The elusive 224/3.7 MerCruiser banger

Late block - early block. slowly getting acquainted with the differences. From what I have found there are the 76 to 82 up to SN 6218035 kind and above that SN, for 83 to 89. One disconcerting issue on the later one is the lack of the bell housing alignment pins. The holes are just rough from the casting process at .55in. Has anyone else put a late block on an automotive bell housing - and if how did it go? As it is, I have to make my bell housing (using an 8.5 inch clutch) just so I have enough room to put in the clutch pedal. In that case I can make the engine bolt holes a slip fit when machining them and a possibly align that way, but am a bit squeamish about it. Comments or corrections very welcome on this.

 

Sean, thanks for the information. I had to work with the dowel pins and holes to get them to fit . The block holes I worked with were smaller but they were finished holes so, taking a conservative approach, I reduced the diameter of one end of dowel pins that I bought at a hardware store. The other end of the 5/8" dowel pin fits the bell housing with no modification.
It has been a decade so the details are unclear to me but it was a simple lathe job with a carbide bit. I may have sanded the outer diameter of the dowel pin for fine adjustment of diameter.

Dowel pins are very cheap. Blocks are very expensive. Modify the dowel pins, not the block. This assumes accurately located finished holes in the block.

 

I did not record the diameter of the block's dowel pin holes. I just made dowel pins to fit.
I do not blame you for being concerned about proceeding without good dowel pin holes.

I once fitted a ford 6 cylinder bell housing to a 289 v8 by bolting it loosely and then moving the bell housing around to the middle of its travel and then tightening the bolts. It was half-assed but close enough to work. The dowel pins may have been loose at one end , I don't remember much as it was 40 years ago.

 

The holes in a chevrolet bellhousing are a good fit for the back end of a 5/8" drill bit.

Check your block's dowel pin holes with a plug gauge or the back end of a drill bit just behind the flutes.

An old 3.7 block here has dowel pin holes measuring about 0.45" I say about as I used a digital caliper and got a measurement for the other hole that was different by 0.01" . That is why I suggest using a plug gauge to measure the dowel pin holes , there is less to go wrong in measurement.
I checked a different block and it's dowel pin holes are 0.620 and the bottom of each is roughly cast. The Mercruiser flywheel cover has dowel pin holes drilled to the same size as chevy bellhousing dowel pin holes.

 

This popped up and I don't think I need a 4th core....

https://hartford.craigslist.org/zip/d/longmeadow-free-boat-and-trailer/7627724712.html

 

Does anyone what to buy a "cheap" Boss head and a valve cover? I bought a magnesium AR valve cover from Flatrod17 that had been powder coated at some point. The cylinder head is a Ford part that was damaged and then someone started welding and grinding the ports. I am taking a break from this project, and want to clear out a few items. I rarely get on this thread anymore, so send me a message.

 

I wrote about engine temperature a page ago but forgot to say that my first engine head was straight out of a truck so as it had no Mercruiser coolant spigot at the front of the head, I used the existing coolant passages in and out of the head.. There were too many things changed with my engines for me to know what was responsible for them finally operating at a lower temperature but as Randy Dupre wrote "connecting the rear coolant passage may help" as with coolant inlet and outlet both at the front of the engine , it would seem that the rear of the engine will get more water circulation if there is a water connection back there.

It is not difficult if you are using a Mercruiser manifold. To make a coolant passage drill and tap the rear of the manifold flange for a screw in spigot. They will protrude through the manifold flange so it will be necessary to remove the excess of the spigot that sticks through.

The head gasket has greatly reduced size water passages in it at the front to force water circulation to the rear. That may be enough. I have photos of my manifold with its spigots early in this thread.

 

Big Chief I need some help on a 3.7 Mercruiser motor, thanks

 

Try this @BigChief

See above post

 

I have always made cork oil pan gaskets. This once I had commercially made oil pan gasket so I tightened it to the published spec. and before it was up to the specified torque, the gasket was squeezing out from the joint. Cork gaskets are good and will seal joints that other gaskets fail to seal. You are better off tightening the bolts down by feel as the spec is for some other kind of gasket as it is off roughly 300%.

 

This mystifies me: The ford flywheel and pressure plate each have three holes matching the dowel pin diameter. In my previous use of the parts I could only use 2 dowel pins. I am faced with the same thing again (one dowel pin does not match) but this time with a different Mercruiser (Ford) flywheel. Each flywheel had only been used in a boat application. So I can only assume that the flywheels are
ok but the pressure plate was mis-drilled. The pressure plate worked and did not vibrate when i used it on two other mercruiser engines so I expect that it will be fine on this mercruiser engine. It was an ebay purchase and that may explain its odd nature.

Six bolts secure the pressure plate to the flywheel, but both the flywheel and the pressure plate have 12 holes. Some of the extra 6 holes in the flywheel have the threads partly drilled away and one has all of the threads drilled away on one extra hole.

It is tempting to put bolts in the extra holes, but doing that will throw the assembly out of balance.

It is odd.

 

Being die cast aluminum, our engine focuses us on problems of tightening bolts into it. Bolts loaded in tension are tightened until their metal is a certain % of the metal's yield. During tightening it encounters friction at the thread surfaces and finally under the head. The aluminum can gall and fret. In use, the bolt shank can seriously corrode. Mercruiser used Perfect Seal to protect the bolts by sealing under the head of the bolt to block entry of water. Sealant on the threads will also keep water out but it also should stop galling and fretting of the aluminum threads. Non hardening Permatex is suggested as perfect seal is no longer available.

Having struggled with the caps on tubes of Permatex in my youth, I came to doubt its non-hardening quality. I usually had to use pliers to remove those little black plastic caps . Some did not survive my removing them.

I called Henkel and the tech said that Locktite 242 will protect the threads from galling. It will also seal the threads and provide a minor locking action.. Fretting takes place with repeated movement so I don't expect it. It lubricates about as much as oil does.

We can not ignore that shear strength of aluminum is much less than that of high strength steel. the female threads in aluminum will shear stripping off the threads if excessive force is applied. I expect this to be the limiting factor. Increasing thread length would overcome the shear problem but it is complicated because the threads at the beginning are more highly loaded than those further down the fastener. So they strip off first at one end and the failure proceeds like a zipper.

Our dilemma is made worse by manufacturers nor specifying whether their published torque values are oiled or dry. Lubrication makes a big difference.
If you lube and torque to mfg. dry spec. it will be over tightened.

 

Dennis g : Although a bit simplistic, might it be a solution to add a steel insert (Heli-coil, threadsert, etc) of some kind as a more durable replacement for the threaded aluminum in our MerCruiser blocks? Also possibly suggest "sinking" those replacements to the bottom of the available hole to provide a depth of material to help the aluminum block better resist "spalling" or otherwise "blowing-out" under load? Or of using an insert with full depth threads to better spread out the load rather than "point load" with the standard short-length inserts?

 

Almost nobody here is driving whatever vehicle they are putting this engine in in road salt let alone salt water.

There's no reason to do anything above and beyond anything you'd do for any modern aluminum engine.

I'd focus on more important things.

 

You are right. Volkswagen studs tended to pull out, thread inserts solved the problem. They would be good for our blocks also.

 

I had a chevy v8 distributor and as I don't run that engine, I wanted to see if it could, with changes, work on our engines. Its larger diameter an be overcome by mounting it higher as its lower housing is much longer than ours. I cut the housing shorter, pressed out its bushing and pressed it into what remained of the lower housing. It was necessary to reduce the outer diameter of the bushing for it to fit into the shortened housing but the outer diameter of the lower housing is about like ours. Parts will not interchange between that distributor and ours as the points plate is at the top of the v8 distributor that I have.

Parts do exchange between our Mercruiser delco distributors and the delco vacuum distributors used in 6 cylinder Ramblers and small GMC cars of the late 60's. The easiest way is to put our engine's distributor shaft and 4 lobe distributor cam into the vacuum distributor body an use the points plate and distributor weights of the vacuum distributor. I used the gear and lower shaft from our distributor. With minor drilling and filing, our distributor body can be used if you prefer. The distributors are for all intents and purposes, nearly identical.

The desired distributor can be easily identified as :
1. the advance weights should be beneath the points plate, NOT above the points at the top of the distributor.
2. the cap attaches to the body with screws
3. the body is cast iron (check it with a magnet as ours are plated)

The usual price for what you need is $20. If the vacuum can is still good you will save a few dollars, but as it's diaphragm is rubber, a new vacuum unit is a good idea.

 

Advice for a novice in assembling transmission to block:

1. The sintered bronze bearing is supposed to be more forgiving than the pilot bearing. Do NOT grease it. Oil is already in it and adding grease will block the oil.

2. The large dowel pins will take the shear load of engine torque, small ones would seem to be enough to position the bell housing but they would be hard pressed to resist engine torque. They should be tight, but not so tight that you break things putting them in. Nearly anything that is done to modify their size will reduce the load they can carry.

3. the transmission input shaft will find the pilot bushing hole easier if you chamfer the end of the shaft.

4. Do NOT jamb the assembly together by tightening the transmission to bellhousing bolts. It will break the transmission bearing retainer which is thin cast iron. (I broke one and learned that lesson years ago).

5. Use two 9/16" studs in the upper holes to position the transmission to slide the transmission into place.

6. Its weight makes the job difficult. It is easiest to do this out of the car with a cable hoist to lift the transmission.

7. If the throw out bearing is pushed well into the clutch fork, it will jamb the parts as you attempt assembly. If it seems to go together but stops about an inch out, pull it apart and free up the throw out bearing and now the parts will slide together.

8. I exaggerated the ease of step 7 as it seems to take the strength of a gorilla to slide it together. toward the end. This is what I do: Shake the transmission up and down and side to side and it will push together. As the gap between the transmission and the bellhousing gets down around an inch, I replace the studs with 9/16" bolts. With a caliper compare the distance at 4 corners of the front of the transmission. Adjust the hoist and the 4 bolts to get EXACT alignment and then, if it is exactly positioned you can shake the transmission around and space will appear under the bolt heads as the transmission bumps into them. Tighten the bolts (use a very short wrench) taking up the space under their heads.
Use a caliper to be certain the the transmission front face and the bellhousing are always exactly parallel. With a 4 inch long wrench you can gently pull the transmission the last few millimeters into place.

Now you can check the clutch fork action. If its movement is blocked by the bellhousing, take it all apart again and change the ball stud. Some trucks used a 1 7/8" long ball stud others used a 1 1/2" ball stud. I have two bell housings that need the 1 7/8" ball stud they have 5 bolt holes for transmission mounting. The bell housing which used the shorter 1 1/2" ball stud has 4 mounting bolts for the transmission. You cam buy adjustable ball studs. Lakewood and Mcleod make some.

I could not find the long one locally so I made mine from a shorter one.


Longer throwout bearings are also available.

 

Anyone got a stock marine exhaust manifold they don't need?

I threw all of mine out like an idiot and I'm gonna run into clearance issues with any normal V8 exhaust manifolds.

 

How can one even use the huge marine exhaust? I gave all of mine to the boat shop which sells me the engines cheap. An exhaust manifold is easy to make from mandrel bent tubing. I run the tubes straight out from the head for a foot before they bend to the rear. Is your interference with the engine or the car?

 

A long time ago someone cut the water jacket off of one of the marine exhaust manifolds and the end result was a fairly decent rear dump log. I'd like to copy that. Most of the OEM 3.7 marine exhaust manifolds dump upward to a riser between cylinders 3 and 4 (in contrast with the one pictured). Flipped over that would dump between 1 and 2 which I think I could work with even if the net result is a few horsepower down from a normal manifold that has better scavenging. I'm working with a Ford Ranger so space is very much at a premium on the driver's side of the block.

 

Having it dump downward at the front of the engine would free up some room as you could run straight back under everything after you get clear of the front suspension. I was going to do that years ago. What is in the photos looks somewhat like a 460 pickup manifold, would one of those do?

For a pickup, you could run the exhaust straight up with a rain cap on it like on a tractor. You could avoid the hood by running it out through a sheet metal box rivited inside the top of the left fender It would solve most clearance problems.

 

The plan is to go under the front sump and then under the passenger motor mount/beside the oil pan. Might have to oval the tube to get proper clearance but shouldn't be a big deal.

The photos are from earlier in this thread. That's the log that's left when you cut the water jacket off a rear dump marine manifold. The more common 3/4 back dump marine manifold would likely be similar.

I can't use a passenger side 460 pickup/van manifold (I've never seen a car one so IDK what they look like) because they dump at the very rear which, when swapped to the driver's side of the block means my pipe bend wants to occupy the same space as the alternator.



Sure, I could move the alt around to the other side but I don't wanna do that because all the "good" bolt holes for mounting an accessory bracket are on the driver's side. I could also build a custom header. I just don't want to. If I have to do something I'll just build a custom log.

I don't want to draw attention to myself anymore than a "no longer seen on the roads" age of vehicle normally does. I'm going to run a normal exhaust system with a muffler.

 

You are certainly right about the alternator mounting possibilities.
Attracting attention? With usa flag tied to the exhaust, it will look like just another flag waver. (joke).
An uncle tied two coconuts side by side below the end of his car's tailpipe. A cop told him to take them off. I liked the idea and copied it in Germany.

I will look at the old manifold I have today and report back. I do not know if it is for a car or?

 

The manifold I have is for a Ford 460's left side. Its dump tube comes out under the third opening and the dump tube is inclined downward and outward. The dump tube is at an angle to the rear at roughly 30 degrees. from horizontal.

 

Pics? Sounds like the 70s-80s truck manifolds I'm familiar with.

 

couldn't reply as my computer power supply died. Hard to know which kind to buy. Putting engine in chassis today, made a few original mistakes including dropping the engine 3 feet onto concrete, I'm hoping they are not serious. It is much more satisfying to work with machinery than electronics. I like to be able to see what went wrong. Ford V8 valve covers have much more clearance under them than the Mercruiser ones which look way nicer.

 

Although I have not confirmed it I found the Chevy Vega distributor looks to be the same as the 470's and looks to take the same cap. Can anyone else confirm or refute this? it has the vacuum advance. only the early 71-73 is small enough to nest in there the later HEI is too big.

 

I can't help, but I did find that a Corvair vacuum advance will mount right up to the Mercruiser distributor by drilling and tapping 2 holes. You need the points plate too.

If the Vega cap works I'd like to know that, too.

 

Looking for tool info for assembly of Mercruiser 3.7 L, done right and you’ll have oil pressure, alignment tool? Thanks

 

I used parts from a 1969 rambler distributor (6 cyl) to add vacuum advance to a mercruiser distributor. The 2 holes should be added for mounting. I worried about too long of a machine screw intruding into the spinning parts so be careful, but you could braze or solder part of a little bolt threaded in there to use as a mounting stud.