Rebel_Heart

Since I don't have the technology skills to scan this in - here goes. This is my run with my 540s. What do you think?

rpm torque hp BSFC
3800 640 463 .456
3900 620 460 .474
4000 609 464 .458
4100 604 472 .478
4200 600 480 .460
4300 604 495 .449
4400 625 524 .424
4500 636 545 .406
4600 657 575 .396
4700 678 607 .403
4800 684 626 .405
4900 681 636 .421
5000 692 659 .431
5100 692 672 .431
5200 690 683 .435
5300 676 682 .443
5400 663 682 .447
5500 662 693 .457
5600 654 698 .470
5700 646 702 .487
5800 642 709 .480
5900 618 695 .491
6000 607 693 .490
6100 589 684 .494
6200 546 645 .539

articfriends

iTrader: (1)

Could you post the lbs of fuel per hour used at 5000 (tq peak) and at 5800 (hp peak). How much did the head gain you and did you lose any tq any where from it,Smitty

cobra marty

What are your engine specs? Why the dip in TQ at 4200rpm?

SB

iTrader: (1)

I agree, more info is needed to be able to truly judge this set up.

As the old guys say (lol) this engine is 'coming on the cam' around 4400-4500rpm. Basically, where cam timing and induction system tuning are starting to work together.

It does have a pretty narrow power peak though. Peak torque is 5000-5100rpm. Whereas, peak hp is at 5800rpm. 700rpm-800rpm spread. Many are 1200rpm +/- 100 .

Without knowing your engine specs I have to ask - what cam are you running and what valvetrain parts (lifters, pushrods, retainers, springs (manufacturer, type, seat psi at actual installed height, and open psi) .

Just wondering if cam or rest of valvetrain (maybe something else?) is causing it to be so narrow.

Can I guess this is a hydraulic roller ?

PatriYacht

If it's a hyd. roller, it's starting to valve float at about 6000 rpm. That would be why the power shuts off so abruptly. It is an engine with the power band high in the rpms. Good power for a 540. Now you need tube headers in the boat and prop it to rev high or it won't make near the hp in the boat. What components were used in the engine?

SB

iTrader: (1)

I'm glad you agree with me on this. Post #63 and #64
http://www.offshoreonly.com/forums/s...66#post1745166

Unfortunately not many others in the business / hobby do for some reason. I guess it's not being able to find trends from dyno session to dyno session from all the different builds.... I don't know, but it's a majorly important fact that needs to be understood and worked around.

PatriYacht

Sb, I missed that post you made in the other thread. Good points. With Morel lifters, Comp behive springs, titanium retainers etc you can raise the rpm limit to maybe 6300. After that you're going to have to go solid with high spring pressures and lifter longevity issues. Maintanence skyrockets above 6000 rpm.

Rebel_Heart

Heads (dart pro one) were ported by Jim V. using the retainers, springs and valves that he chose. The comp. ratio is 10.25. The cam in Crane #139651 with 1.8 rockers on intake and 1.7 on the exhaust. We plan to prop around 5800 to take advantage of high torque band. What caused the band to be narrow? Does 800 vs 1000-1200 make a difference?
Prior to Jim V. 680 hp @ 5600 and 675 lbs @ 4900.

5000 fuel A - 126 fuel B - 112
5800 fuel A - 154 fuel B - 128

I am rather new at this. Are these acceptable numbers? Is there anything that you would question? Although, there probably isn't much to be done now. We are testing props this week. Thanks for the input.

Rebel_Heart

What results would an engine builder strive for when converting 502s to 540s? I think these are pretty good numbers, just do not want to lose too much in the engine compartment. What would have been better numbers and how would I have experienced a difference in the boat?

I do appreciate you input. Most of you have had years of experience with this type of thing.

cobra marty

What intake and ?carb are you using?