GeneD
11-11-2000, 10:35 AM
All you know the trials and tribulations of 007, mainly the engine problems I have encountered as of late. I for one, do not hold anything back from you guys. I tell all. And not because I’m bragging, who really wants to brag about their boat breaking down? But because I truly believe that everyone can benefit from my mistakes or bad experiences.
I have done a mess of research into this motor thing, and now the real story has unfolded. In my research, I found some disturbing info for me personally, since I owe someone an apology. More on that later.
Let us re-cap the past. I suffered two "tuliped" valves in the past year. My Sea Ray buds were saying,
"Yeah, that’s caused by…, Gee I remember in Merc school they said it was…"
No one could remember. The final thought was, it caused by bad fuel.
I scoffed at that.
I also found two plugs (in the blown out piston cylinders) that had no electrodes. I thought it was a manufacturing defect and brought them back for replacement. At $5 ea for plugs, I wasn’t so willing to eat the cost.
Then two weeks later, I blew the engine. 3 bad pistons, 3 spun bearings, and a cracked block. The area around the cracks, which were cracked across the main bearing webs, looked to be super heated. Nothing unusual with that considering the bearing spinning against the block right? But the burned out pistons bothered me.
On to a new engine. The new motor is perfect. Everything was to spec, and meticulously assembled. But…no power. At least no power like the other engine. I could feel that something was wrong. Also, unreported, I think, was my 4 bbl bog. Not always there, but often it would bog on full throttle application. Timing? Advanced the timing 2 degrees, and got no gains at all. No improvement.
Checked the plugs, very dry. Nice tan color.
Then I started doing some research on Thunderbolt ignition timing. That is when I found the Mercruiser Service Bulletins. While going through the bulletins, I found one that talked about secondary metering rods in the Quadrajet and how you needed to change them out for high altitude operation.
The chart went through a number of engines. I looked at the metering rod code for the stock sea level 5.7 Alpha, and it calls for a CL rod. Then you go down to the 350 Magnum, and it calls for a CH rod.
Hmmm, I thought, I’m going to change out the secondary metering rods on my Q-Jet to the rods they call for in the Magnum, and see if that makes any difference. Perhaps I can pick up my lost RPM’s from there considering I now have a different cam, and I do not have the Alpha engine anymore, but still have the original carburetor.
So I go to the shop and remove the rods. What did I find in there but DW rods! The DW rods are the secondary metering rods that should be used on the Alpha engine at 9000 ft and above! But what does that mean? I did some more research and found out a bunch of things about the Q-Jet. For one, they make only two castings. A 750 CFM version, and a 800 CFM version. Both of which are jetted for the various CID’s engines on which these carbs are used.
I had a rather heated discussion about this with someone recently, and I apologize. My info was garnered from my old engine builder on Long Island, a man I trust explicitly. I think what he was getting at was that the formula used to calculate jet sizes, called for a 450 CFM jetting on most 350 Chevys. I was wrong about the CFM castings, and I’m truly sorry that I was a stubborn jerk about it.
On to the rod change. I found another chart that talked about the diameters of the rods and what the codes meant. Thank Don for the Internet, (he invented it didn’t he?). On that chart it said that the codes vary in diameter according the alphabet, kinda. For instance; letter code "CC" is .030 diameter. Letter code "AX" is .040 diameter, and letter code "DA" is .044 diameter. I had DW’s in there. The same code for the 9000 ft and above altitude. A much bigger diameter than the "C_" codes it calls for at sea level. The bigger diameter of the rod, the leaner the fuel mixture, conversely, the smaller the diameter, the more fuel you pump in.
So in the end, I was running a very lean condition. Causing extreme heat and the resulting "tuliped" valves, and the eventual breakdown of the entire engine.
So, the other day, I went around to all the junk engines we have laying around and ripped off all the secondary metering rods I could find. I found the ones I was looking for, and found out some other interesting things. The late model motors have bigger diameter metering rods. I think this is for producing a lean condition for emission purposes.
I also found the air valve diaphragm on my Q-Jet unit bad. Couldn’t hold vacuum in it. Didn’t find one of those, but we will find one soon. I believe this is the cause of the secondary "bog".
In the end, we will put the correct rods in there and see what, if any, difference it makes. How did this happen with an engine bought in Florida? This is what happens when you buy a motor that came from the Prototype Design and Development Division of Sea Ray. Apparently, they had a high altitude motor on consignment for some project that never got off the ground, and sat on the crate forever until they decided to sell it at an employee auction.
Caveat Emptor!
I'm taking the boat out for a ride right now. Hopefully it will make some kind of difference. I will report later on this.
------------------
GeneD
007
Melbourne, Florida
I have done a mess of research into this motor thing, and now the real story has unfolded. In my research, I found some disturbing info for me personally, since I owe someone an apology. More on that later.
Let us re-cap the past. I suffered two "tuliped" valves in the past year. My Sea Ray buds were saying,
"Yeah, that’s caused by…, Gee I remember in Merc school they said it was…"
No one could remember. The final thought was, it caused by bad fuel.
I scoffed at that.
I also found two plugs (in the blown out piston cylinders) that had no electrodes. I thought it was a manufacturing defect and brought them back for replacement. At $5 ea for plugs, I wasn’t so willing to eat the cost.
Then two weeks later, I blew the engine. 3 bad pistons, 3 spun bearings, and a cracked block. The area around the cracks, which were cracked across the main bearing webs, looked to be super heated. Nothing unusual with that considering the bearing spinning against the block right? But the burned out pistons bothered me.
On to a new engine. The new motor is perfect. Everything was to spec, and meticulously assembled. But…no power. At least no power like the other engine. I could feel that something was wrong. Also, unreported, I think, was my 4 bbl bog. Not always there, but often it would bog on full throttle application. Timing? Advanced the timing 2 degrees, and got no gains at all. No improvement.
Checked the plugs, very dry. Nice tan color.
Then I started doing some research on Thunderbolt ignition timing. That is when I found the Mercruiser Service Bulletins. While going through the bulletins, I found one that talked about secondary metering rods in the Quadrajet and how you needed to change them out for high altitude operation.
The chart went through a number of engines. I looked at the metering rod code for the stock sea level 5.7 Alpha, and it calls for a CL rod. Then you go down to the 350 Magnum, and it calls for a CH rod.
Hmmm, I thought, I’m going to change out the secondary metering rods on my Q-Jet to the rods they call for in the Magnum, and see if that makes any difference. Perhaps I can pick up my lost RPM’s from there considering I now have a different cam, and I do not have the Alpha engine anymore, but still have the original carburetor.
So I go to the shop and remove the rods. What did I find in there but DW rods! The DW rods are the secondary metering rods that should be used on the Alpha engine at 9000 ft and above! But what does that mean? I did some more research and found out a bunch of things about the Q-Jet. For one, they make only two castings. A 750 CFM version, and a 800 CFM version. Both of which are jetted for the various CID’s engines on which these carbs are used.
I had a rather heated discussion about this with someone recently, and I apologize. My info was garnered from my old engine builder on Long Island, a man I trust explicitly. I think what he was getting at was that the formula used to calculate jet sizes, called for a 450 CFM jetting on most 350 Chevys. I was wrong about the CFM castings, and I’m truly sorry that I was a stubborn jerk about it.
On to the rod change. I found another chart that talked about the diameters of the rods and what the codes meant. Thank Don for the Internet, (he invented it didn’t he?). On that chart it said that the codes vary in diameter according the alphabet, kinda. For instance; letter code "CC" is .030 diameter. Letter code "AX" is .040 diameter, and letter code "DA" is .044 diameter. I had DW’s in there. The same code for the 9000 ft and above altitude. A much bigger diameter than the "C_" codes it calls for at sea level. The bigger diameter of the rod, the leaner the fuel mixture, conversely, the smaller the diameter, the more fuel you pump in.
So in the end, I was running a very lean condition. Causing extreme heat and the resulting "tuliped" valves, and the eventual breakdown of the entire engine.
So, the other day, I went around to all the junk engines we have laying around and ripped off all the secondary metering rods I could find. I found the ones I was looking for, and found out some other interesting things. The late model motors have bigger diameter metering rods. I think this is for producing a lean condition for emission purposes.
I also found the air valve diaphragm on my Q-Jet unit bad. Couldn’t hold vacuum in it. Didn’t find one of those, but we will find one soon. I believe this is the cause of the secondary "bog".
In the end, we will put the correct rods in there and see what, if any, difference it makes. How did this happen with an engine bought in Florida? This is what happens when you buy a motor that came from the Prototype Design and Development Division of Sea Ray. Apparently, they had a high altitude motor on consignment for some project that never got off the ground, and sat on the crate forever until they decided to sell it at an employee auction.
Caveat Emptor!
I'm taking the boat out for a ride right now. Hopefully it will make some kind of difference. I will report later on this.
------------------
GeneD
007
Melbourne, Florida