Can I run my Mercruiser 888 (Ford 302) with one bad cam lobe?

[bobcox]

So the Ford 302 in my 1972 Formula 233 started spitting through the carburetor last week. After some investigation I found a sticky lifter on the #3 cylinder intake valve. When I pulled the lifter, I found it worn into a cup. Worrying that the cam was similarly worn, I used a micrometer to measure the lobe lift. Sure enough, the lobe lift on that cylinder was only .092" when the book says it should be at least .26". All the others are fine. I replaced all the lifters and put it back together. When I run it now, it sounds great, though I have not run it loaded.

Clearly it needs a new camshaft. But its the middle of the season and I am out of wrenching time. My question is, can I run it as it is for a bit while I save my pennies for a new camshaft? The #3 cylinder wont be doing much work, but will that hurt the engine in any way? I always run it gently anyway, keeping it under 3500.

 

[09TNRT]

You *COULD* run it but with that lobe already wiped out you're just going to be doing the motor more harm. I'm sure there is all kinds of shavings floating around in the oil. The #3 will be doing the same amount of work as the other 7 so under a load it may not run quite right. IMO you've got 2 options, run it till all those shavings get in places they shouldn't and something starts knocking then just rebuild the whole thing. Or yank the cam out, flush the motor really well and hope those shavings haven't already scared the bearings, and put a new one in with a fresh set of lifters. I'm new to boats but not motors by any means. Not sure how hard it would be to swap cams in your boat but that's the direction I would take. I know I could swap cams in a vehicle from that time frame in a few hours and be back on the road. What's your oil pressure looking like by the way?

 

[cdhunter]

I would put money on the fact that #3 has a bent valve, you described a valve stuck open position when you said it was spitting through the carb! lifters just open valves not close them. Like 09tnrt said you could run it and see how much more you hurt the motor, or pull the head and the cam. The big question is how much money do you want to spend? Old motors don't always like new parts especially if it affects compression. I've put new heads on a motor just to blow the bottom out. I guess my question to you would be if you had your family parents grandparents children would you take them out on the water as is? unlike a car you just can't hop out and start walking sadly.

 

[bobcox]

Thanks for the input! I have been worried about shavings floating around in the motor... but flushing the engine and changing the cam are two different operations, especially when one involves pulling the motor. If I flush the engine and get rid of shavings that already accumulated, am I out of the danger zone? Or will the cam continue to wear even with a new lifter? One thing I wondered about was if the cam is fully hardened steel or if it is only capped, if so I may have worn through the hardening already and it might continue to wear even with a good lifter.

I don't think its a bent valve, I think the lifter was sticking, not allowing the valve to close all the way, hence the spitting. I haven't done a compression test but with new lifters the spitting is gone. If the valve was bent I would not expect the new lifter to fix the problem.

 

[bobcox]

Oil pressure is good, running slightly high actually.

 

[GA_Boater]

Your are wasting time and money by sticking in a new lifter over a bad cam lobe. More scarf will be circulating through the motor. It would be better to leave the the lifter out, best is to fix it right.

Re-think the stuck lifter. The only place to stick is in the lifter bore and a working lifter is a hydraulically controlled solid lifter once it's pumped up for the automatic lash adjustment. You have a bent or stuck valve stem.

 

[Scott Danforth]

Clearly it needs a new camshaft. But its the middle of the season and I am out of wrenching time. My question is, can I run it as it is for a bit while I save my pennies for a new camshaft? The #3 cylinder wont be doing much work, but will that hurt the engine in any way? I always run it gently anyway, keeping it under 3500.

you could, however trying to save pennies will cost you thousands of dollars as the crap in your oil will take out your bearings, crank the remainder of the lifters, etc. and you will need a complete whole motor

pull the motor, replace the cam, check the bearings for embedded crud and rebuild your heads

as GA pointed out, your valve stuck in the head, not the block

 

[bobcox]

Ok, so I see a consensus forming! Just want to make sure I understand it..

I realize there are shavings in the engine that wore off the cam. Can I get those out just by flushing?

It seems like folks are saying the cam will continue to wear even though I replaced the lifter. Is this because it already wore through the hardening and the soft metal underneath will wear more easily? Or because the lifter was not the problem and whatever caused the wear is still there?

Why is everyone so sure I have a bent or stuck valve? When I ran it with the valve covers off I could see that that rocker was not moving and it looked like the valve was partially open, but I could push the valve stem down by force and it seemed to move the same as the others so I'm pretty sure it wasn't stuck. I know the lifter was stuck because it was hard to get it out. If I have a bent valve, then why did it stop popping when I replaced the lifter? It was popping through the carb every rotation. Now the rocker moves fine and it doesn't pop at all. To hear it now you wouldn't think there was anything wrong with it.

 

[09TNRT]

You will honestly probably never get all of them out unless it was diasembled and hot tanked by a machine shop. I've seen a bunch of people wipe new fat tappet cams out during break in and just change the oil a couple times and put a new cam in with a set of lifters and go. Most of the time it's fine, however there is that chance that the damage is already done to the bearings. Personally I would pull it out and check the cam bearings, main and rod bearings and if they looked good through a new cam and set of lifters. My gpa always told me you never put new lifters on an old cam, new cam on old lifters(unless they're a roller set up). Much like not putting old brake pads on new rotors and such. I personally am overly anal about these types of things in cars and now that I'm into boats I've noticed it's even worse. It's possible the lifter froze up in the bore, then because it got stuck the pushrod bent. I'm not sold on the bent valve yet, because I'd then have to find what bent the valve. Based off what you've said the only way that valve would've bent is if water leaking from manifold tried to compress. But i would think you'd have more than one.

 

[09TNRT]

Another thought, I would check that push rod on a surface plate or something you know is perfectly flat. Doesn't take much, you may not even be able to tell just looking at it.

 

[kenny nunez]

I do not feel that you have a bent valve, what is happening is the exhaust valve is not opening and the combustion is backing up in the manifold. Another thing that may have happened if you have a Holley carberator the power valve is probably blown out fron the positive pulses in the manifold.
You may not be aware of the oils on the market that do not have the zink in them which is a good reason why the cam is gone. You may have a few more lobes on the way out also. If you do pull the engine now it will save you $ as everyone is suggesting. Make sure with the new cam to follow the break in to the letter and also use the additives with every oil change.

 

[Scott Danforth]

I realize there are shavings in the engine that wore off the cam. Can I get those out just by flushing?

NO, aint going to happen. the shavings that made it to the oil pump have already eaten your oil pump. the higher than normal pressure is from the crud now embedded in your bearings - think of it as sand in your speedo's when at the beach

It seems like folks are saying the cam will continue to wear even though I replaced the lifter. Is this because it already wore through the hardening and the soft metal underneath will wear more easily? Or because the lifter was not the problem and whatever caused the wear is still there?

lifters and cams wear in together. if the cam and lifter make it thru the break-in period, they should last forever or until you use oil that is low in zinc or you have a hanging valve.

Why is everyone so sure I have a bent or stuck valve?

because you wiped out a single cam lobe long after the break-in period

When I ran it with the valve covers off I could see that that rocker was not moving and it looked like the valve was partially open, but I could push the valve stem down by force and it seemed to move the same as the others so I'm pretty sure it wasn't stuck.

unless you pull the head and pull the valves, you cant know.

listen to us, dont listen to us, its your motor. if you continue to run it and ruin it, we will say we told you so.

 

[cdhunter]

As mentioned earlier unless it's a roller cam new lifters don't mix with old cams. As for the bent valve it's usually a chain reaction valve sticks in the closed position for what ever reason, lifter twists in the bore only place where tolerances allow for a failure of this nature wedged against the cam wearing the lobe out. Then one day the lifter comes free drops back down the lifter bore and starts working again activating the valve to the open position where it sticks again except in the open position and you hear it popping through the carb. After your diagnosis you removed the rocker possibly freeing up the valve to close again while you replace the lifter. The valve at this point no longer travels to where the bend is because of the wear on the cam lobe causing the issue not to happen again. I've seen this happen on refer gensets in the transport industry on numerous ocasions.