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Agreed - I don\'t by any means feel I can 100% say one route is better than the other so I guess i should watch how I word things. This was the reply I saved in my PM box on tech, so I thought this was the most beneficial. I\'m going to leave the name out since obviously the poster intended it to be private.
Good morning,
I note that you\'ve received a range of responses to this sometimes touchy subject. Please allow me to offer my experiences privately for your consideration.
By way of introduction, I build only engines that will be run on the drag strip in NHRA Stock, Super Stock, and fast bracket competition. My observations will not be particularly relevant to mild street use, blowers, nitrous, or other modifications.
In every case that i\'ve worked on a two-bolt main block that has seen use in Stock Eliminator (no NOS, no blowers, no bull) there has been evidence of main cap movement after a season of running. These blocks see a maximum of about 7500 rpm near the end of a run. The evidence of the cap-walk is seen in the presence of shiny spots on the bottom of the main cap, sort of like freckles caused by minute shifting of the cap on the block. This seems to happen whether the cap is studded or bolted and whether the fasteners are stock or ARP. These motors have been align-honed, balanced, and carefully assembled but there is still movement. The motors live for at least 150 runs but they need to be looked at after that.
The ONLY bottom end failures I\'ve experienced have been in two blocks that have had splayed caps installed (at significant expense). I don\'t know why these motors have failed but two of them did. There was no less attention paid to the selection of parts or assembly detail on these motors. They saw roughly the same sort of usage but they experienced bottom end problems. There are many possible explanations but it\'s difficult to isolate precise causes after a catastrophic failure.
I have used a factory 4-bolt block (filled water jackets) in a Super Stock motor with stock caps and stock bolts (although I would have preferred ARP studs). Over five or six years that motor has seen over 400 runs at 8000 plus rpm and there is NO evidence of cap walk. I\'ve changed the bearings about every 75 runs, changed from a cast crank to a steel crank, changed pistons, camshafts, and other accessories but it\'s still the same block with the same caps. Two weeks ago, that LT1 won the ***** class trophy at the ***** national event, running multiple passes in the 10.20s at 3000\'+ density altitude. It held the **** record of 9.7xxx @ 135.xx mph in ****. I suspect that part of the answer is in the rigidity of the filled block and part is in the fact that the caps are adequately anchored through factory design but there is no evidence of cap walk.
Bottom line, I\'ll take the factory 4-bolt configuration over splayed caps any time. And, 2-bolt caps will move around at over 7000 rpm with studs or bolts.
I\'m sure that you\'ll take the time to review all the information presented and make a decision based on your own situation. These are my experiences and I wanted to share them with you.
Feel free to ask questions if I\'ve not adequately explained my theories.
Good luck.
I note that you\'ve received a range of responses to this sometimes touchy subject. Please allow me to offer my experiences privately for your consideration.
By way of introduction, I build only engines that will be run on the drag strip in NHRA Stock, Super Stock, and fast bracket competition. My observations will not be particularly relevant to mild street use, blowers, nitrous, or other modifications.
In every case that i\'ve worked on a two-bolt main block that has seen use in Stock Eliminator (no NOS, no blowers, no bull) there has been evidence of main cap movement after a season of running. These blocks see a maximum of about 7500 rpm near the end of a run. The evidence of the cap-walk is seen in the presence of shiny spots on the bottom of the main cap, sort of like freckles caused by minute shifting of the cap on the block. This seems to happen whether the cap is studded or bolted and whether the fasteners are stock or ARP. These motors have been align-honed, balanced, and carefully assembled but there is still movement. The motors live for at least 150 runs but they need to be looked at after that.
The ONLY bottom end failures I\'ve experienced have been in two blocks that have had splayed caps installed (at significant expense). I don\'t know why these motors have failed but two of them did. There was no less attention paid to the selection of parts or assembly detail on these motors. They saw roughly the same sort of usage but they experienced bottom end problems. There are many possible explanations but it\'s difficult to isolate precise causes after a catastrophic failure.
I have used a factory 4-bolt block (filled water jackets) in a Super Stock motor with stock caps and stock bolts (although I would have preferred ARP studs). Over five or six years that motor has seen over 400 runs at 8000 plus rpm and there is NO evidence of cap walk. I\'ve changed the bearings about every 75 runs, changed from a cast crank to a steel crank, changed pistons, camshafts, and other accessories but it\'s still the same block with the same caps. Two weeks ago, that LT1 won the ***** class trophy at the ***** national event, running multiple passes in the 10.20s at 3000\'+ density altitude. It held the **** record of 9.7xxx @ 135.xx mph in ****. I suspect that part of the answer is in the rigidity of the filled block and part is in the fact that the caps are adequately anchored through factory design but there is no evidence of cap walk.
Bottom line, I\'ll take the factory 4-bolt configuration over splayed caps any time. And, 2-bolt caps will move around at over 7000 rpm with studs or bolts.
I\'m sure that you\'ll take the time to review all the information presented and make a decision based on your own situation. These are my experiences and I wanted to share them with you.
Feel free to ask questions if I\'ve not adequately explained my theories.
Good luck.
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