In-boat camshaft replacement - 7.4 Mercruiser

[snowbrd84]

Couldn't get above 3,800 RPM and had tapping from starboard valve cover and high compression in number 8 cylinder. Ended up being a wiped intake cam lobe - thanks to everyone's help getting that figured out in this thread - https://forums.iboats.com/threads/high-compression-in-1-cylinder-7-4-carb.768144/

Here's the destroyed lifter and could actually feel ridge on the camshaft:


Boat is in the water at marina slip, and I don't have a trailer, so doing this in-boat in the water.

So here we go - 3.5 hours this morning to drain the oil, empty the water tank (it will have to move to remove camshaft), get the intake manifold off, valve covers off and lifters out. Also cleaned up the intake manifold surfaces to be ready to go.



Camshaft and lifters get here today.

One question I have is what do you all typically do for resealing the intake manifold? The manual lists multiple different sealants, one of which is $50 which seems overkill. I was going to rtv top and bottom of rear and front strip gaskets and then spray both sides of the new manifold gaskets with Copper spray and call it a day. Is rtv around all the ports really necessary, if so, is it on both sides of the gasket?

 

[stresspoint]

ultra grey RTV sparingly around the water crossover and that's it, modern gaskets are not meant to have sealants used unless specified by the manufacture , and if required , its usually supplied with the kit.

 

[flashback]

Your fortunate to have enough space to do this. Most folks would have to pull the engine..

 

[kenny nunez]

Place a strong magnet on the oil pan to hold the small chips from the worn cam and lifter.
The Grey RTV will also seal the lower timing cover seal area in place of the original rubber strip as well as the china walls of the engine block to seal the manifold. I also always go around the outside of the oil pan to timing cover edge with the RTV. I cannot stress enough to follow the camshaft instructions on preparing the lobes with the special grease along with the break in procedure. Be VERY sure that the distributor is exactly correct and every thing is tight before start up. You want the engine to continue running for at least 20 minutes @ 2 -2500 rpm.
Just drop in the intake lifter for #1, turn the engine by hand in the correct rotation and watch the intake lifter raise and lower so that the marks on the balancer line up for the #1 firing position. This should get the distributor close enough for starting. Add more cam lube to that lifter and whatever is left on the rest of the lifters before installing them. Since the rocker arms are “positive stop” then finish it up. Good luck

 

[Scott Danforth]

I would pull the motor to get the bits out of the oil pan and to get a good seal on the pan/front cover

 

[Lou C]

Agreed that’s a really good idea!
I used grey RTV on the China walls & Permatex aviation on the water ports. Sealer is advised there because there will always be some pitting in the cast iron on the head & intake.
For motor oil I might use Valvoline VR-1 20/50 for break in it has about the highest level of zinc you can find good for flat tappet cams. I don’t think any other oil even the diesel cert oils even comes close.

 

[snowbrd84]

I had bought some Ultra Blue but sounds like everyone uses Gray so will pick some up along with that Valvoline VR-1.

Removing engine is not an option at this point. Rhe cost would be prohibitive as it would have to be at a marina shop and then they are doing everything. Only other option was just to run it as is for rest of the summer. It was already run like this for quite a while by previous owner. I removed and cut open the oil filter on Sunday and it did have some metallic speckle but nothing bigger than dust.

Before removing distributor, I hand rotated the engine to TDC based on timing mark on harmonic balencer and rotor pointing to #1. Then marked exact position of the distributor. So I am hoping I put everything back together in same exact position then it should fire right up and throttle up to 3k and hold there for 10 min then vary between 2000 and 3000 for 20 minutes.

 

[snowbrd84]

Your fortunate to have enough space to do this. Most folks would have to pull the engine..

Single engine and 40 gal water tank is about 20 inches in front of motor. I don't have generator, so there is space on the tray it sits on to slide over and make about 36 inches clear in front of camshaft. Might have to cut the tray a little depending on where it lands, but very lucky it wasn't a bulkhead.

 

[Scott Danforth]

Don't be surprised if you have an oil leak

Break in is 2000 RPM for 20 minutes.

 

[snowbrd84]

The crank pully should come off with the 3 bolts removed and the crank bolt still in, right? Just want to confirm before I start prying on it.

 

[stresspoint]

sounds like you have a fun project at hand .
i for one hate the thought of a in hull engine job when the sump has to be dropped down or taken off .
i hope you are capable of bending like a pretzel to get at things .

the harmonic balancer will need a puller ,most likely a good solid one.
as a rule when replacing a camshaft i replace the balancer and timing gears as well.
start a fresh with timing , those old marks are now obsolete the with replacement camshaft , timing chain , gears and balancer.
a through inspection of the distributor drive gear is also a must if not replacing it.

you need to drop the sump all the way off , however , IIRC this is not possible on a BBC without removal of the flywheel (correct me if that is incorrect) , so you may have to improvise there and remove as many bolts as possible to get it to drop enough for the front cover to clear + a bit to spare.,
in which case you will need to somehow keep the original sump gasket in place and intact. otherwise fitting the new one and getting a good seal is going to be a nightmare.

take your time and try avoiding cutting corners , otherwise you will be doing the job again to seal an oil leak or 2 .

2000 for 20 min , a cool cycle and then run under load without laboring or over revving for a while.
avoid allowing long idling periods during camshaft break-in.

have fun .

 

[jimmbo]

Not going to be fun, installing the New Cam, as it will not be easy to keep the Lobes from damaging the Cam Bearings as the Cam is removed/inserted. I don't even like installing the Cam with the engine on an Engine stand, prefer doing it with the engine standing on it rear, so as to just lowering the Cam straight down. Timing Chain Cover, as already mentioned is PIA, at the best of time too, and just about guarantees a Leak in the Future.

 

[04fxdwgi25]

Couldn't get above 3,800 RPM and had tapping from starboard valve cover and high compression in number 8 cylinder. Ended up being a wiped intake cam lobe - thanks to everyone's help getting that figured out in this thread - https://forums.iboats.com/threads/high-compression-in-1-cylinder-7-4-carb.768144/

Here's the destroyed lifter and could actually feel ridge on the camshaft:
View attachment 387573

Boat is in the water at marina slip, and I don't have a trailer, so doing this in-boat in the water.

So here we go - 3.5 hours this morning to drain the oil, empty the water tank (it will have to move to remove camshaft), get the intake manifold off, valve covers off and lifters out. Also cleaned up the intake manifold surfaces to be ready to go.

View attachment 387574

Camshaft and lifters get here today.

One question I have is what do you all typically do for resealing the intake manifold? The manual lists multiple different sealants, one of which is $50 which seems overkill. I was going to rtv top and bottom of rear and front strip gaskets and then spray both sides of the new manifold gaskets with Copper spray and call it a day. Is rtv around all the ports really necessary, if so, is it on both sides of the gasket?

Do not use regular old "RTV" around the intake ports. Gasoline melts RTV and will cause vacuum leaks.

 

[tpenfield]

+1 for engine removal. You can then get a good look at both the engine and the bilge area of the boat. I know it has some scope creep to your original intentions, but it may allows you to clean things up and fix things that you would not normally be able to reach with the engine in the boat.

 

[Scott Danforth]

The crank pully should come off with the 3 bolts removed and the crank bolt still in, right? Just want to confirm before I start prying on it.

No

Pull the damper bolt too

Get a damper removal/install tool

 

[snowbrd84]

No

Pull the damper bolt too

Get a damper removal/install tool

Thanks, appreciate all your and everyone's help. Bolt - pulley - washer - dampened it was. Bent my harmonic balencer removal tool not realizing that washer was recessed in there but no other harm done.

New camshaft is in and smothered in Joe Gibbs Driven Assembly Grease. Rotates nice and free. Timing chain reinstalled.

Need a timing chain cover gasket before I can continue reassembling. Then it's time to try and put this engine back together.

Will follow up later with pics and progress.

 

[stresspoint]

Thanks, appreciate all your and everyone's help. Bolt - pulley - washer - dampened it was. Bent my harmonic balencer removal tool not realizing that washer was recessed in there but no other harm done.

New camshaft is in and smothered in Joe Gibbs Driven Assembly Grease. Rotates nice and free. Timing chain reinstalled.

Need a timing chain cover gasket before I can continue reassembling. Then it's time to try and put this engine back together.

Will follow up later with pics and progress.

now lets hope it does not leak oil

 

[snowbrd84]

now lets hope it does not leak oil

I hear that and understand the risk. Pulling motor just isn't an option right now so have to do what I can. It didn't leak any oil in the bilge and level stayed constant on the dipstick in the 2 months I've had the boat. If it leaks now it's cause I screwed something up on the install.

I did stick a pen magnet down into the oil pan through the motor when cam was out. Front to back fishing around the pan. Didn't get a single speck of debris, just a coating of oil. I have no idea when the cam lobe started wearing but it was Def before I got the boat.

 

[jimmbo]

It doesn't take much time for a Lobe to be wiped. Once the Hardened Layer is compromised, the Lack of EP additives in the Oil, allow the Spring Pressure to do the rest. Myself, I would have put a Roller Cam/Lifters in, with them, you can get away with just about any Oil

 

[Lou C]

Agreed roller cam is a good upgrade especially with todays low zinc oils. Even my lowly old ‘88 4.3 came with a roller cam. When I replaced the cyl heads I pulled out the lifters to check the lobes & they looked like new, no visible wear. It was 29 years old then!