[PHILLYGOAT]

I plan to mix & match the X(extra clearance) and std "H" series Clevites on my BBC rods to get the .0025" clearance I want. With std only, clearance is .0015" to .002", great for street only engine but I would feel uncomfortable with that for my application. The mains(3") came in at .002" which should be just fine. Engine will never see 6000RPM as peak TQ is @ 4200rpm(630) and peak HP is @ 5250rpm(590).
A couple of engine builders I have talked to said I should not have any problems doing this. They said to use the X bearing half on the rod side .
Have any of you tried this?

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Oh please,oh please,oh please let me run tens!!!! Oh yeah, a wheelie or two would be nice too!

[PHILLYGOAT]

I plan to mix & match the X(extra clearance) and std "H" series Clevites on my BBC rods to get the .0025" clearance I want. With std only, clearance is .0015" to .002", great for street only engine but I would feel uncomfortable with that for my application. The mains(3") came in at .002" which should be just fine. Engine will never see 6000RPM as peak TQ is @ 4200rpm(630) and peak HP is @ 5250rpm(590).
A couple of engine builders I have talked to said I should not have any problems doing this. They said to use the X bearing half on the rod side .
Have any of you tried this?

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Oh please,oh please,oh please let me run tens!!!! Oh yeah, a wheelie or two would be nice too!

[Goatman]

A buddy of mine had to do that on his Buick 455 Stage 1 and he makes slightly over 700HP. Drives it on the street as well (limited use). I would say go for it. Its better than machining the crank!

[Half-Inch Stud]

Phillygoat,

I'd just love to tell you it's OK, but I have not checked my rod bearings in 10 years ! They could be wiped for all we know.

Back in the day, I played those games on the crank mains as standard reasoning. Got lucky on rod bearing fit every time.

[PONTIAC DUDE]

Go fer it. It's done all the time. Even stock bearings can show a difference mixing and matching. There not "THAT" good at the factory. LOL.
Luckily, an engine is very forgiving. I know....I run Nitrous.Hahahahaha

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N.O.S. is like American Express.....You don't leave home without it.
"Keep the Pontiac engine breed pure, No mutts allowed"
http://www.angelfire.com/fl4/pontiacdude428

[PONTIAC DUDE]

And ATI Procharger's.........

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N.O.S. is like American Express.....You don't leave home without it.
"Keep the Pontiac engine breed pure, No mutts allowed"
http://www.angelfire.com/fl4/pontiacdude428

[TTS]

Like PDude wrote, an engine is very forgiving. But I can't help but think, in the overall scheme of things, in a long stroke engine in particular, there has to be problems at the bearing parting line around 90 and 270 crank degrees as the rod bearing will not be in a position to maintain a constant oil film. It just looks like a step to me, although a very small one. Still possibly a good place to grab the crank when oil gets behind it. Just my 2 cents, since I probably wouldn't do it- it will work no problem! [img]/infopop/emoticons/icon_smile.gif[/img]

[PONTIAC DUDE]

Your right to a point dude. The same theory applies to half grooved main bearings. The oil was found at high pressures to try and work behind the bearing. Closing down the supply to the rods causing rod bearing failure.
That's why the 2/3rd's groove main bearings came into focus. Been 2/3rd's grooving my own main bearings for years.
However, your only talking .0005 to .001.
Grab that feeler gauge and look.
Also torque your rod with the bearing installed and check crush. More then once has this occurred with stock bearings.
Rod sizing tolerances are in the .005 range alone.
BTW: I run those same rod and main clearances in my Nitrous and Race engines with synthetic oil. I wouldn't touch those specs. Less flex, more horsepower and less friction.


------------------
N.O.S. is like American Express.....You don't leave home without it.
"Keep the Pontiac engine breed pure, No mutts allowed"
http://www.angelfire.com/fl4/pontiacdude428

[This message has been edited by PONTIAC DUDE (edited 10-17-2001).]

[larry davis]

P'Dude, I'm confused.
What clearances are you reccomending?

[PONTIAC DUDE]

I have run tighter clearances then most people. Different theory. I have always tighten up oil clearances since racing synthetic oils became available years ago. The old days are gone (New school/old school, hahahahaha) and technology has changed. Better lubrication, paying attention to details and you can tighten up the clearances for less flex. I'm going to do an article on my Website on this and try and get into more detail as to why wide clearances and Pontiac don't mix anymore. Remember now. Pontiacs are making a lot more horsepower then they did 15 years ago as the aftermarket parts and heads to flow bigger #'s are out there, more rpms required to make horsepower and stress the bottom end twice as much. Hell, Pontiac blowing up were a common occurrence a few years back and still are, However that can be controlled.....to an extent. Probably lose a lot of business to other builders giving away learned secrets, but Pontiacs need to stay together so they can Whoop some Chevy and Ford BUTT!!!!! LOL.

------------------
N.O.S. is like American Express.....You don't leave home without it.
"Keep the Pontiac engine breed pure, No mutts allowed"
http://www.angelfire.com/fl4/pontiacdude428

[Half-Inch Stud]

P-Dude ;

I recall your partial-grooved main bearings being superior to the grooved upper/flat lowers. But Manual-cutting is no fun. Would you pursue Licensing it out so you are compensated for your Championing the effort? BOP, Spotts, IA, or Ccass ought to provide Market Credibility. I'd bet you could sole distribute these rod-savers.

Fixes bearing oilhole #1 too.

H.I. Stud Community Service Note #1801


BOP {Wade} still lagging on the HEI stainless advance kit...Stud Community Service Note #0301 - reissued.

[Will]

Main bearings with partially grooved lower halves are commercially available. Federal Mogul competition series. Unfortunately, I believe they are only available in standard and .010" under. At least this is true for the 3.25" mains, I don't know about the 3" mains.

Pontiac Dude, if you run "tight" clearances on the rods, say .0015", would you expect the need for a lengthy break-in period? What weight oil would you recommend?

If the crank grinder screwed up and got the mains loose (say .003 - .0035") and the rods "tight" as above, would that change your break-in or oil recommendations any?

Thanks!
-Will

[PONTIAC DUDE]

Yes, I would probably use a stiffer weight oil, and loosen up the rod clearance as everything has to be compatible. My thoughts and research. If ya got loose mains and run a thicker oil you need to loosen the rods to help the oil flow to keep heat from generating in the rod bearings. but still a synthetic type. Also watch your side clearance too. I believe in too much rather then too little side clearance. Low oil pressure at lower rpms never killed an engine.

------------------
N.O.S. is like American Express.....You don't leave home without it.
"Keep the Pontiac engine breed pure, No mutts allowed"
http://www.angelfire.com/fl4/pontiacdude428