ZZ502 w 741 cam issues
 

I have a ZZ502 that has a Crane 741, roller rockers, cometic head gaskets, and a edelbrock airgap intake topped with a 850 holley. With Imco powerflow exhaust.
It fowles plugs, I think that it is due to a combination of carb and cooling. As it only foules the front two plugs. It has a bypass cooling system.

Would you add a recirc pump? Jetting, where should it be, it only has about 4.5 inchs of vacuum at idle. OR ultimately I have a friend who has a complete 525 EFI system, which would be the better setup, but I have oval heads, and I beleive it is rec.

Any help would be appreciated.

RT

Oh this is in my Sea Ray, it has NEVER run correctly.

Vacuum is very low. Check your ignition timing. Adding initial advance will usually improve a poor idle. Some ignition systems give you the option of changing the ignition curve. Msd uses a bushing and spring assortment to adjust the curve. Merc Thunderbolt can be adjusted by using a V-6 module with less advance. This allows you to turn up the initial advance without exceeding 34-36 degrees total. I don't know much about those carbs but I suspect something is opening early like a power valve because of the low vacuum.

I am trusting that you currently have a crossover water system attached to the front of the block? Are you using a thermostat? That's why you have the bypass hose connected?

Its in the tuning, most likely. When does it foul the plugs???? at idle or while running???? Where is the initial timing and full advance set???? How did you determine where to jet the carb in the first place???? What spark plugs???? What ignition system???

You can't just bolt stuff together and expect it to run right. The same goes with just bolting on a 525EFI system.

:DGiven the information, you may even have your head gaskets on backwards blocking the rear water passages and making the front cylinders run cold....has it always had this symptom?:eek:

It has a stainless marine crossover cooling system with a thermostat. I think that the COLD water is not allowing the front cylinders to build any heat. This I am sure is contributing to the front plugs going out. They are black as hell. It is not oil fouling, it is fuel.
The total advance is 36, I do not know what the initial is.
The Cometic gaskets were put in by Active Engines.
When running it never really gets much over 120-130 degrees, so I think the first order is to install a recirculating pump, and look at a V6 module.
The motor only has 20 or so hours on it, when it has fresh plugs it pushes the boat low 80's..... then if you idle more than a few min 60's. New plugs and away you go.

GOD I hate 4 strokes!.... and carbs LOL

RT

here is the motor, before installation, and while it was going it, it isn't complete here but you get the idea.

Crane 741, did you degree in the cam when it was installed? Are you bringing in water at idle.
I run a much larger cam than that from RMBUILDER and I have no issues. I also have Imco powerflow exhaust.
Like mentioned above I would start looking at tuning issues, like the jetting.

The cam was installed at Active engines, the motor was dyno'd there, but with dyno headers and cool fresh air. It now has the powerflows and mufflers. And a flame arrestor.

There is some milk in the tops of the valve covers, nothing down on the head, and the oil pan and oil is clean, I suspect that this has as much to do with there being no heat in the motor.
The original ZZ cam with the silent choice tops on the exhaust filled the motor. The longer tops seen in the pictures seem fine for reversion.

I belive the cam is in straight up.

RT

1BIGJIM, I just noticed you have a Pachanga, is yours a 22 or 27?
If 22, if you had RMBuilder make you a cam that is larger I am going to assume you have more power than I do. ( Actives Dyno was 560 something ).
What is your setup?
I am going to work the bottom of mine, add a 2" shorty and get BBlades on the prop ( he does my drag stuff )

Looking for mid 80's

RT

RBT - It may sound trivial, but have you checked the thermostat? If you're engine is running cold it could be the thermostat is passing coolant.

Yes, that was one thing I did check.
But it does make sense that the cooling, specially with the aluminium heads needs to be changed.

RT

Are you running a power valve in the carb? If not, you may want to jet down in the primaries and install a 6.5 PV. If you're running a PV, which one is in there? You may have the wrong PV or it could even been blown and with that cam it's activating the powervalve at idle causing you to foul plugs.

When the engine is at idle take off the flame arrestor and look down into the venturi of the primary. If you see fuel slowly dripping down from the venturi you know you found the problem.

if you really do have 4.5 vacumn at idle in gear and you are idling in gear at 750 rpm or above, then i would recommend a 2.5 power valve and jet accordingly

Please don't rip off the cylinder heads and tear into the engine before looking at the carb..... A lot of which has been posted could be possible but I really doubt it.

Also, what plugs are you running?

I think it's your tune... Just my .02.

Oh I know it is my tune, and the external parts. The motor has perfect leakdown. Mechanically it is perfect.
I am so used to EFI ( I program Merc box's, Race, Optimax and Verado ) and I am too damn young to care about carbs.

RT

EFI get thrown off by temperature flutuations (open loop/closed)...not so much on carbs...

I run 100* water temps all day long with a huffer on top, two carbs, 580 cubes, decent size cam, 30 minute idle out to the ocean etc....and not once have I ever fouled a plug.

It's the setup, whether it be carbs, timing or wrong heat range on the plugs IMHO.

It might not run good, but it sure looks good. Doug

See, I can make a 430hp drag outboard idle at 700 rpm all day, shift gears without stalling and turn 11 100 rpm pass after pass. The only part I cannot compensate electronically is humidity, and that is becasue we cannot run O2 or Lambada due to the oil.
TUNE IS EVERYTHING, I can read plugs..... I just need to know where to go to make them read right!
I figured the cooling, and know that carb is off...... but where and you guys are giving me some ideas!
Thanks

RBT,
Check your vacuum at 700-750 in gear. Adjust the PV as necessary....possible you may need to go to no PV and increased jet sizes.

May also need to adjust secondary butterfly if he's not running a PV. I've seen a lot of carbs without PV's load up when using big cams without PV's because the primaries have to be open more to idle at the correct rpms and the carb actually comes off the idle circuit and starts pulling fuel from the boosters.

Recently ran into a similiar problem with this boat.... It's a 454, 9.6 comp and an 850 holley and 741 cam, which in a 454 makes it hotter then the same cam in a ZZ 502. It didn't have a PV when I started. When I took the carb apart I found that one of the primary jets came loose and fell into the bowl. I then jetted down the primary and installed a 6.5 powervalve. We also went from a #8 NGK race plug to a #7. The engine idles all day long now, no fouled plugs and you can beat the snot out of it.

http://media.putfile.com/Billys-JC-Performance-Motor

Its a 22. I have a 496 and I don't remember the duration(236-240?) but the lift it was around .610 lift on both intake and exhaust. I have the same heads also. About the only difference between engines is I have a Barry Grant carb.:D
I never put it on the Dyno.
Brett did my prop last spring. Worked great, 25 Mirage plus. I turn it around 5,000 at 77 GPS

The tail pipes in the picture, are those for swim platforms?

Yes, the pipes are for swim platforms, with the bottom turned out to exit the sides rather than back.
I have a stock 26 bravo and turn it 5400 with the 1.50 gears in my Bravo.
What drive do you have?

Aluminum heads run colder - change the t-stat to a NEW 150 and you're probably on the right track. :D

Vacum Read
 

I am no expert, but I think a vacum of 4.5 is too low. Even with the cam. Where are you getting the reading from? Check out:
http://sbftech.com/index.php?topic=3020.msg29472

Did you have any backfires? The rich condition could be a blown powervalve.

Personally I don't think a crossover would cause the front two cylinders to run soooo much cooler than the rest. I ran a crossover but went back to circ pump because I could not get the temp over 130. But I loved the look and simplicty of no moving parts, I just wanted my water at 160 and more importantly, my oil above 212.

I am also running a crossover. Oil never gets above 180 and water temp never above 130. Any long term problems?

there something going on with only 4.5 vacume, you need to look there, as stated before, if you have a power valve(and you should) and it's anything over 4.0 it's open at idle and will cause a over rich condition....but that vacume seems way to low for that cam and set-up...Rob

i agree, do we have a vacuum leak below the carb somewhere? i would think he should idle with 10-12 in vac below the carb not just 4.

.02

Interesting, I know of a someone who had a combo close to yours with about the same HP as yours too....a 509cid engine with Dart Iron Eagle 308cc heads with just some clean up in the bowl/pockets of the heads, Air-Gap intake, and Crane 741 cam and made 563hp @ about 5600-5700rpm on Tyler Crocket's dyno with dyno headers about 6 years ago.

I would think a bit warmer thermostat might help as well. Also, look for a needle/seat that may be sticking a bit in the float bowls....it doesn't take much to make a needle get stuck---just a tiny grain of dirt can do it. It gives the same symptoms as a blown power valve where you have a slow drip from the booster.

That really depends on where the oil temp reading is being taken. The oil needs to be at 212* at some point to properly burn off condensation.

I just reread your initial post RBT. I thought you had an Edelbrock carb :drool: Water temp is not an issue on this engine. I'm running 120 degree therm's on my engines with AFR alum. heads and 1050 Holleys and they will idle at 700 rpms all day and not foul. A 741 cam is a large cam for a 502 but it is common and a good power maker. It should idle at more like 10 in. How many rpm's are you idling at? You may have to turn up the idle some. If the timing is set for 16-18 dgrees initial and 34-36 total, the next thing I'd check is the carb. Standard power valve is 6.5. Under 6.5 inches of vacuum it is open. Changing it to a 2.5 will end that problem. Have you ever checked the float levels? Needles and seats? What are the jets?

Kaama, I just looked at the dyno chart last night, 562.9 Hp at 5500 rpm. I forget the torque numbers.
PatriYacht, the boat is away for it's winter nap. It is in heated storage for the winter and I am going to make some changes over the winter.
I am going to get all the numbers from the carb and convert motor from crossover cooling to a recirc setup.
The current water temp in the summer with the lake at about 80, is 120 at best. The oil temp does rise if you are on the throttle to 240/250 which is hotter than I would like to see. It has a 2" X 10" oil cooler, the temp is picked up off the block.
Oil is Merc 25/40.
The motor idles at 800 rpm.
The spark plugs are NGK 5587, the other number on the box is R5671A-7
If I have not also stated the intake is a Victor Jr, exhaust is Imco Power flow, with BIG inline mufflers.
The ignition is from the old 330 that was in the boat, total timing it 34 degrees.......so what does that mean for initial?.... I have a V6 module from a blower motor I had.

Thanks for the help.

RT

I'm pretty sure the V6 module gives 14* of advance, that would put your initial @ 20* if you're running 34* todal.

Something is still not adding up with your vacuum being that low. check to make sure your carb isn't miss adjusted and the secondary butterly is open....either that or you need a small powervalve such as a 2.5.... but like I said before, I put a 6.5 in my friends 850 carb and it's a 454. something seems strange.... Maybe you have an intake manifold leak or something?

I wouldn't even worry about the circ. pump. With that much power I think you stand better having a crossover. If anything buy a crossover kit with a t-stat so you can run 140* water temps.

Your oil temps...are they at cruise speed or WOT?

Oil at cruise is 180-220 depending on how long it runs.

The motor needs more heat in it...... I think. The inside of the valve covers is caked in milky oil. The engine oil is fine though.

If you run a crossover kit with a bypass for a t-stat and a 140* t-stat you won't have any problems with condensation. I'd go that route before putting on a circ. pump. IMHO, the circ. pump is one more part that can fail on you.

Your oil temps are fine IMHO...

What are fine oil temps, I mean how HOT is too HOT?
I think it will see 250-270, I am thinking of going to synthetic.......thoughts suggestions?
Oh and I should mention that I run all season, so that is water temp from in the high 30's to low 80's, Brownie at Stainless Marine didn't think the crossover was a good idea.

Thanks
Keep the info coming, I am learning.

240-260 for an exteded WOT period is fine. If you run synthetic tou can go a bit higher. If youre running those oil temps (220) @ cruise you should also be burning off th moisture.

I still don't think you're fouling plugs from a cold engine unless the plugs are too cold to begin with.

The only 2 plugs that I am fouling are the front 2, where the water is the coldest. As you pull the plugs and move toward the rear of the motor they look better and better.
My bet is that is heat related.