Problems with first rebuild

[nothingspecial]

Hi everybody, I need help. I have been pretending to be a mechanic for the last two months as I rebuild my first engine from the block up. I am working on a 92 Mercruiser Chevy 350 5.7. New crank, pistons, cam, lifters and refurbished carb. The boat originally had a Thunderbolt IV ignition, but that had some missing components that I could not find at any store, so I put an EST ignition on it. I made a run stand that has a power switch, start button, tach, oil pressure, and temperature gauges. Now that the initial base timing is set to 8 BTDC - she starts right up- every time. That's a partial victory!! It sounds awesome- deep, crisp, powerful and LOUD!! However, as it idles I can see gas with the water coming out of my exhaust tubes. A lot of gas. When I rev the motor- I get a white smoke cloud out of the exhaust as well. The smoke seems to stop when idling, but it billows up when I get on it. I think the problem is carb related. I have a Rochester 4 barrel. I have tried to adjust the mixture screws, but can not eliminate the wasted fuel or smoke. The engine consumed about 6 gallons of gas (93 octane) in about an hour or mostly idling. I started the mix screws at 1.5 backed out and tried what seems like every setting moving both a quarter turn at a time. Am I right in thinking this is the carb? Bad jets? When I look down in the carb with the choke open, I don't seethe fuel 'misting'. I can see fuel dripping-steady heavy. Should I upgrade to a better card? What is causing the smoke?

 

[Fishermark]

Re: Problems with first rebuild

Q jets are notorious for leaking out the bottom of the fuel bowl. You mention that the carb is refurbished. You might want to take a look and see if they epoxied the plug on the bottom of the bowl. It also could be a the needle seat is not closing completely and flooding out the engine.

 

[Fishermark]

Re: Problems with first rebuild

By the way - what kind of cam and lifters? Hopefully not flat tappet - as they do not like to be at idle speed at break in.

 

[MarkSee]

Re: Problems with first rebuild

.... I have been pretending to be a mechanic for the last two months as I rebuild my first engine from the block up....Chevy 350 5.7. New crank, pistons, cam, lifters .......

Welcome to IBOATS

...man, I'm jealous; that's the kind of "mechanic pretending" I wish I was doing but probably going to have to wait until I retire and get a bigger home with extra garage/workshop space......
So until then, I "pretend" by buying all the different kinds of grease Merc. recommends each in their own gun, tools that I'll probably lend to neighbors before I use myself, a HF shop press for who-knows-what, and a few pairs of Dickies mechanic clothes I have yet to wear....out::faint2:

Mark

 

[dan t.]

Re: Problems with first rebuild

Sounds line you are overfueling, too high of float level will give you a drip in the venturi at idle. as has been said check the fuel well plugs in the underside of the float bowl ( center section of the carb). The stock foam floats will start to leak with time, they get heavey which will efectevly raise the float level. Initial setting of the idle mixture screws is backed out 2.5 turns

 

[BigDog98]

Re: Problems with first rebuild

Welcome to iBoats!!
I wish i could pretend to be a mechanic! I am tackling a project like this myself.
Well if i had to take a guess then i would probably check the carb bowl to see if the plug is closed up. Although i dont know to much in Rochester Quadra Jet carburetor but i would also check the seals in the fuel pump! Something tells me it might be just that. But dont take my word for it listen to the other users, they probably know more then me! Good Luck

 

[Silvertip]

Re: Problems with first rebuild

White smoke is not a sign of over fueling either. That is a sign of water getting into the cylinders. I hope you used sealant on the head bolts that go into the water jacket in the block. Pull the plugs and see what they look like. That much fuel going through the engine should have them black/wet and the exhaust should smell rich as heck. I think you have more than one issue.

 

[BahamaBarnBoat]

Re: Problems with first rebuild

When you pull all of the plugs for visual inspection as recommended above you may want to do a compression test on each of the cylinders and a leak-down test if you have the tools required to do one.

 

[Maclin]

Re: Problems with first rebuild

What do the spark plugs look like?

What does the oil look like and smell like?

Have you done a compression test since the breakin?

 

[Maclin]

Re: Problems with first rebuild

Wow, see what happens when I type something in and forget to hit Submit for 10 minutes or so!

 

[BahamaBarnBoat]

Re: Problems with first rebuild

View attachment CompressionTest-LeakdownTest.pdf

 

[BahamaBarnBoat]

Re: Problems with first rebuild

LOL Or it takes me 10 min to figure out how to attach a PDF. I think my last post has officially wore out the compression test.

 

[nothingspecial]

Re: Problems with first rebuild

Thanks for all the response. You guys have given me plenty to keep me busy for a while. I ll be back with results and most likely looking for advice on next issues. Thanks again

 

[Walt T]

Re: Problems with first rebuild

good luck!

 

[nothingspecial]

Re: Problems with first rebuild

Hi Again, I have had a little time to do some of your suggestions. I am going to try to get some video to show exactly how much white smoke come's out the exhaust when i give it throttle. The first thing I did was a compression test on a very cold engine( I will do another soon with warmer engine temperature )

cylinder #1-107 psi,#2-100,#3-95, #4-100, #5-100, #6-110, #7-95, #8-95.

I read that no one cylinder should read below 100 HOw bad is this? Does engine temp affect readings? How about thinned oil(2 quarts gas with 6 quarts oil is very thin)

The plugs were black and wet I cleaned them and put them back

I drained the oil and filter. I originally put 6 quarts in. I had about 1 hour of break in- run time on motor when i drained oil. I drained out 8 quarts of oil and gas mixed. I did not notice any sign of water in the oil. Only gas and about 2 quarts of it. Why ??

I put new oil in and am afraid to start it with out addressing the carb issue first.

I took apart the fuel filter and cleaned it up the best I could. Diaphragms look ok to me or I should say that I did not see any holes,rips, or tears.

I am assuming that if I start it up again ...... I will flood the oil again with fuel

 

[FreeBeeTony]

Re: Problems with first rebuild

Maybe your fuel pump is shot dumping fuel into the crankcase?............assuming you have a mechanical pump.

 

[Maclin]

Re: Problems with first rebuild

Nothingspecial, please verify to this group that during your test...:
1.) ALL spark plugs were out
2.) Throttle was wide open

Those are low numbers, but the above conditions mentioned can make a slight difference. Also let us know if you squirted oil in each cylinder and tried again to see any change.

 

[Fishermark]

Re: Problems with first rebuild

Maybe your fuel pump is shot dumping fuel into the crankcase?............assuming you have a mechanical pump.

That's what I would suspect as well. That's a LOT of gas in the oil. And unfortunately for you, having gas diluted oil during break in is not a good combination.

 

[Bondo]

Re: Problems with first rebuild

Hi Again, I have had a little time to do some of your suggestions. I am going to try to get some video to show exactly how much white smoke come's out the exhaust when i give it throttle. The first thing I did was a compression test on a very cold engine( I will do another soon with warmer engine temperature )

cylinder #1-107 psi,#2-100,#3-95, #4-100, #5-100, #6-110, #7-95, #8-95.

I read that no one cylinder should read below 100 HOw bad is this? Does engine temp affect readings? How about thinned oil(2 quarts gas with 6 quarts oil is very thin)

The plugs were black and wet I cleaned them and put them back

I drained the oil and filter. I originally put 6 quarts in. I had about 1 hour of break in- run time on motor when i drained oil. I drained out 8 quarts of oil and gas mixed. I did not notice any sign of water in the oil. Only gas and about 2 quarts of it. Why ??

I put new oil in and am afraid to start it with out addressing the carb issue first.

I took apart the fuel filter and cleaned it up the best I could. Diaphragms look ok to me or I should say that I did not see any holes,rips, or tears.

I am assuming that if I start it up again ...... I will flood the oil again with fuel

Ayuh,.... Welcome Aboard,.... Who adjusted the valves,..?? those numbers say they're too tight,....

It sounds like ya took the fuel Pump apart,...
It also sounds like it's Junk, 'n needs replacin',...

Fuel Filters are replaced, not cleaned too,...

 

[NHGuy]

Re: Problems with first rebuild

Yup my money is on the fuel pump. BTW if it's a roller motor there's no problem with the break in. If it's a flat tappet setup you run it for it's first 30 minutes at 2000 to 2500 rpm, on break in oil. If it's a flat tappet motor and you didn't use break in oil don't start it till you check the oil filter that you ran for the hour, check it for bits of metal. Low compression could be from wiped off cam lobes.

To set your valve lash you bring the motor to top dead center, # 1 firing position. Use the zero degree timing mark on your front cover and look at the rotor to see when it's 8 degrees past the #1 post on the distributor cap. While it's at TDC adjust the exhaust valves on 1,3,4, and 8, and adjust the intake valves on 1,2,5, and 7.
Back off the adjusting nut til lash or movement is felt at the pushrod. Just try to wiggle and move the pushrod til you can make it move with your hand. Then tighten the nut til the movement is just gone. Then turn the nut 1 full revolution.
Now turn the crankshaft 360 degrees, stopping at the timing mark. That will put you at the firing position for #6.
Using the same process adjust the exhaust valves for 3,4,6 and 8. And adjust the intake valves for 2, 5, 6, and 7.

You can do the valve adjustments and recheck your compression while you wait for the fuel pump to come. Remember to do the compression test with the throttle open, no other spark plugs in the motor, and the ignition disabled. Crank for about 5 or 6 puffs to get the compression info on each hole.

If the compression is still low come back and tell us how you fitted your piston rings. A 64cc head should give you over 180 lbs of compression. A 76cc will be less but still probably over 150. If you have a good ring assembly process maybe the cam is timed wrong or the heads aren't sealing correctly.
I hope your valve lash is the compression issue, it's the cheapest easiest solution.

How did the exhaust smell, steamy? or like fuel? What did the wet black plugs smell like?