wannabe

Hot Rod magazine did a test on the NEW 720R. On Race fuel it pumped out 800 HP

On 93 octane with the timing retarded 5 deg. it still pumped out 787 BHP.

This is a bad a$$ motor for not so many $ given the hardware. You could buy the long block for about 10 k on sale and have some tolerancing work done.

Wannabe

aTX427

There are few budget crate engine places that I have found that seem to have better part options:
http://www.crateengine.net/

http://www.eagleracingengines.com/pr...hort_block.asp

http://www.primediapowerpages.com/cg...03931&2D104461

Infomaniac

Not everyone is having good luck with these in their boat.

[urlhttp://www.hotboat.com/forums/showthread.php?s=&threadid=49104[/url]

Infomaniac

Duh !!!

Not everyone is having good luck with these in their boat.

http://www.hotboat.com/forums/showth...threadid=49104

rmbuilder

The Zz 572 problems stem directly from reversion issues when used in marine applications. The factory cam is unsuitable for use with wet exhaust. The 620 HP version (hyd roller) ships with the following cams specs:
316*/326* @ .004”
254*/264* @ .050
.632/ .632
112* LSA
This nets 97* overlap @ .004 and 35* @ .050
Using one of Cranes most aggressive marine profiles (139741) as a comparison the cause of the problem is clear.
296*/304* @ .004
234*/242* @ .050
.610/ .632
112* LSA
This nets 76* overlap @ .004 and 14* @ .050
The Zz 572 cam has a full 21* more overlap @ both ratings than the 741.
The exhaust valve failures experienced are the result of running at mid to high rpm levels for periods of time, then backing out of the throttle. When the engine returns to idle the (relatively) cold water reverts onto a still very hot exhaust valve causing a fracture at the stem/head area.

Infomaniac

I am able to sell the Deluxe ZZ-572 for the same price as Scoggins Dickey 12,900.00 or long block only for 12,000.00

Disassemble and increase all of the necessary clearances, add inconel exhaust valves, severe duty intake valves, Isky's latest greatest hydraulic roller lifters. Isky premium Cryo treated valve springs set up at 150# on the seat. Crane 741 cam (or cam of choice). Marine head gaskets. Oil pump prep. Moly ring set, $1,900.00 plus shipping once (me to you) and exchange of removed parts.

Bob280Silencer

Saw two at Precision Marine last week.They are pretty,but no inconel exh. valves.I think closed cooling would be the way to go also.BOB

rv

Infomaniac,
What would your guess at power be when you get through setting it up for marine environment with your cam and running on 92 octane.

Rick

Infomaniac

That 741 cam is not going to boost the HP. It is a pretty hot cam for a 540 and a 572 will tame it just a bit. HP should stay close to the original 620 unless GM has it under rated as usual.

The torque curve will flatten out quite a bit and reversion should be less of an issue.

I do like this engine combo better than a 4.5 x 4.5 combo. Even though the block is taken out to 4.560 as mentioned earlier in this thread as a negative thing.

dlbCheckmate

Why do you say you like it better then the square combo ? (4.5x4.5) What would you say are the differences ?