The elusive 224/3.7 MerCruiser banger

Good Job Beck,
Now you got the gears rolling in my head. I need to find a couple more blocks to play with some ideas I have.

 

I have never cut metal with a router and my wood use has been limited. My method for making a router bracket doesn't appear to be the best way to do this. The use of a router template guide looks much easier. This was pointed out to me by another member here, and he is correct.

 

Another possible cause for my head leak pictured on page 79 in post # 2342 was presented to me last night.
There is a "fire ring" or "compression ring" in the head gasket that surrounds each cylinder. That ring is typically thicker than the rest of the gasket. Those rings could be taking all of the clamping force and not compressing far enough to allow the rest of the gasket to seal. That would allow the coolant leak that I am seeing. I have not taken that head off yet to do any measuring of these pieces. The guy that suggested this cause recommended a copper head gasket with no O-ring and Copper Coat for the cure. He thought an O-ring in the gasket may cause the same problem.

 

When we used copper gaskets, we put a .041 wire in the head and cut a receiver groove in the block. (Somewhere for the metal to go when its pushed down by the wire.) I'm not sure of putting a receiver groove in this block would be good. But you could put more wire in the head so less to push somewhere. We did a lot of Cummins with the a .041 wire cut in to .037 and no receiver groove.
If I were to go to a copper gasket and wire and still a open deck, I think I would try a thin bead of the Right Stuff on both sides of the gasket at the lifter wall.
We always put the wire in the head because that is what would move under load with a closed deck iron block. So in our engines is it the cyls moving or the head moving under load?
I think if it were me Beck, I would use your original Mercruiser gasket and that seeping will go away.
On the other hand with your closed deck and your use of this engine a copper may be the way to go.

 

A bit about grooving for o-rings:
https://www.jalopyjournal.com/forum/threads/rebuilding-after-the-crash.991650/page-151

Post# 4513

Complete with Isky Groov-matic

 

I think the Merc gasket will get some black RTV on the outer areas too. I have never used Right Stuff. Is it worth the extra cost? Yamabond #4 (it's grey) has been my "go to" for years.

 

We used Yamabond on a lot of snow machine cases as well as motorcycle cases. Worked well there and I would think it would work here to. I like The Right Stuff, its far better then just Black RTV. I think once you use it you will never go back to black RTV. I do think Yamabond would work better with your Merc gasket and would use it over the regular RTV.

 

One warning with The Right Stuff, once its set it is really tough to get things apart! Its like use it on a water pump gasket, when set you don't need the bolts anymore!

 

I have been told that you almost need to machine jack bolt holes into anything you want to get back apart.

 

Sounds like The Right Stuff would be a good glue to install the deck plates.

 

I am a parts driver for an Auto Parts Store and I deliver a lot of The Right Stuff to our commercial customers when they order gaskets, especially intake and water pump.

 

It is just a better RTV, so it doesn't set solidly. That would allow the plate to flex at the glue joint and loose clamping force.

 

Here is some more information to add to your deck plate knowledge:

In searching the internet for details about installing a plate like we have been discussing, I found several videos showing how the Honda guys do it. It appears that the Honda engines are much more consistent in having the outer cylinder diameters concentric with the actual bores. You can buy ready made plates from several sources, even Amazon. These are drop ins with little or no fitting. The blocks are not likely to be machined in this area, so it must be a case of newer, more accurate casting methods.

Keep in mind that their purpose is to reinforce the top of the block. They are not trying to provide more surface area for the head to seal against. They are referred to as 'block savers' and sit below the deck surface.

Several folks on here have been looking at having plates made for the 3.7 that could be installed with little or no machine work. Beck found that the fabricated plate he made for his engine took 16 hours. Part of the problem was that the cylinder towers are not round. So, it was necessary to hand fit the plate to the somewhat oval cylinders. Also, the bolt bosses have an irregular shape which requires even more time consuming fitment. As he pointed out, this can be remedied by milling down the bosses to a predetermined depth along the line of the inner wall of the water jacket.
But how to make the barrels round? I have a block that has a crack in one cylinder so I can experiment with it without fear of messing up a good engine. What follows is a description of what I did. It was an attempt to show proof of concept. I found some difficulties and will point out how this could be done better.

By locating off the cylinder bore, we can cut the outer diameter of the barrel and then our plate can have a round hole instead of some crazy geometric shape. Using the original pistons, I drilled and tapped them in the center. This was done on a lathe from the bottom side so that the round part of the piston was clamped in the 3 jaw chuck. I then made 4 disks from some leftover flooring. These were turned on a mandrel so that they are all the same diameter with a hole in the center. These were then screwed to the top of the pistons and put in the bores.



Using a woodworker's router with a template guide bushing, I was able to follow the disks and shape the outside of the barrels. As you can see from the photos, there are some refinements that need to be made for this to work well.







The problems:
I used a 1/4" four flute endmill mounted in my plunge router. This diameter was chosen for two reasons. The outer part of the barrel is very close to the bolt bosses in several areas, and the radius where the cylinder barrels join is close to that cutter size.
The cutter tends to load up when cutting thicker part of the wall. I tried to minimize this by cutting a depth of only 1/8" at a time. I also tried some lubricant, which helped some. A 2 flute endmill or router bit would be better. My preference would be to use a 1/2" cutter, but that would necessitate cutting the bolt bosses down first. The router I used is a single speed (29,000 rpm) unit, much too fast. A larger variable speed version would undoubtedly be better suited to the task.

While the bushing guide does work, the problem I had was that I was working blind. The router base hides the cutter/workpiece interface. You can see that I put a couple of notches where I didn't want them. Beck's idea of swinging the router from the center of the cylinder allows the cutter to be seen, but doesn't provide a stop at the ends of the cut. Maybe a combination of the two.

I was able to move a couple of the pistons, while routing, which makes the final piece less than perfect. This is probably due to the fact that I had to drive them out of the block originally and one is pretty badly cracked. The were blasted with coal slag which made them grow a bit. Also, I had thought about using the rings to help stabilize them in the bore but broke several while removing them from the pistons. It may be better to make some thick disks to go into the bores.
I'll see about making some these adjustments and update this at a later date.

I did not cut the bolt bosses at this time as I want to use this block to build a large bore 'Monster Motor' and have another idea for plating that one.

One thing I found disturbing, is that the bore centers were not consistent. They varied by as much a .080".
This means that any universal deck plate would have to be made with enough material so that they could be 'fit at assembly' to compensate for that. They do, however, seem to be very consistent side to side in the block. Mine measured + or - .002".

My current thinking is that a more or less universal plate could be made with the following parameters:
The outside should be a rectangle with radiused corners. This means that the block would have to be milled to a predetermined depth and shape. The head bolt holes and cylinder bores accurately located to each other using the 4.900" magic number. The bores made slightly smaller than the barrels so that they can be fitted with the minimum hassle. My measurements indicate 4.860" dimension, but that needs more research and is dependent on the ability to make the barrels round and to size.

Comments welcome

 

Short of having the block fixtured in a CNC mill to machine around all the cylinders to duplicate his efforts, the way he is doing it is about the best option to do it. Good job!

 

I share with you the problem that adequate gaskets with sealant beads are not available and that the problem is coolant leaking across the open deck block's edge into engine oil. This edge's narrowness is the design flaw responsible for this. It is too narrow for good sealing and too narrow for reasonable o-ring grooving of the stock block. Adding aluminum just within the edge of the block around the water jacket may be one approach.

Beck's filling in the open deck is a big step toward solving the problem. The hard part is in the details of doing it. I like the way he did it as it fills in the water jacket, supports the cylinders, supports the plate, and expands thermally at the same rate as the rest of the engine and should solve the problem leaks. It does involve a lot of time in hand fitting.

The Honda forum emphasized that in their words "tapping" in the filling plate distorts the cylinder bore so the plate should not be a tight fit unless the cylinders are bored again. From Photos, the Honda engine appears to be built heavier than Mercruiser engines so we must watch out for cylinder distortion. Do the thickened areas of Mercruiser cylinders play a part in maintaining cylinder shape?
Instead of machining the outside of the cylinders round, could filling in the gaps around them with an adhesive have advantages?

Machining the cylinders to fit the plate will clearly provide good support for the plate as does machining down the area around the head bolts or studs. Epoxy blobs under the plate could provide some additional support for the plate.

 

I intentionally left about a .040" gap between the deck insert and block, including the cylinders. I did this to allow the installation without scraping off all of the epoxy. My plate fell into the hole before I applied the epoxy.

On early fit ups of the deck insert, before I had a loose fit, it was difficult to remove the deck plate from the block. If using my method you will have the deck plate in and out of the block a LOT checking fit-up and marking tight spots. I marked the tight spots with a Sharpie. After more grinding I would wipe it down with acetone removing the Sharpie marks, so I could make fresh marks.

I did not make my cylinder OD round. I made my deck plate fit the irregularities of the cylinder. I did roughen up the outside diameters of the cylinders to provide better adhesion of the epoxy.

 

Your fit of the plate requires some effort but it can not distort the cylinder. Using jbweld in the gap will support the cylinders. RTV should also work in there to seal the gap but as it is flexible, it can not contribute support.

 

Sealing the outer edge of the block and gasket will require a sealant.

Randy said that silver paint failed to seal there. It may have been too thin to work.

He tried permatex (which one I don't know) and it failed to seal also.
I can see that if rigid, as some is, permatex would break loose and leak.

The grey Mercruiser gasket sealant beads remain stuck to old gaskets. I did not see them sticking to the block. The material is weak as a thin layer of cured rtv would be. Not tall to begin with, they are squished down in use. The gasket company that made gaskets for Mercruiser would not tell me what the sealant is. The uncompressed sealant bead stands 0.0028 inch above the gasket surface on each side.

I would consider using Locktite 518 which is a good flexible flange sealant.
Locktite #515 is flexible and for surfaces which move against eachother, this sounds like our engine sealing situation. 515 is for aluminum to aluminum surfaces and cures more easily.

Yamabond 4 is another respected flange sealant I'd guess it is more flexible than 518. (I posted locktite product information on our page 76)

Hylomar is now sold under a different name by Permatex It costs much less now than 15 years ago. $10 for a tube about 2" diameter about 6" long. 15 years ago it was in a short tube about 1/2" in diameter and as I forgot the price. I'd guess $5.

Chris reports that using a dead soft copper gasket and spray on copper seal worked to seal the coolant. Doesn't a copper gasket require a better fitup than a fiber gasket?

I just scraped a little of the sealant bead from a used gasket. It is very stretchy, as stretchy as one would expect cured rtv to be and weak just like cured rtv. I think the sealant bead is a .003" layer of rtv. The gasket beneath the sealant is not shiny like the rest of the surface so perhaps the transparent shiny layer was applied over the sealant bead

 

A couple of bits of information to pass along:
When test boring my cracked cylinder, I found the iron sleeve to have a minimum wall thickness of .100" (Bore size of 4.560") But, I was @ 4.770" before the iron was completely gone. So, when boring the stock sleeves out .060", you might have a wall thickness as little as .070" in some spots. That seems pretty thin, but since it is supported by the aluminum barrel, I'm pretty confident that it is enough.

Another thing I noticed was that my head bolts have a reduced shank diameter of about .500". This lends credence to @iadr and @randydupree concern about bolt stretching and clamp load.
I have a friend that might be able to check the stretch at rated torque for us. My suspicion is that if using studs that are 9/16" diameter, full length, you may not get the necessary clamp load.

 

Ok guys stock bore is 4.360 so at .080 over you only 4.440 bore. That leaves you with more than .100 thickness. A 9/16 stud torqued to 135 foot pounds (as it should be) with have more clamp force than a bolt of the same size.

 

Chris,
I think you misunderstood what I was saying about the cylinder thickness. I was boring out a cracked cylinder to see if I could do it on my Bridgeport. What I found that is that I hit aluminum in one spot @ .200" over, meaning that that sleeve was only .100" thick at that point. Earlier some folks here questioned whether a .060" overbore was safe on these blocks. I was merely pointing out that @ 60 over there would be only .070" steel at that point in that block.

Very early in this thread, one contributor was very adamant about 9/16" studs (or bolts) not stretching enough to maintain sufficient clamp load. I found it interesting that the Mercruiser head bolts had a portion of the shanks reduced to .500". They must've understood this too.

Current thinking in the Auto industry is to stretch the head bolts just past the yield point and not reuse them. The final tightening is done by turning a certain number of degrees after the joint is preloaded by torqueing to a lower value.

As a retired engineer for Snap-on Tools, I do know a bit about studs vs bolts and bolt stretch. I completely agree that studs are a superior method for holding heads in place. But, are 9/16" studs torqued to 135, stretched enough?

 

I'd be skeptical of torquing one that much in a die cast aluminum block very many times....!

 

Using flange disks we could live load the head fasteners as springs would. Acting as springs they keep a predetermined tensile load on the fastener through temperature changes. Necked down fasteners, if they are reduced in diameter enough will also act as springs.

The goal is finding the best spring force as others have mentioned. Some of us use aluminum heads, others use iron heads and as the thermal expansion is not the same, diffrent springing would be needed. Gasket compression recovery also enters at this point.

Metal fatigue can indeed lead to failure.

the following is helpful
https://cdn2.hubspot.net/hubfs/2535282/Flange Sealing Guide_EN.pdf

if you are in a hurry at least read page 37. The rest is worth reading.

this is a table from one company but the individual disks are too flexible and must be stacked ( concave sides in the same direction) acting as parallel springs
https://www.fandisc.com/uploads/8/4/5/1/8451677/fl-inch-revised_orig.gif

 

I have just Edited post # 2341 on page 79. In that post I stated I had used a Mahle head gasket. That was incorrect. Upon disassembly I discovered the head gasket that I used was a Felpro 17068, which is listed as a 460 marine gasket.

This is the head gasket that I had sealing issues with. Upon disassembly and inspection of the gasket I cannot see why air seeped through it. There was a visible compression of the gasket at the outer edges on both the top and bottom. Now I am wondering if it would have leaked water or not. Air leaks easier than water. I am fairly confident that if I had used it I could have sealed it with the little pellets like recommended by GM in several engines.

When I measured the thickness of the fire rings compared to the outer part I saw that the fire ring was about .003” thicker. However I suspect that the metal fire ring had a bit of a memory and was compressed to the correct thickness while installed.

Another interesting discovery which you should take note of; On my aftermarket head an accessory mounting hole lines up with the front head bolt on the exhaust side. There is no bottom in that accessory hole and it is open to the head bolt. I had put a long bolt into the accessory hole and it bottomed on the head stud. Initially I thought I had bent the head stud since I couldn’t pull the loose stud out of the head bolt hole. It turns out I had pealed a little aluminum from the head and it was wedged. This wasn’t the cause of the coolant leak. The accessory bolt had been installed after the motor was fully assembled.

 

Update to my post #2395 on page 80;
This is referring to me installing a deck plate using JB Weld for retention.
I waited a little while just to be sure everything was totally cured. I haven't drilled the coolant passage holes into the deck plate yet. I plugged the coolant system and put 3 # of air pressure on the coolant system. It held the pressure, so no leaks. I was afraid of putting more pressure on the system for fear the whole plate would blow out.

Just to clear any confusion; I am working on 2 engines. The post above this one is about a different motor.

 

I got my crank back from the crank grinder. I had it stroked to 4". I am using aluminum rods so had to chamfer the one side and narrow the bbc bearings a bit, still wider then the stock Ford bearings. Also cut new tangs in the caps so I don't have to buy two sets of Cleveland main bearings. Also been just mocking up things to see how things are going to fit on the front of the engine.

 

The Mercruiser 3.7 cylinders are irregular . I ascribe this to poor quality control of the block casting. However it may be by design as the cracks I see are where the aluminum around the cylinders is thicker. But as to quality control, I saw one side of the aluminum of a Mercruiser cylinder very thin but the side opposite it was quite thick. Evening out the thickness of this lopsided casting would leave the cylinder liner but hardly any aluminum. Most cylinders are better than that, but as I burst one 30 over cylinder in another Mercruiser 3.7 engine, so I'm pessimistic about the strength of the cylinders especially when bored larger.

In spite of these shortcomngs, this engine is addictive in an 1800 lb car.

 

Nice work Flatrod17. Pictures are worth 1000 words, and yours tell the story.
I am trying to understand your jig to turn the bearings. I understand what it does, but not how it was made.
#3 main cap doesn't get a new tang slot?
Did you have a steel or cast crank stroked? My local shop won't do a cast one. I haven't come across a steel one yet, but I am not to that motor yet either.

 

I'm trying to understand the Cleveland main bearing deal.
Do I have this right?
We would like to use the Cleveland bearings because they are only grooved on the block side?
The cap side halves have the bearing tang on the wrong side?
So, we cut a new notch in the caps for the tangs to fit?
How would buying a second set of bearings avoid this?