The elusive 224/3.7 MerCruiser banger

Is there any option to mounting a temperature sender in the upper radiator hose or radiator on the 3.7 merc ? There is a small coolant drain on the left side of the block under the original voltage regulator location.

 

Does anyone know when Merc-cruser stopped using the 5/8 sized dowel pins (Chevy), I'm looking for the range of serial numbers that would have the large dowel pins.

 

As temperature senders are not normally mounted in a Mercruiser 3.7L engine, we have to find places to mount them. I have used an upper hose coupling for this. My first effort was a big ugly brazed steel housing for the cooling thermostat and for a fan switch. It worked. For my next one, I used a "y" shaped mid 1970's BMW thermostat which came in its own housing. It required an extra hose for radiator bypass at low temps. I still had to come up with a place for for the fan switch.
A pretty anodized aluminum fitting is available for $10 but fan switches to fit its 1/8" opening are hard to find.
So I made my own to fit easy to find 1/2" fan switches and temperature senders:
material:
-I used 6 inches of 1" copper tubing (outer diameter 1.125 inch)
- and two brass 1/2" pipe to hose barb adapters $2.85 each
- and a foot of #14 copper wire

procedure:
-cut off the hose fittings. Mount the rest of the brass fitting in a milling vise and cut off the un-threaded end with a 1.125" hole saw. The fitting now has a 1/2" pipe thread end and a saddle shaped end which I cut with a hole saw to fit the copper tube.
-Drill two 0.684" holes in your copper pipe to fit your modified "hose fittings"
- solder the two fittings to the copper tube over the holes.
- clean the threads of the fittings with a 1/2" pipe tap.
- wrap a single #14 copper wire around each end of the copper tube. solder them in place. This is the ridge that keeps the hose from popping off.
-my hose was not quite tight enough so I used 3 tight wraps of self-vulcanizing electrical tape on the copper tube for a tighter fit. Clamp right down on it so oxygen can't get to it and it lasts better than I ever expected.
---------------------------------------------that is all there is to it------------------------------
Two other places for temperature sensors for your gauges:
1. the left side of the block has a 1/8" coolant drain that could hold a water temp sender. Use a sender short enough to not contact a cylinder
2. the oil drain plug is a 3/8" pipe thread plug. You could screw an oil temp sender in here.

ps: If you buy the aluminum hose fitting, be sure to order one 2mm larger than the size you think is needed. ( they come undersized)

 

PRW sells a small block Ford flex plate with Chevy & Ford converter bolt patterns
I bought a neutral balance 157 tooth & small block crank to chevy pilot adapter drilled the crank for the adapter & made spacers for the convertor bolts to mock up a 700r4 behind my engine still need to assemble the engine but mock up is done

 

I had severe overheating problems with my first 3.7L Merc engine. This time around, I'm trying lower compression and more ignition timing advance.
This evening I read the cooling system advice from Stewart Components (race car cooling system specialists) as would be expected, they really know their stuff.
https://www.stewartcomponents.com
read their "tech tips " it is superb.
Lots of myths are dispelled.

 

Not much to report. I refurbished an old sprint car last spring and raced it last summer. That took me away from my champ car project. Gotta live your life!
My thoughts lately are the champ car. Not getting any younger!

current situation:

I may have posted some of these earlier. IDK .
Plans from here: finish bracketry on chassis, then weld up and send off to powdercoat. then work on engine. finish intake manifold, fuel injection, and build a home spun lost fire ignition.
to answer probable questions- rotating assy will get balanced, won't run a harmonic balancer. fuel will be methanol.

just little stuff lol

 

The car is coming along and it's nose looks much better.
Now some questions:
What does or will it weigh?
What wall thickness on the small frame tubes?
and Could you post a photo of the front of its frame showing the complete torsion bar ?

this pandemic is an ideal time to work on cars.

 

1300 to 1500 lbs I would guess when complete. This is about the norm for cars of that era, no more than that.

This drawing I found is probably same material, (thickness, rest is same). Mine is a Don Edmunds copy. Refer to upper drawing

 

BTTT

Looks like I am FINALLY going to get my very own Mercruiser 3.7! This was a long term deal for me from the start, but I didn't think it was going to be THIS long. Basically getting 2 engines in baskets. The plan is to build one from the best parts, and use the other one as the basis for a "Monster 4". My immediate problem is that the engines are 200 miles from here and the seller lives near me. He can't go to his summer home until the 'shelter in place' order is lifted, hopefully in the next month.

I love to fabricate and try stuff, so that is the focus of the second engine. It will have the cylinders bored completely away and iron wet sleeves installed. This brings up my first question. How long are the bores? The quill on my Bridgeport has 6" of travel. I think I can probably get another inch or so by raising the table once the boring bar is in the cylinder.

I'd like to see some updates on the guys that have been working on these engines and posting on here.

Stay Safe,

Bruce

 

What will hold sleeves up on an open deck?

 

It will have a deck plate. A THICK deck plate.

 

How about an update on your 3.7 projects
@beck, @dennis g, @Hitchhiker, @iadr, @Three Widow's Garage, @Rootsgroup, @Unique122s, @Boss9 Brian

And anyone else working with these BIG 4s

 

You're going to spend a fortune on sleeves even doing it yourself. But I'll look forward to any updates you post.

 

I'm not doing it to save money
Took a full year of Auto Machining at Ferris State College. The program is gone now that they are a University, but the flame is still lit.

Melling's are $75 ea.

 

So is your plan 4.5" bore and cut crank for BBC rods for 260 CID?
It will be a shaker.

 

Phil,
A lot of talk here early on about vibration. It seems that the guys that have been running them don't think it is excessive. I'm not settled on a final bore & stroke combination, but I want it BIG.

Since this seems to be just you and me right now, can you fill me in on your combination? As I recall, you were using a Kaase Boss 9 head.

 

Nope. Just the stock head with the AIR stands cut out of the exhaust. Still sitting as another project ahead, Ford 2.5 with 16V Volvo head, still working at a job and at 67 getting tough to do as much.

 

Wow!

Do I have bad computer breath? Nobody working on one of these engines? Or reading the HAMB?

 

I have an extra block in good condition I could turn loose of without breaking the bank if you or others would like to start a project and get started sooner so you don't have to wait. Shipping wouldn't be horrible I don't think.

 

My project update is above on this page. I have gone far enough on the engine to use as mock up, then when chassis details are complete, it will go to powdercoat. Then I will finish up the engine.

 

Rootsgroup,
Thanx for getting back. I really like the header. How big is the outlet? Did you roll the cone yourself?

That engine really sits back doesn't it?

Very cool project!

 

I built the header from two 2" u-bends, and a piece of 4" exhaust pipe. Lots of thought and figuring went into it. The cone part is a a piece of 4" I pie cut down to to 2" one one end.

 

I'm currently preparing to get mine started. Just ordered a gear reduction starter from RareElectrical.com. Its set up with an aftermarket alloy (Ebay) head, decked the block, recurved a custom distributor built from the original but added vacuum advance from a 6 cyl early Nova distributor, water pump on order from Summit Racing - the electric setup from Davies Craig which worked beautifully in our Bonneville race truck. It'll be combined with an early Land Rover 5-core radiator in a '64 Series 2A. I hope to get the intake manifold modifications completed by the time the weekend is over. Does anyone have pics handy of how they modified theirs? Yes I'm being lazy. I'm a bit short on spare time to surf 71 pages to find it with slow internet.

 

I'm still working at it. I began breaking in an engine last week had to abort it twice.. a violent irregular clanking perhaps from a drive pulley I forgot to torque down, and overheating possibly from air trapped in its head by the inline BMW thermostat's position I tried....

 

you should read the pages near the front as there is much essential information there.
see page 9 for a photo of the rear end modification of my intake manifold, the front end has a similar water outlet that has to be carefully located to miss the distributor. I took advantage of the water passage in the intake manifold for some extra cooling. It required making the rear connection with a bit of hose up from rubber electrical tape under a complete hose clamp cover there also are copper tubing angle fittings to make the bend ...sounds wonky but it withstood the pressure of water at up to 260 degrees* and was still good after 2 years use. The side coolant connections work very well indeed. That self vulcanising tape must be protected from any air or it will crack at the temperature there.

It would be good to run a 5/8" or 3/4" hose forward from the back of the head for improved cooling distribution , I used copper tubing except to the radiator, hoses would be much easier and look nicer. Mercruiser head gaskets control water flow by water hole sizes. A side by side comparison with an automotive gasket and a Mercruiser gasketshould show differences in that as the exit flow path of water from the head is quite different.

* My first Mercruiser engine tended to run hot but it did not knock until I bought a new cam that produced 211 psi cranking pressure with flat top pistons and reduced combustion chamber size from zero decking ( the cam I like resulted in 165 psi on flat top pistons and with it and low compression pistons it is 125 psi) .the new cam was awful but served as a core for regrinding. As my engine always ran hot I'm dropping down to 8:1 and running more distributor timing advance for lower engine temperatures.

electric water pumps are a worthwhile improvement.

 

Gentleman;
I've followed this thread for many years and think I've read all of it. Enjoyed all comments, and insight that has been applied. I know it's been beaten with a stick over and over but a do think I've read anyone with what I'm planning to do and why.
This block now shares a common built as a modern LS when you look at the block deck (aluminum block) cylinders and push rod wall. This block also uses a laminated steel gasket (3) layers. Instead of the steel gaskets, why not a copper gasket ( old school)?

 

Dennis G asked for these - from suspension pics

 

There was an embossed copper head gasket which came in a Mercruiser 120 that I rebuilt. They were also used in Yamaha 2 stroke 350cc twins 50 years ago, their dealer shop manual said to anneal the head gasket before reuse. The procedure was to get it hot and quench it in water. I did and it worked.
I would expect that copper costs more than what is commonly used.

 

thanks . It is supported by center-secured torsion bars with strong lever arms at the ends. I have one car with that sort of suspension and it is trouble free.