Quote:Yes I have considered the E15 or E16 engines [we never got the 13's in the US]. It's OHC design should be more efficient than the A-series. I love the 15M cylinder head with it's 17.9 cc chambers. Flat tops yield over 13 to 1 in those. I have one ready to go here, but have not figured out the flywheel and starter dilemma to mate the A-series RWD trans to it. For one thing, the starter is mounted 180 degrees differently between the two.

No worries though, as I unearthed a '74 B210 parts car today with an A13 in it. Now I need a set of standard bore A12/A13 factory flat top pistons. Nissan Motorsport used to sell these to us in the US [I believe they are simply standard issue Euro pistons] but are no longer available. The part number was 12010-H2361 for the standard bore set.

Do any of you have a set? New or used, it doesn't matter.

Mike

Wonderfull. Now on a slightly different track, can I ask you to send me, via e-mail, a picture of the engine number for my records.
In fact, some gratuitous pictures of the whole engine & some more of it during th teardown process & I would be eternally in your debt.

As you no doubt are aware by now, particularly if you follow my rantings, there were two different A13's, The long stroke/small bore [1974-USA only?] version that you now have with it's 1288cc & the big bore/short stroke version that was used in Asian market B310/Sunny's which displaced a paltry 1270cc

All of the A13's I have so far encountered are the later short stroke versions that use the format A13 xxxxxx A & I suspect that the 'A' suffix is what differentiated the two variants of this engine designation.

As for the flat top pistons, it's the A10 piston that you seek. In Australia these came only in the rear drive B10 cars but elsewhere they were also used in front drive Cherry's, however I have no idea if these pistons were flat top or not.

Does your A13 engine use hot spot manifold heating, or is it like the A14 head with water heating?

I will be happy to document everything about this engine. I too, look forward to learning about the differences of the two different style A13's being discussed. However, I must clarify my earlier statement where I used the word "unearthed". I meant that a co-worker told me about the car and that he promised it to me. I don't physically have it in my possession yet. It's in the woods and will be difficult to get out [but I will prevail, trust me]. The property owner said that he will allow me to get it on Monday the 15th. The car was parked with 125.000 miles and is believed to be 100% original, so it should be an A13. I sure hope they had antifreeze in it!

Quote:I'm sure it wiill be the hot spot type manifold as I believe the water heated intakes and heads did not appear in the US until '79. Which style intake would you guys think to be more efficient for fuel mileage the hot spot or the water type? I'd think the hot spot type would be hotter [which should be better for fuel economy right?].

I don't agree, but don't have the proof to back up the statement, but consider the following.

The hot spot is just that, a 'spot' while the remainder of the manifold is still technically 'cold'
The coolant passages in the later manifold run underneath the intake runners & under the carb in the 'hot spot' position, thereby heating the whole thing from the bottom which is where unvapourised fuel droplets would tend to migrate.

These water heated manifolds were introduced at a time when the smog laws were becoming more & more strict. The emissions that are measured include unburned hydrocarbons. This is unburned fuel & in order to get this number down, & fuel mileage up, it is necessary to convert ALL the fuel to a gas because it is ONLY the gas that actually burns. Fuel in a liquid state does not actually burn, so unvapourised droplets were finding their way into the exhaust.
This unburned fuel was not producing useable power & that's bad for the owner [wasted fuel] & bad for the planet.

To maximise the return in an economy engine, every micro droplet of fuel must be converted from a liquid to a gas & heat is the only real way to do it. Remember that there is a substantial temperature drop as the air & fuel pass from the atmospheric pressure of the world outside the carb & manifold, to the high vacuum world inside the manifold.
The conversion from liquid to gas absorbs a great deal of heat, particularly in a near vacuum which is what you are trying to achieve in economy cruise mode, so it's necessary to replace at least some of it with manifold heating.

Using a 'winter' thermostat with the highest setting you can find will also be good, after all, ... all of the the late model, smog compliant & amazingly thrifty new-car engines run at temperatures undreamed of not so long back. These elevated operating temperatures are a part of the overall engine management strategy for good reason.

The more fuel that you can convert to a gas, the less fuel that the carb needs to pass into the airstream in order to achieve the best air fuel ratio & in the end, the purpose of the exercise is to pass the smallest volume of fuel into the intake airstream & still have the engine running well, it's really as simple as that. This is why I have been advocating warm air induction to the carb, although there is a limit to just how hot this air shouls be. It's ALL about making combustable gas from unconbustable liquid & at the very low power settings that this engine will be running at, with the relatively low gas velocities in the intake tract, this lower density of the heated intake air will have no negative effect on engine operation whatsoever.

Looking forward to seeing how this pans out.
I'd say 'more power to ya' but that's not the purpose of this exercise is it.

I think the hot ticket may be a fuel injected A13. Do you have access to an A13? I think that the longer stroke coupled with the small bore diameter would yield better torque in the RPM range that you are seeking to run in. Other good suggestions that I have seen in this thread have been the 3.54:1 final drive and the 5-speed box to hold the revs down. The round port early A12 head with the quench chambers should yield a good compression ratio with reasonable pistons. Some of the things that make power also make an engine more efficient for the purposes of economy. Smoothing the short turn radius a bit (not polish as that will separate the fuel from the air mixture), a good valve job as cylinder filling will equate to less throttle position for a given power output to maintain speed. Good luck and keep us posted on the results.

Quote:Yes I've located one and should have it in a week or so. Yes, I have read that a small bore and longer stroke is a good combination for economy. Quote:I will, and thanks for the excellent suggestions.

Mike

Dodgeman,

Great explantion. I like your reasoning regarding the water heated intakes likely being more efficient. My 990 casting round port "mpg" head is of the water heated type. I've got to keep searching for a matching '80 A14 round port intake. If anyone's got one please let me know.

I definately plan to duct heated air into the air cleaner.

Mike

Yep, I would vote for the water heated intake manifold also. Hot air induction is also a mandatory setup for maximum economy. The US spec air cleaners have a thermostatically controlled hot air system that provides 2 benefits. 1- The hot air helps vaporize the fuel. 2- thermostatically controlled intake air temp removes one of the major variables for carburetor tuning. With the intake air at a constant air temp the carburetor can be tuned much more finely.

The 1200 and B210 air cleaners are pretty much the same. The B310 air cleaners added a flexible plastic cold air pipe that pulled in air from outside the engine compartment. The cold air source allowed the thermostatic control system to work at higher outside ambient temperatures.

Does anyone have a recommendation for a spark plug heat range for this hot air high compression A13 I'm building? Just stay with the stock replacement plug?

Or would you go up or down a heat range?

Mike