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Main cap broke in half ****UPDATE*****
#960069
03/27/11 05:48 PM
03/27/11 05:48 PM
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Joined: Aug 2009
Posts: 2,054
Mooresburg, Tn
'72CudaRacer
OP
top fuel
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OP
top fuel
Joined: Aug 2009
Posts: 2,054
Mooresburg, Tn
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Yep. Built this engine last winter and put close to 300 passes on it. Wasn't planning to do anything to it this winter, except fix the oil leak at the pan. My machinist talked me into at least pulling a couple of rod caps and check the bearings, so I pulled the engine, checked the rod bearings and all looked good...until I saw something "that just didn't look right".  #2 main cap broken into 2 pieces. I am going to disassemble the rest of the engine this evening, hopefully everything else is OK. Anyone have any ideas what causes this? Stock block, crank and main caps, EVERYTHING else is aftermarket. Arp main studs, H beam rods, Ross 13.5:1 pistons, Milodon gear drive & SS oil pan w/ swinging pick up, Stealth heads, Team G intake w/ 1050 dominator, 2" Hooker headers, ect, ect. 1 week before 1st race, what are my options??? Thanks, Brian Dunnigan
Last edited by '72CudaRacer; 04/01/11 04:12 AM.
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Re: Main cap broke in half
[Re: '72CudaRacer]
#960072
03/27/11 06:09 PM
03/27/11 06:09 PM
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Joined: Nov 2009
Posts: 3,410
Belpre,Ohio
CHAPPER
master
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master
Joined: Nov 2009
Posts: 3,410
Belpre,Ohio
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Seen it happen several times. As for the cause,,,IMHO..when this happens, as you have said, with stock caps/crank/etc.,,,,you are pushing the envelope as they say, to the "limits". I would say the main cause is cap movement/flex. It is time for some good caps. 
If you like drag racing, support your local track.
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Re: Main cap broke in half
[Re: '72CudaRacer]
#960073
03/27/11 06:10 PM
03/27/11 06:10 PM
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Joined: Jun 2003
Posts: 52,972
Romeo MI
MR_P_BODY
Master
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Master
Joined: Jun 2003
Posts: 52,972
Romeo MI
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1 week before 1st race, what are my options??? Thanks, Brian Dunnigan
You need to pull it apart so you can see IF anything
else has a issue but right now its a set of caps and
a line bore... I've seen those BB crack a cap and the
owner/driver didnt know when or how it happened...
BB tend to do it... just my opinion... detonation
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Re: Main cap broke in half
[Re: '72CudaRacer]
#960075
03/27/11 06:35 PM
03/27/11 06:35 PM
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Joined: Aug 2003
Posts: 43,308
Bend,OR USA
Cab_Burge
I Win
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I Win
Joined: Aug 2003
Posts: 43,308
Bend,OR USA
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Is this a 400 or 440 block? In either case take the motor all the way apart and have the main webs magnaflux very thoroughly before preceeding If the main webs are not cracked then you have to decide on how you want to fix it, steel or aluminum main caps  As far as why they break to start with I would bet on detontaion I've seen several 400 blocks break the main caps along with splitting cylinder walls at the same race  That motor split the #2 cylinder and broke the #5 main cap  The owner says that it never hydrauilic or treid to kickback like it was hydraulicked I would probally look at a set of Aluminum main caps, not the four bolt type either, in your motor if it was mine
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
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Re: Main cap broke in half
[Re: Dodgem]
#960077
03/27/11 09:15 PM
03/27/11 09:15 PM
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Joined: May 2007
Posts: 1,443
Maryland
Dads426
pro stock
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pro stock
Joined: May 2007
Posts: 1,443
Maryland
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Brian,
If you want to keep the stock caps, I have a #2 that I can send to you for a RB block. Let me know. Jon
2012 422 Allstars NSS Champion
2013 422 Allstars NSS Champion
2014 422 Allstars NSS Champion
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Re: Main cap broke in half
[Re: Dabee]
#960082
03/27/11 10:47 PM
03/27/11 10:47 PM
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Joined: Nov 2003
Posts: 6,293
Rock Springs
Bob_Coomer
master
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master
Joined: Nov 2003
Posts: 6,293
Rock Springs
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Tough break Brian... Sucks for sure....
[color:"red"]65 Hemi Belvedere coming soon [/color]
[color:"#00FF00"]557" Indy engine 1.07 60ft 144mph in the 8th 2100 lbs package [/color]
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Re: Main cap broke in half
[Re: 383man]
#960084
03/28/11 02:39 AM
03/28/11 02:39 AM
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Joined: Oct 2003
Posts: 3,698
NE Oklahoma
Von
master
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master
Joined: Oct 2003
Posts: 3,698
NE Oklahoma
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I should have a #2 cap (RB), if you need it.
72 RR, Pump gas 440, 452s, 3800 lbs, Corked, ET Radials,. 11.33@117.72.
Same car, bone stock 346s, 9.5 comp, baby solid. 12.24@110.
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Re: Main cap broke in half
[Re: Mr.Yuck]
#960085
03/28/11 09:27 AM
03/28/11 09:27 AM
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Joined: Jan 2003
Posts: 21,085
Niles , Ohio
therocks
oh wait.but hey.lets see.oh yeah.
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oh wait.but hey.lets see.oh yeah.
Joined: Jan 2003
Posts: 21,085
Niles , Ohio
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Yuck I had a 70 Imp that didnt break the caps but did break a main bolt.I had low oil pressure also.It started to get a slight knock so I dropped the pan.Found the head of the bolt and the bolt in the pan.I probally drove it like that for 5000 miles before I pulled the pan.Now the block is in my 65 with ARP studs.The block that was in my 65 when we took it to the machine shop had a bent rod.Never had any problems even spinning it to 6K.My machinist couldnt believe it was running with that rod.Rocky
Last edited by therocks; 03/28/11 09:28 AM.
Chrysler Firepower
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Re: Main cap broke in half
[Re: '72CudaRacer]
#960086
03/28/11 11:25 AM
03/28/11 11:25 AM
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Joined: Oct 2003
Posts: 7,506
Az
Crizila
master
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master
Joined: Oct 2003
Posts: 7,506
Az
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Quote:
Yep. Built this engine last winter and put close to 300 passes on it. Wasn't planning to do anything to it this winter, except fix the oil leak at the pan. My machinist talked me into at least pulling a couple of rod caps and check the bearings, so I pulled the engine, checked the rod bearings and all looked good...until I saw something "that just didn't look right". #2 main cap broken into 2 pieces. I am going to disassemble the rest of the engine this evening, hopefully everything else is OK.
Anyone have any ideas what causes this? Stock block, crank and main caps, EVERYTHING else is aftermarket. Arp main studs, H beam rods, Ross 13.5:1 pistons, Milodon gear drive & SS oil pan w/ swinging pick up, Stealth heads, Team G intake w/ 1050 dominator, 2" Hooker headers, ect, ect.
1 week before 1st race, what are my options???
Thanks,
Brian Dunnigan
Great catch! You owe your machinist a  . Probably detonation - The bearings might confirm it. Besides what's been mentioned, you might want to look at your fuel / timing situation. IMO, this is why it pays to leave a little on the table when it comes to staying out of detonation. Most aren't as lucky as you. 
Fastest 300
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Re: Main cap broke in half
[Re: earthmover]
#960088
03/28/11 06:02 PM
03/28/11 06:02 PM
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Joined: Mar 2003
Posts: 1,629
pa
572charger
top fuel
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top fuel
Joined: Mar 2003
Posts: 1,629
pa
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i got brand new billet caps for a 440 $100.00  jphemi68@yahoo .com
606 hemi pump gas best 9.60 at 142mph on motor
05 hemi daytona 1500 go-mango 4wd quadcab
2007 hotrod mag pump gas drags runner up, roadkill nights dodge big tire winner 2018 2019 back to back
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