575sci ate a cam lobe....
 

Well, my 575 decided to eat a cam lobe... so.... I am doing a complete overhaul on it and have some questions...

First: Is it better to use a flat tappet cam again or hydraulic roller?

Second: Pending no damage to the lower internals, I was just going to replace the bearings, balance, re-ring, hone, ect, and re-asseble. What else should I be doing? I plan on rebuilding the heads too. The motor has 270 hours on it.

Third: Any upgrades to do while i'm in there?

Thanks

Todd

Hydraulic roller would be better but there is more work and expense to set one up, about 4 times the price of a flat tappet.

Have the crank journals polished and inspected to be sure it don't need to be ground.

Should be no need to do any balancing.

Being a 575 I would think it already has several upgrades, however the skys the limit. It just depends on how much you want to spend.

Do you plan on doing both of them???????

If not, you need to stick with the stock cam. You can make more power with a roller cam and that would be the way to go if you are doing both engines. You will also need to have the ecm's recalibrated and they should probably done on a dyno unless you can find a builder with a specific combo.

I recenetly rebuilt a pair of 575's . That is exactly why we decided not to switch to roller cams. It was impossible to duplicate the flat tappet cam to a roller. You can duplicate the lift and duration but not the ramps. The concern was the vacuum signal would be different, requiring the ECU to be re-programmed on a dyno. Once the heads were apart, we found most of the valves needed to be scrapped. Most were tuliped. A new set of Manley inconel exhaust and stainless intakes were installed, along with new springs, retainers and 10* locks. BTW... Mercury used 7* locks!! WTF!!

If you find you need some stock pistons, I have 16 of them available. We took the blocks .030 over to get fresh bores.

Thanks for the input guys....
As for right now, I plan on fixing motor, then pulling the good motor and going through that one as well this winter. It all depends how quickly I get moving. Last night I was ready to work all night to get it pull out but this morning I am slowly loosing my enthusiasm... So... We'll see... lol

I had a head gasket starting to let go on mine
a couple years ago, they had around 388 hours on them,
ran great otherwise.

I pulled them out, was planning to just do the top ends,
but found out the heads were cracked around the ex. valve seats.

That changed everything....I really couldnt see spending
good money on GM heads.

I got a hold of Dean Gellner, (he's done several 575 upgrades) I had him build me a set of Dart Iron Eagle heads,
his custom hyd roller cam, lifters timing chain and ECM upgrade that he uses in his recipie.

I had the block honed, decked, ringed and bearinged it.

They run great, probably picked up 4 to 5 mph,
idles good, they dont load up any more

Deans # is 216-398-8500

Since it sounds like you are doing both motors, I would do the cam upgrade, raise the compression to 8.5/8.75, reprogram the ECUs and raise the rev limiter to 5800.
There is also horsepower to be found by raising the boost from 4 PSI to 6. Just change your snout pulley from the 4" to 3.5". All this can be done and safely run on pump 93.
Your heads should be upgraded with the springs from the cam kit, and sent off to a machine shop for clean up and setting spring heights.
With more boost, these motors also like intercooling.
Eric Betty (EB Marine) has a ECU curve that should be close for this setup. I would bring one motor down to run on the dyno, and then duplicate that curve on the other ECU. Or you could dyno them both. EBM can handle your entire project.
We've done what you are doing (and more) to several 575s.
The good news is there is plenty left. The 575 is a well built, very undertuned motor from the factory.
Let me know if you need Eric's #.
Regards,
Steve

hydraulic roller, .030 over, .010 deck, a clean on the heads, Chiller and 3.5" pulley=704HP and climbing (rev imited at 5350) with stock ECUs. Fuel map is good. Figure I'd have to replace fuel system if I raised the limiter so I didn't. The engines have run great for 3 years.

Engine does not load up while idling through the cut for an hour. Not much soot on the back either.

This year I sent the injectors out for a check. Everything seemed fine, just being safe. 1 didn't flow at idle and flowed 15% more at WOT. The others flowed about 5% more after cleaning.

No noticable changes afterwards.

If the heads are in good shape, then i'd re-use them. If they arent, i wouldnt spend the money too go thru them fully. For not that much more, you can go to a better head. I'd go to some aluminum darts and bump compression to 8.5.

They seem to be in good shape. My plan is to have the heads completely gone through. Both engines are ready so I once I get this one apart and rebuilt, the other one will be pulled down. Definetly going roller... from the talks of it... I think we can make it happen. Not really looking for more power, just something that will get me by for the next few years. Then again... we are sooooo close to the triple digits mark....sigh.....