Mech opinion on Bogging

[FreeBeeTony]

Had a mechanic look at the boat today. Took him out for a test ride. Gave him a list of things I have done already. His opinion is a worn cam. I am going to try and get a second opinion, but at this time of the year it isn't an easy task.<br /><br />Here is my plan if I get a second opinion that concurs with the first:<br /><br />I am going to pull the engine anyway due to a suspected leaky rear main seal, it only leaks until the level goes down to the add mark on the dip stick then doesn't leak anymore. I had a van that did this once. While the engine is out I was going to do the following: replace manifolds and risers, (they seem fairly cheap compared to what I paid for the manifold for my IL6), have the heads and valves done, and replace the cam and lifters with a roller set (if it doesn't already have rollers). I wasn't going to get into the bottom end, the compression was very good (140-170lbs). I was also thinking of replacing the intake manifold with an Edelbrock (its FWC'd so I don't need to worry about salt). When I replace the cam which one should I get and from where?<br /><br />I would appreciate any opinions (w/o the sarcasim). I would like to tackle this job myself (with the help of the guys on the board of course) and not give it to a mechanic. as we all know, it's very hard to find a capable tech who is honest. Being that I can do this work myself I really don't mind as long as the outcome is positive. My last project came out very well ( with your help) and Iwould like to do another one...........<br /><br />BTW, this will be a winter project, provided I can get the block into my basement.<br /><br />Here is my plan:<br />1) Take engine out of boat fully assembled and mount on engine stand in driveway ( neighbors will love this!)<br />2) Disassemble manifolds (intake and exhaust), risers, and heads.<br />3) Move block to basement<br />4) Remove cam<br />5) Send out heads to be redone<br />6) Wait for spring to reassemble and reinstall.<br /><br />Any guesses on what this will cost me in parts?

 

[Reel Poor]

Re: Mech opinion on Bogging

Its hard to second guess a mechanics diagnoses. I will say that if the cam is worn that they will usually cause a popping sound thru the intake/carb (worn exhaust lobe) and "may" actually cause what feels like a miss-fire. If it is a worn intake lobe that may explain slightly low compression on the one or two cylinders (cant remember exactly-didnt go back and read all the post) as you described. You have described your problem as a "bogging problem" and stated you still have throttle left when the "bogging" occures. Stated it wont run over 3400 rpm or it boggs down.<br /><br />You can verify worn cam lobes by removing the valve covers and measuring the lift at each rocker arm. <br /><br />Diagnosis is questionable (based on your description) but possible. <br /><br />If this turns out to be the problem, I would say the agrivation you have been having has been exagerated by your description of the problem.<br /><br />Good luck and please keep us posted.

 

[FreeBeeTony]

Re: Mech opinion on Bogging

Something else just came to mind........is it possible I have the wrong cam in this engine and I am currently "over carbed"?

 

[Buttanic]

Re: Mech opinion on Bogging

Before I would tear into the engine I would get the lift specs for the cam and a dial indicator and check it. All you would need to do is pull the valve covers to do it. You don't know if it is a roller cam or not but if it is a roller the chance of a worn cam is slim to none. Get the cam specs for both the flat tappet and the roller cam. If the carb rating is not larger than 600 cfm you are not over carbed.

 

[Bondo]

Re: Mech opinion on Bogging

Have you done any Vacuum Testing on this thing Tony,..???....<br /><br />You're Not over carbed,...... You've got that Edlebrock 650cfm,.. Right,..?? Even the 750cfm is only slightly over carbing a 350.........<br /><br />Under Cammed,..??... I'd think even a Caprice cam would push your boat better than 3500rpms.........<br /><br />If the cam has wiped out lobes,..... Either measuring the lift at the rocker,... Or the Vacuum test should tell you..........<br /><br />Just Curious,..... Has this boat Run Right,..??. Ever,...????.....<br />If So,........ What Changed,..????

 

[Don S]

Re: Mech opinion on Bogging

For a cam to be "Worn" means that a lobe has to be partially missing. I stated in a previous reply to measure the lift from one to the other. Did you do that? If you did you forgot to mention the results.<br />If you have a worn cam, the engine will not run properly at any speed. Plus you would notice popping, sputtering and all sorts of things when trying to give it throttle and at any rpm under load. But nothing has ever been said about problems below 3500 rpm. Overcarbed, wrong cam ???? I doubt it.<br />Every possibility of this problem has been asked before. Go back through all your posts and write down all the possible problems that people have suggested. Then go back and recheck and verify every one of them. You WILL find the problem. It's just a matter of eliminating every possibility.

 

[Reel Poor]

Re: Mech opinion on Bogging

Tony <br /><br />Didnt Don check the serial #s and give the info in one of your threads about the motor and the year it was replaced. "If I remember" correctly it was a factory marine replacement. <br /><br />If all of these post were in ONE thread it would be easier to go back and refrence them, instead of starting a new thread for each new idea for the same problem. These threads can be multiple pages long.

 

[steve n carol]

Re: Mech opinion on Bogging

FBT, Why do you want to go through the heads? <br />If there was low compression on any of the cyls, did you use oil and take another reading, to varify the the valves had a sealing problem? <br /><br />Also, Forgive me, but in my ignorance of the particular style of the rear main seal retainer on this engine...if you have to remove the oil pan, would you plasti-gauge any of the crank/rod journals?<br /><br />And last but not least, You are trying to think of a way to get this into the basement, besides 'down the stairs'. Could you go through a basement window? build a 'ramp' and lower, (slide), it down with a winch? <br /> <br />just a few thoughts...sl

 

[FreeBeeTony]

Re: Mech opinion on Bogging

See new post.

 

[ziggy]

Re: Mech opinion on Bogging

fbt, i'm gettin out of my league here and know nothing about yer 92 350 magnum. but. have you got anything on that engine that will switch things on and off, like a computer or some other type of engine sensors that control engine performance?. i just had a issue with my 350 fuelie on my van kinda like that. was a dirty mass air flow sensor. acted just like a switch to me. ran horrible on a warm start up, with no power at all, then just like ya threw a switch it would come to life after 30 sec. or so. and my problem did get worse with time (longer time running horrible to the pt. where it finally failed while towing the boat on the interstate). my auto mech kept thinking fuel. i kept thinking it was electical. ie a switch or engine sensor of some kind. maybe ya got some kinda problem like that. seems like you've covered the mechanical happings pretty well. <br />ya might check into the distributer advace a bit more too since it sounds like all you've confimed is that it appears to be advanceing. maybe one of themz advance timeing lites would be helpfull for that. i obviously don't know what yer problem is and am just throwing ideas out for what it's worth. good luck.