The elusive 224/3.7 MerCruiser banger

Reminder that the Cleveland bearings are half groove and the Mercruiser ones are full groove. Either may be preferred depending on your intentions with the engine.

 

I know your pain. After being away from this thread for a few months, I have started from the beginning again to freshen up my notes. I have tried three or four times now...

 

I knew there was a difference, but not the advantage of one versus the other.

 

A topic index at the front of the thread would be invaluable to find specific information. A lot of worthwhile information is here. I worked on one but I only got to the first half of the thread. It is only rudimentary and does not look like much.

 

Index
There is a search function, but this is human produced and possibly better.
Feel free to add or modify this as this is only an incomplete beginning.
Additions are needed and should include post and page numbers.
[ index below covers pages 1-17]
alternator p243 p365__etc
bearings pg98, pg99
bellhousings post 34, post 69 p188,p189,posts 2887,2891,2901
_ adapter ,BH post2904,2907
block surfacing p_
block cutting/milling post 73 post 2887,2891,2892,2901
block posts and block guard page 10
block warping post 187
bolt stretch page 10
boost post 390
cam hole plug p112
cam (knockless) p39 p263
cam, standard post 19 p204
cam wear p262
carb autolite p199
carb gasket cutting post 2959 page 99
carb jetting p34
carb updraft pix p197
carb quadrajet p198
clutch disk and pressure plate post80
coolant connections post 41 p92 p93 p109p131p136
connecting rods page 99
cost (in 2010) post 76
dampener p267 p269 p270
distributor p35,p37
deck plate pg54
dowell pins post 161
engine pictures post 281 , 284 and 313
engine mounts post 171 p214,p221 p218 p224-231,p343
engine source post 13, p94
engine specs pg29
engine faults and fixes post25, 26, 417
fixes post 71 post 25 and 26
flywheel pg40 post 70, 349, 352,354,355, 401
flexplate p40
generator post 477
Hardblok post 78
head bolts pg19,30
head choices post 296
head studs p30, p321
head gasket p____
headers post
ignition coil p_
ignition, HEI pg46, post 205
ignition timing p_
injection p203
manifolds p18 p101
manifold exhaust p113, p209,326
manifold warping 190
manifold welding p125
pilot bearing post 452 (drawing),2897
piston post 48 p241
pressure plate post74, post 80
Randy Dupre advice: posts 210,288,293,297,304,305
rocker post shims p254
starters post 317
starter nose hole in bellhousing post 276
stroking post107, page 99 posts: 2946,2948,2950,2951,2952,2955
supercharger page 99 post 2956
thermostat post 16 p145
transmissions:
_ automatic pg 30,34 etc
_ manual post 400, 2902
turbocharger post 104
valve cover p___
waterpump:
cam nose hole blockoff plug p462, 463, 479
Chrysler/Hyundai/Mitsubishi waterpump p462
_Toyota waterpump adapting plate p___
_electric waterpump p151
_Toyota belt drive pump post 306, 466
_pulley p
waterneck p41 post 347(picture)
zero decking the block post258_

 

I want to thank Dennis for the work on an index. This board is by far the most valuable repository of information out there on the 470 and I too have spent hours too going "I know I saw it here somewhere".

I also wanted to pop in and give you some gasket files and an update.
The gasket kit I got has no pan, timing cover or water pump gaskets, (Mahle) just a big sheet of material for a frustrating DYI project. If you get the same or just need one of them, these templates will give you the design - either print them and trace or as I am going to do, use the zipped DXF file to laser cut them out.

I have completed drawing the short block of the 470 in 3D and post a sliced and complete view here. The next step is to add the head. It has been a lot of work as I am a bit of an OCD accuracy freak, but it is proving invaluable to "fitting" the motor and transmission into the roadster - which is also being done completely in 3D. It is a tight fit in the roadster and this it is very quick (and cheap) way to make adjustments. I would be happy to pass on the model as a stp. or such to anyone here crazy enough to do the same.

Trying to fit engine internals like con rods to check clearances would be a breeze as I have digitally probed the blocks internal dimensions so have an accurate crank case to check clearances by, but to get even an outline of a con rod from any manufacturer is met with dismay. The recommended procedure seems to be buy a set of rods and see if they fit. - you have to be kidding? If I can get some con rod models I will post up what stroke is possible in one of these engines. All I know so far is it's somewhere between 4.25 to 4.5 using a 2.2 journal. The limiting factor is the side of the block where it is very thin so there is no ability to grind anything in that area to go bigger.

Enjoy the files and pictures and best regards to everyone.

 

I would be very interested in max stroke for my dragster project.

 

I think that the maximum stroke possible is somewhat dependent on the rod journal diameter and the design of the rod big end. When offset grinding the rod journal the arc described by the outermost section of the crank throw does not change.
Since the original diameter is 2.500", offset grinding down to 2.000" will give you an increase of .500". The original stroke is 3.75" giving you a max stroke of 4.250". The practical limit of offset grinding is probably closer to .475". A 2" crank pin (SBC) would be the max I would consider. For the very brave, the Honda size might be a possibility.

Now, if you weld up the journal to get more material out there, that changes things. The limit would depend on the space inside the case and how small you could make the rod big end. (as Sean pointed out).
Those 3D drawings are absolutely beautiful! I wonder if you could get some connecting rod samples from an engine rebuilder on a loaner basis.

 

It does depend a little on the rod as Gearheads points out. The only actual model I have gotten is Bill Miller aluminum rods which I thought odd as he gives out a totally accurate model. Everyone else is paranoid that someone might see something to copy which is not he case with a 1D view that would show the outer most line of the rod, cap and bolt - which is all you need to check the clearance.

Oh, and the aluminum rods are huge and have no chance to swing in a stroked 470, so we are looking at good steel rods.
Thanks for the complement on the drawing Gearheads

 

Sean,
Tom Rockwell over on FB is building one with a 4.150" stroke. He is using Oliver C6800SMBB rods. These are steel 6.800" long use a 2.100" bearing and .990" pin.
Oliver might give you the dimensions you need.
I have a couple of potential candidates that I'm exploring. I could trace them out and send you dimensions. They both would need narrowing on the big end.

Bruce

 

I have GRP alum rods in mine with a 4" stroke. Plenty of clearance that I didn't bother to measure it! My next crank will have a 4.125 stroke and I don't think it will have issues either.

 

What am I looking at here?

 

Looks like he is making a dcoe weber intake for the other Mercruiser, the Chevy 181ci.

 

3.500, 3.590, 3.750, 3.850 and 4.150 are the strokes I have written down, depending on which combo I go with. So, 4.150 with aluminum rods would be the one I am curious to see how tight it is.

 

Actually, I'm using the Webber manifolds as cheap formed runners into the head for which a plenum box will be attached with 2 inlets. The adapter allows me to convert the 6-bolt head to individual intake and exhaust flanges. I'm building a blown 4-banger, and I'm driving the 4/71 blower off the crank---Potvin style instead of normal belt drive

 

Can we see more of it?

I have a pair of IDA VW intakes I didn't know what to do with. New uses for them!!

 

Engine is in the progress state, gathering parts and pieces

 

Vinyl sign shops can cut nice gaskets. I needed a difficult to cut carburetor floatbowl gasket and the shop made an exellent gasket for me using the old broken gasket as a pattern.
It is easier on thin flat gasket material.
Most gasket material is curled and needs to be ironed flat.
A broken gasket is useful as a pattern. The shop owner had never cut a gasket and was interested so he had it ready in a day.

Most other gaskets are easy to cut.

 

Does anyone have a high res copy of the Ford Motorsport ad, that isn't a photo? Chris Diggles made a poster for his shop wall, and I would like to do the same.

 

Calkins, would you like the catalog? I have them from back then.

 

I have the catalog and the magazine with the catalog in it already, I just don't want to cut it up to get a good scan of the ad.

 

I'd be interested in a poster if you get some made. Let me know the cost and my wife will buy it for me for Christmas

 

[QUOTE="Sean Lougheed,


View attachment 5518583 View attachment 5518584 [/QUOTE]
Beautiful, will it do something like this to a photo of a face?

 

How far out of concentric is too far out for a pilot bearing?

I'm making an insert to fit inside the coupling hole in the Mercruiser flywheel and locate a pilot bearing. I can get it within .0015 of concentric on my rotary table. I think that's good enough unless someone tells me it's not and has a good reason why.

 

I would think .0015 is plenty close. I would expect .002 at least input nose to bearing clearance. I say go for it!

 

In case anyone seeks to bolt in an adapter for a flexplate or some other sort of coupling, the ID of the bore on the stock mercruiser flywheel is 6.500+ a few thou. Mine came out at 6.503 or 6.504 depending on if you trust the inside mic that I've never calibrated or the outside mic that I've never calibrated.

 

A few pages back, I was asked how much the compression ratio changed with the piston change from flat top to bathtub style but I could not give a good answer as there were several variables and I did not know.

Here is a comparison of two of my 3.7 engines:
Although the first ran too hot ( up to 265F coolant temp), ignition timing advance was 32 degrees at 2200rpm it never detonated, not even a little. In all cases I used a stock 102cc head. Throttle response was good. I put about 1300 miles in it.

Then I changed to a new stock cam from Elgin and it ran hotter (1740 F exhaust temp)and detonated under most operating conditions. Its ignition timing coud not be advanced beyond 28 degrees or it detonated. With that cam it was basically useless.

The "stock"cam made a good blank for regrinding.

The second engine had 21cc bathtub pistons, a head milled about 20 th by operator error, and a vacuum advance distributor with ignition timing between 32 and 40 degrees advance. It did not overheat. It did not knock. It had excellent throttle response,
as I remember, better than the first engine. Unfortunately, it smoked at idle and burned more oil than I've ever seen an engine consume. The lower compression ratio will use more fuel, but running more ignition advance will gain some fuel mileage.
So after 40 miles on "smokey", I'm building a third engine.

The following works for me:
1. don't use the stock cam profile.
2. lower compression ratio by not using stock flat top pistons
3. use a vacuum advance distributor.
4. you can zero deck the block but must lower compression.

Simple static compression ratio calculations can be misleading. Dynamic compression ratios mean much more

 

Compression changes from machining parts notwithstanding this just doesn't make sense in light of the fact that Mercruiser managed to run these things on 87 in a marine application with stock cam, stock flat tops and a mechanical advance distributor (albeit retarded a bunch).

 

A car application with varied loading on the engine profits from a vacuum advance which is not needed in a boat. I used the stock centrifugal advance for years but I wanted the advantages of advanced ignition timing.

These engines have a reputation for detonating. Retarded ignition timing results in overheating but the power of the cooling system in a boat may overcome some of the heat. The cooling system in a car can be limited (as mine is). Aluminum heads are popular not only for being much lighter but also as they transmit heat better than cast iron. I have read that one can run a higher compression ratio with aluminum heads but I've no experience with that. I had the deck milled down to match the piston crowns, for detonation resistance from tighter squish. A side efffect of it was a higher compression ratio. That engine ran well with a very mild cam profile but it detonated badly with a stock cam. The cam made a much greater difference than the tight squish.

It is a good idea to begin with a stock engine and fix problems as you find them. That way one will not do anything foolish. To know what actually works you can only change one thing at a time. That takes time, years of it as it is not easy like a car engine with everything already worked out years ago.

There are some remarkably gifted individuals who have contributed brilliant advice to this forum and the internet. Their cars go very very fast. My car is slow and that is ok as going fast can be wildly expensive.