martybose

It's all a matter of squish control and engineering. My flathead has 9 to 1 compression, runs 91 octane and just barely pings occasionally. My Bimmer has 11.5 compression, runs the same gas, runs smooth as glass and has twice the horsepower and torque as my flathead despite being a smaller displacement. Of course replacing that Bimmer engine would cost more than every dime I've invested in my 47 over the years, but that's modern engineering. Marty

If you decide to use the head, make sure you check to see what length sparkplug thread you need. I found out the hard way that my Edmunds head needed a longer length sparkplug that a cast iron stocker, and apparently that's fairly common with these alloy heads. Marty

I just used a standard C-shaped valve compressor with the head and manifolds removed. I tried a setup like Don's, but found that since it didn't hold the valve down that sometimes I would just lift the valve up with it. As always, YMMV. Marty

You won't be able to duplicate Don's setup because his motor is a 25 inch motor that has a factory oil filter setup. The 23 inch motors only had a bypass oil filter as an option. That said, there are a number of us that have done various conversion to add full flow "modern" oil filter setups to a 23 inch motor. Most involve some amount of drilling and tapping adjacent to the oil pump, and really can't be done in the car. You should be able to use the search function to find directions. Marty

I'm familiar with that pump, because I modified one when I made my external oiling system. For reasons that I'm not familiar with, the Hydrive cars move the oil pressure valve from the block to the revised oil pump cover. There are no connections externally, it's just the same spring-loaded plunger system that most of us have in the block on the other side of the engine. Marty

The boat tach on my car is a Chrysler Marine 270 degree 5000 RPM tach for marinized Slant 6; works great with my HEI ignition! Marty

I used a Rhode Island harness that wound up with about a dozen custom touches that worked out perfectly! Everything from turn signal wiring to headlight relays with larger gauge wire to the headlights, and things like deleting the voltage regulator wiring because I was using a 1-wire alternator. Not cheap, but highly recommended! Marty

Yes, you want the relays! Don't forget that the original headlights were roughly 35 watts, and the halogens are usually 65 watts. Don and I have argued this point before, but when I put 6V 65W halogens in my car the headlight switch and the dimmer switch both got pretty hot until I put in headlight relays and used a larger gauge wire to the headlights themselves. Marty

I don't have the info here at work, but the primary factor is that the 200r4 has the overdrive in the main body of the transmission, while the A518 has the overdrive in an oversized tailshaft housing, which makes the transmission tunnel a much bigger problem. The overdrive unit on the 518 has been somewhat problematic with reliability issues on aftermarket installations, while the 200r4 has been rock solid. I also believe that the 200r4 has a much lower power loss than a 904 or 518, like maybe 10 HP less loss. Not to mention that there are dozens of companies making hop-up parts for 200r4's, and only a few for 904/518's. Marty

Just make sure that when the weight is on the front suspension there is still some suspension travel yet. We made our own brackets, and the first ones were too short so the shock was totally collapsed and riding on the bump stop. We had to lengthen them a couple of inches to get the shock in the middle of its travel at ride height. Marty

They are supposed to give the bore more space to breathe through; sort of the flathead equivalent of porting the head. The downside is that it reduces the compression ratio, which partially (or totally??) reduces anything you gained ...... Marty

I have to admit, as much as I like Ma Mopar, if I was doing an automatic behind a flathead I would use a 200r4; it's a much better transmission than a 904 or 518. Marty

A fan wench? Seems to me that someone posted a picture of such a damsel some time back ...... Marty

Not true! There is an extra hole in the back of the OD transmission so that the longer shift rail can push the OD section out of overdrive when you shift into reverse. You have to have the entire OD transmission, you can't just change the tailshaft. Marty

Don't forget that you are also driving a fairly high pressure hydraulic pump to accomplish all of the automatic shifting. That takes a few horsepower. Marty

Okay, I'm good with most of your list, but why the 1955 or newer crankshaft? What's different? Marty, curiously ........

Greg's point is well-made. My first attempt at a multi-carb setup on my 230 was two 97's on an Offy manifold, and it ran like crap. It either ran well at cruise but knocked at full throttle or it ran great at full throttle and wouldn't idle. The second attempt was a pair of Carter-Webers on an Edmunds manifold, and that setup works really well at any speed. Marty

Not really. The OEM cam might be fine with the single one-barrel carb and log exhaust manifold, but if you are going to add carburation or open up the exhaust to a set of duals you might have an opportunity to increase the available power beyond what could be done with the OEM components. Plus, as Austinsailor put it, it can sound nice! Marty

It's probably a later model R-10, which means that you have to have the entire overdrive/transmission assembly, you can't add to overdrive pieces to a standard transmission. The tranny case and some of the internals are modified so that shifting into reverse will automatically lock out the overdrive. Marty

... and the crankcases are big enough that you have to take a ladder inside of them to reach the bottom of the piston at the top of the bore ...... Marty

Well, we're dealing with mid-size stuff, ferries and tugboats and such. A lot of them are both high torque and high horsepower; they need the grunt to get going, and horsepower to stay there. Typically 2000-4000 HP each, 2 to 4 engines (plus generators and more). Most are not direct drive, as the engines run in the 2000+ RPM range with props maybe a quarter of that. Tugboats maybe 10-12 knot max, but with bollard pull strength of 40-50 tons of force. The four engine catamaran ferries can run 40+ knots, very spectacular. Some of them used to be gas turbine-powered water jets, but all have been converted to diesel/prop boats over time. Even with the ever-increasing pollution controls (the SF Bay has the tightest specs in the country) the engine builders keep coming up with more powerful diesel engines, with some of the trickier ones approaching 1 HP per ci. Marty

Oh yeah! Before I decided to build the flathead instead I had been building one of these for my 47. With a 0.520 lift hydraulic cam it was projected to have over 500 lb/ft of torque from 1800-5400 RPM, peaking at almost 600 at 4800 RPM. Maybe move mountain RANGES ........ Marty

Having worked on a couple of motors that were turbocharged for racing, I don't see the point of doing all of this engineering for our flatheads. For one thing, any decent amount of boost would turn the OEM rods into pretzels just before the crank gets pitched out on the road. This could be fixed with ca$h for a set of custom Carillo's, but the point of this thread was a motor to tow an Airstream, and there are way more effective solutions than spending multi-thousands of dollars building a modern interpretation of a 1930's-engineered flathead. Personally I'd put a stroker B-block (chosen because a 383/400 B-block is easier to fit than a 440), and it is easy to get almost 500 ci with off-the-shelf parts) with a mild tune and a Torqueflite in it, and cruise up the mountains with no worries. Marty

+1 Marty

I've never been a fan of straight pipes; for this thing I would think something along the lines of these http://www.sandersonheaders.com/Sanderson-Twister-Outside-Chassis-Header-for-Small-Block-Ford.html would be neat. Marty