The elusive 224/3.7 MerCruiser banger

My measurements in 3 spots are 1.0235 1.018 1.0215. What should I turn the pilot bearing down to make it as tight as possible without crushing it? I'm going to shoot for a .0025 press fit or .005 over the biggest measurement. Because if it comes loose it will slide out onto the input shaft loosing the centering capability.

 

Don't know if this will work for for you, but normally press fits are .001" per 1.00" of diameter.
Your average diameter is 1.021, making .001" a pretty close number. The problem I see is that you are trying to put a round bushing into a triangular hole and expecting the inner hole to remain round. Might work but I kinda doubt it. As some of the others posted above, the pilot holes in a crank are bored on a lathe and maybe reamed to final size.

 

I'm going to try to poke it in there at 1.022 and see how it fits. I have an hour of manufacturing and 2 of autos and things get done in high school for me.

 

Got it. Just need to get a bolt for the clutch and a few more the oil pan and it's ready to go in. I did have to sand the input pilot surface a bit.

 

I will see if this photo of the engine from the top will stay up long enough for you to ask any questions about the engine.

I am nearly done with the chassis electrical harness. We are waiting for the newest version of the engine controls computer to be manufactured. As soon as I have it I will wire the engine controls and sensors.

 

What are the turbo specs? How much boost does he plan to run?

 

WZ what are you using for a water pump?

 

Just under the alternator is an electric water pump. There is another electric water pump for the intercooler and it is located inside the car. The water for the intercooler is cooled by Co2, that can be turned on or off as needed. The intercooler water tank is in the back portion of the car.

I will get the specifications on the turbo from the owner.

John

 

WZ,

Thanx for posting.
I'm more curious about the nuts and bolts part.
Bore and stroke?
What material for the sleeves?
Who made the pistons?
How thick are the sleeves?
Does the cam have a distributor drive gear?
What timing sprockets and chain?
How thick is the plate between the block and head?
What head is used?
Is it welded to the block?
Was the deck closed?
Are the head studs off the shelf or custom made?

I believe we can keep this thread going if we stick to the basics. In other words if we don't talk about the computer controls and stuff that is not HAMB friendly, we are probably okay.

 

What electric water pump is he running? I think one could run a BMW external electric water pump.

 

Be sure you click expand to get all of the responses. I should have presented the answers in a different format but I am tired and do not want to redo the post.

 

Your format for answering is just fine.

I appreciate the effort.

One more detail:
Since the 'spacer is just a spacer' is it gasketed top and bottom or somehow otherwise sealed to keep the coolant where it belongs?

A picture of the spacer itself would be GREAT!

Thanx again!

 

Cool stuff. A possible issue I see with that turbo is I don't think that header is going to pulse the twin scroll correctly if the motor has a stock 1342 firing order. The reason I say that is volvo 5 cylinders can't use a twin scroll because the scrolls can't be evenly pulsed. Cummins are the same way, the twin scroll manifold has to exit in the center to make the pulses to the twin scroll even. Just a thought. Just saying I'm better on the keyboard then I am with a wrench in my hand.

 

Might not be a twin scroll turbo.

 

I will ask about the spacer gaskets but I think it has gaskets top and bottom.

I am waiting on the newest version of the Fuel Tech engine control computer to be manufactured in Brazil. When it arrives I will wire the engine.

 

Thinking out loud on coolant routing:

It may be possible to have coolant flow between block and head with holes through a spacer or with hoses bypassing the spacer. The aluminum Mercruiser engine is notorious for head gasket leaks, perhaps hoses and either a spacer or a closed deck with no coolant passages would result in fewer coolant leaks.
I piped water out of the head at two points using the intake manifold (see page 5) It gave sufficient flow to cool my engine
Inasmuch as stock point of fluid flow is the front of the head, I think that or taking advantage of "core plugs" may be enough flow for a head, the core plug above the bellhousing mounting holes looks large enough for the block's coolant flow and it is well away from the waterpump area so the whole block would have coolant flow. Although the block core plug is high, the possibility of steam bubbles forming around the cylinders could be a serious cooling problem, They would be lost up into the head through the lower openings in stock heads.

 

Made the throwout spacer. Rougly 1.375 I'd and 2.5 od and .7 legnth. For use with a 1697-c throwout bearing, sag 4 speed, monza bell housing, and cheap 10.4" raised diaphragm clutch. I'm going to break off all the washers off of my bearing, case harden this big spacer, and weld it on.

 

This video demonstrates partial block filling using Devcon over sugar


This next video shows the process of modifying an open deck block with wet sleeves










9+

 

I found the Devcon method most interesting. But why sugar? I read another article where the guy used salt. Again, but this time, why salt? I'd use baking soda. It completely dissolves in water, almost instantly. And a big bag of it is cheap. Really cheap.

How much boost would a 3.7 have to see to have the open deck be an issue?

 

The open deck on a non-boosted Mercruiser is supposed to present a sealing issue due to cylinder movement.
The cylinder walls are thin, but so is the water jacket therefore I can't say how much support would be contributed, however according to Randy duPree there are headgasket problems for the engine. I will go with what he says as he has so much experience with these engines.
Anything that helps I will use.

I like your baking soda suggestion better than sugar or salt in the engine. Saltwater will cause electrolysis in aluminum engines as long as it is in there because there is Iron and steel exposed to the coolant. Sugar water should be much less of an electrolyte than saltwater.
I was concerned that the filler may soften with heat so I used only a little of it to glue aluminum "blocks" around the cylinders.

 

I just checked sugar water is a non-electrolyte as it contains molecules rather than ions as is the case for salt

 

I hadn't read that they have head gasket issues. Must have missed that.

That Devcon stuff is good for up to 450F. Well beyond an automotive engines operating temperature and even beyond an over heating situation. If you over heat an engine beyond 450F you have bigger problems to be worried about.

 

450F gives a good margin. I boiled most of the coolant out of my first engine (radiator leak) it did not get hot enough to hurt it.

Randy mentioned the sealing issue in a post on page 6.

 

We used quite a bit of the Devcon in the chemical industry. We would put temporary patches on pipe until we got a replacement piece welded up. That would allow production to continue until a scheduled shut down. We had great success with it. I would wear disposable gloves when using it. The stuff is difficult to get off your hands and won't come out of clothing. As you saw in the video, there isn't a whole lot in a package. I think I would have wanted it to the top of the block, then machined flush while decking.

I am unsure how rigid Devcon is after curing. I have machined it after curing and it seemed to have a little give in it. However, I normally did the machine work pretty quickly after it set. It may get harder with more cure time.

 

Beck,
I thought that about filling to the top also. But, I think the idea was to have a ring of coolant around the top of the bore. I'm no expert on Devcon but I would think that the 'give' in it might work for a guy to dampen harmonics.

 

The question is which is the greater issue: cooling around the cylinder top where it is hottest
versus head gasket sealing. Beck runs his engines hard for a tractor pull but not for a long time. I run my engines at part throttle for hours. Neither of us should have cooling worries but sealing is an issue, as head gaskets that seal well for this engine are uncommon.

Aluminum added from the cylinders to the outside of the water jacket would carry away heat, would support the cylinders and it would (if milled exactly flat with the block) prevent gasket coolant leaks.
The risk in doing this is warping the block. Less heat is involved in soldering aluminum in place with tin ( it melts between 400F and 500F) Aluminum solders are usually alloys of tin and zinc .
as the zinc content increases so does the alloy melt point to around 700F. (the temps are from memory. I posted the actual temps some time ago). Welding heat treated aluminum weakens it. Soldering (or brazing if you prefer that term) would not cause the distortion a weld does.
All of these procedures are best done prior to getting the deck surfaced.

Yes, Devcon should absorb some vibration. But would stiffening the cylinders act to the same end?

Gear head and Beck have both raised well-thought out points.

 

I have given more thought to addressing headgasket sealing.
a. buy genuine Mercruiser head gaskets and change them periodically.

b. Or completely bypass the head gasket so it can't have coolant leaks. The following
should be reasonably easy to do so you can do it yourself and not be expensive.
It does not involve high heat and should not warp the block.

Fill the top of the block's water jacket with Devcon.
Do not drill water passages in the Devcon .

Plug the bottom of the Head's water passages with devcon or screw in plugs or even
tamped-in lead shot for small round holes.

For water passages drill holes along the sides of the block just below the devcon layer.
Drill an equivalent set of holes in the sides of the head

Solder* tubes into the holes. The fit should be tight for strength.
Rubber tubes would connect the upper and lower tubes but must be kept away from the
exhaust manifold.

Tin solder bonds to aluminum and copper etc. If nearly pure tin melts down around 400F.
Tin alloys melt as high as 800F. Little copper bends would get the tubing
out of the way of the intake manifold but passages on the exhaust side of the head are more
difficult. This is something you would work out first with a junk head.

Proseal, used in aviation, is an outstanding sealant but is not a glue.

* I use the term "soldering", some say "brazing" but either connects metals with a
lower melt point metal between them.

 

I looked at Northstar block photos and was surprised to see much deck area similarity to our Mercruiser blocks. Our engines have way more torque and weigh 100 lbs less. Northstar power is all over the map so I can't say much except that our engines have more power than early 80's Northstar and less than the recent ones.
They are open deck, overhead cam engines with iron or aluminum heads. Many bolt to transmissions for rear wheel drive. They suffered headbolt pullout with their fine thread bolts in hot engines. That problem was solved in 2004 when Caddy changed to coarse threads like Mercruiser has always used. Before that, Northstar engines commonly developed headgasket leaks by 80,000 miles . I read that many caddy dealers would not repair an engine with pulled threads as it did not always succeed.

From the above, it seems most Mercruiser head sealing problems should be on the narrow surface over above the valve train. Randy pointed this out to us long ago.

So why not just build up the side of that narrow surface before surfacing the deck? could be done with a tin/zinc solder more tin lower melt point( a bit over 400F ) versus more zinc for a harder solder and melt point up to 700F. Aluminum could be soldered in there also.

Years ago I used an aluminum solder (from Edmund scientific) that was amazingly easy to use it was soft, melted at low temperature, wetted the aluminum well and flowed easily so it must have had a high tin content. I have used sticks of metal that had to be scrubbed onto hot aluminum being joined. they were more difficult to use and melted at a much higher temperature. I've gas welded aluminum and success/difficulty with it depends on good temperature control and the alloy (irrigation pipe being the easiest ) In welding aluminum, a good filler metal is more of the base metal being welded. Good flux is critical to the procedure.

I have a useless cracked-bore block to experiment on. It would otherwise make a coffee table.

 

BTTT

 

Been thinking about this thread and the top of the cylinder/open deck question. If the top of the cylinders can move around it seems they would move in a motion that is parallel to the crankshaft rotation. To stop that another option would be to add friction fit aluminum rod on both sides of the cylinder between the cylinder and the block. I found a picture of a block and put red dots roughly where I would think they should go. Once installed add a little TIG tacking to insure they stay in place. Send it off to be decked and bored as needed.