598 ford breaking rods cylinder 2 and 6. any ideas

I have a 598 ford that has busted 2 rods on number 2 cylinder. They are oliver rods. It is a Bryant crankshaft and a kasse oil pump There is never any noise and has had good oil pressure. It seams to let go about 300 foot in a run. I had the crank rebuilt by marine crank shaft in CA. If any one has any ideas. This is a c headed nos motor but has busted both times with out the nos on this last time I had 8 runs on it before it broke. The block is a ulta premier block from idt.

what bearing clearances are you using?

would have to check with the machine shop that put it together I think they were .0025 or .0030

If it were me, I would go to GRP or Bill Miller aluminum rods.

Where are they breaking...same place?

Where is the rod broke? Pic's would be nice.

What do the bearings look like?
Usually if a steel rod "breaks" it is when the bearing fails and seizes.

Lean cylinders? Bad tune?

Will try to post picks tonight. It the same rod. Breaks on the big end. Bolts bust off in rod and cap comes off. Then crank hits rod and bust rod or the ears off the rod

Torquing the bolts correctly? How many uses on the bolts?

Have you talked with Oliver?

I had the wsb bolts just install the new bolts the are using. The rod that broke was a new rod from oliver. I has a reputable machine shop do the work I assume they torque them correctly

onefastpickup wrote:I had the wsb bolts just install the new bolts the are using. The rod that broke was a new rod from oliver. I has a reputable machine  shop do the work I assume  they torque them correctly

I'd talk with Oliver.... And I wouldn't assume anything.

Also maybe go over your NO2 system and flow everything.

Check the ignition to and make sure everything is right, that could do it also.

It has broke the rods with the nos off just running on the engine I will call oliver today thanks

I had about 8 passes on mine when it got the bearing out of it and would have failed had I not heard hit just before staging the car. I didn't have enough deck clearance .

I think the Pistons are .020 in the hole if I remember right.

Are the rod bearings black and/or blue?

The bearing is gone haven't checked #6 yet will try to post pic

onefastpickup wrote:The bearing is gone haven't  checked  #6 yet will try to post pic

It aint 'gone' it's in the oil pan....somewhere

#6 is black looking # looks melted to crank

Not the rod's fault .

Not what you want to hear.....junk the crankshaft & put it back together with .0027-.003" clearance on the rods and .0033-.0035" on the mains.

onefastpickup wrote:#6 is black looking # looks melted to crank

What is the side clearance of the rods in question? Any blue on the rod on the big end sides?

Oliver rods and a Bryant crank aint got no side clearance issues.

That what I was thinking I called marine crankshaft about the crank they said they put it back to standard size 2.199 it had 2 new oliver rods. The bearing I took out was .001 over could that of been 2 tight

onefastpickup wrote:I have a 598 ford that has busted 2 rods on number 2 cylinder. They are oliver rods. It is a Bryant crankshaft and a kasse oil pump There is never any noise and has had good oil pressure. It seams to let go about 300 foot in a run. I had the crank rebuilt by marine crank shaft in CA. If any one has any ideas. This is a c headed nos motor but has busted both times with out the nos on this last time I had 8 runs on it before it broke. The block is a ulta premier block from idt.

" Rebuilt" Is it still to Bryant Spec? Got to double check everything and assume nothing.