TomR

How do you change the LSA when it is ground into the cam?? Did you have the cam reground??

TURB02256

Did you purchase the complete ZZ502 or the kit to up grade to the ZZ502 if so you may not have an engine that is properly set up as a marine power unit. The cam you are using is not a marine grind. Your C/L should be closer to 114. If you do not have good headers reversion might be an issue. Also this might be more of a drag cam not really intended for continuous higher RPM use. Piston and ring fits as well as gaskets might not be suitable for marine use. It might all work but reliability and durability might be an issue.

HARRISONMIRAGE

Turbo the engine started out as a zz 502 base kit.The reason I went this route was because it is a pretty good box of parts for 5900$.The cam I had reground to a 112 lsa.My overlap is 5* @.050.You can't play much with these cams because if you lose much of the base circle on the intake lobe the lifter will fall inside the guide.The exhaust base circle is already at it's minumum diameter.I have stainles marine exhaust with no water introduced until the transom tips.This cam will revert if Idle drops below 800.I have run 7* of overlap in the past with short risers with no reversion.I suspect the reversion is from my late exhaust closing.I started a thread a while back on the effects of etended duration at low lift(.006) and the relationship to reversion but got no strong response.I honestly think that there are a lot of engines out there that have been proffesionaly built that are suffering from reversion without the owner knowing.A lot of good engine builders don't seem to have the marine cam experiance.The zz cam has aprox .300*[email protected] lift.This should make for valve train reliability due to the slow opening closing speeds.I degreed this cam and it specs out verry close to a comp 224/230 extreme energy I had in the past but it out performs it with duration slightly from the .25 lift and up.As far as the rest of the motor I tore the bottom end appart and had the decks machined to put the pistons .005 down the hole,had the bores torque honed,and balanced the rotating assembly.The main brg. tolerances were ok but I did loosen up the wrist pins while the rods were appart.The ring gap tolerances were ok and the gaskets were felpro s/s marine.For the heads I installed Ferrea valves and had to loosen the guides a bit.I used comp pro magnum steel roller rockers and bought a new marine oil pan.I would not recomend using one of these motors without careful inspection as I had to get a new block(under waranty)due to a casting flaw and there was also an issue with tight valve stem clearances.So you guys tel me is this a marine motor or not."I can't see the difference can you see the difference"

BadDog

HarrisonMirage,
Sounds like you got it wired!

TURB02256

Some things to concider: at 100% VE you would need 789 CFM, at 110% VE 878 CFM at 120% VE 959 CFM.

I lean towards 110 to 120 on boats because they naturally run higher VE do to the fact they are under a continious load.

Your Dual plane manifold was probably designed for a stock peanut port heads which have an air flow of around 250 advertized at your approx lift figures on my bench I think they were closer to 200. With much work they increased to the advertized figures.

Advertized flow for your heads is aroud 280 advertized but would probably need bowl porting to bump them up to advertized flow. So guessing your around 270. So your manifold is lacking 50 to 70 CFM of what the heads can do.

Your peak HP should be around 576 at 4985 RPM with an air flow of 280 and 502 CI.

TURB02256

Knowing this a Torker intake might be a bit small a oval port Victor might might be the real ticket but might need a spider in the plenum to take out some volume.

Some tips that the carb might be too small would be the need to adjust the idle speed screw in so far that to much of the idle transfer slot is uncovered. There are some fixes for that condition. High vacuum readings at full throttle. This is what happens on restrictor plate engines. This condition can be big trouble as fuel can be pulled from circuits in the carb that shouldnt be opperating at full throttle.

Often a restricted intake maniflod needs a larger carb than a single plane design.

TURB02256

These figures are based on your 5500 RPM you stated above.

HARRISONMIRAGE

Turbo just curious are you into this engine thing recreationaly or do you run a shop.You seem quite up on air flow data.My manifold is a large oval port design but I don't know the flow capability.Maybe I should try an open plenium design?

Reed Jensen

Harrison... that power valve in the primary bowl works only on the primary circuit.When I say "only on the primary circuit" I mean the fuel flows through the auxiliary venturi IN THE PRIMARY THROATS.. it is controlled by the vacuum in the manifold... the power valve doesn't even come into play during idle... it doesn't matter if you have little vacuum at idle... the extra fuel flow that the power valve provides flows through the auxiliary venturi, fuel doesn't flow through that circuit until you start to open the throttle.So... at idle... the valve may be open because of the lower vacuum signal... but no fuel is flowing ... if the valve opens too soon( while the throttle is open).. you will find the mixture is too rich as slow running speeds.So... don't worry what your manifold vacuum is at idle... it has no effect on the power valve's extra fuel flow while you are on the idle circuit. As Liberator 21 says.. you have to get your jetting straight... you need to check your plugs at different running speeds and throttle settings. Idle... just off idle.. light throttle setting... big throttle setting... but secondaries still closed... then after you have the primary jetting and power valve settings figured out... then you can move onto the secondary jetting. The power valve should remain closed during light throttle settings and then open during the larger throttle openings.One other thing to mention... power valves go bad... not just rupture and leak fuel directly into the manifold... but the rubber diaphragm in the valve can go hard and then the valve is stuck open.

Reed Jensen

Carb jetting is best done with the engine on a dyno and pyrometers measuring the exhaust gas temps... then you have a very clear picture of what the carb is doing at all throttle and load settings. Good luck. Part of the confusion about Holley carbs and the power valve is the name "power valve"... they used to be called "economizer valves"... because they were designed to close and lean out the mixture for good gas mileage on cars while "cruising", or very light throttle settings... But boats require larger throttle settings to "cruise" because of the drag from the hull... so settings for cars and boats are different.