DMOORE

Many, many Marc 500 Bulldogs (actually 540 CI) motors have gone well past that time frame. The 540 is a great combo and isn't too extreme ( bore/stroke) at all.


Darrell.

wfo1

I guess you know better. I don't know what the hell you
think everyone here is running their rings on, but it is cast iron. Merc, Eikert, hell even Brigs & Stratton. Most sleeves are cast iron too.
If your only wanting 580hp you don't need a stroker either. 509ci can do it easily and reliably.

Big Block Billy

I had Lab engine (LEE) Build me a 540 tall deck.
I was talked out of a 472-488 etc.
The more you stroke the more side loading the piston does, it wants to cock in the cylinder. This is especially true because we have to move the wrist pin up and have short skirts to clear the counterweights. Piston speed is also increased.
I ended up using a Tall deck block. I would recommend that this be the way to go. Even with a 10.2" deck height anything bigger than 555 Cubes is not going to have longevity. They can be made to last longer by changing oil extremely often. 540 cubes on a 9.8" block ? If it was any good GM would have done it. Sell the 502 blocks to a teenager...
Big Block Billy

niceguy

I'll let you guys know how long they last. I just got my 540's running and they make 721hp n/a. 4.250 stroke is not going to have any longevity issues.

And like what was said... if you only want 580hp... stick with the cheaper 509ci.

Big Block Billy

OK ! I have seen the uneven wear pattern in the cylinder wall. It looks like an eyebrow. This was a pair of 572's that Dean Nickerson himself jetted the carbs on. Whatever you do make sure the carb jetting is perfect. You dont want to dilute the oil this will exacerbate the problem. I can't see throwing that much money in parts into the 9.8 deck block. I feel it's like trying to make chicken salad from chicken $#!+
The 502 Blocks have alot of value. I also agree with the 509 recommendation. I think building a 540 from a 502 is like trying to sew a shirt around a button. In this case you don't even have the button ( The Block )
There's all kinds of people on here telling everyone else what they heard from someone else, most are well intended
I like most of us really can't afford it so I'm piecing my boat together and I'm in no rush to use it until I have everything even if that means next year or the year after that. Just to do it right ! BBB

birdog

"540 Bulldogs" used a Tall deck Bowtie block. Thats how I built mine..Merlin tall decks

FrankRizzo

Thanks to all
I was looking specifically for Gen VI opinions after being told that the Gen 4 block is the only way to go because GenIV way stronger than GenVI. Anyone know about the differences?


I hear your opinion on this BBB, I wish I had the extra bucks for an aftermarket tall deck.

Nordicflame

iTrader: (4)

Mercury Racing has no strength issues using them on the 525EFI, 600SCi and the 700SCi.
Innovation Marine used them for several years on the DPX600 which was a 4.250 stroke 540.
I personally built a Gen VI 548 with a 4.250 Crower crank with an M3 Procharger, R-Tech Supercooler with 7 lbs of boost, closed loop efi that ran 400+ hours and it was questioned as to why I tore it down when we looked inside. Looked perfect.

The Gen VI blocks are of better quality casting process of the old Mk-IVs (non Bowties) and fully cnc finished.

Stud the mains and heads and go make some power. (your horsepower target would not require that however)

Dave

FrankRizzo

Thanks Nordic ! Your perspective really helps, makes sense. I think the guys telling me not to stroke a Gen VI were talking about a 7.4 Gen VI not the 8.2 Thanks to all for the healthy dose of knowledge to help the paranoia

HOW DID YOU GO CLOSED LOOP?? Everyone has told me not to even try. Are you running O2s or EGTs?

Nordicflame

iTrader: (4)

I used a FAST EFI w/WBO2 system on that setup. The setup had a substantial amount of drop in the CMI tails and it seems with the ProCharger the reversion is held at bay by the constant intake pressure.
The same WBO2 sensor has been in there for 5 years and the map is setup to go 5% rich if it ever does fail. Very efficient setup!

Good luck on your build!
Dave