AIR TIME

maybe to small of a cam I think they used the old 454 420 cam which I think is close to what is above. being a baja your drives are deep to start with, maybe a 25 mirage plus would loosen up the slip a lil, you could talk to rmbuilder for custom cam, carbs could be tuned up by nickerson if its been a while, props if you get to that brett at bblades has a prop swap you buy 2 props test if you need to go up down or 4 blade you pay for return shipping and handling charge its great then when your on the money you can have them lab it.

Griff

His cam is bigger than a 420/525SC cam. I pulled strong to 5400-5500 rpms with a cam very close to the stock 420 cam specs. His cam is bigger and should pull harder up top.

I have to wonder if the cam installed 4* advanced or straight up. If advanced, it would pull the torque curve and peak hp down lower in the rpm range. Also where the timing is at full advance???

ezstriper

by those cam specs..looks like that may be the limiting factor...Rob

PatriYacht

The cam is plenty big enough but it really is old school and any hyd. flat tappet has trouble controlling the valves above 5000 rpm. I'd find a good cyl. head guy to do a valve job and set up a new set of springs with a little more pressure than Crane reccomends. Or just change to Crane 741 hyd. roller cams. They are tried and true and will get you 700 hp in a set-up like this. Btw, what ignition timing are you using? in a set-up like this I would use 30-32 degrees.

PatriYacht

It would be good to try a set of 25 pitch props. No boost until 4000 rpm's suggests that you are lightly loading the engines right now. They may pull the 25's to a higher speed and show more boost at a lower rpm.

jeff1000man

Ding ding ding on the timing. how much diferent timing did you use on the dyno? Did you try it to 32,33,34,29,28 etc?

You could have to much or to little.

Carb should be fine. A lot of thes set ups historically used the twin 750's actually.

Roller cam is a good idea, but there is no reason he shouldn't be spinning past 5k IF he has the right spring.

Try adjusting the timing a little.

Check and make sure the belt is not slipping. Do you have the notched pulley set up or the grooved pulley set up. That could be why you are not making the proper boost.

What exhaust do you have on the boat. That could be slowing you down.

Just other factors.

If you had the arrestors off on the dyno, that is not the problem now.

cocktails

Thanks for the continued advice. Was on a cruise to the Carib. back now in cold Roch. NY. I have to think hard on the timing and total advance. I am running a Crane Hi -6M ignition with a 650Sc Ign. Curve. I think I am running 10-12 initial with 32 total advance. I only have a set of 3 balde 19P props to test with so not sure if that would do much for my research.

Let me know if you have any more thoughts.

thanks

cocktails

Not sure of this info I will have to check back with my engine builder. i'll have more info this week.

cocktails

Back from a cruise to the Carib. Now back in cold roch. NY
I am Not real familiar with cam's and specs. does this crane 741 Hyd. roller have the same specs as what I have or would I order a Crane 741 to match my specs??. I am sure I am running 32 total advance. I am using a Crane Hi-6M running the SC650 Ing. curve.

cocktails

Right now I am only running 4 Blade Hydro. Eng 23P props. I am also running 1.36 Bravo 1's. I am changing over to XR's for next year 1.35's. I have to reprop. i am trying to make all the right decisions before I buy a new set of wheels.

Thanks for the input. All opinions are valued.