Twin 454 Crusaders 1 Carb Backfiring

"I am running two 454 Crusader

"I am running two 454 Crusaders on a common 250 gallon fuel tank both have Racor separators installed as well as the cartridge fuel filters on the tank. Starbord engine runs perfectly, rock steady 160 temp. Port engine started poppping at 3200 to 3900 rpm thru the carb. Checked the 10 degree timing...perfect. Swapped ignition modules, could not find the source of the trouble. Under 3100 and over 3900 rpm, the engine is terrific however the temp is about 15 degrees higher above 4000 then the other and about 15 degrees lower under 3000 rpm then starboard. In the range from 3200 to 3900 this popping backfire is continuous but random. Removed the flame arrestor and shook out about 2 tablespoons of NON salty water. Removed the carb to find another tablespoon of water in the Carter to Crusader manifold adapter plate. I notice the hoses that go to the flame arrestor have a small ( pea sized) accumulation of milky oil, likely from mixing with this water somewhere. The crankcase oil seems fine. These hoses also puff out some blue smoke when the cold motor is started. The carb is similiar to the Edelbrock 1410. I cleaned the metering rods and passages thinking it was a lean condition. But this water baffles me. It could be condensing or steam distilling from somewhere but I am at a loss as to where to look next for this problem. Other than SOME OTHER SOURCE spraying water in this vicinity, does anyone have a clue where to go next? Thanks..AL"

do a compression check
is tha

do a compression check
is that points or electronic ignition

"I am doing a compression chec

"I am doing a compression check on Wednesday and it is running the Delco EST electronic ignition. I am also going to measure temps on the exhaust manifold for unusal differences between sides, check the plugs for a super clean plug and next (and I hate to think of this) I may have to pull the manifolds to check for a leak there possibly a clean valve or rusty valve. The inside one is a piece of cake but the outer side .... AGH! I am starting to believe it is not carb related at all."

"Here is a dumb question BUT..

"Here is a dumb question BUT...Are both engines cooling pumps plumbed the same way. Do they both come up from the seacock, into the strainer into the sherwood pump and then into the transmissions? Is it possible that a reversal of the cooling sea water could create these conditions? Since I did not do the work in this area I suspect that this may be an issue but my lack of familiarity puts me at a disadvantage"

"Al
That small amount of mois

"Al
That small amount of moisture your seeing is being cooked off of the oil in mist. It cools and reforms on that cap and the runs from the valve covers. Check for milky oil on the dipstick, if you see that you have a small head gasket leak, if the oil is clear, change at 50hrs, run it and watch for more to happen. As for the carb, sounds like it needs a new acelerator pump, i.e. complete rebuild."

"just went thru the same thing

"just went thru the same thing
first check the fuel filter in the carb, do not use the one with the check valve in it
next if above is ok pull the carb and insure the power valve is not stuck also is the carb clean
total timing should be 22 deg advanc at 3000 rpm"

"Thanks guys for all these gre

"Thanks guys for all these great suggestions. Here is the progress I have made so far. I removed the carb and took it entirely apart. Cleaned and installed the rebuild kit which was primarily gaskets, new needle seats in the floats,a few new springs,new accel pump. I thoroughly cleaned every conceiveable passage and bolted it back on. I will say this...I have NOT tested it under load, BUT...this motor never started as easily or ran so smoothly as it did this afternoon. Additionally, NO exhaust smoke and NO smoke OR MOISTURE from the manifold hoses to the flame arrestors. Previously, these hoses spewed smoke and moisture, today I re-used paper towels tied to the ends to check for water to wipe the perspiration from my face...they were as dry as when I attached them. I truly HOPE this is the answer I have been searching for. I will be out this weekend and will run the boat under load. I will post my results......Thanks Again AL"

"go get yourself a simple vacu

"go get yourself a simple vacuum gauge at your auto parts store and hook it up to the engine at a direct to intake manifold point, not through a ported connection like on the upper portion of the carb.

Run the motor through various RPMS and see what the guage reads. Compare it to the recommendations that come with the guage. It will give you an easy impression of the interior engine conditions.

Also, change the small stone filter in your carb, it could be clogged up, at the fuel line connection to the rochester carb, it is in the body of the carb. A lean burn condition will cause the popping, as well as a slightly higher engine temperature. A single bad spark plug wire will cause this as well.

If you do not have high tech test equipment, run your engine in the middle of the night with no lights, as dark a night as possible-no moon, and look for arcing coming from a plug wire, or from the center coil lead on the distributor to the outer rings of the coil.

Check your firing order on the engine, standard rotation is 1 8 4 3 6 5 7 2, make sure all your plug wires are in the right location on the cap, and go to the correct spark plug as well

if it is reverse engine let me know and i will give you the order for that side too.

Tom"

"Tom,
Thank you for these new

"Tom,
Thank you for these new suggestions. Here is the latest. The rebuilt carb may NOT have been the problem BUT it surely does start and run much better. About 50 minutes into our run today,Saturday 9/29, the backfiring started all over again despite the 1st hour of GREAT running. I took a series of infrared heat measurements while running and found a VERY HOT spot on the intake manifold between the 3 & 5 cyclinder. Nearly all zones were around 135 but this spot was 280 and up. It lies between the raised intake passages between 3 & 5 with a burned blistered paint spot on the manifold about the 3" in diameter. I am anxious to pull the manifold and investigate further but after 4 weeks (weekends) of trial and error, I would like to solve the issue prior to this seasons haul out in about 4-6 weeks. Running temps on the dash gauges seem to make this engine run cooler than just before the carb re-build and there were no big differences in temp gun measurements between starboard (normal) and port (popping) engines. Does this suggest something to those more informed than I? I need to add that I am running Carter/Weber carbs that seem to be mirror images of the Edelbrock 1410. Other than the Edelbrock label, I would be easily fooled into thinking they were the 1410's but they are Carter 9780S and they were both running perfectly all season long until this started.

Thanks for all the help gang!........AL"

"Al, try the vacuum gauge - do

"Al, try the vacuum gauge - do it with the engine cold, then after your run it for a while. You may have a leaking intake manifold gasket, it sucks air in and allows a lean burn condition. Remember that engne parts expand when they get hot, and that may allow the engine to leak manifold pressure to create your lean burn condition.

However, most of these types of running problems can be electrical in nature. If you get an ohm meter at Radio Shack you can spend about $20 for a digital read out one. Take your distributor cap off, and set the ohm meter to read ohms. Attach one end to the center lead of each spark plug lead, the other end to the terminal on the inside of the distributor cap. Do each wire one at a time and see what ohm reading you get. If you get substantially more than 1000 ohms per foot of wire, you have a wire, that when it gets hot, is creating resistance in your primary (high voltage) side of your spark plug wires. Then test them when the motor is hot ( I know, what a pain in the butt that is!) to see if you have any significant changes. Again, more than 1000 ohms per foot of wire, you need new wires.

Now, another way to test your wires is an old one and some of the guys on this forum may object but here goes: Get a one quart spray water bottle and fill it with clean water. Set the tip to mist (MIST, not soak) and spray your wires at the distributor cap when the engine is warm, and you are safely at the dock. You do not want to soak them, just dampen them. This has to be done on a dark night so that you can see any arcing of the wires. You may be surprised to see the blue arcs, and you may see the wire into the coil actually arcing from the center high tension lead to the small 12 volt terminas marked either + or minus on the top of the coil. What ever results you get, you have to thoroughly dry the wires with clean cloths, as well as the inside of the distributor cap.

You also have a white ignition ballast resistor attached to your coil. Its purpose is that when you start the engine, it gives full voltage to the coil at 12 volts. However, when you release the key to the run position, the circuit that energizes the ballast resister and it drops the voltage going to the secondary side (12 volt) side of the coil to about 8 volts. You should check the ohm rating on that as well, both cold and warm, but you do that with the engine off and the key off.

If these low cost suggestions do not pan out, the vacuum gauge will show you any change as a result of vacuum leakage in the motor caused by a leak between the intake manifold gaskets and the heads.

Remember that on a domestic automobile, that space between the # 3 and # 5 in the manifold is for the choke stove that heats up when the engine is warm so that the choke opens up.

My guesses are bad wires, cap or misfiring plug, then a vacuum leak. You will be amazed at how much you can learn about the internal condition of an engine though with a simple $15 vacuum guage hooked up to your intake manifold. If you get a long enough piece of hose you can run the guage temporarily up to your steering station and watch it as you run the boat.


Vacuum leaks sometimes occur in the strangest parts of an engine. I had one that leaked through the carb mounting studs, around the threads. A little RTV on the threads fixed that one !
Happy hunting!"

"Whew !

Tom, That is a GREA

"Whew !

Tom, That is a GREAT LIST OF THINGS TO DO... Rest assured I will be on this VERY EARLY Sunday dark morning. I absolutley thank you for this electronic diagnosis potential. I will get these results and post them. Thank you so much AGAIN !

AL"

"Well I think this is strange

"Well I think this is strange BUT I still remain uninformed, All I was able to accomplish Sunday Morning due to time contraints were to change the spark plug wires to the new distributor cap. While the 3200 MAGIC rpm mark did not materialize, it did run well up to about 3500 for quite some time (2 hours) then she started over all again on the way back and during the trip out to Barnegat Ridge popping around 3200 and fine over 3900. My brother still believes we may have water infiltration thru and bad gasket. I have picked up the vacuum gauge and hope to be back out there this week one night to follow thru with the possible light show under the hatch cover. I sincerely appreciate the guidance you all have to offer"

Still having a problem. I trie

Still having a problem. I tried switching the ignition modules from the other side and it did nothing different. Had this same load problem. Ran at 3400 without backfire in a straight line. Steered to port which created a bit more drag to the port motor and it started backfiring. Straighten the wheel out and it ran normally. Oil pressure is about 15lbs less on this port side compared to the starboard that is about the only difference between these two engines. Any thoughts?

I have two 1984 350 hp 454 Cru

I have two 1984 350 hp 454 Crusaders in a Gibson Houseboat. One intake manifold is running 280 degrees between the #3 and #5 cylinders and the other is running 330 degrees. These are infrared readings with the engine running under load at 1200 RPM for 2.5 hours. Any idea what the normal temperature should be? The temperature at all other places on the manifold runs about 130 degrees.