|
700 NA is completely doable and can be reliable. A 540 at 1.3x for CI gets you there. Personally is the 10-15 extra CI worth it? Leave a little in there for future refreshes etc.
A good set of AFRs, properly spec’d hydraulic roller, 10:1 cr, single plane and a 1050 will get you to your goal. My 540 with Dart 310s and a relatively mild cam 114 630ish lift made peak tq 640 at 4700 and peak hp 620 at 5600. I’m leaving a lot on the table with these heads, but I already had them so reused them. Eventually I’ll put on a set of 335 CNC heads and swap them cam which will get me there. Nothing real trick about it. |
Originally Posted by Smitty275
(Post 4861975)
I'm going a route most wouldn't consider. Looking for max torque all in by 5-5200rpm. Just haven't decided if going 540 or 565. 10:1cr, roller cam, probably solid since I have lifters already. Intake from a Merc HP500. Holley 950 or 1000cfm 4150 with annular boosters. Floteck Oval port heads, 290cc intake ports that peak flow at over 340cfm at .600 lift. Should have a high flat torque curve from 2500-5000rpm or a little longer.
Didn't build for max HP since it not a race boat (weighs 25K) wanted big Tq. |
I think many spend too much time focusing on the HP curve snd not the torque.
When we have a single speed transmission…….., the motor comes on peak once, if you can get it there.
Originally Posted by Sonic30ss
(Post 4863722)
I built two 540's with 5200 max in mind- used Iron eagle 308 heads, 9.5:1, 850 Quick Fuel, and Comps version of the 525 efi cam. 640 hp at 5200 700ft/lbs at 3900
Didn't build for max HP since it not a race boat (weighs 25K) wanted big Tq. |
Originally Posted by Twin O/B Sonic
(Post 4863788)
I think many spend too much time focusing on the HP curve snd not the torque.
When we have a single speed transmission…….., the motor comes on peak once, if you can get it there. Made over 600 ft/lb from 2900 to 5300 and it was lean on the dyno, I tuned it with O2 sensors in the boat. |
Exactly what I was looking at.
Looks good to me!
Originally Posted by Sonic30ss
(Post 4863812)
Made over 600 ft/lb from 2900 to 5300 and it was lean on the dyno, I tuned it with O2 sensors in the boat.
|
Originally Posted by Smitty275
(Post 4861975)
I'm going a route most wouldn't consider. Looking for max torque all in by 5-5200rpm. Just haven't decided if going 540 or 565. 10:1cr, roller cam, probably solid since I have lifters already. Intake from a Merc HP500. Holley 950 or 1000cfm 4150 with annular boosters. Floteck Oval port heads, 290cc intake ports that peak flow at over 340cfm at .600 lift. Should have a high flat torque curve from 2500-5000rpm or a little longer.
|
By the way, I DO have a pair of brand new "Low Shock" mechanical/solid roller cams from Comp Cams ...and Isky tool valve springs to match if you're interested, but they will make peak power up to about 5800rpm or so on a 565cid engine...text me if you're interested. 616-two9one-793two
|
Originally Posted by Smitty275
(Post 4862535)
CR/ Compression Ratio is efficiency. Higher the CR the better the efficiency which equals more torque. So you want to run as much CR as the fuel you plan to run will tolerate based on cam timing, and iron or aluminum heads, etc.
|
Originally Posted by Brad Christy
(Post 4862489)
BBYSTWY,
That's what I'm reading. That said... If I were to start my fantasy engine, ideally, I'd have 4.53" bore pistons with 1.29-1.30" CH, which is not on their list of options. Did I read somewhere here on OSO that JE will make pistons to custom specs? Being a toolmaker of some skill, it doesn't seem to me that it would be any real feat to machine wrist pin holes .020" from a stock dimensions. BTW... I completely agree. I love the idea of doing Frankenstein builds. My model boating racing partner and I have cobbed together some pretty impressive engines in the past, boring out crankcases for larger cylinder sleeves, grafting non-OEM induction housings, shimming cylinder sleeves for longer rods and such. It's kinda fun when it all comes togther and actually works. I don't really see much of a difference here. Thanks. Brad. (937)545-8991 |
Originally Posted by Batmeat
(Post 4875746)
loved building my motor and odd ball builds. Next project is 540 for a 1000+ HP for a formula 1 off-road build. Look up Icelandic formula 1 off-road and watch vids if you don’t know what it is. As getting to 700hp that won’t be an issue. but longevity, like one of the other members mentioned, will be the issue on a NA build unless you start with a bigger block or switch to a diesel build.
I'm currently clocking 770k kms on my 2003 Cummins engine. Still gets 18mpg usg. I'm really liking the relatively mild BBC with great heads, and a big blower. You don't create much boost from the great flowing heads, the cruise can happen with no boost but the blower is filling the cylinders. The newer style roots are really efficient as well. Cons....adds weight and parts to fail. The B&M 420s weight 85 lbs...no intake. 700hp...If I have to dial up the blower a bit to get there if I need it...ideally, the heads flow well enough etc that I can underdrive it 25% to get to the 650-700. I'm finding it to be really great tuning aid. Even more so with the Arneson drives, and more difficult prop availability, tuning and costs. |
| All times are GMT -5. The time now is 08:55 AM. |
Copyright © 2026 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.