mo3d

I've searched the forum high and low and still can't find the info I need.
I have a '97 24 Outlaw with a M1 454 Mag (carb). I'm running a Holley 650 DP and can't get the jetting right. I started with 88/92 as per a recommendation from a Procharger dealer and she ran strong for about 30 min and started to miss, and plugs were very black. After beating it around, changing plugs, wires, cap, rotor, decided to look again at the jetting. Thought those jets sounded way too much given the fact Procharger say 8-10 sizes over what the carb came with, which by the way was 67/72.
I rejettted the carb to 77/82, and all the power came back and engine ran strong. I upped the secs to 84 and still ran great. Took a wet weekend trip to Raystown Lake on Memorial day and she ran great (5100 rpm at 81 mph).

The wife and I took on Tues, after Mem day, and again no problems until the end of the day when I decided to see what my sppeds would be at 500 rpm increments. Started at 3000, 3500, 4000, 4500, and WOT. Held WOT about 15 sec and engine felt like it backfired and lost power. I got out of throttle and back on and power came back but was definately lower. Now down to 70mph @ 4600 rpm. Came to find the source was a broken off ground strap on #5 plug. A little of the porcelain was chewed up , but I acct this to the broken ground strap. The plug wag not melted and had good color around the base ring. I pulled the other plugs and they too were black (rich). I replaced all the plugs and the engine ran ok, but it down a bit on power (72 @ 4700). Plugs 2,4,6,8 are black and 1,3,5,7 are noticably lighter in color. These plugs and about 2 hrs on them. Friend told me There is black smoke from exhaust when revved at idle.

I replaced the plugs again (MR43T) w/ the equivilant NGK but 2 steps colder.
Engine starts and runs but still is lacking some power and has an overall light roughness, not like a misfire, but like all the gas is not being burned (or too much gas to explode). I seem to be going thru a lot of gas also. Another fried said that the left bank plugs are either lean or too much fuel washing them clean.

Help !!!
What jetting should I be at for this setup ??

GPM

You might want to do a leak down test to make sure you didn't blow a head gasket.

mo3d

I'm planning on doing a compression and leakdown test this weekend. Engine oil is clean and does not smell like fuel though.

Turbojack

When the plug went you were detonating the motor. You may be lucky but when I have done that to a plug in the past the motor was comming out. You can distroy all kinds of parts.

Detonation is not your friend & is caused by low grade gas, too much timming, engine temp too warm, and/or too much compression/boost.

I had a friend that had that same setup & he ran his boat wot all the time. I was inpressed that the motor held up for 2 years until he sold the boat & got another one. So I know the kit works.

What kind of water temps were you running? How much timming are you running? I do not think jetting is your only problem.

Hopefully I am wrong about your engine & you have better luck then I do.

tssteph

Fuel pressure under boost is also important.... What about the blow through carb kit or carb modifications, has this all been done? I also heard that some people with carbs were hooking the boost reference line to the wrong location. So fuel pressure at idle verses boost was not correct.
My guess is you now have one cylinder with low compression.

mo3d

I'm running 93 octane gas, 29 degrees total timing, engine water temp just barely past 100 degrees, and 5 lbs of boost.
Boost is being measured from fitting on carb box enclosure.
Fuel pressure is set at 8psi at idle (measured by both installed guage and a mechanical guage). Fuel pressure goes up on guage 1-1 with boost to a max of 13lbs of fuel pressure to 5 psi of boost.
Fuel system is set up with an electric feeder pump suppling to a
mechanical fuel pump. Boost reference is also taken from carb enclosure to the mech pump vent nipple. Pressure is being taken at a fuel block attached to outlet side of mechanical pump and splits into 2 tees to feed each bowl with its own fuel line. (this is a Procharger set up).
I'm heading to the boat tonight with a cylinder balance tester, compression tester. I'm gonna keep my fingers crossed that compression is ok/balanced.
I'm really hoping it is the shotty routing of plug wires that i didn't put back into the looms.
Since cyl #5 and #7 fire back to back, I hope it's just an electrical issue.
Again the last plug check I did the plugs were pretty colored.
Needless to say they'll be back out tonight (at least 5/7).
I thinking if compression checks out ok, then I'm jetting down to
76/82, and see how she runs.

Mo

Turbojack

Most times when an engine backfires it is because of a lean condition. With your plug being distroyed, that may have been why it back fired.

I do not think you need to lean out the secondary. If anything you can lean out the primary but leave the secondary's rich. I want to say you were lean when plug went south. What power valves are you using? Does your carb have power valves in both the front & back. Since you had a backfire I would replace with new since you might have blown them.

There is a thread where Tomcat helped someone get there jetting correct. Do a search on power valves then you might find that info.

Hope when you come back to read this you have good info about the shape of the motor.

articfriends

Be careful not to mistake a rich idle or part throttle condition darkening your plugs for a rich top end condition,its easy to do,Smitty

mo3d

Well, I did a compression test last night and the bad news is 0psi in cyl #5.
#3 and #7 have 150psi.
Bad news for me huh ??
I'll be pulling the valve cover today and hope its only a broken arm, retainer or something easy, but the way this project has gone, I doubt it.
I did get 4 hrs of good run time since it been installed though !!

JLANE

Sorry to hear... you ran lean........

Your fuel pressure needs to be boost referenced. Areomotive has a great regulator for that. Always remember for every 1 pound boost you'll need to increase your fuel pressure 1 pound as well. You also need to have a power valve in the secondary metering plate. I had the same setup 2 boats ago. It took a while to dial it in but it worked great. Keep checking #7 as that will be your leanest cylinder. We ran 84 in the primary and 92 in the secondary @ 2558 feet with 7psi I hope that helps. One other thing make sure your hatch is well ventelated if your running in hot weather. You need lots of fresh air for the Procharger to be happy.

Good luck