What's a good cam upgrade for a 575SCI??
 

I'n reading KAAMA's thread on cam selection, I'd like your opinions on a decent cam upgrade for the 575SCI.

I never could understand why the Merc engineers chose a flat tappet cam for this motor over a nice roller set up.

Anyone here tried the 741 in a 575SCI? Or, the same profile as the 500EFI?

I do like the reliability of the stock GM roller lifters and dog bone retainers but I believe you are limited to a .600 lift with them.

Kurt

Re: What's a good cam upgrade for a 575SCI??
 

Good question...they moved to the roller in the new 600.

Re: What's a good cam upgrade for a 575SCI??
 

I'm getting the cams in my 575's replaced with Crane custom ground hydraulic cams and using Morel hydraulic lifters.

I'll try to get some #'s. The engine builder has specified how to grind it. I wouldn't have a clue.

I'm not sure my #'s would help you anyway. My blocks had to be bored and the pistons replaced.

Re: What's a good cam upgrade for a 575SCI??
 

Biggus,
The factory Chevy lifters will accept up to .326" lobe or .560"-.570" valve with the stock base circle cam. Any more than that and you will need to upgrade to the retro-roller.
Bob

Re: What's a good cam upgrade for a 575SCI??
 

The consensus seems to be that the 741 will fit in just about any 502 based engine regardless of CID.
I find it hard to believe that such a cam exist that will do everything for everybody.
Old School thinking to say the least.

Re: What's a good cam upgrade for a 575SCI??
 

Anyone here running a hotter cam in a 575SCI?

Quiet Storm, ours have been bored to 509" with flat top pistons. I'm very interested to hear about your cam selection.

I absolutely hate running tie bar lifters. Are the tall body Crane lifters (dog bone style) a reliable choice?

Re: What's a good cam upgrade for a 575SCI??
 

The crane replacements are a good choice. The problems you run into with the stock ones are as the cam gets larger in lift, the base circle gets smaller and the lifters then fall out of their guide bars. The lifters do NOT rise any farther as the lobe can only be as tall as the journals of the camshaft.

Re: What's a good cam upgrade for a 575SCI??
 

True, but the rest position can be lower.

Before camming up the 575, wouldn't we want to install an intercooler?

Innovation Marine I have heard does great work on the HP500EFI in terms of rebuild and netting like 600hp out of them, proven! In wounder if they have rebuild these and what the out come is? Does anyone have a link to they web site?

Re: What's a good cam upgrade for a 575SCI??
 

For reference comparison, what are the original 575 cam specs for lift and duration?

Re: What's a good cam upgrade for a 575SCI??
 

zahndok

Crane single pattern
Lobe H 240/329
300/300 @.0042
240/240 @ .050
148/148 @ .200
.559/.559
105 ICL
115 ECL
110 LSA
INTAKE 43 BTDC 77 ABDC
EXHAUST 83 BBDC 37 ATDC
Bob

Re: What's a good cam upgrade for a 575SCI??
 

So the original cam doesn't seem that aggressive. If I have already added an intercooler and bumped the boost to 7lbs with ecu reprogram, would a more aggressive cam wake up the motor more or would I need different heads also. Looking at the recent thread on the 500efi cam it appears much more agressive than the 575 cam. Am I comparing Apples to Oranges since one is a efi and the other a blower motor? Which cam specs should be changed from oem to hop up this motor?

Re: What's a good cam upgrade for a 575SCI??
 

Biggus

I spoke to my engine builder about the cam selection and he asked me not to share the information. He said that there are so many variables involved in the changes to my original engine set up that it may not work as well for your engine. I guess it's like one of those trade secrets too.

Cam selection seems like black magic to me. I know just enough to know I don't know enough but I'm learning a lot here.

Good luck with your selection. I wish I could have been more help.

Re: What's a good cam upgrade for a 575SCI??
 

Look how much more agressive (relatively speaking) the 500EFI cam is compared to the 500HP cam to make the same power......kinda shows you how much MORE power an old school carb and dart intake make over the EFI stuff.... :rolleyes: :p :p

Re: What's a good cam upgrade for a 575SCI??
 

Mercury's cam choice for the 575 goes against everything I know about supercharger cams.It should have 8-10 degrees more exhaust duration to help rid the additional spent exhast gasses and it should have 112-114 lsa to shorten the overlap period. More hp could be gained by using a roller with higher lift and more time open "under the curve". The Crane 741 would be a good choice but I would have one ground at a 114 lsa and retard it a bit to make up for the 5 degrees of advance that they grind into it.

Re: What's a good cam upgrade for a 575SCI??
 

The lobe separation of 110 is what has me confused as well. rmbuilder stated in another thread that a blower motor likes a late intake opening and a good exhaust flow or duration and a lobe separation of 114. Mercury seems to have chosen the exact opposite extreme of 110. It would help to understand their reasoning here.

Re: What's a good cam upgrade for a 575SCI??
 

I'm not saying this is why Merc did it, but keep in mind the overlap cycle in blown applications help cool the surface temperature of the piston and combustion chamber thereby helping to control heat.