The elusive 224/3.7 MerCruiser banger

In retrospect:
With the crank and flywheel in place, anyone can cut his block if that is what is desired. (There are other ways of doing this)

It is easy to accurately cut away some of the aluminum flange.
It is terribly messy so don't do it in your shop.
It is not easy to clean up.
Do scribe a line on your block.
Don't remove the aluminum in only one cut.
Prop the engine up at its rear.
Expect to make accidental slits in whatever is under the engine.
Use the top handle option on the grinder.
Reverse the handle and chain it down .

 

On one of my engines a previous owner stripped out the block threads for one 3/8 NC bell housing bolt. Then it was tapped for a 7/16 NC bolt and he stripped some of those threads.
I bolted an aluminum block to the flywheel to properly align a drill bit to extend the hole. The bit was undersize so I could protect the existing threads from the drill bit with shim stock.
The threads I cut seem ok but there are not enough of them because of his incompitent work (the rule of thumb for engagement length in aluminum is 2 to 2.5 x diameter of bolt) so the next step may be a 3/8 coarse helicoil as there needs to be about an inch of engagement.

 

The valve sizes speedmaster chose for their head (Melling V1173 and V1174 or equivalent) are particularly annoying to source if you're just looking for cheap stock parts and not fancy race stuff because they are for a Ford Cleveland Boss/HO/4V cylinder head used in car applications for only a few years. Big block Chevy valve sizes seem like they would have been a much better choice. Total cost wound up being almost exactly $70 shipped which about what four valves cost if I were to buy performance oriented ones.

Thankfully the valve stem OD and ID match a Chevy 250/292 I6 so at least those are cheap and available.

Anyone have recommendations on studs/rockers? Stock cam, stock RPM range. I know I don't need roller rockers for my application but I would like to go to a 1.8 ratio to get a tiny bit more out of the stock cam and I don't think anyone makes roller tip stamped rockers in such a high ratio.

 

Changing the cam profile solved the detonating problem that our engine is known for and you can also get a little more lift with the stock rockers.

 

Got the speedmaster bare head in the mail over the weekend.

I can't find any flaws with it. The inside of the water jacket isn't the most elegant casting in the world but it is more generously reinforced than I expected.

Now to fix my sandblast cabinet so I can actually clean up my three cores worth of parts...

 

I polished my crankshaft using sandpaper I lubricated with WD40. I worked up to 2000 grit in stages. The usual way is to wind sandpaper around the journal and a shoestring around the sandpaper. I found
slipping between the string and the sandpaper to be a problem so I put a rubber band around the sandpaper and used a nylon strap instead of the shoestring. This method only polishes one side of the journal at a time so you also need to do it from the other side.
with a 6 foot strap you can attain both speed and pressure. I also ran a drill through the oil holes in the crankshaft.

 

Arse_Sidewards, in going to a roller cam, how did you work out connecting the valve lifters when the side-cover retaining bolts are in the way?

 

I'm not going to a roller cam. I am reusing the stock flat tappet cam. I think you may have gotten confused when I brought up roller tipped rocker arms.

 

I did indeed. Thanks for putting me straight.
As to studs, I bought a $100 set last year and sent them back when I saw the amount of threads was wrong.
There should be lots of coarse threads engaged in the softer aluminum and fewer fine threads for engagement in the hard steel nuts.
A nicely made stud will have its diameter not exceeding the minor diameter of the coarse threads.
Volkswagen had trouble with fat studs causing failure. They reduced the diameter down so the stud would flex in use and there were no more failures. Fasteners stressed to this level are considered single use fasteners.

This can be easily seen in photos.

 

I bought the speed-master studs and guide-plates figuring they would at least be compatible with their own head.

Also, if anyone is planning on buying some cheap roller rockers and stud girdles I'd be interested in splitting the cost.

 

arse

I would call Harland Sharp.

They will sell you a half set of each.

 

I bought BBC rockers

 

BBC rockers make for some goofy geometry and really odd push rod lengths. Most will rub somewhere. Been down that road. But they can be made to work, but why use something with less ratio. Less ratio=less performance.

 

note: the following is about the headbolts or studs holding the head on.
The compatibility problem is in the block as die cast aluminum (A380)shears at 27,000psi . They'd more likely get by in cast iron (grey cast iron shears between 21,000 and 88,000 psi)
Threads fail in shear the stud itself fails in tension. The threads in the block would fail first shearing off and the stud would pull out.
Not all of the threads pull out at the same time, the top few pull out putting more load on the next few, which shear off overloading those immediately below and failure progresses sequentially downward.

ARP studs, nicely made and strong at (180,000psi to 200,000psi)
ARP tech service told me that " 3/4" engagement in an iron block is 'golden' but you need 1 1/2" for aluminum".

 

ARP spends all day talking on the phone with people who are spinning engines to 7k and beyond and running hydraulic rollers with tons of lift and the accompanying stiff valve springs in order to do it because the people who's needs are mild don't wind up calling ARP tech support.

With a stock cam and springs I'm not worried about it. We'll cross the helicoil bridge when we get to it.

OEM pedestals get held in with a 5/16 bolt. Granted that's in cast iron but still 7/16 vs 5/16 is a pretty huge step up.

 

You and I are talking about completely different studs. My concern is only with headbolts or head studs threaded into the aluminum block.

The force on rocker arm fasteners can be effectively dealt with as you pointed out.

Out of curiosity did SP make those studs the same goofy way they make the head hold down studs? (ie. few coarse threads and many fine threads).

As you said, as they make the head, they should be expected to make proper studs to screw into the head for the rockers. And yes the increase in stud size will solve a lot.

 

I've never seen a thread in rocker arm stud that wasn't that way.

Here are the specs for Speedmanster PCE260.1002
Base Thread Size: 7/16-14 in.
Rocker Arm Nut Thread Size: 7/16-20 in.
Guideplate Locator Shank: No
Rocker Arm Nut Thread Length (in): 0.700 in.
Effective Stud Length (in): 2.300 in.
Base Thread Length (in): 1.020 in.
Quantity: Sold as a set of 16.

Mine came in NOS ProComp packaging which I thought was highly amusing but I get the feeling many here would not due to ProComps reputation.

 

Looking at them, I've no issue with their design as the fine threads at the top have more than one benefit and the coarse thread end may well be large enough to hold with the springs you and I use.

 

Those that are running an aftermarket aluminum head, are you plugging the stock oil drain back holes ?

Or does a stock Mercruiser head gasket block the hole off ?

Jeff

 

All the blocks I have none are drilled for drain back. They just drain down the push rod openings. I did drill my block for them on Bruce's recommendation. It may not be needed on a regular head but the Boss head, well it fills and holds a lot of oil up there otherwise.

 

On the Edlebrock Performer head, there is an oil drain next to the last inside head bolt hole on both ends of the head. It is right next to the valve spring pocket and valve cover rail. That is what Jeff is asking about.

 

Yes, but on the block it goes nowhere. The block can be drilled to make the stock head drains work. Mercruiser just let it drain back through the open push rod area.

 

With the head bolted on, I drilled through the stock head gasket to extend the stock head's oil drain. The long drill continued into aluminum of the block. As I drilled I grew increasingly concerned that I'd be hitting coolant water with my drain hole so I aborted the experiment. Nothing was gained or lost.

 

I marked the holes with a head gasket, drilled straight down. Don't remember how deep but I think it was just deeper than the head bolt hole, then drilled in from the lifter cavity under the head bolt to hit the first hole. I skimmed the bottom of one of the head bolt holes, but I didn't think that will be a problem. I have run mine and it was not a problem. As I remember the down hole was 1/2 and the angled hole was 3/8.

 

The thing didn't have drainback issues running 4500rpm for an hour on the water. It's not gonna have drainback issues in your cars.

 

I was drilling on the exhaust side with a 12 inch long drill bit. It was an 1/8 inch bit as it was only a test hole and I wanted to be able to plug it with a lead ball if it came out in a bad place. (Good I stopped as it would have hit coolant.) Lead ball plugs in stepped holes, common on carburetors, are easy to pound in or drill out. Fishing shot weights are a source for the lead balls.

 

Early in this thread the use of alternative main bearings was explained. I looked for that valuable post yesterday and could no longer find it present after reading over 50 pages. Does anyone remember the alternate bearing source for our 3.7? I found currently available Mercruiser bearings badly price gouged (400%). I think the alternate bearings were from a 351 Cleveland but only the bottom half of the set could be used so it sounds like mains.

As our rods are big block Ford I assume that BBF rod bearings are the right ones for our 3.7 Mercruiser.

 

Two sets of 351C, using only the upper halves. If you add a groove for the tang on the main caps, you can use one full set.

 

I talked about 351c bearings back on post 2427. Showed pictures of the main caps i cut to use cleveland bearings. Only need to cut caps 1,2, 4 and 5. The thrust can be used as is. It is on page 81.

 

Thanks guys, that helps. After reading 53 pages again, my eyes were tired.