Headlines
my new motor
- Thread starter bajabob 718
- Start date
MarylandMark
Charter Member
I think I need glasses but the graph looks like it looks good!
Rookie
New member
Did you redo your....I think a 540?
bajabob 718
New member
sorry about the picture i try to make bigger it is not working for me. rookie yes i redone the 540 and made it a lot better
bajabob 718
New member
i hope this come out better
bajabob 718
New member
here my motor on the dyno trying the spacers that go under the carb . they do work
jeffswav
New member
Did they check that with wideband or narrowband O2? Looks a little lean at spots. I have mine at 12.5 in the higher RPM range. Are you planning on running it at peak RPM? 6100 RPM is pretty high for a Bravo Drive. Even if you only run 5500 RPM that is still really good power. How does it Idle? I used RMbuilder for my cam and I was blown away by the power and drivabillity.
bajabob 718
New member
jeff i am not shore on the band use . i am prop my boat at 5500rpm . rmbuilder is a real nice guy he no alot about cams i talk to him i got good info from him . how did your motor come out
jeffswav
New member
I have a 489 stroker with large ovals heads and Holley MPI with wideband O2. When I switched from the (performance) flat tappet cam to the Roller I gained 5MPH and better idle. I used the Isky springs and Moral lifters. Bob said to expect 500HP, I think I was about 450 before the cam swap. I think I gained at least 50HP. He set my cam up to make peak power at 5400 RPM. I tried a few props after the upgrade. I could pull a 21 pitch prop over 5600 RPM, the 23 pitch will pull 5400 RPM and my labbed 25 pitch pulls 5000 with the best speed of 70MPH. I am raising the x dim up 3" this winter. My propshaft is 8" below now that will raise it to 5".
bajabob 718
New member
jeff that great70mph . my old motor .i did 66.6 gps 71on dream speedo. now with this 540 i am over 80mph i can t wait for summer .
Geronimo36
Charter Member
Don't mean to bear bad news or pick on the setup but the cam seems too big to me. Torque peaked at 5300 rpms, that's very high for a boat engine, even naturally aspirated...
Anyone else?
Anyone else?
jeffswav
New member
I agree, you want your peak HP at about 5500 not at 6100. If it were mine I would get a cam from Bob. I went through all of this before, cut your losses on the cam and get one that works best in your RPM range. Just my .02 cents.
Geronimo36
Charter Member
Peak torque is usually 1000 rpms lower than your peak HP and you want to get you PK tq about 1k lower than your target RPM range. If you plan to run the engine at 5500 rpms and pk torque is at 5300 you're going to be loading the engine which could cause detonation and possibly some blown bravo drives.
Rookie
New member
I have to agree with Geronimo, you will be loading the engine pretty hard. I saw twin 496's (stroked 454) die an early life cause the guy propped it at or just below peak torque. The engine was losing power, after tear down the engine looked like it had 500 hard hours on it.
I would prop it to 5800-5900 it will be a lot easier on the engine in the long run.
Your dyno sheet looks almost identical to my dyno sheet, you seem to be on the low side for torque on a 540. What heads are you running and any work to them?
Very different?
I would agree with others here, that cam you have in that engine seems to be to big on the top end and running that setup at 5500rpms will be so to speak lugging the engine that far below the HP peak. The peak toque should be down around 4300 to 4500 rpms, not at 5500rpms. The duration numbers must be really large on this cam and I suspect some potential reversion issues at a decent idle rpm??
Good Luck with your engine project.
Best Regards,
Ray @ Raylar
I would agree with others here, that cam you have in that engine seems to be to big on the top end and running that setup at 5500rpms will be so to speak lugging the engine that far below the HP peak. The peak toque should be down around 4300 to 4500 rpms, not at 5500rpms. The duration numbers must be really large on this cam and I suspect some potential reversion issues at a decent idle rpm??
Good Luck with your engine project.
Best Regards,
Ray @ Raylar
Similar threads
