The elusive 224/3.7 MerCruiser banger

Dennis,
I thought I read somewhere that the Mercruiser gasket had bigger coolant holes toward the rear. It would be very interesting to lay a Ford gasket on top of the Mercruiser piece, and the other way around.
If nothing else, maybe they would mate and we could have baby gaskets that would have the proper sealing along the starboard side. Probably only fit a Honda until they grew up, though.

 

Beautiful, yes I saved my old gaskets and they all have the big holes to the rear. Randy thinks widening the edge there would work. he suggeted laying a long rubber band there for sealing . 60 years ago, I bought Pirelli straight rubber "bands" to power model airlanes however they may be too thick to work on top of a gasket .

 

It was suggested to me to have the "edge" of the block o-ringed. It is pretty narrow for that, but if it was widened it could work.

 

every once in awhile i find those engines on ebay as well. ive always wanted to mess with one.

 

@Greenbullitt,
Go ahead and get you one. Lot's of fun to be had.

 

Hey guys,i drop by sometimes to see what you are doing.
I made all my intake manifolds and i put a coolant return line out of the back of the manifold,and one out of the front of the manifold.
On 2 blocks i put 4 1/2'' pipes into the side of the block down under the exhaust,i pumped coolant into those pipes and out through the head/intake manifold on each end.

I never blew a head gasket,on the cylinders,when i had problems it was coolant going over the narrow bridge and into the lifter area.
I never had a compression failure,just to clarify.

 

Randy sugested something along that line a few weeks ago.
I measured the thickness of the sealant bead where it was not smashed. 1.5 thousandths of an inch on each side of the gasket . there is a figure for desired compression of the o ring I think it is 25% to 40 % of the o ring diameter. So looking at available orings, a thin one would have the right thickness if it fitted into a slot cut through the gasket. I'm not sure I like the idea of cutting a slot.
The measurement would give us the depth of the o ring groove which would be cut into the head and also the block if we use two o rings, one under the gasket and one over the gasket. Or would one o ring do?

 

@randydupree,
I guess my question would be, "If you were to build a Mercruiser today, would you close the deck with a plate, use a filler like Devcon at the top or do something else?"

 

You asked the right man. Randy has vast experience and is generous with his help.

 

[QUOTE="randydupree, post: 13857218, member: 6282"
On 2 blocks i put four 1/2'' pipes into the side of the block down under the exhaust,i pumped coolant into those pipes and out through the head/intake manifold on each end.[/QUOTE]
seems like a clever idea, did the 4 water inlets spread out make much improvement?

 

I just purchased what is advertised as a factory Mercruiser head gasket. It paid $70 for it, delivered. The photo had visible sealant lines at the lifter rail. Even if I fill the deck in the future and don't use it I may need to know the location and size of the coolant holes for a filled deck block.

Randy has had the most success with modifying these motors. If it was me, remember I haven't proven myself with a running modified motor, I would plate the top of the block. I would do it as much for upper block strength as water sealing.

 

I don't know why, but I have been shopping the classifieds for another motor. I already have 3. I started shopping when the conversation about filling the deck started. I found a pair of them for $350. The add said "neither are turning over". I saw a photo of 1. It looks pretty clean. What is the going rate other places? The decision would be easier if they were closer, but there 270 miles away.

 

Beck,
I recently bought a running engine for $250, delivered. Have a deal pending for 2 short blocks @ $150 ea. Still trying to find out exactly what is included. Mine are a bit closer than yours, but it's still a haul.

 

OK<its been a few years,but thinking back i never had a gasket leak on the first 2 engines i built,both had filled blocks with hardblock.
Both had the 4 pipes welded into the side of the block.
The lifter side of the block was filled higher than the other side,i did this by tiipping the block over slightly on my engine stand and then pouring the concrete in.
I ran both of those engines for a long time,5-6 years?

Then i let an engine builder convince me filled blocks were bad for making HP. and i built 2 new engines,new blocks and the same old internals.
Interestingly the small engine,183cu,had water leaks on that narrow bridge until i used Mercruiser gaskets.
The merc gasket did fix my issue.
I did go fast,but i think looking back i made all kinds of mistakes.
I had never raced a 4 banger engine before and theres more to that than meets the eye.
Big 4 bangers shake.
I should have bolted in a stock engine right out of a boat and went racing,as a test.

Speaking of boats,i did built an airboat and put a stock used engine in it,with a header and a adapted 4 barrel intake with a holley on it.
All the v8 airboat guys laughed at it,but i did not have any issues running with most of them,only the huge big block boats could really make me look bad.
The mercruiser ran with the stock 500 cadillac engines with no problems.

 

Thank you.
I'm back to deck plating my first generation hot rod Mercruiser. Seems like it is worth the effort to me.

 

Beck, I pay $100 per complete salvage motor without the out drive at a nearby boatyard unless it is something special. If anything is wrong with them the shops don't want to fix them. I paid $300 to him for a nice looking "runner" That we both thought ran but didn't. Without my asking he gave me another motor saying he would not sell anything that looks like what the "runner" was, it was really nice on the outside but was rusted inside. The 4" heat exchangers are in demmand and if you sell one it will pay for a few motors. The exhaust manifolds are also in demmand and are also useless to us. So the motors, with effort, are free. ( I give my extra parts to the boat shop as it is in my interest that they prosper.) It is after you get the engine that the money goes away. $70 for a head gasket is fair, it is what I bought my first one for several years ago. Anyone into these motors can't help but accumulating a number of them. Randy had 30. Look in boat repair shops for your engines, they will be in a pile of things that they don't want to fix.

 

When buying a motor, look inside the cylinders with a borescope for water damage. Any running motor is cheaper than a non-runner. I had two that would not turn over, one block was warped slightly and would lock up the crankshaft when the journals were torqued. the other was full of water and would turn only 270 degrees because of water and rust in it. Any motor running antifreeze is a better buy than one cooling with seawater
or even river water. The mercruiser 120 and 140 can be sleeved, but their power is dismal compared to the ones we like.

 

My project for the day was making an oil pump alignment tool. I don’t know if it looks anything like the Mercruiser factory one. It seems pretty rigid. I think it will work.

I started with 2 parts from McMaster-Carr, 1 ½” x 1’ HDPE Rod (part # 8701K47) and 5/16” Wide x 1” Steel Hex Bar (part # 6512K141). The parts were cheaper than the shipping.

I cut the HDPE rod to length with my wood chop saw then chucked up the part I wanted in the lathe. I bored an 11/32” hole as deep as my drill bit would go. My first turning cut was to the diameter of the distributor top retaining flange. Then I moved on to the critical part, the part the actually fits in the block distributor bore. Lastly I cut to the diameter below the cam gear. See the photo it will help understand my poor description.

I made each section longer than what the distributor is to gain some rigidity. The section that fits into the block must end before the cam gear. The lower section that is below the cam gear location can be longer also. I don't know if there will be any crank interference or not.

The 11/32” hole is slightly smaller than the outside of the 5/16” hex shaft, but the shaft will easily press into it. I measured how deep my hole was and marked the hex shaft. With the turned rod still in the lathe I put the 5/16” hex into my drill chuck. Using the drill feed I pressed the hex shaft into the turned plastic rod. When I felt it hit bottom I stopped.

I took the part out of the chuck. I could have stopped here and had a workable tool, but I flipped the turned plastic over and rechucked it on the smallest part of the plastic rod. I didn’t want to make any distortion on the part that fits into the block. I then turned the top to match the diameter of the top of the tool. Then I drilled a 5/16” hole in that end and tapped it for 3/8” NC. I installed an eye bolt in that end while still in the lathe chuck and locked it down with a bolt and washer. I thought I may need something to grab onto to pull it out of the block.

After removing the tool from the lathe I cut the hex shaft to the length of the distributor and beveled the cut end slightly.

I haven’t tried it yet. I have 1 concern. The hex shaft is spring loaded in the distributor. I don’t know if this spring is compressed slightly when the distributor is installed. If it is, I will need to shorten my hex shaft slightly.

 

Beck,
That's perfect! I envisioned much the same thing. I have a bunch of Allen wrenches but not sure I have one that long. I like the idea of the eye bolt to be able to extract the tool after use.

 

i toyed with welding a plate in the top of the block,lots ofwork and then you need to machine everything all over again,plus line bore it too.
But,one idea i had but never did was this,fill the water jacket with sugar to about an inch below the deck,then fill the top with epoxy.
Once the epoxy gets hard wash the block with hot water and the sugar will desolve and wash out,mill the op of the block flat and you have a filled deck.

 

I was talking with a very knowledgeable aluminum guy yesterday that I have the upmost respect for. He is modifying one of these motors, so is quite familiar with them. I asked about using epoxy to attach a deck filler panel. He didn’t think it was a good idea because of the different expansion rates of aluminum and epoxy. I ask about the very little thickness that would be between the block and the filler panel. He still thought the joint would fail.

If the whole filler section was epoxy it would be worse due to more area to heat and cool. The expansion and contraction would be acting over a larger area.

I ask him about TIG welding the panel in. He said the block has a lot of zinc in it to make it mold better. He said the problem with zinc is that it has a very narrow window where it is a liquid during welding. It quickly turns from solid to gas leaving nothing behind. He said any aluminum casting that has high detail, like ours, has higher levels of zinc.

His motor’s coolant inlet is set up like Randy’s was, with 4 inlet pipes going into the block under the exhaust passages. His outlets are the factory Ford head outlets. He has cut 1” off of the top of his block and added a 1” plate to it. The whole cylinder bore, steel and aluminum, and the top plate have been bored for large sleeves. His top plate is not welded to the block. It is sealed with a Ford head gasket and sandwiched between the remaining block and head. Like mine, his motor has not run yet, but the workmanship is flawless.

 

If anybody is looking for one in the seattle area I've seen an ad on craigslist for a complete built one already setup for automotive use its not cheap but sounds like it has all the right stuff done to it.

 

Great posts, this is information we need.

Beck you did well on that alignment tool, beautiful.
Randy and Beck thanks for the valuable information on dealing with the top of the block. I glued aluminum cylinder support blocks in the water jacket, concerned about blocking heat transfer, I made the fit close. I've an hour on that engine and opened it up after overheating, the small blocks have stayed in place and seem secure. They are only a couple inches long but there is nothing to prevent them being made full length between headbolts. Randy suggested permanently bolting them to the block. For bolting there would have to be access holes across the lifter chamber and all of the new holes would have to be sealed. As long as the aluminum is captured, I don't imagine it going anywhere.

We have three levels in this :
1. little filler blocks for cylinder support
2. long filler blocks for improved block edge sealing and
3. the whole plate filling for even better sealing

4. epoxy fill (not part of sequence)

As far as warping goes I bought a block that was warped a couple thosandths but it locked the crank...it does not take much. honing fixed it.

 

low expanding epoxies exist but most common epoxies expand twice as far as aluminum would given the same temperature change. Iron changes length about half as much as aluminum does. Given the short distance across the coolant the expansion will not be a lot, but it will not take much dimensional change to pop a joint loose.

Masterbond EPA2HT-3AO expands at virtually the same rate as aluminum and it is good to 400 degrees F. the gap to fill varies between 3/8" and an inch. I do not know what it costs.
-------------
temp.change is 70F to 230F or 20C to 110 C = 90C degrees
fill distance maximum is 1 inch =2.45cm
fill distance minimum is 3/8" = 0.925cm
the thermal coefficent of expansion :
common epoxy is 45 to 65 x 10^-6 let's assume 55x10^-6
aluminum is ....... 21 to 24 x 10^-6 let's assume 22x10^-6
thus: 55-22 = 33 x 10^-6 relative change (our only concern)
so: 0.0000036 length change per deg. C x 90 deg. x2.45 = 0.00079
0.00079cm/2.45cm per inch= 0.0003 inch = 3/10 thousandth in.

cast epoxy changes length , depending on the its type, between 0.0000045 to 0.0000065 inch per degee farenheit.
aluminum changes length, depending on its type, around 0.0000013 inch per degree farenheit. Assuming the block warms from 70F to 230F, temperature change is 160 degrees farenheit, then the change in aluminum is 0.0000013 inch per degree x 160 degrees = 2/10 thousandth at the widest part of the block fill.
( the numbers we began with are approximations so we can not say that there is any difference between 3/10 thousandth and 2/10 thousandth)

Another variable is that epoxy loaded with other materials (for example, limestone for JB Weld and whatever is in titanium Devcon) expands at a different rate when heated compared to pure epoxy.


for your reference:

https://www.engineeringtoolbox.com/linear-expansion-coefficients-d_95.html

https://www.masterbond.com/properties/epoxies-low-coefficient-thermal-expansion

 

Oil pump priming tool. When I purchased parts for the oil pump alignment tool I should have purchased another 5/16” hex shaft. There was enough HPDE (polyethylene) rod left for a guide at the block distributor hole. The 1’ hex rod would have been used full length. From the polyethylene rod a bushing could have been turned to fit the distributor hole. It could have had a couple thousandths clearance to make it easy to put in and out. The center hole would have been a little bigger to let the hex shaft spin freely. The hex shaft would chuck into a drill motor. The HPDE rod is very tolerant to wear. I make chain tensioners out of it. It would work as a top bearing for the hex shaft spinning the oil pump.

 

The following is a little story on thermal expansion. The parts I am referring to are NOT for our engines. The aluminum expert I referred to before passed this information to me. He was approached by a racer who was having valve cover leakage issues. He went to check it out. The valve cover was made of carbon fiber. There was a metal tube in the top of the valve cover for oiling. The valve cover was failing due to the different expansion rate of the tube and carbon fiber. The solution was to make an aluminum valve cover and aluminum tube, or put a carbon fiber tube in the carbon fiber valve cover.

We are all looking at the short distance between the block outer wall and the cylinders. We are forgetting that the full length, 20.5”, of the deck has the same expansion issues.

I’d still like to try it, but it could be a very expensive and time consuming mistake.

 

That makes great sense.

 

dennis g, You are only looking at the distance from the block to the cylinder wall. What about from one end of the block to the other. That's 20.5".

 

If possible, avoid mismatched coefficents of expansion...and we can as low thermal expansion rate epoxies have expansion rates close to that of aluminum [see post 2335, reference #2 masterbond]. We can integrate aluminum sections into the epoxy. The joint of a complete epoxy fill will be under pressure if its expansion coefficent is slightly higher than that of aluminum so it should not fail at the joint. I'd be concerned about joint failure in tension but it is not in tension unless it gets much colder than the temperature when the epoxy cured. There is also some internal heat produced when fluid monomer plastics become polymer solids.
Yes, the length of the fill is 20 times more than its 1" width and thus will have a theoretical lengthening exceeding that of the block by 0.0003inch per inch x 20inches or 6 thousandths of an inch. The plastic is locked in place by the complex shape of the interior of the block water jacket. This is for common epoxies. The problem disappears if we use aluminum instead of epoxy or if the epoxy is a low expansion epoxy. And there is another issue, some plastics shrink when curing. The amount of shrinkage must be known.

 

In any case, there are reasons to avoid the heat of welding. We might use brazing or soldering. Their strengths exceed glue joint strength. I do not know what amount of heat distortion to expect. It is only possible to say that it would be less probable if the block was warmed before any soldering or brazing was carried out.