The elusive 224/3.7 MerCruiser banger

My Apologies for running fast and loose with the three letter word used in my earlier post. I mean to offend no-one and will keep the chat to more vintage lines. The 470 is a major part of the protect and more so as it is an odd duck and will take a lot of time on its own to get where it needs to be as part of a greater project. As such one looks at corners to trim. Yes, I had considered mechanical fuel injection using lost foam casting to create the manifold and throttle bodies. Also acquiring an original Offy Hilborn - they are only slightly outrageously priced, but the ports on the Offy are spaced 5.3" - too far to adapt. Side draft carburation is still in consideration if the right size could be found. The post on MFI is a good read thanks for that.
One thing this faux pas has made me realize is that casting an intake to accept carbs or other bolt ups would be the simplest way to make it as any adaption in bore shape can be carved in to the pattern prior to the metal work, keeping machining to mostly clean up.
PS: Insanely nice work on the distributor

 

I've never seen anyone take offense at much of anything here so don't worry.
Say anything you like.

I like simple things as there is less to go wrong with them.

Carburetors are reasonably straightforward especially the Ford(aka. Autolite) 2100 and Mikuni motorcycle carbs. The easiest way to assure success is to get the carburetor from an engine of the approximate size and power output as the 3.7 (like the Ford 260 and 289 in Mustangs.)

Frustration increases exponentially with the number of carburetors, but if you bought a rack of 4 carburetors (from a motorcycle with enough power), they'd be linked together mechanically (cables don't count) to stay adjusted relative to eachother. For cable operated carburetors, no problem if there is just one of them but otherwise cable adjustments with multiple carbs are imprecise.

 

So, to bring the clutch/flyweel/bellhousing subject up once again...

I have the following situation.

On the engine side it's stuff you all know:

• This engine has the crank set 5/8 deeper than it needs to be relative to the bell face
  
• This engine uses a Ford crankshaft bolt pattern.
• This engine mounts the starter on the block and uses stock 157-tooth Ford car flywheel/flexplate stuff with respect to ring gear size and location relative to the crank.
• The crank is not drilled for a pilot.
  
• The later model mercruiser flywheel is not useful for a clutch in stock form.
  
• the OD of the relief cut in the later model mercruiser flyweel to locate the big rubber coupling has a 6.5" ID therefore the usable friction area starts at 6.5+ (we will come back to this)
• The inner-most bit of friction material on an 11" Ford (and presumably Chevy but I don't have one around) truck clutch with a 1-3/8 spline is right at 6.5"

I have a Clark 5spd medium duty truck transmission I'd like to use and it has the following properties:

• Typical GM/Ford 6-whatever inch stickout.
  
• This is not the normal stickout for this trans, someone swapped it with a different part over the years. I do not know the original application for the short shaft. All I know is it had something to do with a diesel swap before it was parted out and I bought the trans.
  
• This transmission will take a standard chevy bellhousing with the 5.125 hole
  
• This transmission has a 1-3/8 input spline.
• This transmission has a large pilot OD. In OEM applications the flywheel holds the pilot bearing
  
• the bell-housing that fits it larger (for the big flywheel) and deeper than typical GM light truck stuff.
  
• The bolt pattern and IDflywheel for this application is nowhere close to fitting a 250 I6 (SBC compatible) crank. While there may be one out there that does, mine does not I am not sure why since I know for a fact it came with a SBC pattern gas V8 because I have the engine to bell adapter plate that came with it.
• Those of you familiar with truck stuff can think of this as a standard 80s chevy MDT transmission but with 6.xx stickout instead of the longer stickout (9.xx?) they typically use.

So as it stands this looks like pretty easy match right?

I slap the stock mercruiser flywheel on. I make a metal plate that bolts in where the mercruiser rubber coupling used to go and holds the pilot bearing at the appropriate length for the transmission. The mercruiser flywheel is only 1/2" thick where it bolts to the crank so I shouldn't run out of space. I might need bolts with low profile heads and may need to countersink them (in order to clear the outer race of the pilot bearing but that's a minor detail.

I drill the mercruiser flywheel for pressure plate bolts and use a stock 10" Ford car pressure plate. Sure I'll have up to 5/8 less spline engagement than a stock clutch behind stock dimension block but the extra spline size should more than make up for that. I run a 10" Ford clutch disc for a Flathead V8 (1-3/8 10-spline). I don't think I will run into issues with spline engagement.

On the GM MDT flywheel the inner pilot bearing race is only 1/8" or so below the friction surface and the transmission shaft is very nearly a straight step from the splines to the pilot OD (which will make installation less than fun but whatever) so if my clutch disc is riding on the mercruiser flywheel and the bearing is sitting in the same spot relative to the friction surface I should be all good.

I use the GM MDT clutch fork and change the pivot location in the bell to match. I may need to space it out to account for the fact that the pressure plate fingers are 5/8 or so farther away than usual.

Other than potential shenanigans involving the clutch fork and throwout bearing needing to play nice with fingers that are 5/8 farther away than usual this all seems really easy.

Does anyone see any glaring issues with that plan?

 

Hey arse, what are you planning for the throw out bearing...?

 

NATIONAL CA02135C or NATIONAL F2065C (or equivalent part numbers).

The former came with the assortment of clutch/flywheel/bell parts I got from a 1980-something GMC medium duty truck. It is too big to fit my input bearing retainer. Obviously this could easily be fixed with a sleeve.

The latter is for a 50s Flathead V8 and fits my input bearing retainer. I would need to get a clutch fork that fits it.

I would prefer to use the GM clutch bearing and fork since it's 35yr newer and therefore replacements are more readily available

In both cases I'll probably have to change the pivot point location in the bell but that's minor and easily solved.

 

arse, I thought my clutch setup was hard. It is nothing compared to yours.
I do know that the clutch setup doesn't like long spacers. A fellow tractor puller had about a 3" spacer in his. It shook apart, twisting off crank bolts as it went. This happened several times. He used a long Browell bellhousing with a full centrifugal Crower clutch and a Doug Nash 2 speed. Of course we run at a higher rpm than most do. My spacer is about 1/2" but since I haven't run it yet, I don't know what it will do.

 

This graph shows cranking speed on our 3.7 motors. The crank speeds up/slows down with each compression stroke. The tall bands getting wide then narrow are what the crank is doing. These pulses are 36 times faster than a crank revolution. You can see that the crank speed varies during its revolution. The blocks at mid height on the graph are how often the cam is turning. There are 4 narrow to wide tall bands inside each of the cam rotations. The wiggly line is the battery voltage. You can see that the voltage drops with each load on it from cylinder compression. This was taken on my small reground cam 12.1 : 1 compression motor.

I think this has been my starting problem. I believe I am going to change to a magnetic crank pickup. The SBF "flying magnet" will bolt right on. I will have to take 2 of the magnets out (180 deg apart) to make it 4 cyl applicable. Naturally I will have to change pickups and make a new adjustable mount.

 

I began with a 3 speed "truck" transmission which was useless as low gear was only of use for about ten feet. I began with the "truck" bell housing (very good thing because the car bellhousing is too small to contain the Mercruiser flywheel (which is a Ford flywheel) I cut down a small block chevy bellhousing to see how big the cut has to be. After it finally fitted, my cutting had removed more than a third of the bell housing which I then discarded.

(I never saw the "trucks" that supplied my bell housings. Having owned a real truck for 20 years I don't consider pickups to be trucks.. Pickups might be truckettes.)

I used and reccomend:
1. Autolite 2100 carburetor for 65-68 mustang v8 it bolts on with an adaptor
2. Any camshaft but the Mercruiser one, particularly not the Elgin cam
3. Rubber mounts for a chevy v6
4. remove 5/8" from the rear face of the block.
5. use a chevy truck bellhousing.
6.. use a 3 or 4 speed chevy saganaw manual transmission, but replace the nose of the transmission with one from a "truck".
7. drill the crankshaft for a throwout bearing
8. use the old Mercruiser flywheel, it is about an inch thick and the holes for bolting on the pressure plate are already drilled and tapped. All you have to do is scrape off the paint from the friction face.
6. use a chevrolet clutch disk
7. use a Ford pressure plate. I used one from a 1984 Mustang v8 [78-84 fits].
8. A hydraulic throwout bearing is a nice. The stock mechanical lever action one I used wore out quickly...less than 1000 miles, so I made a cable linkage. It is cheap and easy. You have
The engine has enough torque (280 ft lbs stock)so that 5 gears would be a liability in my 1800 lb car.
It depends on the car's weight(1800 lbs), the rear axle ratio(3.07) and the tire diameter (25" to 29").

 

The shorter (6") input shaft sideways mentioned may be a good thing as it compares favorably with the saginaw + 5/8" shorter block combination. Way up toward the front of this thread we have a listing of several transmission input shaft lengths.

 

Nice looking car Dennis G!

My block is not cut the 5/8 like some say to do. I started with a Muncie M20 trans. With a "621" Chevy bellhousing the input just touched the crank, no polit hole. Then I was given a T56 6 speed, it bolted up and did not touch the crank, so I planned to press a bearing in the flywheel like fatheads have with a extra support bolted to the Merc flywheel. But neither of these trans fit my car very well, so Now I have a S10 T5 5 speed. I had to rough drill a hole in the back of the crank to get it to bolt up. (I will fit a polit bearing when it comes back apart). With the Muncie and the T56 the clutch disc left about a 1/16 of inch from having all the spline engaged. I thought that would be ok. But now with the T5 it looks like it is going to bolt together just like any other manual set up. I am glad I did not cut the 5/8 off the block.

 

Beck : As far as your starting issues, have you thought of spinning the motor over before you switch on the ignition(like the sprintcar guys do)? that way the starter isn't turning against the firing charge, bur using the momentum of the flywheel & rotating mass to help the starter

 

Not machining the block saves $200 plus searching for a big milling machine. And at $200 one guy whined about losing money because of the setup time needed for his horizontal mill. I figured out a way to do the cut with a cutoff wheel & grinder indexed to the rear face of the block. A bolt up solution from stock parts plus easily made parts is a big improvement. Thanx for the compliment on my car.

 

My motor is spinning before the ignition turns on. The lack of rotating mass is some of my problem. I am not running a flywheel. I have a flex-plate with a very small dirt track 2 disc clutch bolted to it. The flywheel part of that clutch is aluminum. I have installed a SBF harmonic balancer which is lighter than the original. Weight is the enemy in my pulling tractor application. I have to be under 1350# with me on it. I also want to have moveable weight on the tractor so I can tune it to track dirt conditions. Everything I have used is as light as possible. That has translated into major issues.

 

Exactly. I need to leave the block at stock length because I need space for the pilot bearing behind the crank (vs in the crank for a typical installation). My pilot is 25mm so there is no way a bearing that fits that is fitting nicely inside the crank.

If I hadn't lucked into a trans that someone had already swapped the input shaft on I would have had to use the big truck clutch/flywheel/bell setup which is not really appropriate for a 4000lb vehicle and wastes 3" of drivetrain length that could be much better spend getting the shifter farther from the seat and getting the driveshafts running at happy angles.

 

Would this fit?
full]5326615[/ATTACH]

 

That looks like the throw-out bearing behind my motor. The one I bought specifically states that it is for small diameter racing clutches only. They may make them for the larger diameter clutches also. The front of my transmission is the same as a Saginaw. This bolted up nicely, but remains to be tested.

 

No.

If I was a normal person running a normal Chevy trans it would.

 

My clutch takes a push that seems like a lot. I'd guess 30 to 40 lbs at the pedal but I never measured it.
I don't like hydraulics as my cars sit a lot but hydraulics may be easier than anything else so they appeal. I remember needing a long bearing in the fork and having to mount the fork pivot on an extension.

 

"If I was a normal person running a normal Chevy trans it would. "

 

Greetings everyone, A question to the Board.
Does anyone know if the crank journals are supposed to be centered on the bores on this engine? I have been doing some extensive measuring on the crank and block and it looks like the rod journals are all towards the rear about .020. (the mains seem centered on the bore centers.) I have heard that when you use Chevy rods in a 460 you will end up with the rod not centered in the piston. Is this a Ford thing with the rods ? If anyone can help on this it would be really appreciated. Thanks much

 

They appear not to be centered to me. I am using centered aluminum rods and noticed they are tight to one side of the piston. Also when making my windage tray, they were not on 460 bore spacing.

 

Anyone know if cheap stainless shorty headers will bolt on cleanly?

They have truck ones that are offset rearward, presumable for crossmember clearance.


And more universal "460 swap"center dump ones that have a more angled outlet.


The other choice is this truck manifold.

 

I don't recall seeing which head your are using. The headers shown will only fit the standard style Ford head. If you are running SCJ or one of the higher performance aftermarket heads they will not port match. There is an Edelbrock and Speedmaster head which they will work on.
Due to the 45 degree head mounting of a V8 those headers outlets may point at quite an angle away from the oil pan.
I had to do quite a bit of modification on mine to get them where I wanted them to go. I'd like to play with the straight back one in the top photo. That appears to be a turbo setup.

 

I'm planning on the 95CC Speedmaster head but if I can find something cheaper locally I'll go that route. It basically comes down to price. I am going to get an aluminum head on this engine as cheaply as possible. I have no power number in mind and a stock 3.7 is 0.7L and ~50hp upgrade over what the vehicle has currently and any aluminum head is a big upgrade over stock. I just want the vehicle going down the road and going down the road cheaply.

 

I searched that Speedmaster head. It appears it does use the SCJ exhaust header. Could there be 2 versions?
I didn't see a link to the headers you posted. Could they be SCJ exhaust?

Others here probably know more about the SCJ vs standard Ford ports and alignment.
Please chime in!

 

I have a Speedmaster head. The ports are a modified with a flat floor not the oval of the original Mercruiser head.
The headers you posted will probably work okay but will be overlap the bottom of the port.


I made some individual header flanges to the shape of the ports. Way more work than I anticipated. But, a 1 7/8" X .062" wall tube can be formed into the flange with no cutting or stretching of the metal.

If you are serious, I can post a drawing of the flanges I made. I have to modify it some as I made some last minute changes while milling them.

 

Timing questions; I've read here about the base timing being reduced from 8 deg to 4 deg in a MerCruiser
bulletin. I don’t think I have ever seen how much mechanical advance there was in the distributor. I am trying to figure out what timing values I want to use from idle to full rpm. Some of the timing tables from other engines I have seen scare me a bit for this motor. I know, start low and build up. I thought the factory timing would be the place to start.

Mine started for the 1st time tonight, but it didn't stay running. I expect it isn't getting enough fuel, but it could be timing?

 

Finally,
So, did you start with 4 degrees? With no load, you can get away with a bunch of lead. I would put it at 8 to start.

I recently rebuilt a BBC and inadvertently had the timing retarded to almost TDC. It would start but not stay running. As soon as I put it @ 8 it ran perfectly. Since you don't have vacuum advance you are relying on the ECM.

How did it crank? I know you went through a bunch of work to get it to start. What was the key?

 

It was an accumulation of several things.
1) I believe the biggest issue was the very high cranking cylinder pressure. I took .140” off the tops of the pistons and added another .035” thickness to the head gasket. That brought the compression ratio down from about 14:1 to about 12:1.
2) I posted a photo of a graph before that showed the engine surging between cylinder firing. The ECU wasn’t happy with that fluctuation so it wouldn’t fire the ignition. That was using a 36-1 crank wheel. I switched to a one-pulse-per-fire system. (I cut all the teeth but 2 off the trigger wheel) The motor still changes speed, but the ECU doesn’t see it so it’s happy.
3) My battery system kind of sucked. I installed a pair of 630 CCA motorcycle lithium batteries ($$$) in parallel. That gives me 1260 CCA at 12V. I put in a big buss bar between the batteries to insure good current flow.
4) I installed larger battery cables. #00 cable was recommended but I installed #1 welding cable. That seems to work fine.
5) The cam is degreed at 111 instead of the recommended 109.

I don't have a distributor at all, so all timing is done in the ECU.

I thought I had set the base timing to 8 deg, but when I went back into the program after the start-up it didn't appear I transferred that information correctly. It was probably more like 20 deg. Programing is very much a learning game for me.
It cranks well with the battery & cable upgrade.
Now I need to get the tune figured out.