BadDog

Dang, here we go again. Nothing lives longer on this board than cam or oil threads!

Looking for a cam for Gen 6 502 with 8.75/1 using a B&M 250 with 5lbs. Boost. Lightning headers, 1050 single carb and Crane Hi6 ignition. I don not plan on spinning the engine much more than 5300 and would spend a good deal of time at the top of the primaries cruising. Fairly light 24 ft. boat (Baja Force 235) for a 502 with blower.

Called Crane Tech Line and they recommended the 168731 and not the 168741. This blower combo was used on a similar 502 with good results with the 741 cam. Crane rep said that the 731 would be a little better and was good to 6000 rpm. He also said that the 741 would tend to be a bit lazy in the middle. My hull will run a best of 70 in stock form (basic 502 crate engine, nothing special not the HP500 version). I know these guys just read from a sheet for most questions so that is why I am asking here, bear in mind the hull type, not a big 29 ft. single.

Anyone running a B&M 250 at 5lbs. Boost with either of these cams? I need to choose one or the other. As is said this combo came off an engine setup and the jetting was correct for the 741, boost reference etc. If I used the 731 would the jetting still be correct? If not which way would it tend to run going from the 741 to the 731, rich or lean?

Crane said I would be fine with my stock roller lifters and pushrods. I will use the Crane Gold rockers and the recommended spring or equivalent. This brings up another question, should I machine the heads for 7/16 or use the screw in adapters?

Other things I have considered as part of the project;
Upgrade Rod bolts
Use Fel Pro head gasket

In a nutshell-
741 or 731 cam
Rod bolt upgrade required?
Alternatives to Crane Gold Rocker arms?
Alternatives to Crane springs?
Machine the heads or use the screw in adapter?

Whew, almost getting there!

Tim T.

Brad Perry

I ran that blower with a 731 cam, but in a 454. Ran great, never spun it over 5600 (I didn't have the good lower end, and was being conservative). If I had it to do over, I was thinking I would have gone with the 741...??

Brad Perry

Almost forgot, 4 and later 6lbs boost with Nickerson 980.

BadDog

Here is another twist, just talked with Lunati, they have a part 54849.

Lift at valve Intake .578 Exhaust .598
232 / 242
112 Lobe Separation
Intake Opens 6 BTDC
Inake Closes 46 ATDC
Exhaust Opens 55 BBDC
Exhaust Closes 7 ATDC

Crane
http://dab7.cranecams.com/SpecCard/...B1=Display+Card
http://dab7.cranecams.com/SpecCard/...B1=Display+Card

Might be best to stick with what has been done before?

blown1500

I love the 741 and have had better results with it, through the rpm range from about 2,000 up. I have run this before. Your carb is too big.
I would use your rod bolts here. They are pretty good.
Crane gold tockers are good. I like to use Comp or Crower Stainless. They haver been bulletproof with this size cam.
Crane offers an "offshore" valve spring that is very good. Comp Cams also has good springs for this application. I don't know the numbers-I NEVER trust my memmory for those, but if you need them, post and I will look them up. Isky makes good springs, too.
If you use the screw in adaptors, use a stud girdle. 7/16 studs are better.
Your lifters and pushrods are fine if they are in good condition.
Don't turn over 5,800. Recommend the rev limiter be at 5,800, keep rpm below 5,600.
Happy boating!! If you want more, just ask

BadDog

1500,
I was hoping you would chime in, seems like you have done this before! What would be a good source for the Comp or Crower rocker arms and about what cost am I looking at? The Cranes are not rebuild able, just a trade in for 244, not much less that new.

Yes I would like the numbers for the Comp springs. I would like to order this from one place if I could. I forgot to inquire about the exhaust valves. I was planning on having the seat angle changed. Is this really important? Seems anything you can do to keep the heat down is good. What would be the ideal temp to run the engine as measured at the intake manifold? Is too cold bad?

Tim T.

blown1500

cpqtim, the Crane Offshore spring number is 99896-16. The Comp spring number is 924-16, and you will need rertainers for the Comps #741-16, and locks-didn't look up that number. You can get all your parts from Atlantic Racing at 1-803-329-8658. Ask for Scott or Pete. They know what we use and are very helpful-for Yankees!
We run stock valve seat angles with .080" wide intake and .100" wide exhaust seat width. Changing angles can help power, but there is a lot to be done to make that work, and I don't think it is worth it. Strongly recommend Inconel exhaust or better. Even Manley Severe Duty Stainless will come apart in a blower boat!!
Oil temp is the important thing for temperatures. Here(Charlotte, NC area), we commonly run as cool as we can for water temp, but if you don't warm the oil, you will cause problems!!!
Great Boating need more, just ask.

bobby daniels

tHE 741 IN A LIGHT BOAT IS GREAT ! 1500 IS RIGHT ON THE REST
MANY VALVE SEAT WIDTH

BadDog

Ok, seems like I have some answers! Only several small things before the order is placed. Are the Crane 7/16 screw in rocker arm studs sufficient and if not would the use of the Crane stud girdle be required?

Screw in studs 99152-16
Girdle 13602-1 (about 220 bucks)

If I were to have the heads machined for the full 7/16 stud is the girdle still needed?
Choice 1, screw the stud in and forget about it.
Choice 2, screw the stud in and use the girdle.
Choice 3, machine for full 7/16 stud.

You guys are great, getting this project off the ground before my wife finds out what I am up to!

Tim T.

bobby daniels

Tim you would not have to have girdle but it would be safer to drill for full stud with the 741 cam,or 1500's