The elusive 224/3.7 MerCruiser banger

Just before reading this I cut the old battery cables out of the wiring harness to be replaced with new #2 welding cable.
The oil drain holes were there.
Motor and trans are now in the chassis and wiring is under way. I still need to make a bigger battery box and install a larger battery. That is going to require fuel tank removal, and more.
EDIT 12/31/21; Most of the wiring is now finished. I cranked it over to measure cylinder pressure. It is now down from 275 psi to 215psi. I'm going the right direction. I'm going to try to get it fired before making the battery box changes. That will allow me to see how big of a battery I need. Now I have to wait on a tuner, so it will be a while.

 

First post:
First up I would like to thank everyone on this board for the wisdom, skill, l knowledge and experimentation that they have shared. I myself have read the thread completely once through and will again shortly. This is the go to place.
My project is an early 60’s indy roadster replica. The original was powered of course by the big 255 Offenhauser. The last one of those I saw for sale was 80 grand, so… here I am. You can do a lot to a 470 to get the performance needed for peanuts compared to that. It also is dimensionaly similar and the exhaust intake layout is the same ( the Offy was a little bigger).

I intend to start in earnest in a year but am planning and acquiring now.

My engine will be a fairly extensive build, I would not hesitate to put a billet crank into it if I can find who has done one. The so far specs would be: A 4.39 bore x 4.25 to 4.375 stroke (depending on internal clearance), Oliver or Crower 2.200 big end maxi-light rods, diamond pistons, a Jon Kaase head, Sr-71 or Boss 9 depending on what he recommends. A hydraulic roller cam also based on Jon’s experience if they will to share it. External oiling and probably efi and ignition management. Compression would be as close to 14:1 as possible for running methanol like the original car. I want to emulate the Offy and it is a pretty high bar to come up to. The target is 300 -350 hp at 5000 rpm and to be capable of extended periods at that.

I would like to pass on some findings to all of you. On the subject closing the deck I found a couple of resources. I called Darton about their MID sleeves and they relayed me onto one machine shop that has done this engine with MID sleeves. Darton will not sell the sleeves directly as Steve Demirjian [race-engine-development@cox.net] has them done to his design. The engine he has done was a girdled stroker, (I could not get that person’s name but he said the engine ended up in a Pinto). Price for 4 sleeves installed and decked – $3500. Cough. This may be a route for very extreme builds but I don’t see It needed with a naturally aspirated engine. One thing I learned out of that is that he decks sleeved engines at two levels – the sleeves are left a couple of thou high. He is not the only one I heard this from. I intend to spend some money on this engine but…

The next is Jeffrey Morgano jeff@cncwerx.com. https://www.cylindersupportsystem.com/ he has never seen one of these which I find odd so he priced me at $895 a single block, if he saw more of them the price would be $695 which is really pretty reasonable for the work done. He is too busy to do the other machine work at the moment, so that needs getting another shop to do the bore, hone and maybe move the cam. But still If anyone else considers this option, he has my CAD drawings of the deck and gasket so is pretty much ready to go.

 

Welcome to the 3.7 world! My vote would be to use a Boss 9 head, but other heads can make more hp. Mine is 242 ci just a 4" stroke. I would like to have a roller cam but didn't see a way to get one. I have a hemi bbc injector but have seen 426 hemi's used as well. Good luck with your project.

 

Sean,
Sounds like quite an ambitious project. I read your other post about the Indy car(s) you want to emulate.
From what I can tell, closing the deck is not as difficult as the big boys would have you believe. I have a non-CNC pattern for a plate. Some of the other guys have made and installed plates, too. I used the Chris Nichols approach and recessed the block to allow the plate to be welded in at the original deck height.
At the power level you are anticipating I think that the 'Cylinder Support System' is way overkill. With a .030" overbore, you wont even get into the aluminum surrounding the sleeves. Several guys have built these with 4.5" bores.

Some more radical builds can be found here:
https://www.facebook.com/groups/431992443615823
This is not updated often, but if you look back through the posts, there is a lot of information.

When we were trying to find someone to grind cams for these engines, I spent quite a bit of time talking with Steve Lowe at:
LSM Systems Engineering
4670 Hatchery Rd
Waterford Michigan 48329
tel:248-674-4967
fax:248-673-7089
email:lsmeng@sbcglobal.net

They have experience in machining these engines including moving the cam. I was unable to find out who their customers were but I am confident that you would be happy with their work.

If you decide to have them do work for you, I think there would still be interest in the cams. We just couldn't get a commitment from enough guys to initiate an order.

Good luck with your project and welcome to the board.

Bruce

 

A tractor pulling buddy of mine has put a killer 3.7 up for sale. It's priced at $16800. There was over double that invested. On the down side it has a filled block. Trick Flow A460 head, Tim Engler mechanical methanol injection, MSD 7AL-2, distributor moved to the front of the cam, Inovators West dampener, external oil pump, and so much more. The header won't fit anything but a tractor. I didn't see the dyno sheet, but was told it made over 500 hp. The power was consistently turned down to try to let the little tires catch up. It probably has about 20 hooks on it. I'm too deep into mine to buy it. If anyone is interested I will direct you to the add.

 

Welcome to the site.
I know of one guy with an affordable billet crank. I called the guy that made it for him. He said "No more". The machinist was an older gent who did motorcycle cranks. He said the 3.7 was too heavy for him to move around.

I called Jon Kaase's shop when I started messing with these. I was quickly told they never did any work with them, which I know is false. They weren't interested in talking to me at all.

The hydraulic roller cam is doable at a not extremely crazy price since you are wanting to go to external oiling. Remember that the roller cams lobes are spaced differently than non rollers.

I have a small cam in my motor. With that and 14:1 compression I had way to much cylinder pressure when cranking. A bigger cam could help that somewhat. Because of that high pressure the little gear drive starter that we have talked about on this forum couldn't hardly turn it over. That same starter company makes one with a stronger but bigger motor. I would recommend one of those. It raises the price to over $500.

 

Flatrod17, I'm really liking that track roadster.

 

Thank you, Beck. I'm doing the best I can with it, still have a lot to do. Hoping it will run by summer, which for us is another 4 to 5 months.

 

@Flatrod17,

YES, that track roadster is too cool! Do you have the exhaust mocked up yet? With the 3" injector stacks you just about have to have a huge upswept header coming out the other side.

 

I was going to hang it out the side but didn't like the look. They were going to be 2.250 tubes. I slipped down to 2.125 tubes and ran them inside. I have a Ice kit that was given to me. Seemed to work great, now just have to make them.

 

And that's why we build them. We each have our own particular like and dislikes. Mine will be different than yours. But, I still love yours.

 

My car is a glass body with both doors that open. I ran the pipe out below the door, no not that way, out about mid door, looked a lot better. But at 5'9" I am having enough trouble trying to package myself in it and not on it, and jumping over the door is not a option. I think the key word there is upswept. The exhaust ports are up so high it doesn't get that look.
Bruce, is your car a steel body? Looking forward to seeing yours and other people's cars or trucks that are using the Mercruiser engine.

 

Mine is in the dream stage. It will be a glass body, no doors, over the side. The engine is in the mock up stage.

 

Thank you guys, I appreciate the welcome very much. There is some very nice craftsmanship here.

I like the boss 9 but I hope to keep some torque, I would love to hear feedback from those who drive their Boss nine on the street and see how bearable or not they are. If I can go for a crank it will be about 257 cid so that should help use those ports. I like others, I have heard of stroker cranks but no live leads.

The deck and cams, boy, how much of this board is dedicated to those? Hi Gearheads, thanks for the machinist info I will follow upon that. I was pleasantly surprised to see you on the roadster board too.

You may be right to do the deck plate myself, really after a good tight fit and don’t mind paying someone either if time doesn't allow. I am not comfortable with the idea of welding the block though; my preferred choice would be cold and pressed in lightly. I have a very good (big) ATC router I do aluminum on, the block would take some special fixturing, but once mounted up it only needs 3/8 nibbled out and a 3/8 plate cut out and my machine can do that. I may work along that line as shipping the block is a real pain and I would like to do that as little as possible. I have to agree that the open bores move with the heavy pistons. I will pick up an extra block before an attempt though. I have a boat repair not 6 miles away right in the middle of the prairies here and he is my go to guy. The engine I have only has 300 hours on it and of course came with a failed head gasket. Those low hours come from 6 months of ice 4 months of freezing breeze and 2 months of possible boating. Why people own boats here I have no clue. Snowmobiles sure. I do have my deck all in CAD already – but thanks much for the offer – I did that before finding this board, in fact I am slowly pecking away at the whole engine.

I did download the cam blank template and can go from there. If I hadn't sold off my cnc lathe I could have made the blank myself. Yes, one of my worst Doh moments ever, if you ever get one make sure your wife has to sell it at your estate sale.

If at all possible I will retain the water pump, as I don’t have much room for ancillaries. The seals are not a big deal - other than mercury cheeping out and leaving the cam bare steel it is a very good idea. My solution is to machine the pump shaft .015-.020 small, hard chrome and grind it. Hard chrome is incredibly smooth - seals love it and no rust . The Chevy timing chain gear seems logical at that point. One problem I have is The engine is offset super close to the left side frame of the car and there is only room on the right for the oil pump and alternator, nothing can go on the left.

The cam grind is a research project. I want to maximize the power at 5000 RPM, so there will be overlap but not as much as a drag cam that breaths best past 6000. I want to research the Winfield grinds that went in the Offy as those in the know say they are still good grinds and worked really well producing lots of torque and HP on alcohol (not so good on gas), but no luck finding any real data yet. I think that information is buried under the feet of the Sphynx .

I know it will take a good starter at that 14:1 I have built a couple of high compression engines but they had more and smaller cylinders, for sure it will take a lot of crank to get over the hump on this one. Using a gear reduction starter is pretty much a given. Again - thanks for the advice everyone.
and a little CAD preview

 

SEAN LOUGHEED : A slight thought for your starting sequence : a high compression engine on alcohol sounds a lot like a sprint car motor, so why not start it like we do ? As in get the motor spinning first, then turn on the ignition to fire it off(it sure saves wear & tear on the starter!!) And most of the sprint car guys don't use starters anyway... LOL!

 

Sean,
Sounds like you have a good plan for your project. What do you plan for intake? Injections or carbs? Whichever head you use that will have to be made. The Boss head with a 7 degree tip seems to be a little harder to make. I just finished making mine for my Arias injector for the boss head. Got a lot of time in it! What is your plan for distributor? That gets in the way sometimes.
Mine is not a working engine yet, but I expect good torque. It will have the open deck for now. If I can find another engine I will make a closed deck block. I had my cam reground to a solid cam spec with a 6500 rpm limit. I think it is too small but will go with it for now.

 

For the open deck, I suggested several years back in this discussion for R&D'ing the Honda cylinder girdle. Those guys were making over 1000 HP in the early 90's using those, so I thought it would easily benefit the 3.7 Merc, and it does.

For the crank, I had a contact at Cosworth Racing Pistons that later went to Scat, and he told me that Scat makes billet cranks private label for other big name crank companies as well, so I would contact them for a billet crank. It will also need to be fully counterweighted.

Roller cams still require you to make a billet yourself, Comp has finish ground blanks before for several Comp Eliminator racers that have raced these engines. Even though they are tight lipped about the actual lifters that are used, I'm going to guess for that level of output those engines have in that class(470 HP on the dyno, 4.600 bore and 4.125 stroke), the simplest approach is keying the lifter bores....

 

Hello everyone, I'm new to the forums, and I wanted to say "hello" and let everyone know that I have a 1987 Mercruiser 470 for sale. I just removed the engine from my boat yesterday, and it has 951 hours on the meter. Don't know if it is appropriate to post a link here, but I have an ad up on Craigslist with lots of photos, send me a private message with any questions. I'll also make a post over in the classifieds. Thanks for looking!

 

Welcome, but not really appropriate to make your first post a "for sale" post here or on any forum. And no links to craigslist or ebay are allowed. It kinda makes the moderators feel that's your only intention to be here, instead of contributing knowledge and info.

 

My apologies for the rude introduction CNC-Dude. If I'm being honest, the reason I'm here is to try sell the engine...but let me explain: I work as tug boat captain- I know a fair amount about big diesel engines, but we have an engineer on board who does the repairs. I'm a boat guy, not really a "car guy", but I'm active on other forums for boating and other interests.

I'm not a hot rod enthusiast, nor do I know much about building automotive engines, so sadly I don't have much to contribute in the way of knowledge when it comes to that. I only learned about this forum when I was researching this particular marine engine. Before last week I had no idea that these inline four cylinder Mercruiser engines were popular with a small niche of the hot rod community. So yes, I am looking to sell the engine, but I did not come here to spam links to my listing. As the title of this thread suggests, the elusive 3.7L Mercruiser is not very common, especially in good condition, and I thought if anyone here was searching for this particular engine that they might be interested in this find.

I mean no disrespect to this community, please forgive my lousy introduction. Happy to answer any maritime related questions anyone might have.

 

You will still need to make the cam blanks yourself. These days, most any cam company can heat treat and finish grind them. Comp finish ground them about 10 years ago for several Comp Eliminator racers. Just about any thing you can think of has been done to these engines. Billet main caps, roller cam bearings, mechanical fuel injection. The Comp engines were making 470 HP with only the C-460 cylinder head too. Who knows the potential with the other heads available now including the Boss head.

 

It is a relief to find so much has been done with the engine. Comp eliminator may be a learning ground too, like I said I would gladly trade a bit of HP for drivability and torque. The boss head has the look of something unique which is the draw for me and I am not after ultimate HP. The Offy in the late 50’s early 60’s belted out 415 hp at 6000 which was its max RPM and power on a dyno, but for racing 5000 RPM was tops and that made 350+hp (maybe 375 if A J Watson or George Bignotti walked past it). The roadsters don’t need huge power, as you know they are pretty much a missile, In 59 Jim and Dick Rathman posted over 170mph at Daytona with Offy roadsters of that HP. Pretty sure the 470 can do the same without being too extreme, but I would fill my pants 30mph before that so no need for more HP.

Very nice work on the fuel injection Flat rod. I can see the challenge in Square injector – round port but the execution is excellent. 3” sounds big but on so much of this it comes down to if the engine likes it, and it quite well may – you are absolutely correct that anything that will work on a 500 V-8 will apply at 50% to one of these, which is what is to like about them.

I am a carb guy, and the leap to EFI is uncomfortable but I think it makes sense for a few reasons. 1) fuel injection systems like yours are beautiful but non-existent here. 2) carbs of the cross draft type are expensive (if you want something new that works) they are usually made for smaller engines. 3) Once running the tuning is very tangible, all on screen. Carbs are kind of esoteric and you need that sort of Zen to get it right.

This is what I have been looking at https://www.aemelectronics.com/products/programmable-engine-management-systems With this it makes sense to go to ignition in the same system. Kind of a trade off. A bit more complex but do away with the cam gear and not worry about cramping the distributor under the FI but having to fit a reluctor wheel, sensor and electronic “stuff”.


I hope ems and efi's will become more talked about here as I think it was Chris Nichols that said, don’t build these engines like they did 30 years ago, they have a lot more potential. And it is so true. We stand to get some big benefits if we use the new engine management technology.

 

Well Sean, that post will probably get deleted. The mire mumbling of EFI and the EFI cop here will be along to delete it. My post was deleted and I don't think I said anything about EFI, other then mentioned it. That said, there may be benefits to it, but they are not going to let use talk about it here!

 

Mechanical fuel injection(Especially "Home-Made") might be interesting, & certainly should be "legal" on this thread!!

 

I had considered making some casting patterns for a dual side draft intake and a mechanical fuel injection intake if enough interest is there...

 

My friend's thread on his fuel injection build.

Technical - Fuel injector Fab | The H.A.M.B. (jalopyjournal.com)

 

HJmaniac, I have read that thread and thought I saved it, but guess not. I have been looking for it off and on for about a year now. Thank you for posting it!
Everything I have here is mechanical injection.

CNC Dude, I'm not a cnc guy its all cut by hand. But I would like to offer assistance if I can in any way if you move to casting anything.

 

Here is a mechanical injection setup custom built for the 3.7 using the Trick Flow A460 head.

 

Bruce and Tom asked about my msd dist, so I made another with real msd parts and thought I would try to show how I did it. I hope I can get the pictures lined up.
I started with a small block Ford and a vw dist. Broke them down to the parts I will use. The small block was cut off at the mounting flange. A slip ring was made to set height and I used a Mopar dist bushing for the lower support. The housing will need to be reamed to .687. Pressed in and reamed to .501. The Ford main shaft was cut to length. I was able to buy a new gear, but not a oil shaft, so I made one from a 460 Ford shaft. Put it all together and hopefully I have something that will work. The real msd is in the middle, the red cap one is the cheap knock off msd. Comparison picture. If you want to try to just use the VW to make a dist, you can make a sleeve for VW housing but you will need to fill the gap between it and the gear. And you still need a longer shaft. The difference in the shafts. That is why I used the small block Ford parts. Its just .030 off the housing to fit and the shaft can be cut down. I chose that way rather then trying to lengthen the Vw shaft.
Hope this helps others. Any questions I would be happy to answer them.

 

Also I had to chamfer the lower part of the vw black plastic housing to get it to sit down lower and some minor trimming to the stock side cover was needed.