Engine Pops and Sputters

[Flames]

Hello everyone,I am sorry for the long post. I have a friend that has a 1986 44' Welcraft Portifina (not spelled right) that has twin 454ci engines. He started having problems with it popping out of the carb and had a guy come out to take a look at it. The guy told him it had a flat lobe on the cam and told him he could move some plug wires around and make it run good, he could'nt (both motors only have about 30 hours on them). He asked me to take a look at it, so I pulled the valve covers off and a rocker had come off. I repaired that problem and moved the wires back as they should be and I am still having a problem with it missing and staying running.All the popping is gone. I have replaced the plugs and adjusted the dist. in all directions with no luck. <br /><br />Anyone have any ideas?<br /><br />Thanks, Rudy

 

[Don S]

Re: Engine Pops and Sputters

Rocker arms don't just "Come Off" you might want to look again and see if the stud for the rocker is pulling out of the head. I would also think a proper Compression Check would be in order and having a look at the spark plugs for any damage.

 

[tommays]

Re: Engine Pops and Sputters

with only 30 hours is there no one standing behind there work??<br /><br />first thing i would do is a compresion test and a leak down test <br /><br />with the rocker comeing lose you really need to rule out any damage to the motor it may have caused<br /><br />as for backfire it is one of those areas were people will have many many ideas what it may be a lean carb due to cloging seam to be one of the more common<br /><br />tommays

 

[Flames]

Re: Engine Pops and Sputters

Im sorry, I neglected to say that a push rod guide had broke and caused the push rod to move radicaly and thus causing the rocker to come off.<br /><br />I intend to do a compression test on monday evening.<br /><br />Thanks to both of you, Rudy

 

[Bt Doctur]

Re: Engine Pops and Sputters

Rockers dont just come off,do a compression check to verify good cylinders,check cap and rotor for arcing or tracking,inspect plugs for proper color and condition.it this a standard rotation or reverse rotation?

 

[Don S]

Re: Engine Pops and Sputters

Something caused the guide to break. They do not contact the pushrod in normal operation. Look for bent pushrods, pulled rocker studs, stuck valves, collapsed lifter ?????

 

[deputydawg]

Re: Engine Pops and Sputters

Make sure the push rod is straight. This happened to one of my stock cars. bent the push rod just a little. Also check to see what kind of valve guides it has. If it is a rebuild it might have brass guides. These need more clearance that older low performance guides. When the engine gets warm at high rpm, the guide will swell and cause the valve to stick open. This could have caused the push rod to become sloppy loose and come off, when it cycled it could have shoved the push rod over breaking the push rod guide. If this is the case a compression test won't show anything unless you can figure out how to do one at higher rpm's. Also if this is the case the valve guide needs to be knurled a little bigger.<br />I am tryin to figure out why someone would say to move the spark plug wires around.<br />Also pull the lifters and check them. On my stock car I put in a new camshaft, right after that a lifter collapsed causing the above problem.<br />Either way the engine should be broke down and all clearances measured. As Don said they don't just come off and things don't just break. Something caused it, and it could have caused other problems.

 

[Flames]

Re: Engine Pops and Sputters

Ok, I checked the compression on all 8 cyl. and all are around 120 psi. My main concern right now is to get the engine to stop missing and to have some power. I also adjusted the valves. I looked at the cap and rotor and they look fine but am going to replace them anyway. I ohm'ed the plug wires and they check out good (they are new also). It has new plugs already.<br /><br />Anymore ideas guys?<br /><br />Thanks, Rudy

 

[deputydawg]

Re: Engine Pops and Sputters

If you had trouble with a push rod, and it is now running bad, you probably have a problem in the valve train. It sounds like a fuel problem, but following the valve trouble it might be best to pull the heads and check everything out. Check your valve openings and see if everything is good. Pull the heads, put a bit of modeling clay in the cylinders, replace the heads and slowly turn the engine by hand. This will give you a pattern where the valves open. Make sure this is the same on all 8. Be sure to do one cylinder at a time thoughg.<br />First check your lifters. There is a reason your rocker came off, find that reason and you will probably have your problem solved.

 

[Flames]

Re: Engine Pops and Sputters

Ok, i will do that. <br /><br /><br />Thanks everyone, Rudy