B210 A13 with 728 round port cylinder head...

[Stoffregen Motorsports]

On 11/4/2022 at 8:35 AM, Stoffregen Motorsports said:

Just curious why you're bent on maximizing your MPG. Is this a pet project or are you really trying to save money?

Touchy subject?

[Stoffregen Motorsports]

I need an A series 5 speed for a project of mine. Got one laying around?

Edited November 5, 2022 by Stoffregen Motorsports

[datzenmike]

HRH (Matt) did some crazy stuff with his D21 Hardbody, like a sheet aluminum pan on the underside to reduce air turbulence and drag.

[74 B210]

I have 63 5 speed trans a home bought from a junk yard in yuba. but the tail shaft housing where the rear seal is has a piece of metal broken, the housing that holds the rear seal in..  I would sell it for 275.  I dont know what condition the gears are in.. it does shift between gears on the ground..

 

[74 B210]

Thanks mike.  I have to tune the engine more and maybe swap out for my A15 and see what it can do.. to find the optium engine combo.  its fun, but sometimes,

frustrating when things dont happen.. DATSUN is  a harsh teacher sometimes.

[datzenmike]

Increasing the displacement is a huge MPG penalty. Generally smaller is better.

 

A friend bought our neighbor's '70s Ford Country Squire station wagon with a 460 cu in engine. I expected about 8 MPG (and probably right for in town driving) but on the highway at speed and continuous it gave an unbelievable 24 MPG. With the right gearing the 460 just idles along.  

[Stoffregen Motorsports]

There's a general rule that I've had in my cerebrum forever that says a smaller bore pulls a stronger "pulse" through the intake allowing for more accurate fuel metering, and thus, better mileage.

 

It's been in my databanks for so long and I don't know where I learned it. What do you think Mike? I know you're big on theory.

[Stoffregen Motorsports]

13 hours ago, 74 B210 said:

I have 63 5 speed trans a home bought from a junk yard in yuba. but the tail shaft housing where the rear seal is has a piece of metal broken, the housing that holds the rear seal in..  I would sell it for 275.  I dont know what condition the gears are in.. it does shift between gears on the ground..

 

I'd be interested in the 5 speed. Can you snap a pic for me? I'm not local to you, but not far either.

[datzenmike]

5 hours ago, Stoffregen Motorsports said:

There's a general rule that I've had in my cerebrum forever that says a smaller bore pulls a stronger "pulse" through the intake allowing for more accurate fuel metering, and thus, better mileage.

 

It's been in my databanks for so long and I don't know where I learned it. What do you think Mike? I know you're big on theory.

 

Some theory mostly opinion.

 

If you mean same displacement but different bores then the stroke would be different and in that case if the rods could be any length, say shorter OR longer pin height, it's possible to have both pistons at their maximum speeds at the same degree on the crankshaft rotation. Maximum piston speed is when the crankshaft arm and the rod are at 90⁰ to each other. The long stroke would be going faster to cover longer distance on a smaller bore, but filling the same volume.

 

If the rod lengths were the same then the longer stroke would reach maximum speed ahead of the shorter but would it be filling the cylinder faster ahead of the short stroke? The end volumes are the same but the cylinders would fill at different rates following the piston speeds. The longer stroke would have a suction peak ahead of the short stroke though they may be the same.   My head hurts from thinking about this. 

 

 

 

 

[Stoffregen Motorsports]

Blah blah blah, piston.

Blah blah blah, stroke.

Blah blah blah, cylinder.

Blah blah blah, volume.

 

Yes, theory is a great place to live. It must be right next door to bliss.

[74 B210]

Hey guys how goes the debates.  I have been thinking I am only getting 38 to 40 on the freeway doing 60mph, Can my engine not have enough compression cause no cylinder head will help or make more mpg if the engine is weak. my compression test data shows 150 to 155 on cylinders #1 dry 155, wet 160, #2 dry 150, wet 155, #3 dry 152

wet 162, #4 dry 155, wet 161... I bought the car with 26 OG miles on it, it sat for 20 years, the cylinders look good when I pulled the head. sorry the pics are too big to show...

compression was done with a hot engine, all plugs out, and throttle open.

[Stoffregen Motorsports]

38 to 40 and you're not happy?

 

You have to put this into context. The old engine was not designed with lightweight components like modern cars. Neither was the chassis or drivetrain. Weight of those components, especially reciprocating components, has massive amounts of energy lost.

 

As a fun experiment, it would be great to see how much one could do to an old engine like this, in the name of economy. You'd have to lighten the rods, the crank and pistons, use low tension rings, single row timing chain, thinner valve stems, hollow pushrods... Where would one stop?

[74 B210]

What about the compression? If the engine is low on compression nothing will help the economy. What the stats on a13 engines?

[Stoffregen Motorsports]

I don't know the stock CR on an A motor, but I bet it's in the 8.5:1 range.

 

Yes, low compression is going to affect economy. Have you done a leakdown test? Not a compression test, a leakdown test is different and tells you more.

[74 B210]

 No. I didn't do a leak down. I have to buy the kit. But head was rebuilt like new. It's mint.

[datzenmike]

 

 

What head came stock on the A13 and what was the chamber size? Have to know the combustion chamber sizes on it and whatever you put on it to know if there is an increase in compression. You may have put a larger combustion chamber head on your engine.

 

155/160 is.... ok. but an 8.5 to 1 compression I would expect compressions above 170. A compression test with the original head would give you a comparison between the two.

[74 B210]

sorry too clarify, those are the old compression number on a stock H62 head I believe.  so the old compression data  I have. is 

on bone stock engine 1974.  the FSM says 178 to 206 PSI And I did adjust the valve lash to specs.... I have not checked the new compression numbers 

with the new head.  so if the compression is down 10 20 percent, would a ring job bring the compression back up???

[74 B210]

would a header make the engine more efficient?  I seen articles for economy and they advised against it, that the stock exhuast manifold is fine 

and pipe. I am not running high rpms either only up to 4k. usually runs around 2500 to 3200 power band.

[74 B210]

I am getting all the mpg data and tips and tricks for  the article done datsun 1200 site. A completely different A series build.  he managed

to get very good numbers, and I would be happy at 50mpg,  so I am trying to replicate my motor to match his, so if the A13 doesnt pan out

I was thinking of building my A14 like mike kamms A14 with a 990 head. but he was running a header with 2 inch exhaust, I want to try and keep

my stock exhaust.  he also ran no alternator.  I took out my fan and run a electric setup. I would also want my A14 to have great compression and I have dished

pistons for it but if it need s a rebuild to get like new numbers I will do that, but it might only need a ring job..  I was up in cool CA this week, dang I could have brought the

63 5 speed trans by for a look see.

[datzenmike]

As you are not going to be revving very high you want good air speeds in the intake and the exhaust system so larger ports and valves and a 2" exhaust isn't much help, even harmful. High intake/exhaust velocity increases inertia so that when the valve closes the air can't help but keep moving towards it. When it opens the air has built up slight pressure and pushes it's way in for free. A larger port and slower air will stop while the valve is closed and require the piston to move down and pull the air in increasing the work the engine has to do.    

[Stoffregen Motorsports]

34 minutes ago, 74 B210 said:

I am getting all the mpg data and tips and tricks for  the article done datsun 1200 site. A completely different A series build.  he managed

to get very good numbers, and I would be happy at 50mpg,  so I am trying to replicate my motor to match his, so if the A13 doesnt pan out

I was thinking of building my A14 like mike kamms A14 with a 990 head. but he was running a header with 2 inch exhaust, I want to try and keep

my stock exhaust.  he also ran no alternator.  I took out my fan and run a electric setup. I would also want my A14 to have great compression and I have dished

pistons for it but if it need s a rebuild to get like new numbers I will do that, but it might only need a ring job..  I was up in cool CA this week, dang I could have brought the

63 5 speed trans by for a look see.

Header...maybe, maybe not. Two theories - back pressure and flow. The two opposing theories both have evidence that back up the science, but they are opposing theories, so it would be trial and error.

 

Dang it. I would have bought it if you brought it...

[datzenmike]

I would call back pressure resistance to flow. Not a problem at low RPM and light throttle even with the crappy stock exhaust manifold.