The elusive 224/3.7 MerCruiser banger

That makes much more sense. I wasn't aware that you had taken some height off the deck in the "otherwise stock" engine.

 

The head gasket has difficulty sealing the narrow ledge between the water jacket and the area where the pushrods are if the mating surfaces are less than perfect. To this end, the deck is commonly skim cut if there is any warping or other surface defect. This may be done each time the head gasket is replaced and as there are complaints about short headgasket life in this engine, I expect the deck height to be reduced to improve gasket sealing with a fresh deck surface as the engine is worked on throughout its life.

Whatever the cause, damage can occur to the piston crowns if they overheat badly or if the operator ignores detonation. The 3.7 engines that I buy often have pitted piston crowns. Detonation and overheating are said to cause this.
I also commonly find difference in the deck heights of the cylinders versus the outer water jacket. This would have to be removed by milling the deck lower.
Thus a new engine and a used engine are likely to be different.

 

Reducing compression pressure can be done in a number of ways:

1. The easiest is to use a thicker head gasket. Thicker headgaskets expose more area to gas pressure and are thus more likely to fail. You are limited to how thick gaskets can be made.

2. The next easiest is a decompression plate of annealed aluminum or annealed copper. It can be sandwiched between two head gaskets. Some say that the uppermost headgasket can be replaced by sealant. To anneal aluminum, smoke it lightly from an acetylene torch and then heat it until the carbon layer burns off. To anneal copper, heat it to redness and quench it in water. You will need to remove the scale after this. As copper work hardens, it is reccomended to anneal it before reusing.
A sealant is applied to the surface to fill the very small surface flaws that the copper or aluminum can not flow into. The softest aluminum I ever saw was some that Boeing was selling. It was about as soft as lead.
The metal can be cut with a band saw or hole saw when sandwiched between plywood. Tin snips and files work also.

3. low compression pistons can be used.

4. slightly shorter connecting rods can be used.

5. the piston crown can be cut down a limited amount.
Flat crowns need thickness so as to not deform under pressure.
A piston needs some thickness to carry heat away.

Lower compression allows more boost pressure to be used.

 

Chiming in on a couple of things
If anyone has a profile of a rod or measurements they want modeled for clearance I will see if it works for you, the more we all know the better. The incl. picture is what measurements I need. just print it and fill it in with good caliper measurements send it to me and away we go. Like I said I am happy to build a model and see if it fits. I have to do the disclaimer thing though - and of course there is no guarantee expressed or implied. I would like a tracing of the rod too although most rods clear the bottom of the cylinders just fine.

On head gaskets - if you look at the next picture you can see why these fail. The drawing in black is the deck and Cylinders, the red layer is the Mahle gasket from merc- marine. If you look at the area I circled you will see just how little gasket contacts the head and sleeve, where those pockets are its .090" to .100" that is all that is holding back something like 1700 PSI in normal operation, If you had knock I think it could work that gasket to death very quickly. I couldn't believe it and reminded me of those famous last words: "The engineer says its good"

To answer Dennis in post 2864 The 3D cad I use does mechanical stuff great but is really not good with organic shapes

 

The gasket you drew has an irregular, out of round, shape around the cylinders. Is it a used gasket ? I have removed used gaskets that look like that.

If a new gasket is round and regular in its shape at the cylinders, a possible explanation for distortion in an in-service gasket might be due to the deck height being irregular. Could the gaskets be squirming out of shape?

As engines heat up and expand the expansion will be more where the metal is hotter. Add to that the different rates of expansion of steel, aluminum and cast iron, the expansion gets complex. That steel connecting rods have half the expansion rate of aluminum saves those of us with zero decked engines.

In some engines, there is a slit in the block between the cylinders, supposedly to allow otherwise trapped air bubbles to escape. It is another place where headgaskets blow out as sealing area there is limited.

Randy identified the sealing surface between the water jacket and where the pushrods operate as a problem area for water leaks. The aluminum there is narrow.

 

Hi Dennis,
It is a brand new Mahle gasket out of the 470 "kit" I got. Those notches would never be an issue on an iron decked 460, but with the free standing liners in the 470 look to be problematic to me. I am pretty sure this is just a 460 gasket as I doubt Mahle or anyone else would make a special one for the 470.

I would think that having part of the gasket less exposed to the combustion would be more problematic than a round one that can expand equally all the way around, although in both cases the heat would probably go to the liner or head PDQ. I am curious what the notches are really there for? They are on the valve side but there is miles of room - the valves are well inside the cylinder area and these notches (and part of the cylinder) are all covered with the stock head. Anyhow, this notch thing is something to be aware of when putting one back together.[/QUOTE]

 

About to finish my head and deck surface. Nobody seems to sell a MLS head gasket for the stock 4.36" bore.

What are those of you that have gone this route using?

As an aside, SCE's copper head gaskets appear to have the sealant bead where we need it per their catalog images...

Edit:
Should have googled before I asked. The internet is recommending anywhere from zero to 60 thou over and people are reporting up to 100 thou as not having any ill effects in practice. So 40 thou should be fine.

 

My bore is 4.390 and I used a Cometic 4.400 gasket. If you used the same, that is only .020 over your bore, I don't think that would be a problem.

 

Sean,
The composition gaskets which had sealant beads matching the water jacket were, I believe for Mercruisers because when the 3.7 has sealing issues, Randy Dupree wrote that the problem area was between the water jacket and the chamber where the pushrods run up and down. Check the flatness of your deck. It is better quite flat even when the gaskets are the forgiving composition ones.
The metal gaskets are more "fussy" about the surface and that may be why sealant is added on them.
Sealing the cylinders is usually ok, but if there is detonation, a much greater load is on the gaskets at the cylinders. It seems that a round opening in the gasket is a better match for a round cylinder. If a removed gasket is distorted around the cylinders, I would guess that it was due to an uneveness in the gasket, the deck or the torque. The gasket may be required to distort to seal an uneven place. That the casting around the liners is usually not even in width and may play a role in this.
[edit: I had not read sufficently carefully what Sean wrote. My reply would not apply to his carefully worded question. So I wrote the next post, 2980.

 

Sean, I read your post again, this time more carefully, and looked at your illustration. The deviations from round that you show on your gasket would seem to be less than ideal considering the limited sealing area available on a Mercruiser 3.7 block. I suggest calling Mahle tech suport 1-800-223-9152 about this concern. I just checked several gaskets. New ones from Mahle have the odd deviations in them but the others (also new but made by Felpro and Sierra) are perfectly round. It strikes me as odd and yes , as you wrote, the out of roundness would not matter on a closed deck Ford 460...but on our open deck engines it may indeed matter.

 

In response to mr Arse-sideways question on proper gasket bore size , it may not matter greatly.

I once bought a BMW opposed twin 900cc motorcycle that ran well but made an odd noise.

Someone had substituted a composition headgasket from an 800cc engine. The smaller gasket overhung the bore and its fire ring was completely out over the piston. I removed the improper gasket which worked but looked quite frayed where it had been flopping up and down as the piston moved. I ran it 1000 miles with the odd gasket I can not guess how far it was run with the odd gasket before I had it.

I would never have believed a gasket could withstand that much abuse.

 

I just read that copper head gaskets seal the water passages better with black rtv on the block and head surfaces than they do with Hylomar.

The above came as no suprise to me as when I used Hylomar to seal a joint of the oil distribution system (on a bmw engine) It was ok until the engine warmed up but then the Hylomar extruded out of the joint followed by engine oil. That was the first and last time for me with Hylomar.
I have no complaint about copper head gaskets on my old air cooled yamaha motorcycle. It was a factory gasket and was reusable. The Yamaha dealer's manual said to get it hot and quench it in water to anneal it before reusing it. ( Just the reverse of what happens if one quenches streel. ) You aso have to remove scale after quenching copper.

 

Is there a different source for the mini starters in the US besides IMI Performance Products, Inc.? I am looking for a higher voltage version for a drag car, but also need to stick with the open gear style.

 

A 12V starter will run fine on 18v.

Remind me, what's the IH application for these starters?

 

Any gasoline International Harvester slant 4 and V8 "Comanche" engine.

I am looking at a 24v system. IMI told me;
We recommend 12 volts – using 24V will decrease the standard life of any starter that is built at 12V.
We understand how quickly the motor fires under 24V, but we cannot recommend it.

 

D B electrical sells them. I bought one. They only cost $55 so why even worry about life? run them on 16 volts or more and just have a spare in your truck.

Mine is not as strong as the non geared starter. More voltage would help. If yours is in a race car, I'd consider a plug in starter, no alternator and a minimal electrical system in your racer with a motorcycle battery for onboard power. The military uses higher voltage systems but getting one of them to fit would be the stumbling block..

 

It will be a total loss system with a magneto. I need an onboard battery so I can run the car alone, starting it multiple times a day while fully belted in. Batteries aren't a problem. I can use an ultra lightweight and compact 12v lithium battery if I need to, but one of the series sponsors makes a 24v battery and I would rather support him for supporting us.

 

If the engine does not start well on 12 volts, there are several options: you could increase the amperage available with either an ultracapacitor or a second lithium battery wired in parallel with the first. My first choice would be to connect another battery in series thus adding one or two extra cells. I used to cut cells out of batteries if I wanted only 2 volts. Extra cells would be easier than rewinding the starter with a longer wire to withstand 24 volts.
I assume it will also work on lithium batteries if you want to use them. In either case, you will need a higher voltage charger.

 

The only PMGR starters I can find are $200+ and DB electrical doesn't list a model on their website anymore. I'm probably going to go with a traditional starter for $50ish. DB electrical doesn't even list IH

The weight reduction would be nice but not +$150 and the inconvenience of using a less available service component nice.

 

The starter shown in post 2989 is not an open snout starter but it worked for me after I cut a hole in the bellhousing see post 276. The snout on it is narrow compared the other starters.
One that I used for several years looks like that an is strong enough to split a cylinder end to end.( mine did that)
My narrow snout starter turns the engine over faster than the smaller geared one from db electric. the price is great. I'm pleased to see that you are not just standing back and throwing money at it.

 

I tried the DB Electrical website and found it useless.
I suggest contacting them by phone to see if they still sell what you need.

LiPO4 batteries put out over 14 volts. So they will work better than a lead acid battery which gives around 12 volts ( the glass matt lead acid batteries put out a little more)

 

Are you saying the snout is narrower than the Mercruiser starter? I intend to cut and weld my bell to leave ample room for any starter I could possibly want to run in the future so if that's the case I may have to go digging in my scrap pile.

It uses the same pump as a Chevy 153 so you can punch "mercruiser 3.7 fuel pump" into any eccommerce website and you will get pumps that fit both applications at very reasonable prices.

Edit: The above is bullshit. The cheap pumps that are listed as fitting both don't.

(yes I know this is an old post I'm replying to, I just happened to be fuel pump shopping today)

 

I have several old starters from mercruiser engines. Most have huge bulbous noses and would need an immense hole in the bellhousing. One which was supplied new has a narrower nose the tapers to an end carrying an outboard bearing.

Be wary of warping the bellhousing when welding it. Aluminum can be connected with tin containing metal mixtures that melt at much lower temperatures. Try it on a scrap first. It may weld easily. Irrigation pipe is quite easy to torch weld with good flux.

I chose the word "connecting" so I could avoid the word "brazing" which implies using brass. or "soldering" but that is what may work with a tin/zinc "solder" . The "hole" being bolted on both sides to the block has some reinforcement from that. Stress risers are to be carefully avoided.

 

It has been stated many times that most modern mini starters have an exposed starter gear with no nose cone (gear support). Using a starter without a nose cone typically clears an automotive bellhousing or needs very little clearancing to fit. Therefore, it is a nearly bolt on deal. The great thing about most mini starters is that they usually have a universal body design, that allows you to "clock" the starter body to clear things like exhaust and steering.

In my case, you are not allowed to cut into racing bellhousings or you void the SFI safety certification. Also, I am not looking for cheap street or ag parts. The battery and starters I am looking at are in the $800 range. I am not concerned with price, I am looking for an application that fits my needs. That is basically what everyone in this thread is trying to figure out, what odd ball parts will directly bolt onto a relatively unknown boat motor.

 

I have an iron bell. It's not my first rodeo welding cast and my application will never spin north of 5k rpm let alone get a tech inspection. I'm not worried.

The only thing I don't know is whether I'll use brazing rod or nickel rod. I guess it depends how I feel that minute.

 

I know of one of these engines I can get cheap ( sub$100) Im told they think it got wet in several cylinders . I have to act fast if I want it .
Ill read through all of the 100 pages here eventually but right now I have a couple quick questions.

Are these blocks able to be bored like a nomal block to a oversize/ does the sleeves in them take a over bore ? Is there any major costs or things needed to get a Chevy trans on it ? I know the bell housing pattern is the same mostly what flywheel works ?

I do know there are some water pump issues and all that but is there any great problem out of the ordinary rebuild to get these to work ?
Can a remote electric water pump be uses to eliminate the existing one or something?

I apologize for not doing my homework and readng this I only had a few minutes to look at work .

engine spins over so its not seized Im told . was told it has " coolant" still in itso Im hoping it had a closed system with antifreeze.

I know the chevy 2.5 and 3.0 but this is a new animal for me . know it uses a 460 head .

Need a quick break down of if if its worth it for a street rod not race and what im getting into .

Don't want to collect junk I cant use shop is full of that now .
Thanks

 

[/QUOTE]
Sean, I just got off the phone with Mahle. Their tech support is excellent. He checked blueprints of the headgaskets, all they had were from the 1980's and the "notches" are not on them. I sent him your excellent drawing and it compares well with gaskets in my hand.

He said that this is the first report of the headgasket notch concern and naturally he is quite interested in it. The notches do not show up on mahle gasket drawings....something strange there.

He asked if the mark from the gasket on the tops of the cylinders show an adequate fit. I surface all of my decks so I could not reply on that one. We agreed that any leak around the cylinder will quickly erode the cylinder.

He wants to know if we encounter any problems with the gasket.

 

I would surely pick it up for $100!! I did not cut the back of my block, I just put it together like anything else, mock and check to see if it fits. I pic of mine. You can see I have the Toyota water pump and a alt, but other wises its not that special.

 

back of block

 

1bigun:
I normally buy Mercruiser engines for $100. As parts, they are worth much more than that.

They can be rebored. Most rebores are 30 thousandths over as that is the commonly available size. Sometimes you see engines which are 60 over but I think, at that point, their best use is for a coffee table base like on Top Gear..

mid 80's Mustang pressure plates bolt right onto the older Mercruiser flywheels.

It makes an outstanding street rod engine.