3 or 5 main

[BAMUZ]

Been doing some research on the r16–
And have come across forum posts talking about 3 main 5 main
I’m sure this has been beat to death as the posts I was reading were pre-2010
Buuuutttt uuhhhh

What’s the difference, and how do I tell which one is which?
I seen something about sae heads vs metric (bolt) heads

Haven’t found a post talking of the clear differences of each
Looking into strokers and came across the 3 or 5 talking point

[Habitat.pat]

Early 1600 engines were 3 main & later were 5 main. The switch occurred @ engine #40,000.

I’ll post more later this evening.

[DAC21]

Been doing some research on the r16–
And have come across forum posts talking about 3 main 5 main
I’m sure this has been beat to death as the posts I was reading were pre-2010
Buuuutttt uuhhhh

What’s the difference, and how do I tell which one is which?
I seen something about sae heads vs metric (bolt) heads

Haven’t found a post talking of the clear differences of each
Looking into strokers and came across the 3 or 5 talking point

Have a look at my picture (red circle) That is where you will find your Engine number. R-XXXXX. If the number is under 40,000 you have a 3 main SAE engine, above 40,000 a 5 main metric. Difference? mostly internal parts / bolts are not interchangeable. I believe there are some exceptions like gaskets that others can talk to.

roadsterblockidA.jpg

[BAMUZ]

Been doing some research on the r16–
And have come across forum posts talking about 3 main 5 main
I’m sure this has been beat to death as the posts I was reading were pre-2010
Buuuutttt uuhhhh

What’s the difference, and how do I tell which one is which?
I seen something about sae heads vs metric (bolt) heads

Haven’t found a post talking of the clear differences of each
Looking into strokers and came across the 3 or 5 talking point

Have a look at my picture (red circle) That is where you will find your Engine number. R-XXXXX. If the number is under 40,000 you have a 3 main SAE engine, above 40,000 a 5 main metric. Difference? mostly internal parts / bolts are not interchangeable. I believe there are some exceptions like gaskets that others can talk to.

roadsterblockidA.jpg

Okay interesting, thank you!
So it seems like knowing whether one’s engine is a 3 or 5 main would matter when it comes to ordering replacement engine parts and bolts, correct?

Just want to make sure I understand this crystal clear lol—just found out about this!

[DAC21]

Been doing some research on the r16–
And have come across forum posts talking about 3 main 5 main
I’m sure this has been beat to death as the posts I was reading were pre-2010
Buuuutttt uuhhhh

What’s the difference, and how do I tell which one is which?
I seen something about sae heads vs metric (bolt) heads

Haven’t found a post talking of the clear differences of each
Looking into strokers and came across the 3 or 5 talking point

Have a look at my picture (red circle) That is where you will find your Engine number. R-XXXXX. If the number is under 40,000 you have a 3 main SAE engine, above 40,000 a 5 main metric. Difference? mostly internal parts / bolts are not interchangeable. I believe there are some exceptions like gaskets that others can talk to.

roadsterblockidA.jpg

Okay interesting, thank you!
So it seems like knowing whether one’s engine is a 3 or 5 main would matter when it comes to ordering replacement engine parts and bolts, correct?

Just want to make sure I understand this crystal clear lol—just found out about this!

Correct, you can go to Datsun roadster parts .com and look at engine parts and get a feel for the different parts between SAE / Metric for the R16 motor.

[BAMUZ]

Correct, you can go to Datsun roadster parts .com and look at engine parts and get a feel for the different parts between SAE / Metric for the R16 motor.

I really appreciate that, thank you
And if there aren’t numbers there , is there another way?
On the other side the block says Japan Datsun

[BAMUZ]

Shot of both sides

[BAMUZ]

This was the engine that came out of my 70 1600 that’s goin vg30.
This would be a 5 main, right?

[DAC21]

Correct, you can go to Datsun roadster parts .com and look at engine parts and get a feel for the different parts between SAE / Metric for the R16 motor.

I really appreciate that, thank you
And if there aren’t numbers there , is there another way?
On the other side the block says Japan Datsun

No numbers means its not the original engine and was replaced with a new factory motor which didnt come with numbered engines. Possibly a under warranty replacement. I'm seeing some blue paint, if that's original then that's probably a metric engine.

[DAC21]

Correct, you can go to Datsun roadster parts .com and look at engine parts and get a feel for the different parts between SAE / Metric for the R16 motor.

I really appreciate that, thank you
And if there aren’t numbers there , is there another way?
On the other side the block says Japan Datsun

No numbers means its not the original engine and was replaced with a new factory motor which didnt come with numbered engines. Possibly an under warranty replacement. I'm seeing some blue paint, if that's original then that's probably a metric engine. I also don't see air injection holes in your intake manifold so it may well be a 1967.5 metric engine. If you have a thread checker tool you can take one of the two nuts off that retain your valve cover. One of them is right next to the oil cap in your photo. Metric engines will have a M8-125 thread on that nut. SAE engines have a 5/16-24 threaded nut. (Acorn nut is the correct style, but nothing to worry about until your ready to pretty things up)

[Curtis]

Engines numbered 40001 and above as noted are metric, mostly. Things to watch out for.
Aluminum heads can be either SAE or metric. Heads get swapped. Later heads have the lovely smog ports.
Head bolts are not metric.
Fittings such as for water and the oil line and temperature sender are BSP thread.

According to Ross Mullen and one other as near as they can figure Datsun began painting engines blue when they started putting aluminum heads on. That means engines might be SAE.

[BAMUZ]

Have the fuel tank off at the moment but it does run haha!
Here’s a couple shots of the engine farther out so more can be seen

[DAC21]

"According to Ross Mullen and one other as near as they can figure Datsun began painting engines blue when they started putting aluminum heads on. That means engines might be SAE."

That's what I though, but last year Les Cannaday assured me they were black on my early 1967, so who

[Curtis]

"According to Ross Mullen and one other as near as they can figure Datsun began painting engines blue when they started putting aluminum heads on. That means engines might be SAE."

That's what I though, but last year Les Cannaday assured me they were black on my early 1967, so who

Early 67 were supposed to have iron heads I'm told.

[DAC21]

"According to Ross Mullen and one other as near as they can figure Datsun began painting engines blue when they started putting aluminum heads on. That means engines might be SAE."

That's what I though, but last year Les Cannaday assured me they were black on my early 1967, so who

Early 67 were supposed to have iron heads I'm told.

Mine is aluminum, I was just trying to differentiate it from the half year model. Maybe I could have used a better choice of words.