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Old 11-04-2005, 02:43   #1 (permalink)
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The Limits Of Standard Conrods

JUST FOUND THE LIMITS OF STANDARD CLEVELAND CONRODS THE HARD WAY.
MOTOR IS STD STROKE 40"351 WITH 302 CONROD COMBO, BALANCED WITH ARP STUDS. CAM IS CRANE F-238 SOLID, MAX POWER IS 332HP AT THE TREADS AT 6300rpm WITH 750DP B-G AND HOLLEY STREET DOMIATOR MANIFOLD, 34 DEGREES TOTAL ADVANCE AND 3600 STALL C-4 WITH 3.9 DIFF.
I WENT TO A BURNOUT COMP AND IN 28 DEGREE HEAT, SHE WENT TO 7500rpm WITH NO PROBLEMS.
COME FINALS AT NIGHT TIME, IT WAS ABOUT 17 DEGREES AND THE CAR WAS SO MUCH MORE POWERFULL I THOUGHT IT WAS STILL IN SECOND GEAR.
THEN WHEN I LOOKED AT THE AUTO METER, I SAW 8200rpm IN TOP GEAR. (SHOCK)
GOT THIRD PLACE AND WENT HOME.
3 DAYS LATER, PUT EXHAUST BACK ON AND COULD HEAR BOTTOM END KNOCK. (NOT GOOD)
PULLED MOTOR OUT( SPUN BEARING) AND REGROUND CRANK AND FITTED NEW BEARINGS.
FITTED 125hp NOS KIT AND 3.7 GEARS,(408HP ARW) THEN WENT TO ANOTHER BURNOUT COMP.
FIRST BURNOUT WAS GREAT, SECOND WAS AS GOOD BUT NOTICED THE TACH READ 8000+ A FEW TIMES. COME FINALS IN 26 DEGREE HEAT, SHE LET GO WITH 2 CONROS SNAPPING IN HALF, (FROM TWO STRIPPED ARP STUDS) OVER HEATING
PULLED MOTOR DOWN AND PICKED UP PEICES. TWO BEARINGS MUST HAVE SPUN FROM OVER REV IN THE FIRST OR SECOND BURNOUT AND THEN TURNED THE CRANK PIN HOT BLUE.
THE RODS WERE NOT BEAM POLISHED OR SHOTPEENED.
WELL NOW I KNOW AND IT COST ME HEAPS, BUT NOT BAD FOR STOCK RODS. PITTY I DIDNT HAVE A REV LIMITER!!!!
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Old 11-04-2005, 04:03   #2 (permalink)
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Re: The Limits Of Standard Conrods

Dam, get that MSD 6al box in there next time.
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Old 11-04-2005, 05:07   #3 (permalink)
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Re: The Limits Of Standard Conrods

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Originally Posted by falcon coupe
Dam, get that MSD 6al box in there next time.
I HAD A CRANE HI-6 WHICH I THOUGHT HAD A REV LIMITER BUT IT TURNS OUT IT IS STAGE RPM ONLY. HA $10,000 LATER.........
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Old 11-04-2005, 06:23   #4 (permalink)
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Re: The Limits Of Standard Conrods

Quote:
Originally Posted by xrglen
Just found the limits of standard Cleveland conrods the hard way.

Motor is std stroke 40" 351 with 302 conrod combo, balanced with ARP studs. Cam is Crane F-238 solid, max power is 332hp at the treads at 6300rpm with 750dp BG and Holley Street Dominator manifold, 34 degrees total advance and 3600 stall C4 with 3.9 diff.

I went to a burnout comp and in 28-degree heat, she went to 7500rpm with no problems. Come finals at night time, it was about 17 degrees and the car was so much more powerful I thought it was still in second gear.
Then when I looked at the Autometer, I saw 8200rpm in top gear. (shock)
Got third place and went home.

3 days later, put exhaust back on and could hear bottom end knock. (not good) Pulled motor out ( spun bearing) and reground crank and fitted new bearings. Fitted 125hp NOS kit and 3.7 gears, (408hp arw) then went to another burnout comp.

First burnout was great, second was as good but noticed the tach read 8000+ a few times. Come finals in 26-degree heat, she let go with 2 conrods snapping in half, (from two stripped ARP studs) over heating.

Pulled motor down and picked up peices. Two bearings must have spun from over rev in the first or second burnout and then turned the crank pin hot blue.

The rods were not beam polished or shot-peened. Well now I know and it cost me heaps, but not bad for stock rods. Pitty I didn’t have a rev limiter!
I'm not sure what you learned about what stock rods can or cannot take. How much stretch or torque did you apply to the rod bolts? It seems to me that the first (shock) would have been enough to fetch a working rev limiter before adding the NOS...but what do I know? Give us an update when you figure out how to QUIT SHOUTING...okay?


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Old 11-04-2005, 06:43   #5 (permalink)
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Re: The Limits Of Standard Conrods

All I can say is you must have some pretty good valve springs!

Dude, you've got to look at your tacho more often. Get yourself a big fat shift light that will give you sun burn over 6500-7000!
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Old 11-04-2005, 15:08   #6 (permalink)
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Re: The Limits Of Standard Conrods

thats definately doing it the hard way. I only had the bend some valves before I fitted a rpm limiter. The 351 was limited @ 7000rpm. You've possibly seen a few vids of my car which you can hear it hitting the limiter.
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Old 11-04-2005, 19:20   #7 (permalink)
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Re: The Limits Of Standard Conrods

Maybe before you blame the factory rods on letting go have another look at what is being said. The crankpins are blue in colour which would indicate that a severe lack of lubrication is more than likely the culprit in this case and not the rods.Closer inspection will probably reveal the true cause of failure. Goes in a sequence.Rods receive mimimal oil and friction causes the bearing to spin.Once oil flow completely stops the crankpin and rod continue to build heat until the metals attempt to fuse.Thats when it gets ugly.
Xrglen,do you have a hi volume pump on board, restrictors,a larger capacity sump or not?
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Old 11-04-2005, 19:20   #8 (permalink)
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Re: The Limits Of Standard Conrods

Yeah I second that suggestion that a working rev limiter would be a smart thing to do..

Either way, sounds like quite a legendary effort there xrglen.
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Old 11-04-2005, 19:46   #9 (permalink)
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Re: The Limits Of Standard Conrods

So 3rd place on the 1st comp!...........I'm hoping you go a higher place on the second?

And some cool trivia for you............

8200rpm with 3.5's = 274km/h.........but, if you have a true burnout car you'd be using 2.7 gears which would spin your back wheels to 360km/h

That would have been an instant win!!
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Old 11-04-2005, 21:12   #10 (permalink)
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Re: The Limits Of Standard Conrods

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Originally Posted by TruBlu351
So 3rd place on the 1st comp!...........I'm hoping you go a higher place on the second?

And some cool trivia for you............

8200rpm with 3.5's = 274km/h.........but, if you have a true burnout car you'd be using 2.7 gears which would spin your back wheels to 360km/h

That would have been an instant win!!
I love your trivia bits Adrian, i suck at maths and find them very enlightening.
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