More Circling Around
I know that this is largely just more talking about things that have been talked about before but I am finding that the process of just massaging the information is helpful. What I'm going to do here is look at all my questions and explore each one. The answers come later.
What are ALL the reasons that manifolds come stock with coolant and exhaust passages?
I know that this is done to heat the manifold but why do they want to heat the manifold? I have read that this maintains a consistent air temperature to aid in more precise air fuel mixtures in carburetors. This also aids in fuel atomization or evaporation so it may help with mileage. I think it may also help with carburetor icing by warming up the manifold and heating the carb on top of it.
Heating the air before it enters the cylinder is anathema to performance engine builders. Warmer air is not as dense. The denser the air, the more power you can make. I, however, am not building a performance engine. I am building an engine to deliver the maximum of a specific type of performance. This leaves me with three questions to answer. Actually four questions.
Is there any fuel mileage to be gained by heating the air fuel mixture and if so how much?
Is the gain great enough to offset the loss of power?
How much power is to be gained by cooling the temperature?
Is the improved atomization worth it?
Can I get the same or at least sufficient fuel atomization from a well designed and chosen carburetor that has a very high vacuum signal at the booster venturi and that shreds the fuel as it is released?
At what temperatures does carb icing become a problem?
Will the Jeep ever be operated in these temperatures?
What effect does heating the intake manifold have on the range of temperatures that an engine is serviceable in?
Are there other solutions to this problem (if it is indeed a problem)? Especially solutions that do not always have to be in use or can be switched off?
Why else is the manifold heated?
I guess that is more like a slew of questions than four and they are to answer this one question:
How much heat do I want or need in my manifold?
What, if any, reliability issues are there with a 4" stroke?
I really need to find out what the trade offs are with this long of a stroke. A 4” stroke significantly reduces the rod stroke ratio. I need to have rods almost 6” long and an accompanying compression height just over 1”. These are certainly obtainable specs with parts like this quite available but how reliable are these parts. I'm not really concerned with the rod length but the piston is definitely and issue. It also occurs to me that the length of the rod effects the size of the piston skirt. So is the 4” stroke a candidate for the project? This leads to the next question.
What is the minimum durable compression height (or distance)?
As the compression height is reduced the rings start getting packed tighter together which reduces the amount of metal in the piston to support them. There is an amount of metal that is the most that makes an improvement in strength and any more is not necessary but I don't know what that measurement is. Additionally, I don't know how thick the rings need to be in order to be reliable and seal for a long time. This leaves me with two questions.
How much metal is needed to support the rings?
How wide to the rings need to be for high mileage durability?
This leads me to the next question.
What is the lightest durable piston?
In looking to improve fuel economy I want to find every opportunity to reduce weight. Rotating weight, reciprocating weight, and overall weight. In that order
How much flow do I need for my application?
What heads/ports/port size will barely flow that?
And have good flow characteristics (e.g. Swirl)
What influence does stroke have on this?
What magnitude of difference does swirl make?
How much difference will it make on power, torque, fuel efficiency, etc.?
What other head questions should I be asking?
Gears. Not so much questions but numbers that need to be determined.
What is (and should) the engine speed be at 70 MPH?
Automatic or manual transmission and which specific one.
Transmission gear ratios (especially at 70 MPH).
Differential Ratios
Tire diameter (and circumference)
Carburetor Selection.
What carburetor should be used? (Things to consider)
Price
Tunability
Fuel Atomization
Squarebore vs spreadbore
Mechanical vs vacuum secondaries
Flow capacity
Anything else?
Clearly this plays into the manifold heat question. Frankly, right now the finely atomized mixture going into a heated manifold appears to offer the best possibilities for both complete fuel use and consistent air/fuel ratios. On the other hand, a higher intake air temperature will likely lead to needing a lower compression ratio which brings me to:
Compression Ratios
What is the maximum compression ratio that I can reliably use with poor quality fuel in all anticipated air temperatures and applications?
I know that this rig will be operated off road at low vehicle speeds (crawling) in higher temperatures. Engines can get pretty hot in these conditions. This means I'm going to need a good. . .
Cooling System
What radiator and water pump am I going to need to make sure that this engine never runs hotter than it wants to?
What other parts should I be looking at for this?
High volume water pump.
Big radiator (but how big?)
High flow T-stat.
Anything else?
Rings
Are total seal rings durable enough?
ANWSER – Yes! It would appear that Total Seal rings are durable enough in some variation. Supposedly good for 100k miles.
How much do they cost?
What would the ideal setup be? (i.e. What should the top, second, and oil control rings be?
What is the difference between standard and low tension rings?
Are there suitable cheaper alternatives for the first build?
Are these alternatives worth the decreased performance for the decreased price? (And vis versa)
Engine Block
Price and availability of good used 350 and 400 blocks.
I'm thinking that the 400 is more trouble than it is worth but I should definitely check it out.
Reliability of the siamesed cylinders.
What problems are there? (Specifically with regard to over heating)
What solutions are there to these problems?
Are these solutions adequate for my reliability standards and the temperature extremes likely to be encountered by the Jeep?
I am inclined to think that the 350 is the best choice for this application. First there is, as far as I know, a large supply of 350 blocks but not 400 blocks, so a 350 block will be cheaper. Second, the cylinders in the 350 block will have coolant circulating all around them and more surface area is always good for cooling. Third, the 350 block does not, to best of my knowledge and unlike the 400, have a reputation for having cooling problems. That said, I would like to know all I can about the 400. I may be using a 400 type block in the future (I have an idea for project #004 or #005 where I build a high reving high output engine for a corvette but that is way out in the future).
Oil Pumps
High pressure pumps. Why and why not.
What is the deal with oil pumps? Some engines run 15 psi and others run 60-90 psi. Why? What is the deal with high volume oil pumps? Only so much fluid can be pumped through a restriction at a given pressure. I hear people say that you can pump the pan dry with a high volume pump. This seems unlikely to me if the pressure is the same. People who I look to as a “Christ-like” source for automotive information like David Vizard say that high volume pumps can flood the engine with oil and should only be used if there are things like oil coolers in the line. I have yet to hear David Vizard discuss exactly what theory supports his assertions. As I said before, you can only force so much fluid through a restriction at a given pressure.
As I see it now there are two things about high volume pumps. One, you may get oil to all the parts faster with the higher volume. Two, it seems like the pressure relief bypass will get a work out relieving all the pressure from trying to pump more oil than will fit at the pressure.
What applications are universally agreed upon to need high volume pumps?
High pressure. Why? I have heard that if you don't do it right, the high pressure oil can blow the face off your bearings.
Since your engine will rapidly become so much scrap metal if it doesn't get the oil it needs, this seems like an important question to answer. This rig will be going deep off road. Reliability must be absolute.
Oil Pan
What kind of oil pan should I use?
This falls in a similar category as the oil pump. The pump can't deliver oil that isn't at the pick-up. So how does the oil pan influence that? Do I want extra volume? Is there a particular pan shape that will more reliably keep oil at the pick-up when the vehicle is being operated at extreme angles? Are extreme angles analogous to high cornering forces? Will the pan interfere with the high travel suspension? What about windage trays? What about baffles? What about oil scrapers? I believe that the 4” stroke will require a different pan.
I think that actually covers it for now.
Today I leave this city, wait in another city for a few days, and then fly out to the next country. I feel reasonably confident that I will have the time and resources to begin researching these questions in depth.
I will be off-line for the next four or five days so the three of you who are reading this will just have to wait for the next thrilling installment!
Builder
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