Two Inch NASCAR Bearings

[304065]

So the cat's out of the bag on the 2" SBC/NASCAR bearing. This has been a trick modification for a while so I doubt any secrets will be given away (the guys at the front are probably on to something else) A few questions. . .

Since a standard rod journal is (for my early engine) 57mm in diameter (Ok, 56.971 but I'm going to round off or we will be here all day) that implies a circumference of 179mm, on a journal that's 22mm wide, for total bearing area of 3,938 square mm.

When they went to the 2,4 engine the journal got smaller, 52mm, for circumference of 163mm, but they made the big end wider, up to 24mm, for total bearing area of 3,912 square mm, a decrease of only half a percent or so. So total bearing area remained the same, and friction is proportional to total bearing area.

Now, when you cut down the journal to 2" I assume you use a 66mm crank with the narrow journals. That's 51mm diameter, 160mm circumference, for 3,520 square mm total bearing area. That's a reduction in bearing area of 10% with a corresponding reduction in friction AND bearing life, presumably.

The Part number used for the 2" Chevy (Buick) rod journal is unclear, The Type IV store calls it a 4204. I can't find that number in the Mahle-Clevite catalog, however, but there are dozens of 2" Chevy bearings listed. These are "H-Type" developed for NASCAR racing. They list a bearing bore of 2.1247/2.1252" or 53.97mm-53.98mm.


Finally, from the Pauter Machine web site

As an added option, we offer most of our Porsche line-up with custom big end housing bore to accept GM/NASCAR high performance racing bearings. We can modify your damaged or undersized cranks to accept this type of bearing.

[cnavarro]

John, this is nothing new like you already figured out, but is but one excellent alternative to the poor quality and high cost of current glyco bearings. The Clevite Nascar bearing part number I have from the rods I have helped R&R make are #CB610P. Jerry Wood Enterprises also has some trick bearings made up to their specs for the 3.2s (and possibly others) that are of equal quality to the 2" chevy/nascar bearings. The 2" chevy (actually buick) bearing is common in the VW crowd when running a stroker crank on the type 1 and type 4 engines and we're even playing around with using them on a 356 too! Coatings can go a long way too, like those sold by Calico Coatings (they also sell the 2" bearing already coated, ready to go, right on the shelf) or even using WPC for their treatment process (micron-size MoS2 shot-peening) for bearings and other wear surfaces - http://www.wpctreatment.com. There is an excellent SAE paper done in conjunction with Honda Japan on the WPC process and it's superiority to coatings or REM microfinishing and is used on gas engines in hybrids to improve fuel economy further.

[88911coupe]

OK...this is going right over my head, although I am aware that this is in the English language. Can you dumb this down some for me and help me figure out if this has any application for the rebuild I have just started. I'm hoping it will be top end only but I want to fix what HAS to be fixed now since the engine's out.
Thanks from the slow class...

[304065]

Buck,

The simple version is this.

In recent years, the quality of Glyco bearings, the OEM supplier to Porsche, has left much to be desired, particularly in the racing community where bearing quality can mean the difference between finishing first and not finishing at all.

In an effort to locate an alternative supplier, engine builders discovered that the highest-quality rod bearings currently in production were right under their noses, in production for the NASCAR engines which were based on the venerable small block Chevy.

However, given the larger size of the 911 journal (about 2-1/4" in decimal-inch) it was impractical to use these bearings. But somebody figured out that you could take a damaged 911 crank and grind down the bearing journals to size, in the process increasing the strength by leaving a generous fillet radius where the journal joins the throw. This would allow you to use the NASCAR bearing AND resulted in:

1) reduction of overall reciprocating weight due to the removed metal;
2) reduction in bearing surface area for less friction.

The downside of all of this is that an engine making 110HP per liter, like a high-strung historic racing two-liter, tends to crush even the OEM bearings after a few hours at high RPM. Reduced bearing area makes this problem worse: the same load distributed over a smaller area just wears them out more rapidly. . . however . . .

1) these engines get torn down every 20-40 hours ANYWAY for maintenance rebuilds; and
2) the NASCAR bearings are not that expensive (although the coated ones, and the Jerry Woods ones, are VERY expensive) compared to the Glyco OEM.

So, in short, should you be considering this in the slightest for your street-driven '88 Coupe? Absolutely not, this is a technique that is ONLY suitable for $40,000 race motors that exist for one and only one purpose, and that is winning races at the highest levels of amateur competition both here and in Europe.

Hope that helps?

[88911coupe]

John, thanks, that makes perfect sense. I'll go back to worrying about something else.

[NY65912]

We are going with 2" NASCAR bearings on the new "Skunkworks" project engine that Bill Rudtner has been commissioned by myself to build.

Yes John, I pulled the trigger..........can you say 3.7458 liters of stroked goodness!

Charles I presume that Bill has ordered the P & C's...........yes?

Oh John,

There was nothing wrong at all with the 3.0 It had great lkeakdown and compression #s.

I just had to!

[304065]

Mike, whoa. 3746cc must mean . . .if the biggest cylinder Charles sells for a 930 case is a 102. . . that you are building it on a 76.4mm 964 crank! That is the same as a 3,8 RSR motor.

WOW. This one I gotta see.

[NY65912]

Actually,

Charles can make a 105mm which works out to 3969.3 cc

I am very excited about this engine. We will be documenting everything done.

Just to wet your appetite, the Haltech E8 went in yesterday.

Muahhhhhhhhh! Stay tuned!

[cnavarro]

Well, 102s are the largest on a 3.0/3.2 case. Off a 3.6, I have done 105s and have even contemplated doing some larger ones, but one step at a time I guess :-) Bigger slip fits are what I want to get people using, like slip fit 100s for the 3.0/3.2 or 103s for the 3.6.

Yup Mike, Bill called and we got the final details down and the order went off to JE today and should be on the new forgings too!

[NY65912]

Thanks Charles,

I stand corrected.

I guess 3.7 + should be enough

[cgarr]

WHAT? "like slip fit 100s for the 3.0/3.2" Christmas is only 6 days away, are these in stock? with the new J&E pistons 10.5/1? This would be great with my twin dizzy and PMO 50's Saving up now!!

[cnavarro]

Yeah, the slip fit 100s are in-stock, have been for the last year. :-) They might not be in the Pelican catalog, but just call and ask. No price difference.

[Steve@Rennsport]

Hi John:

Regarding your comment about bearing life,...we've been using the SBC/Buick NASCAR bearings for some time now and have not observed anything that suggests reduced bearing life in these motors as long as the bottom end is prepared properly and one uses a good oil.

These engines are well overbuilt for their displacement and HP/cylinder. The only times we see rod bearing distress is when the above mods aren't done right, the wrong choice of oil is made, or when the engine has been detonating. The latter item is critical since people should NEVER rely on their ears as the defacto "knock-sensors" for detection.

[304065]

Dr. Weiner,

VERY interesting, and I particularly like the "hp/cylinder" analysis. . . I suppose a Carrera RS made 35 hp per cylidner with the larger bearing. A SBC with the 2" bearing would have to make 280HP for the same hp/cylinder rating, and many of the crate motors available today make at least that. The point I'm making is that nobody complains that the SBC is unreliable because of the smaller bearing size even at comparable hp/cylinder.

Now, if one were making 110HP/liter (like the new PCA rules effectively mandate that you must ) in a high-strung 2,0 liter screamer motor, you're still at 220HP divided by six, or 37hp per cylinder. Not a giant increase, really.

Given that I have a 66mm crank that has rust on the journals, the prospect of being able to build a multi-season motor for PCA GT class racing is an attractive one. . . now which Calendar Year budget can I fit it into?

[Steve@Rennsport]

Professor Von Cramer:

LOL,...SBC's have some issues but main bearings (at least the 4-bolt versions) aren't one of them. I used to assist a local gent build some competitive TransAM SBC's and we never observed main bearing wear, even after a few seasons although the rest of the engine was gone through very well.

Even the 220+ HP 2.0's we have done are easy on main bearings,.......the rest of it is another matter,......

As long as you are conservative about compression ratio and peak RPM, these things can last 3-4 years with proper preparation and care.

[turboteener]

Actually the NASCAR bearing of choice is the Honda 1.8in bearing. It is one of the best bearings in the world. Too bad you can't use these on a 911 engine without a custom crank. Before Clevite started offering this bearing Hendrick Motorsports was buying thousands of them from the local Honda dealer.

http://dwolsten.tripod.com/articles/sep93a.html

This bearing is really nice because they offer it in many sizes not available on a normal bearing. Honda offers 8 different sizes just in standard.

[911 tweaks]

now that the best bearing has been informed to us all...now Henry needs to cast his 66mm cranks accordingly to use these bearings!
Henry are you out there reading this post... can you go fwd with your crank ideas now? I'll buy one!
Bob

[cnavarro]

The biggest hurdle at least in the use of the 1.8 honda journal on the four cylinder applications where the 2" chevy is common is that the honda bearing is considerably wider if my memory serves me. As is, at times we even narrow the 2" chevy bearing, and it's already a very narrow journal.

[turboteener]

Yeah the T4 has to have a custom crank. Not sure about the 911 engine. Never investigated it.

The Honda bearing is actually narrower at .857in versus .940 for the Chevy bearing. It would probably require a custom crank for the 911 as well, but you could make the crank stronger, although that is not normally an issue. At least you can still get a much better bearing in either style than anything Glyco offered.

[neilca]

Back to the Chevy/Buick bearings. Let say I turn my crank to fit these bearings, then can I buy the Chevy H-beam billet rods for my 2.0? The rods are a whole lot cheaper for Chevy than a Porsche.