




Damn sniping is going on everywhere--what is it election syndrome

Just chill a bit--kick your wife and the cat, hug and kiss the dog, yell at the kids--leave the pettiness behind

[brainsboy]

Originally posted by cobrashoch


Brainsboy-I grew up child, a long, long time ago. And I'm for sure not out to prove anything to anyone let alone you. Your reply WAS provocitive, and convesant, whether you knew it or not. I'll not reply to this post any more and give you the right of last reply.
If you choose to do so it will indeed say somthing about you and why you are on this board.

DanM - Sorry to take over your thread. I'll try to make it up to you.
Cobrashock

Cobra doesnt sound like you want to be friends yet

Cobra, there is no need to not reply again, we are all still waiting to hear more on your point of view. Im still not sure why you took my posts as provocitive, but I didnt mean anything personal against you all I can say is Im sorry if you took it that way, and sorry for any discomfort you have felt.

Maybe if you can get beyond our differences we can work as a team on this board, I would like to keep you as friend rather then foe. What do you say chief?

Ben

[BruceT]

Sure wish I'd growed up a mecanik...................

[GT4T]

So, after all of that, what are the best bearings for me to use?

Here is what I have: Ford R302 block, Eagle internal balance forged crank, Eagle H-beam rods, neutral balanced Romac dampner (stainless), Racemaster billet steel double roller timing kit and zero balanced KEP flywheel (this is in a GT40 with Porsche G50/50 transaxle.) To suite the G50/50 gearing and achieve a top speed of 200mph (6842 rpm in 5th) , the solid roller Comp cam & Crower HPPO lifters, AFR 205 heads, Jesel SS shaft rockers, Comp 929 springs(titanium retainers) and valves(2.080/1.600) were speced to have a sweet spot of 2500-6800 rpm and the engine will seldom see more than 7000rpm and never exceed 7200rpm. These rpms will be only occasionally seen as this is a street/occasional track days car. (BTW, displacement 337ci with 4.060 bore and 3.25 stroke and Jack Roush 3 piece EFI intake w/ 36# inj.)

So as you can see I have an engine that will be used somewhat mildly interspersed with moments of sheer terror. I haven't torn down the engine to be able to make the decisions talked about in the Clevite article; I didn't get at all having to tear down the engine to see what kind of wear patterns you have in order to decide what kind of bearings to use. I want to put in the right ones in the first place and then "run it like I stole it" without having to worry if I am going to spin a bearing or worse.

It sounds like that with my eagle crank I ought to be using Clevite 77 which is what I had listed since everyone else I saw was listing them :-) I am thoroughly confused on the H or P ? And what about Calico coating them?

Thank,
Lynn