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Author Topic:   ford question
midmod34
Dirt Maniac

Total posts: 124
posted December 10, 2005 10:30 AM  
We just built a 347, n-heads, full roller, stosk block with splayed billet caps, block is a roller block. went to the dyno and were antisipateing a legit 500 hp ended up at 580. My question is how long will the block live, generally turn 7500-7800rpm.

Normal Sullivan
Dirt Full Roller

Total posts: 66
posted December 10, 2005 01:26 PM  
Depends on your crankshaft/balance. Otherwise the block should live until something else lets go.

akadirtracer7
Dirt Freak

Total posts: 221
posted December 10, 2005 04:34 PM  
I run a 70 block 347 for 4 years and its still together.cast crank ,2 bolt mains,and cranked it about 7000.The last year I run it I had it in a late model with 11" tires and I was told it wouldn't last the season.Well it did and its still in 1 piece .I think was around 500 hp but never dynoed it.From what I was told when you get over 500hp is when the block gets shakey.I run a 408 now which alot of folks told me wouldn't last either but its still in one piece and its got alot more balls than the 347 had.

johder
Dirt Maniac

Total posts: 152
posted December 10, 2005 06:40 PM  
gotta watch the stock 302 blocks. i had a buddy split one right between the lifters, in the valley. He was pushing about 530 i think...can't remember it was about 4 years ago. never seen anything like it.

ford5
Dirt Forum Champ
Total posts: 723
posted December 11, 2005 06:12 AM  
It should help a little to have splayed caps installed, but you are still treading on thin ice with a stock block. I seen about 5-6 broken stock blocks on 347s just this summer. A main stud girdle helps alot. Some of the time, a perfectly good block will stress break do to an accident (crash) that happens when the car is hit hard enough to bend the frame when the motor is mounted solidly with a midplate. There is alot of stress in the motor mount area of the 2 mounting bosses and the block can't take it in that area. This situation is in a Alky powered open-wheel car.

johder
Dirt Maniac

Total posts: 152
posted December 11, 2005 07:52 AM  
ford5...have you ever seen one split in the lifter valley?

ford5
Dirt Forum Champ
Total posts: 723
posted December 11, 2005 03:59 PM  
Yep... also seen the front 2 mains and bolts jerked out of the block also seen the cylinder walls crack into water, and the block cracked and weakened such that you can't hold the freeze plugs in.

johder
Dirt Maniac

Total posts: 152
posted December 11, 2005 06:00 PM  
so yes to confirm...575hp is DEFFINATELY pushing a stock block...but it will work, untill it fails

johder
Dirt Maniac

Total posts: 152
posted December 11, 2005 06:02 PM  
oh and i forgot to mention...we were under our 6250 rev-limiter with that kinda power on our roller block... soo 7500+...i'd keep a rabbit foot hanging form the helmet hook..

not to discourage ya put you are REALLY pushing the limits...course its only fun that way. be great if it lasted years

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