fallow up to previouse post colapsed intake lifter

[chris0061]

Before I take the intake off for a collapsed lifter, can I take the rod out, put on my dumby valve cover, start the engine and if there is no knock at all make sure its a collapsed lifter?

 

[dontask]

Re: fallow up to previouse post colapsed intake lifter

If you are wondering if you have a collapsed lifter have you tried putting a known good push rod (not bent) into the position your concerned with. Then slowly rotate the engine over and measure the total lift you can get measured at the top end of the push rod. This would indicate you still have a good cam lobe. If the push rod sits lower in the head and you do get normal lift then you probably have a collapsed lifter. If I'm not clear--------the (known good) push rod will sit lower in the head as compared to the other push rods when your at the same cam lobe position as another cylinder position. Make sure if its a intake compare it to the other cylinders intake position and if its an exhaust position compare it to an exhaust position. The lift on intake lobes and exhaust lobes can be different.

 

[chris0061]

Re: fallow up to previouse post colapsed intake lifter

OK I never thought of that. Since my post I did fire up the engine with the intake rod out. Serious knocking on start up, not so bad after. May be I blew the lifter out of the socket. I'll strip it down tomorrow, What have I got to lose right. take the intake off, if I don't see anything take the heads off, if I don't see anything pull the engine for a main.

 

[remauto1187]

Re: follow up to previouse post colapsed intake lifter

Re: follow up to previouse post colapsed intake lifter

You dont even have to go through all that.... You can have some bump the ignition with the igntion coil disconnected and (pull power to your fuel pump if its electric). Have a known good pushrod in place of the suspected lifter. Do not put rocker arm back on. While the engine is being bumped over.....get it to where the lifter is on its highest spot on the cam or very close to it and this will be known by looking at the pushrod going up and down during engine bumping. Keep constant tension on top of pushrod during all this so it does not get off the lifter and fall down into the engine. Once highest spot is found then take a 10" or just a big crescent wrench or something of the like and lay it on top of the pushrod and with the palm of your hand push down across the wrench which forces the pushrod down. Press really hard... You should feel the lifter plunger go down some and it should be pressing back toward you if you back off it. Almost like you are pushing down on a spring. If you don't feel that then you have a collapsed lifter. They are relatively inexpensive... and I would replace all if you have one bad. I have only seen a lifter collapsed once on a plugged up oil pickup in a Mustang. That was in 1997. Its not a very common failure on a engine these days.

 

[chris0061]

Re: fallow up to previouse post colapsed intake lifter

Ok I'll do that in the morning. I have a set of lifters off another 350 and I put the rod in the lifter and pushed down so I know what your talking about there. I'll let ya know what I found out.

 

[chris0061]

Re: fallow up to previouse post colapsed intake lifter

I got my wife to help me out. she turned it over and the rod just came up a little it went down and when I got the feel how high top end was I had her stop on top and I could not push down on it at all. It did'nt travel very far from bottom to top I'd say maybe 3/4 inches.

 

[remauto1187]

Re: fallow up to previouse post colapsed intake lifter

Did it feel solid when u pushed down real hard? If so then you have a collapsed lifter. I mean you really gotta push REAL hard! Lay your weight into it and you should feel the plunger give some and the pushrod will go down about a 1/16" or more depending on how much weight you lay into it.

 

[chris0061]

Re: fallow up to previouse post colapsed intake lifter

it was like trying to push it into concrete.

 

[MikDee]

Re: fallow up to previouse post colapsed intake lifter

I'm confused, If you 're asking if you can take the pushrod out and run it, not a good idea.You want that valve to be able to open, especially if it's an exhaust valve (near the exhaust port, check to see where your exhaust manifold is?) there's no way for the exhaust to come out of that cylinder when it fires, it might just backfire out the intake valve when it opens.

On a Chevy engine it's Ex-I-I-Ex-Ex-I-I-Ex

If it's an intake valve it's not gonna matter much, that's a different story, you should be able to temorarily remove it and see if the knock goes away. The worst that'll happen is that cylinder won't fire.

either way, check your valve spring to see if it's broken at this time, if you can turn the valve spring on it's base easily by hand, it's shot.

If you want to do any checking for the knock, you're better off removing both pushrods for that cylinder if it happens to be on an exhaust valve!

 

[MikDee]

Re: fallow up to previouse post colapsed intake lifter

it was like trying to push it into concrete.

Yes, I know, lifters are hard to push down by hand, even when they're good, because they're filled with oil, but you must see if you can somehow get it to push down, maybe like remauto says.

Lift at the pushrod, will only be about 3/8", because your rocker arms multiply that ratio by 1.5 times to a little less then 1/2"

 

[chris0061]

Re: fallow up to previouse post colapsed intake lifter

I went a head and took the intake off. The spring wont turn on the base. It was a intake rod I pulled to see if the knocking would go away. It was worse. I put the rod back in and started it virtually no noise. I took two lifters out and could'nt push either one. What do you think I should do now? Since I have it tore down this far I may as well take all the rockers off and see if any springs are busted right?

 

[MikDee]

Re: fallow up to previouse post colapsed intake lifter

I went a head and took the intake off. The spring wont turn on the base. It was a intake rod I pulled to see if the knocking would go away. It was worse. I put the rod back in and started it virtually no noise. I took two lifters out and could'nt push either one. What do you think I should do now? Since I have it tore down this far I may as well take all the rockers off and see if any springs are busted right?

If I understand you right, when you took off the pushrod for the intake valve on that cylinder it got worse? and when you put it back on it was silent?
Then you have no more knock?

For the next step, I suggest you put it all back together, don't bother checking the springs at this time, and just adjust the rocker arms you took off, and see if it runs ok?

If there's still a knock, as I suspect, it maybe a damaged rod bearing, on the suspect cylinder. Sometimes you can tell when it stops firing on the cylinder, if the bearing is bad, the piston rod gets some slop in it from not firing, by being slapped around by the rest of the engine, and you hear a knock,,, this can also be confirmed by shorting out the spark plug with the engine running and listening for a knock.

 

[chris0061]

Re: fallow up to previouse post colapsed intake lifter

yes you understand right. I just left the parts store and talked to a guy that knows 350's and he told me to check the rocker very carefully as it may be cracked then do a compression check on that cylinder to narrow it down and if everything seems OK then like you said it is probably in the lower part.

 

[MikDee]

Re: fallow up to previouse post colapsed intake lifter

yes you understand right. I just left the parts store and talked to a guy that knows 350's and he told me to check the rocker very carefully as it may be cracked then do a compression check on that cylinder to narrow it down and if everything seems OK then like you said it is probably in the lower part.

The more I think about this there are 2 scenario's:

Scenario 1: Either that particular lifter is galled, damaged, stuck, whatever? and is now a solid lifter. My theory is, it would cause a knock usually before, and after you get to zero lash, but not at zero lash, while you're adjusting it.

Scenario 2: That rod bearing is spun, damaged, whatever, and that's the knock,,, and maybe even more noticable, with the spark plug wire off.

You'll have to determine which of these you think it is more likely to be? Or get it running again, and try to diagnose these then. Geez, my brain hurts!

 

[chris0061]

Re: fallow up to previouse post colapsed intake lifter

ha, my brain hurts too. I did the compression test and it was 165. The rocker looked a little worn so what I did was replace the rocker, rod, and lifter. I'm putting it back together now. just had to get cooled off a little. I'll let ya know what it sounds like.

 

[chris0061]

Re: fallow up to previouse post colapsed intake lifter

OK, did the lifter thing. put the intake back on same thing happened. I'm now thinking wrist pin or bearing. Now my decision has to be do I take this engine out, take the pan off and will I be able to find the problem or do I take my other block that dropped a exhaust valve and left a little score on the sleeve and shot the piston to a shop and see if they can bore it out and have them rebuild it? Or just have them bore it out and I put new piston rings and bearings in. The crank looks good and the cam looks good. What ya think as I'm wanting to go the cheapest way but want a engine that will out last this old boat.

 

[MikDee]

Re: fallow up to previouse post colapsed intake lifter

Ok, did you try running it with the plug wire off, and see what it does to the noise? I'm guessing if it knocks louder, it maybe a spun rod bearing, in which case you could either get the crank journel redone and run an oversize bearing, or maybe you could swap cranks (if they're both the same specs), put a set of new bearings in, and you're done. If by chance you damaged the cylinder wall, then you'll have to re-examine your options, and try rebuilding the better of the 2 blocks.

 

[chris0061]

Re: fallow up to previouse post colapsed intake lifter

I forgot to do that, taking the plug wire off. I'll do that tomorrow before I pull the engine. The other block probably only has a couple hundred hours on it at most cause when I took it apart the valve cover gaskets looked good, the head gaskets look good, the manifold gaskets came right off the only thing that stuck to anything was the intake gasket. What caused that valve to drop I don't know. It busted off just above the crown. That engine has the thunderbolt ignition I believe it to be about a 84 and I do have the transom shield and all that.

 

[chris0061]

Re: fallow up to previouse post colapsed intake lifter

OK still knocks. I called a machine shop to rebuild my 84 260. It had dropped a exhaust valve and scratched that cyl real deep. The man is going to look at it and if it's not to bad, sleeve it and I'll go from there. My next question is when I get it back should I replace everything from the inside transom plate, back to the outside transom plate with the ones that came with this engine or just pull my 81 and leave all that stuff alone?

 

[MikDee]

Re: fallow up to previouse post colapsed intake lifter

Could this just be a bad exhaust lifter on #8? That's the one you had so much trouble with. Did you replace the exhaust lifter as well? Maybe you should run it once more, and listen close to, or put your hand on the rocker arm when idling, & see if you feel it match the rythym of the knock?