Compression ratio with 250 B&M
03-26-2015 | 11:15 AM
#21
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Joined: Jul 2004
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From: chicago
All things being equal, I'd be willing to bet the 8:1 engine with 7psi will make more power than the 9:1 engine at 5psi.
Crutching the blower with more compression works great with a 177. Simply because 7psi isn't an option. Well, you could overdrive it engough to make 7psi, but its past the blowers efficiency , and a waste of time . so 9:1 and 5lbs works best. the 250 will be OK at 7psi, but that's about as hard as I'd push it. I wouldn't run 7psi with 9:1 and the 250. I've done it, but its not what I'd recommend to a buddy.
Crutching the blower with more compression works great with a 177. Simply because 7psi isn't an option. Well, you could overdrive it engough to make 7psi, but its past the blowers efficiency , and a waste of time . so 9:1 and 5lbs works best. the 250 will be OK at 7psi, but that's about as hard as I'd push it. I wouldn't run 7psi with 9:1 and the 250. I've done it, but its not what I'd recommend to a buddy.
03-26-2015 | 11:48 AM
#22
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Joined: Feb 2001
Posts: 4,303
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From: Virginia Beach
Jegs and summit have those pulleys. 155192 is the 3", 155193 is 3.34" if I recall. The 3.34 made about 5psi on mine, and 155192 about 7psi.
If you end up going low compression, the 192 pulley would be my pick. 9:1, I'd run the 193 pulley.
If the heads are bare, and need assembly, how about a flat top with some milling of the heads? Those race series heads have thick decks, and can be milled a bit more than the pro 1 series. Down to 105cc /.070
If you end up going low compression, the 192 pulley would be my pick. 9:1, I'd run the 193 pulley.
If the heads are bare, and need assembly, how about a flat top with some milling of the heads? Those race series heads have thick decks, and can be milled a bit more than the pro 1 series. Down to 105cc /.070
Regarding the heads, they're already done in terms of porting, etc. I need to change out the springs and retainers (originally setup for a HUGE solid roller... sad that the titanium retainers have to go) and switch to Inconel valves. I guess I could have them shaved since they're coming apart anyway, but that wasn't really in the game plan. Not much work though.
03-26-2015 | 11:49 AM
#23
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Joined: Feb 2001
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From: Virginia Beach
All things being equal, I'd be willing to bet the 8:1 engine with 7psi will make more power than the 9:1 engine at 5psi.
Crutching the blower with more compression works great with a 177. Simply because 7psi isn't an option. Well, you could overdrive it engough to make 7psi, but its past the blowers efficiency , and a waste of time . so 9:1 and 5lbs works best. the 250 will be OK at 7psi, but that's about as hard as I'd push it. I wouldn't run 7psi with 9:1 and the 250. I've done it, but its not what I'd recommend to a buddy.
Crutching the blower with more compression works great with a 177. Simply because 7psi isn't an option. Well, you could overdrive it engough to make 7psi, but its past the blowers efficiency , and a waste of time . so 9:1 and 5lbs works best. the 250 will be OK at 7psi, but that's about as hard as I'd push it. I wouldn't run 7psi with 9:1 and the 250. I've done it, but its not what I'd recommend to a buddy.
03-26-2015 | 12:35 PM
#24
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Joined: Jan 2006
Posts: 3,869
Likes: 797
From: St. Pete Beach, FL
All things being equal, I'd be willing to bet the 8:1 engine with 7psi will make more power than the 9:1 engine at 5psi.
Crutching the blower with more compression works great with a 177. Simply because 7psi isn't an option. Well, you could overdrive it engough to make 7psi, but its past the blowers efficiency , and a waste of time . so 9:1 and 5lbs works best. the 250 will be OK at 7psi, but that's about as hard as I'd push it. I wouldn't run 7psi with 9:1 and the 250. I've done it, but its not what I'd recommend to a buddy.
Crutching the blower with more compression works great with a 177. Simply because 7psi isn't an option. Well, you could overdrive it engough to make 7psi, but its past the blowers efficiency , and a waste of time . so 9:1 and 5lbs works best. the 250 will be OK at 7psi, but that's about as hard as I'd push it. I wouldn't run 7psi with 9:1 and the 250. I've done it, but its not what I'd recommend to a buddy.
03-26-2015 | 10:29 PM
#26
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Joined: Oct 2012
Posts: 1,332
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From: dfw texas
I hate dipping into this stuff so late at nite but i swore the merc bbc blower builds had quite a dish in the piston to hit that 7.5 with off the shelf heads .could almost do a good shot of whiskey out of one . If it was clean .
