The elusive 224/3.7 MerCruiser banger

I just did a pressure test on my coolant system. Houston we have a problem.

If you put 30# of air pressure on a motors coolant system and blocked it in, it should hold that pressure overnight. My new build doesn’t. Using a squirt bottle, water, and dishwashing soap I found leaks.

Some words of caution; Just pressurize the motor, NOT the radiator (auto) or heat exchanger (boat)! If you are working on a new motor and squirting the intake looking for leaks you need to be sure to have the lifter cover secured, with a gasket, or you will get water into the motor there, soaking the lifters and their bores. The same on the exhaust side, you can’t spray the head to block seam easily without getting water into the heads exhaust ports. Put spark plugs in there holes.

My head gasket is seeping at the front and exhaust side to the outside. I cannot get to the lifter ledge sealing surface to check it with soap water. That is the area that we have been talking about in the last several pages, and the most prone to coolant leakage. This head gasket is from a Mahle HS4909VM gasket set. Mahle is made by Victor Reinz, so I expect their gaskets are the same. They have the same part numbers.
(EDIT; Upon disassembly I discovered I had used a Felpro 17068 head gasket. This gasket was designed for 460 marine use.)
I also have a leak at the gasket between the timing cover and the block. We have talked about some of the aftermarket gaskets not having sealant beads. Most of that conversation has been involving the lifter rail to head seal. That is not where I am seeing my leak, but it is most likely leaking there also.

The head was torqued to factory specs. I am using new head studs, and a new aluminum aftermarket head. The block deck was freshly surfaced. I am at a loss. Do torque specs change with studs or aluminum heads?

These bubbles took several minutes to form.

 

Beck,
That's a real kick in the ass!
Here are some thoughts I have:
If the coolant holes in the head gasket have metal rings around them, maybe they are not getting enough crush to seal against the aluminum head and block. I would try retorquing and maybe add 10 lb/ft to the spec. Since you are using studs you can add to the clamp load without fear of pulling the threads out of the block.

Also, if you actually ran the engine up to temperature, with no pressure on the cooling system and then retorqued it may seal up better. The downside of this is you won't know until you try it.

What happens if you lower your test pressure to 20 or 25 psi? I would think that it should hold 30, but that would give you some indication of how close to the edge you are.

I have friends that work at a GM assembly plant. They tell me that every Cadillac with the Northstar engine got two pellets of stop leak in the radiator. Again, you have to run the engine up to temp to activate the chemicals.

I like the idea you mentioned in the private message. If you can pump hot water with stop leak through the engine it should seal up. One possible way would be to run coolant, with stop leak, from another engine in series with your Mercruiser. I think you need to get the whole mess up to 180 degrees or so.

Keep us up to speed on your progress. You are a smart guy, you'll figure it out.

 

If my head gasket had the metal rings to seal around the coolant holes they definitely will not seal since there would be no block deck on the other side of the ring to press onto.

Overnight the pressure held in the block dropped down to under 5 psi, so no it won't hold at a lower pressure.

I had a Cadillac in probably the late 90's that had to have those pellets put in annually. It was in the service manual. It was pre-Northstar. I really like that idea.

One other issue I may have. I don't think I used lube on the studs when I was tightening. That could have led to a higher torque reading than I was actually applying.

I don't have another motor laying around that I could run in tandem with this one, but good idea. I don't want to put sealant in anything I'm driving.

I am concerned about a potential bigger leak at what I call the "lifter ledge", the narrow part of the block that divides the coolant and lifter/pushrod part of the block. I didn't think I could spray soap water up there to check for bubbles. I can put the motor on a stand and turn it upside down on a slight angle. Maybe I can carefully get some soap water to that junction. I can live with a little coolant seeping to the outside of the block before I can live with coolant going into the oil.

NAPA has a coolant leak detector BK 7652663. It is a UV liquid you put into the coolant. It glows when viewed with a black light. I'm sure it works externally on the motor. I expect it would see coolant in an oil sample also.

 

I guess I wasn't thinking clearly when I said, 'metal rings'.
This is a picture of a Fel Pro head gasket (520SD), supposedly 460 Ford. The rings I was referring to are in blue. Not metal but most likely some variant of RTV sealer. There is no bead of sealer along the 'lifter ledge', but that is to be expected. Interesting that two of the head bolt holes are ringed. I think that these are the ones that have the locator dowels. Also, the steam holes between the cylinders do not have rings.
Based on what you said, my first step would be to back off all the head stud nuts, apply lube and retorque. Another thing I learned when using studs on a SBC is that you need HARD washers under the nuts with a drop of oil on each one before torqueing. This gives the least friction and assures the best clamp load. The nuts also have to be hard. I'm sure you know all this, but just in case.

If that alleviates the weeping, I would try one more thing on the lifter ledge. Paint a line of old style hardening Permatex Form a Gasket #1 on the block, then clamp the head and gasket down on it. I once had a student pull an engine from the carburetor pad with no bolts in the manifold, just the old Form a Gasket holding everything together.


FORD SCE Titan Copper Head Gaskets T354443L
Note the sealing stripe along the top edge

 

I believe the Mahle gaskets do use metal rings not sealant rings. You are correct on the head locator dowel locations. It's interesting that the Mercruiser manual calls for the head bolts to be coated with their "Perfect Seal". None of the holes go to coolant passages. The head bolts do run through the sealing area of the coolant, but the coolant shouldn't get to them. The Perfect Seal would also work like a lubricant during assembly. Perfect Seal is said to be similar to Aviation Permatex. Since I am using studs, I need to seal under the washer, between the washer and nut, and the threads of the stud going through the nut.
The Titan copper gasket looks nice.
Our gaskets should really have a sealant bead all the way around the outside. The rings around the coolant holes on the exhaust side don't do us any good. That is exactly where my bubbles are at.

 

When you say that the exhaust side sealing rings don't to anything, is that because that's where your leaks are, or because they can't seal because they don't capture the holes in the head and block?

 

If you need more I got.em

 

Welcome Chris,
Any and all pictures are welcome. I'm particularly interested in the progression of your engines from the beginning. Most of the guys on here are working on much milder versions of the 3.7L. If you can tell us some of the stuff you tried and what did and didn't work that would be great!

Right now, we are struggling with head gasket issues. It seems that Mercruiser has switched to a different gasket and the original ones are no longer available. The difference is the old ones had a bead of sealant along the divider wall between the water jackets and the lifter bay. The new ones do not have this. One of the earliest contributors to this thread, Randy Dupree, warned that this sealant bead was critical and that he never found a gasket that would seal there except for the Mercruiser piece.
There has been much discussion about closing in the top of the block, either with Devcon/Epoxy or aluminum plate. The aluminum plate solution brings up more questions. Do you just fill the water jacket with a contoured plate or attach a plate to the top of the existing block? Then, how do you attach and seal the plate? If you weld, does it distort the block to the point of having to remachine everything? What about adhesives or aluminum brazing?

Thanx for joining us,

Bruce

 

Chris is way ahead of me, but looks like a similar path I'm going down.

 

Very Cool Flatrod17,

I'd like to hear more bout your build, especially the injectors.

 

I have built a few stock 470's this is the first non stock one. It's a project I'm just now starting. Will be going into a 29 roadster. Either with machical or efi injection.

 

Chris, I have seen your name associated with these motors for a long time. Your experience here would be greatly appreciated.

Flatrod17, It appears your experience is above nearly all of us here too. Any help or advice is always appreciated here.

Welcome to you both.

 

My “new” head gasket just arrived. It was not in the factory packaging. It was advertised as a Mercruiser part. There are, what I believe to be, the correct 27 13709 numbers stamped in it. On my photo the point of the knife is pointed to these numbers. 27 is a line above the 13709. The gasket does have the correct sealant beads on both sides of it as shown in the close up photo. In that close up you can barely see the 27 13709 stamping. The long straight line of sealant on the knife side is what seals the dreaded coolant leak into the pushrod/lifter area. There are no sealant rings around any of the coolant holes. The exhaust side of the gasket has similar sealant ribs on the outer edge but there are skips at the bolt holes. There are no sealant ribs on the ends. The gasket has the proper raised metal rings around the cylinders. It has a shiny non-sticky sprayed coating on it. I don’t know if that is some sort of sealant also. It looks like the right thing to use.

 

Beck, that does look like the head gasket to use, it should take care of your seeping.

GearheadsQCE, The injectors are from a big block chevy Arias hemi set up. I bought them years ago for my Boss 429 as original Hilborn is impossible to find and if found I sure don't have the funds for it! They are a two piece and I plan to make a new part to bolt it to the Boss head. They have 3" butterflys, may be a bit big! I think I can make it all work.

 

I just checked with Masterbond and found that they want $500 to $600 per 30 cc syringe of their nice sounding epoxy. It is not a mistype.
They suggested checking with Devcon or Locktite. I had already done that and found that Devcon's "titanium epoxy" would stand 350F.

 

Copper head gaskets were stock for a 1967 Yamaha 350 motorcycle. The factory shop manual said to heat them and quench them in water for re-use. They were thick but not embossed.

It seems that one could plumb a pressure cooker into a merc coolant system to get stop leak into the gaps rather than having to use a second engine. External heat would have to be applied to the pressure cooker. As suggested, any automotive watercooled engine could be used heat and circulate water to plug the leaks and one only needs to make up hoses to run over to the merc engine. not a bad idea at all.

 

Considering metal warping due to heating The easiest example to explain is warping due to welding. As a puddle of the metal is liquid in the expanded condition in the heat of welding, it later cools and shrinks in its solid condition distorting rest of the structure. So, the less metal is involved and the less difference in temperature between the metal being worked and the rest of the part the less its distortion will be.

Even in soldering aluminum, preheating the general area should result in less distortion.
The closer the preheat is to the melt point of solder, the less the warping will be, but seals remaining in the block must not be melted.
nitrile oil seals have a temperature limit beginning at 250F. Fluroelastomer seals are ok to 320F. For more detail on that see https://www.sciencedirect.com/topics/engineering/oil-seal

 

This is what I have done and it’s worked well so far, I use a .040 copper head gasket, with the spray copper seal spray. Follow the directions!! Anything above 22-25 lbs as water pressure is unrealistic . Just don’t do it . I’m running a 4.600 bore with a 4.125 stroke (274) ci it makes 517 hp on alcohol, it 14 to 1 compression with a 6049-c460 head , trust me it not special. 2.1 W.W. Rockers, and victory ti valves. A custom ground comp cams cam. I made my own billet core. It’s .880 intake .840 exhaust. 278 intake 284 exhaust. On a 110 centerline. Anything else just ask

 

I don’t weld mine in . I make sure and cut a ledge in the block for the plate to rest against, then machine it flat . Hoe ever I’ve seen guys weld them in , I’ve also seen the machine the deck down an inch an install a plate that’s an inch thick with new sleeves . So I really don’t see a wrong way. If you weld just pre hear and take you time. The other ways involve no heat an no distortion. So it’s up to you. I use darton sleeves btw.

 

Chris,
When you say you leave a ledge for the plate to rest against, is that along the intake side? How do you seal the plate to the block on the perimeter?
When the guys cut the block an inch and put on a one inch plate, don't they lose an inch of threads in the block? That doesn't seem like a good plan to me.

 

Well the engine im referencing is Clint Neff comp elem. engine I’ll post a pic of it . It has the JC-51 head aka the wedge pro stock head it makes a tick over 600hp at 10500 rpm. So I guess as long as you use head studs it’s not a concern .

 

The top picture is clint’s set up, the second is my friend in Puerto Rico , the bottom is my block. So as you can see different ideas to achieve the same goal.

 

Chris, we are delighted to see you here. There is only so much we can find in print so we are greatful for the experience of you and Randy to help solve the headgasket sealing problem.
Were you able to just mill a seat for your sleeves or was it necessary to build up some aluminum down at the bottom of them first?
Looking at your photos, how do you secure your block filling plate in place ? There are 8 additional holes beside the cylinders. They look like water passages. 4 are in aluminum over in the lifter gallery so I'm puzzled.
dennis

 

I bored the original sleeve completely out, I pressed the plate in and bought sleeves to my specs. Pressed them into the plate, then o-ringed the sleeve with .042 stainless wire. Used a .040 copper gasket. I did the wire o-Ring on stock blocks also with good results! One thing I learned is in a gasoline engine is the pressure is greatly dissipated after 1 inch . This is with ever gasoline engine. And that’s the reason for the 1 inch plate. The head gasket sealing problem is due to The stock gasket not having the sealing aligned with the merc block , that’s why I use the copper gasket, with the spray. Any water passages are in the head simply copy those and drill holes for them. The block is a heat sink, it will get rid of the heat ASAP hope this helps . Btw my email address is [email protected] we also have a group on Facebook under the 470 racing page . Answer the questions or I’ll think you a bot and won’t let you in . Lots of info there !! Good luck !! Be safe!!

 

Yep,thats the gasket i used and bought from Mercruiser,it stopped my leaks.

 

An interesting thing an engine builder was telling me about the 460 and the mercruiser engines is the head bolts/studs are too big in diameter.
He says they never stretch or stretch enough if they stretch at all to keep good tension on the head.
i guess the head bolt/stud people could confirm this.
but i do agree that a bolt has to stretch to maintain torque.
Race hemis use a smaller bolt,as do small and big block chevys etc.
i do realize that the ford on;y uses 10 bolts,but a necked down bolt may work better.

 

Even lowly Volkswagens were breaking their fat head hold down studs. The cure was to use much thinner ones which stretched instead of breaking. It does not sound logical but as the logic is not obvious, I'll just leave it at that besides, I don't understand the how of it. Studs could be turned down and polished or shot peened but Bolts pose another problem as with old perfect seal on the threads, they have to withstand a lot of torque to remove them (my 18 inch breaker bar with 24" of water pipe extending it,
my age may have something to do with extending the breaker bar).

 

@Chris Nichols,
I had seen the pic of the top of your block before, it just didn't register with me as how you fit the plate. You mentioned pressing the plate into the block. So, you mill the block to a predetermined shape, 1" deep, and then make the plate to a press fit of that shape? I would imagine that this is done with a computer controlled machine, correct? How much press? With the sleeves also pressed in, that would really stiffen the upper part of the block. Very clever!
I also like the way your Puerto Rican friend did his. Looks like he flattened the sleeves where they are adjoining. With the flanged tops the natural gap at the edges gives built in coolant passages. Cool! Do you know what finished bore size he is running?