Heres one as I scratch my head
 

I had to change the headgasket on the starboard motor starboard side of block because it was leaking water out of the front of the block in between head and block. Water didnt not get into oil or cylinder. I will post a pick of gasket tonight just so you can see it is perfect, it like seperated right where the water jacket on the head is blocked by the front of the gen 4 block itself and the gasket seals it. So here is the order I used, I removed air cleaner, carb, distributor, intake, header, valve cover, spark plug wires, spark plugs, and than the Head. Then put it all back together.

I also lashed all the valves as recommended after every 20 hours on both motors. Cold lash on my cam is 21 intake and 23 exhaust. I watched it 10 times on youtube how to lash a solid roller cam and I work at a Cadillac dealer and bugged the old school mechanic 10 times to make sure I did it right and he used to race cars and was sponsord from Kendall back in the day so he would know how to do it right. Port motor still runs like a champ I lashed that one too. Here is the problem I having with starbord.

So I put it all back together and now I have poor throttle response and when it warms up it is backfiring through the carb under load at tempture, and I can only turn 4700-4800 rpm instead of 5200 like the other one, also getting like a white smoke color coming out of the valve cover vents after it warms up.

I check the advance timing 4-5 times it is perfect at 36 degrees full advance above 3200 rpm just like the perfect running port motor. I also changed the distribitor cap, and checked the firing order 2 times, checked my fuel water seperators they no water at all, The only thing I didnt check is when I took the plugs out to remove the header and put them back In maybe I cracked one? I dont know.

I took boat to my Mechnic I was stumped. He relashed the valves and he said a few were to tight on starboard motor. He didnt get a chance to run it because I dropped it off afternoon today. So after work I will run it and see. Would a valve or 2 being to tight cause this problem.

Remember it runs and idles fine in the well and down the canal, I just have poor throttle response and backfire through carb under load above 3200 going into higher RPMs, and after it engine warms around 140-150 degrese is when I get the backfire here and there.

I would not think I would need any new parts because the boat ran perfect before I messed with it.

Any thoughts meaning if I run it tonight after the valves have been correctly lashed by a professonial and Im still having this problem. so I can tackle them in morning.

Justin
586-524-3450
Call or respond.
Thaks Cigarette buddies.

back fire from the carb is both valves open at the same time one could be bent. valve gides to tight. cam could be shot when the rockers are to tight check every thing

The mechanic said valves checked out fine when he lashed them. I noticed to today when I drove it that when I turned the key to on to hit the start button it was turning the gauges on anf off like a bad ignition switch. So I going to change that tomorrow morning and go from there.

just had a simlilar problem on a fountain i was working on. 1 spark plug was fouled and the coil was on its way out. coil finally failed completely. replaced coil and spark plugs.. ran like a scalded dog. 35 dollar fix. coils like to be mounted vertical not horizontal

If I had your money I would quit trying to fix it myself and hire someone who knows what they are doing. Your tried to be a marine mechanic years ago, you had a great teacher just couldn't pick it up, that is why you sell Cadillacs today. LOL

This must be Tim....
I call your dad fred all the time this has him scratching his head.....Ron at Dynamic Speed and marins says Its gotta be a plug or wire that went bad. So Im replacing that today Ill keep you informed

Intake valves are set too tight and hanging open.

I ran it hard pulled all the plugs on the lake they looked fine, then went to switching parts one at a time from motor to motor. the first thing I tried was the coils. I switched them now motors run fine.

Are you sure the coil wire wasn't loose before you switched them?

There's your problem right there. You had the port and starboard coils switched........