Afr heads with PAC 8002 spring upgrade.
#121
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Joined: Nov 2004
Posts: 14,094
Likes: 3,683
From: On A Dirt Floor
Boy I don't miss the anxiety of tech inspections, But I do miss the feeling of the "Okay, you guys are all set." You felt like you won a comtest, LOL, At one stretch I had a 'grab and run' technique for one part at a certain track. Oh, I don't miss the running either. Hah.
#122
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Joined: Mar 2014
Posts: 68
Likes: 4
#123
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Joined: Jul 2004
Posts: 11,332
Likes: 73
From: chicago
#124
At 18:40, he explains why, big diameter intake valves, can suck at low speed torque. My cylinder head guy, explained the same thing to me, when I mentioned replacing the 2.25 valve in my heads, with a 2.30 valve. He told me, my combination, would not benefit from the larger intake valve, as i just don't turn enough rpm to take advantage of it, and I'd likely make less power in my rpm range with it.
Shoot, only time mine are under 3500 RPM is when getting on plane.
Gotta spin my little 454's lol! I like his statement "over sized runners can kill TQ under 4000 RPM.
Great info,
Thanks!
#125
I need to buy some engines to put back in the Panther. Either going with stock power or pull it's old engines back out of the Active Thunder and build some 540's-572's for the AT. I like the 557 Jim built last year. I don't know just looking at options, I'm in no hurry. 2 short blocks would be nice to have laying around just in case.
Last edited by Rookie; 01-24-2017 at 10:09 PM.
#126
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Joined: Jul 2004
Posts: 11,332
Likes: 73
From: chicago
I agree if building a street/strip engine. As he says "cylinder filling at low RPM, 2200-2500 RPM" boat engines are rarely under 3000 RPM
Shoot, only time mine are under 3500 RPM is when getting on plane.
Gotta spin my little 454's lol! I like his statement "over sized runners can kill TQ under 4000 RPM.
Great info,
Thanks!
Shoot, only time mine are under 3500 RPM is when getting on plane.
Gotta spin my little 454's lol! I like his statement "over sized runners can kill TQ under 4000 RPM.
Great info,
Thanks!
What would maybe make a street car that gets lugged around at 1800rpm soggy, doesnt necessarily mean the same will hold true to an offshore boat engine.
He does mention how the valve itself, can dictate velocity much more so than the port volume. Which is interesting, because on one of my cam software programs, you can change throat diameter, valve diameter, valve to csa %, and see big changes in FPS measurements of port velocity, curtain velocity, etc, without actually changing the ports cross sectional area. The reason that is in the program, is to help with cam design. The average cam guy simply picks a cam based on cfm at 28", but i think the high end guys, wanna know more about whats going on. It appears, that basically the higher the velocity, the shorter the cam can be.
Maybe thats why Jimv's 565 can pull to 6000rpm making power with a cam that typically falls off at 5500rpm in the average 540 build.
Most of this stuff is way over my head, but its still cool to even try and attempt to understand it lol
#127
What would the duration be. 236/242 with 1.85 rockers vs 1.70 at 0.3837"/0.3827" lobe 0.710"/0.708" lift. Your software should be able to spit that out. His cam may be a little deceiving.
Last edited by Rookie; 01-24-2017 at 10:34 PM.
#128
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Joined: Feb 2009
Posts: 8,356
Likes: 1,515
From: NW Michigan
I need to buy some engines to put back in the Panther. Either going with stock power or pull it's old engines back out of the Active Thunder and build some 540's-572's for the AT. I like the 557 Jim built last year. I don't know just looking at options, I'm in no hurry. 2 short blocks would be nice to have laying around just in case.
Did you ever figure out what bearings you had in the engine you posted a pic of the bearings out of.
If you get in a bind and wanna keep it low budget for the panther let me know cause I have 2 two bolt main blocks, cranks, rods, and 049's. Cranks, rods perfect low hour. Blocks come from Jims years ago. Just an option.
#129
Did you ever figure out what bearings you had in the engine you posted a pic of the bearings out of.
If you get in a bind and wanna keep it low budget for the panther let me know cause I have 2 two bolt main blocks, cranks, rods, and 049's. Cranks, rods perfect low hour. Blocks come from Jims years ago. Just an option.
If you get in a bind and wanna keep it low budget for the panther let me know cause I have 2 two bolt main blocks, cranks, rods, and 049's. Cranks, rods perfect low hour. Blocks come from Jims years ago. Just an option.
#130
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Joined: Feb 2009
Posts: 8,356
Likes: 1,515
From: NW Michigan
Doesn't it just change slightly @.050. This always confuses me. I've read about it and seems even the experts come up with a different equation most generally. Total duration from open to close stays the same. We also have hyd roller with solids in the mix going on which takes a little strain off the the valvsltrain.


