skunknet

My 572" tall deck was built with the idea that a blower would be added later so the engine was setup with low 8:1 compression and a small cam since blowers don't need big cams. Dyno’d 620hp at 5200 RPM and 660 lbs at 4300 RPM. I will not be adding the blower but now want 80 to 100 more hp at 5200 to 5400 RPM. What size cam do you suggest? Below I’ve listed some Crane Cam specs and part numbers. I will not be spinning the engine over 5400 RPM and understand my peak hp may be over that at 5600 RPM.

Current cam - 222/232 @.50” with .575/.595, 112
Crane #139731 - 226/234 @.50" with .587/.610, 112
Crane #139741 - 234/242 @.50" with .610/.632, 112 (big as I want to go)
Crane #139651 - 244/256 @.50" with .632/.632, 114
Crane #139661 - 256/264 @.50" with .632/.632, 114

How much hp should I expect from the Crane 741 versus 651 cam?
Would there be a significant reduction in valve train reliability using the 741 or 651 compared to my current cam?

Other eng specs:
Merlin 320cc heads, ported, 2.25/1.88 valves flow 360/275 CFM. Dominator 1050 with 89/90 pri/sec jets on Brodix intake. 40 degrees ign timing. The 1050 Dominator seems too big CFM for the 700hp I’m after plus it is older technology. Would a Holley 950 hp or smaller carb work better?

Torque / hp are very flat with 90% of peak torque available from 2600 to 5500 rpm so does that suggest an engine which should respond well to a larger cam?

Dyno results RPM / hp / torque:
6000 = 585hp - 511 lbs
5600 = 604hp - 566 lbs
5400 = 614hp - 600 lbs
5200 = 620hp - 622 lbs (peak hp 620hp at 5200 RPM)
5000 = 603hp - 633 lbs
4700 = 586hp - 655 lbs
4300 = 536hp - 660 lbs (peak torque 660 lbs at 4300 RPM)
4000 = 487hp - 640 lbs
3000 = 360hp - 630 lbs
2700 = 330hp - 607 lbs
2000 = - 500 lbs

585 + hp 4700 to 6000 rpm (dyno stopped) 95% peak
555 + hp 4500 to 6000 rpm (dyno stopped) 90% peak
500 + hp 4100 to 6000 rpm (dyno stooped) 81% peak
460 + hp 3800 to 6000 rpm (dyno stopped) 75% peak

500 + lbs 2000 - 6000 rpm 76% peak torque for 4000 rpm
600 + lbs 2600 - 5400 rpm 92% peak torque for 2800 rpm
630 + lbs 3000 - 5100 rpm 96% peak torque for 2100 rpm
650 + lbs 4300 - 4900 rpm 98% peak torque for 600 rpm
655 + lbs 4300 - 4700 rpm 99% peak torque for 400 rpm

[ 02-11-2002: Message edited by: One Big Screw ]

Dave F

In my opinion I would put the minimum of the 741 cam but probably go with the 651.
However, either way I would boost compression to minimum 9:1 and max 9.5:1 especially with the 651 cam.

In my opinion you have alot of breathing ability, (320cc heads all done up and a 1050) but not much valve movement for the amount of air the cubes can use.

The cam alone wont give you hp. Actually, with that low compression, putting in a larger cam will most likely disappoint.

As far as the carb goes, a 572 can only use a maximum of 910 cfm at 5500 r's.

my .02
DAVE

MIKEHTMSR24

I have a 540, worked edelbrock alum heads. over sized valve, 10.1, 741 cam, Barry Grant 850 flowing 920.
dyno results
683 hp @ 5680 (highest r's took)
676 torq @ 4700
One sweet runnin' motor, idles perfect, doesn't load up, would idle at 400 r's if I would let it.
Running CMI's with wet tailpipes without any reversion problems.

cobra marty

Mike, With your motor I would almost want to get rid of my supercharger. Nicely done.

jdnca

I think your motor is severly choked for air and you can easily pick up another 75-100 Hp with a cam change. Remember bigger cubes tend to tame down longer duration camshafts. My 502 had Fully ported iron heads, with 2.25 / 1.88 valves, dart single plane intake, a Nickerson 1050 Dominator, solid roller with 252 / 258 @.050 .680/.708 lift on a 114 centerline with +2 advance. Never any valvetrain problems over the 60hrs I owned that boat. You should see a big improvement by stepping down to an 875 race demon, you arn't turning enough RPM to take any advantage of the Dominator and your drivability will certainly improve. Don't be afraid to get your duration in the 250-260 range and get your lift up to .700ish, packaged with a smaller carb it will idle smooth at 700 rpm. A wide LSA 114-116 will also help your idle. While you are at it I would bump your compression up to 9:1 and back down your timing to around 35 degrees. My current motor is a 632 with fully ported dart 360 heads, dart tunnel ram, 2 775 Race demons (flow 980 each) 10.5/1, 280/288 @.050, .785/.760 lift on a 115 centerline. Engine will idle in gear @700 RPM. This motor makes 901 HP @6600 @806 ft/# @5200 on 93 Octane. Have not experienced any valvetrain problems to date, do have Jesel shaft rockers. I run 32 degrees of timing. I realize the camshaft I gave you is a blower cam, but it worked quite well in the 502, besides you'll be ready when you put that huffer on later.....

skunknet

OK I get the message... I need more cam! I'll move up to the 741 or 651 and down to a Holley HP 950 carb. I'm curious why the smaller cams had higher lift on intake than exhaust but the 651 and larger cams have symetrical lift .632 for both intake and exhaust? Two of you run the Demon race carbs. Why did you choose Demons over Holley HP's?

cobra marty

Lift and duration go sortof hand in hand. In that you can only lift a lifter so fast up the ramp and you need so much duration to get to a certain lift height. The longer duration allows for more lift. Crane has certain 'propriatary' ramp profiles that follow duration and lift.

Bruce

I've built many engines very similar to your application. In a 572 with flat top pistons, 124 cc combustion chambers, 8.7:1 compression ratio, fully ported cast irion Merlin heads - 345 cc intake, Brodix single plane, Dominator 1050, I use the following camshaft. Comp Cams custom grind, 248/254 duration @ .050 with .646/.646 lift hydraulic roller on a 114 LSA installed advanced 4 degrees. This engine on 87 Octane made the following power:
RPM TQ HP
4000 620 472
4300 650 532
4500 664 569
5000 666 635
5400 657 680
Have Crane do a custom grind for you copying this profile, you won't be disapointed. Be sure to use titanium retainers in your valvetrain. I would not install a 4150 series carburetor on this engine.

MIKEHTMSR24

Does anybody know my LSA on Crane's 139741 part #?

KAAMA

MikeHTM, that sounds like a very good combination on that 540" engine of yours. I am very impressed! I'm shooting for that range with my 540's as well. I was making 630hp @5400RPM with PARTIALY PORTED Dart PRO-1 aluminum heads, 9.1cr, Holley 830cfm HP, Dart single plane intake and cam at .050 was 236*/244* .601"/.601" lift on a 114* Lobe seps.

Mods are: Holley 950cfm HP, FULLY PORTED PRO-1 aluminum heads, 9.7cr, cam @ .050 244*/244* .601"/.601" lift on 112* lobe seps. We're going to throw one on the dyno and see what happens next week or so.