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1966 28 Californian Backfiring

J

jclays

Regular Contributor
At 1000rpm i get a poping out

At 1000rpm i get a poping out of the exhust. Clears up at a little more throttle however at about 1600 rpm i get backfiring thru the carb.the carb is the older Rochester 4j carb. early to mid 60's vintage. I get a strong gas smell and a little smoke (White)
 
"I'd do a Compression Chec

"I'd do a Compression Check,........

It's possible that you're loosing a Cam Lobe.....

The fact that the Backfiring is Moving is the Strange part.......

Backfiring thru the Carb is Usually caused by a Lean Condition,......
Backfiring thru the Exhaust could be the Ign., or the Cam........

How long has it been since the motor has had a Complete Tune-up,..??..."
 
I did a compression check when

I did a compression check when i bought the boat in june. I knew she was going to eventually need a valve job on both engines each engine had one cylinder low at about 27psi.The rest where consistant at 113/115psi. However only the starboard engine is the only one doing this. Havent tune her up. Ignition is electronic. I took the plugs out last month they were pretty clean i wire brushed them and reinstalled them. The carb was recently rebuilt and the fuel pump was just replaced this week. Could it be too rich? instead of lean? I smell gas. the idle mixture screws are 2 turns out from the stop which is about right.
 
""I knew she was going to

""I knew she was going to eventually need a valve job on both engines each engine had one cylinder low at about 27psi."

Even the 14 strong Cylinders are ready for a Rebuild,........
Those 2 are just plain Dead.......

I Don't see any Easy Fixes.........You'r motors are just plain Worn Out......."
 
I was hoping to run along a li

I was hoping to run along a little longer before the valve jobs or repower. Do you think that too rich a mixture could cause the backfiring or maybe too much advance on the timing? It was actually running great then she one day started loading up and missing so i had the carb rebuilt and havent been able to get it right.
 
"Rich conditions do Not cause

"Rich conditions do Not cause Backfires,.....

If it was the Timing,..... The Backfire Wouldn't be Moving........

I hate to say it,.....
But, I think it's time to Bite the Bullet,+ Do something about the Worn Out Hardware Issues that you've got........

No amount of Band-aiding is going to make those DEAD Cylinders come back to Life.......
You've Already milked it as Far as it's going to Get......."
 
I got better results today by

I got better results today by readjusting the timing and carb. I will switch carbs with the port side engine since they are identical and see if things change. If not its valve job time. Does anyone know if spark plugs and plug wires for boats differ than that of a 350 automobile engine of the same year???
 
"If this is a SBC,..... MR43T

"If this is a SBC,..... MR43T is the AC Sparkplugs you need,.....It's an Alloy bodied plug,+ Doesn't Rust....
The automotive Equivilant is the R43T,... It's a Steel bodied plug,+ will Rust.....

The Wires have to have the Right Ends on them,......
Other than the Ends,..... They're the Same......."
 
"James
any pressure under 100

"James
any pressure under 100 pounds means that clyinder is not working. You CANT run an engine on just 7 clyinders, you changed the timimg it helped but you have two engines that need rebuilds, do it now while you have the time, yard rates, are sometimes lower during the winter.
The longer you run the engines in this condition the more you will end up replacing in parts and labor. Git R DOne NOW."
 
"Found 2 plug wires crossed, u

"Found 2 plug wires crossed, uncrossed them re-adjusted air/fuel mixture. will change plugs then take a run a see what happens
signed
"The Milkman""
 
"Found 2 different champion sp

"Found 2 different champion spark plugs in both engines. Replaced them all with AC MR44T the next heat range hotter. Fired the engines they sound like completely different engines then before. Smoother,crisper. took her out side the harbor it was getting dark ran her up to 2500rpm was posting 20 on my gps. The boat never ran this smooth even when i sea trialed her. Will take her out tomorrow when there is more day light for a longer cruise. Hope she continues to run like this. Then its time for the cosmetic stuff.Thanks for the input guys."
 
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