Intake Comparo 427 Dyno Mule

[1967 XR7 GT]

Hi  jayb

Questions about your 427 Dyno Mule:

How did it hold up with the Honda jrl's, do you remember the oil pressure ? Do you have a number for how many Dyno pulls ? Did you pull it down for inspection afterwards ?

What do you think about the motor endurance wise for a street motor, daily driver ?

[jayb]

I pulled it down after the dyno testing was over and the rod bearings were shot.  This was probably after a total of 6 hours of running, and around 70-80 dyno pulls. Oil pressure was 60-70 psi during all the dyno pulls, so it wasn't that.  My take on it was that the bearings were just overloaded due to their small size.  I would not recommend the Honda bearings for anything other than an all out race motor that gets torn down regularly for inspection.

Edit:  Got me thinking about this, so I looked it up and there were actually 137 dyno pulls on the motor.

[machoneman]

Yes, but.....I thought all NASCAR engines run the same small bearings at 800+ hp  w/o any restrictor plate in many 500 mile races?

[RoyceP]

About the same amount of run time right?

Yes, but.....I thought all NASCAR engines run the same small bearings at 800+ hp  w/o any restrictor plate in many 500 mile races?

[jayb]

I'd also wager that the NASCAR engines have significantly lighter reciprocating components than my 427 dyno mule did, which would also be easier on the bearings.

[mummert]

 As of a few years back the unresticted motors ran 2.0" small journal sbc.  The restrictor plate engines ran 1.850 or 1.8890 journal sizes.

 I'm suprised you got that journal size on the crank.  Was is a ground stocker or a custom.  I would think a stocker the oil holes would move outward from the center of the journal by the time it was finished ground.
 Many of the cup motors have 3-9 o'clock oiling or cross drilled rod journals to induce oil into the unloaded parts of the journals..

[1967 XR7 GT]

I'd also wager that the NASCAR engines have significantly lighter reciprocating components than my 427 dyno mule did, which would also be easier on the bearings.

Nascar Rods are around 530g, Pistons are usually around 500g @ 4.185" bore, pins range from 71g to around 130g.   

The pic are used JE Nascar SB2 takeouts 106.172mm-4.180", 1" C/H, and use 866 x 2" wrist pins, rings are .043 top & 2nd with 2mm oil with oil rail supports and weigh in at 378g. Pins are New Casidium coated .866" x 2" x .180" wall and weigh in at 100g.

Rod bearings that are used on the 1.850" & 1.888" jrls run a std bearing on the bottom and a .001' under on the top, this I learned from the used sets I have bought.. The rods are piston guided, so the rod side clearance is set between the pin bosses and the small end of the rods (any where's between .006" & .015" from what I have been told from some one that builds these motors), and the big ends never touch each other or the sides of the crank so no friction.

I am thinking how much more would a 4.250" piston weigh, it's only .070" larger than a Nascar Piston. I have a call to JE asking how thick a pin wall is need for a .787" dia 2.0" long pin for a 4.250" bore piston.

[jayb]

As of a few years back the unresticted motors ran 2.0" small journal sbc.  The restrictor plate engines ran 1.850 or 1.8990 journal sizes.

 I'm suprised you got that journal size on the crank.  Was is a ground stocker or a custom.  I would think a stocker the oil holes would move outward from the center of the journal by the time it was finished ground.
 Many of the cup motors have 3-9 o'clock oiling or cross drilled rod journals to induce oil into the unloaded parts of the journals..

It was a stocker, starting off as a forged steel 332 crank originally put in a late '50s school bus engine.  It was offset ground to get the 3.78 stroke and the Honda journal size.  The oil holes didn't move much since the outside surface of the rod journals didn't move much from the offset grinding.

[cammerfe]

137 dyno pulls is probably the rough equivalent of 200K street miles with weekends at the digs.

KS