HP500 Cam Help
 

I have a HP500 carb with a Blowershop 250 (4psi) and a demon carb in a 25 Daytona. I am wanting to put a different cam in it and run 5psi and not turn it over 5400rpm. Any ideas please let me know... Trying to hit 100mph....

What cam do you currently have? Also I would perhaps look into Mercs cam specs for the 600 sc and pulley accordingly. Their are a lot of Blower guys on the board and will hopefully answer your question a little better. Also PM Griff, he seems to be pretty blower savvy.

here are my factory cam specs
Crane Gen VI#169611 Grind#HR-284-2S-10IG
Adv 284, 292 at .004” Lift with 1.7 .576 / .598
At .050” 222, 230
ICL 105, ECL 115
LSA 110

And if anybody knows where I can find the factory cam spec for the merc 600sci or the 700sci please send me the info or the link

Thanks

What speed and rpms are you at now????? A cam change and another 1 lb of boost may not be enough unless you are already in the upper 90's.

it runs right at 90mph at 5200rpm on a stock 4blade 30. I want to upgrade my drive also and I have read that you can gain a few mph from a 1" shorty?? I have a really reliable boat but the motor has 400hrs so Im gonna have the heads done and I want to get some more power but still want the reliability...

prob will be a custom grind to keep the peek at 5400,come on now just buz that thing,that wil get ya the 1 lb.

what size carb? Dom?

Rob:drink:

its a 1090 King Demon Marine.

cool:drink:

that does not look to be a good blower cam, need a wider lope seperation for the boost to work well, call Bob M.

You are definately going need more than a cam and a pound of boost. You will need about 150hp more to hit triple digits. Really, you need a better set of heads, cam and more boost.
I would do AFR aluminum heads, custom cam from rmbuilder, and up the boost to about 6#.

Heads are just not in the cards for this year.. I better set the sights down to the mid 90's for this season. What cam should I buy for my setup though??

cam chioces......
 

like the others said, your lobe sep. is all wrong for a blown motor! I've built quite a few blown motors , both for cars, and
marine applications, and it really isn't feasible to run anything
less than a 112*. a good example is my current boat, a 25'
Ultimate Warlock SXT cat, with a bone stock 450hp 502 w/ a
2.3 whipplecharger/ intercooler setup. It would run 96mph
all day long (yes on gps) that factory cam is miniscule 480lift
but on a 115 lobe seperation! not the ideal cam by far, but it
makes 6-7 lbs boost, and is packing the cylinders pretty decently. your cam, while the lift and duration is pretty decent,
that 110* seperation angle is blowing alot of boost right out
your exaust! in other words, too much overlap! I'd say pull it out and have itreground, but that is the only thing that can't
be changed when you regrind a cam! my suggestion is to
look for somthing close to what you have, only on a 114*
LC! it would make a night and day difference, been there,
done that!

The 741 is the same on my engine,also have low port velocity.Over lap is bad ,The factory 500efi cam they say is alot better with the blower.

rob

525EFI cam would be a good choice. Its a Crane 741 on a 114 lobe sep.

I have read about that cam but I cant find one anywhere? Do you know of somebody that might have one??

You will probably have to call Crane and special order it.

Doesn't Jegs still have those grinds.

The 525EFI was never available without a special grind order as far as I know. These are about the only 2 cams available off the shelf from Crane for Marine BBC since the company restarted. The 139011 is the old Crane 731. The 139651 will need to be spun faster to make its full potential power. I would spin it to around 5600rpms. Either one would be an improvement, but probably not as good as the 525EFI cam. Like was said earlier, you should contact Bob Mandera aka rmbuilder on this site. He can have a custom grind done to optimize your set up.
http://www.summitracing.com/search/P...yword=camshaft

139021?


http://www.jegs.com/i/Crane/270/1390...d=Crane+139021

That is the regular 741 with the 112 lobe sep.

I can't keep track of all the new part numbers any more. Both Jegs and Summit don't show all the cams available when you do a search, even though they have it in stock. Seems like unless you have the part number, you can't find what you need.

I am not a cam expert but I know somone who is, I did the same thing you are doing with looking at cam specs. Just call Bob Madera RMbuilder, he will know exactally what you need.

Thanks for all the help and he has been mentioned twice so it sounds like he is the guy to call...