Engine build ideas, need some help (looooong story)

[Stoffregen Motorsports]

Ok. Maybe not pointless, but kinda irrelevant now. Good info though for my future builds

Pointless, as far as you're concerned, maybe, but I'm trying to put the debate to rest, since we have it here on Ratsun quite regularly.

[flatcat19]

I can get my hands on new L18 pistons from EPWI for $26 a piece . Today.

I'd be willing to bet these are actually L20B pistons(deeper dish.)

 

L18s weren't around for long, so aftermarket has no reason to provide supply.

 

L18 and L20B both had same bore and piston pin height.

They will fit. But not the same.

 

L18 had a 4cc dish. L20B was 11cc?

[datzenmike]

L18 with L20B pistons and open chamber head........ 6.89 compression.

Above with closed chamber head............................... 8.14

 

Maybe they are just cheap....

 

[Stoffregen Motorsports]

I notice you don't say 'more' but 'better' and 'smooth'. Long rod engines tend to produce their power slightly higher in the RPM range than a short rod, so maybe this would 'smooth out' the power curve? If so great, why are not all Datsun engines with longer rods? Probably because no one drives them at speeds where any advantage is helpful. It simply does not matter.

 

At any rate, we were discussing red lines and 'rev happy'- ness. That long rods like to rev. I don't think they can alter metallurgical properties of them selves or the pistons and are still subject to the 4,00 ft/min red line. As mentioned, they do slow down more gradually towards TDC and add a safety margin. 

OK, so maybe a bit off topic, but it was brought up so I'm going with it.

 

They do make smoother power transitions across the board,  not just in the high RPMs.

 

It's not a coincidence that piston and ring technology was vastly improved around the time people starting building long rod motors. Before that, it was a matter of packaging a large ring pack on a low tech cast piston. Once the MFGs figured out how to make stronger pistons, they also figured out how to make smaller rings that were stronger than before, so now you could get a compact pin to crown height and longer rods.

 

And when you say no one drives them at those speeds...I bet a majority of the members here on Ratsun beat the snot out of their rides. I know I did, so that argument doesn't hold much water.

[G-Duax]

I bet a majority of the members here on Ratsun beat the snot out of their rides. I know I did

 

Not sure about the majority, but you can put me on that list.....

[bajango]

You're right. I asked the guy if it showed the CC on them in the catalogue but he said no. They could be L20B

[datzenmike]

A quick rev to 6K maybe in first 2-3 gears... this is what a street and auto X engine does. Maybe even touch 7k in first. No one drives around at 6k plus on a continuous basis outside of a race track.  

[datzenmike]

You're right. I asked the guy if it showed the CC on them in the catalogue but he said no. They could be L20B

 

Read post #28 L20B pistons would have deplorable compression.

[bajango]

It would HAVE to be L18 pistons. That would suck having L20b pistons in there. Anyway, I too like blasting my L16 to 6k+. Although I'm sure I'm not getting anywhere faster on the rock stock engine. I still like the idea of L28 flat tops and machining a little bit of a dish on the piston on the chamber side of a closed head. Kind of like this.

 

Though I'm sure I should just probably go the L18 piston route on an open head... If I cant find the Z20e rods and Z22e pistons

[Stoffregen Motorsports]

It would HAVE to be L18 pistons. That would suck having L20b pistons in there. Anyway, I too like blasting my L16 to 6k+. Although I'm sure I'm not getting anywhere faster on the rock stock engine. I still like the idea of L28 flat tops and machining a little bit of a dish on the piston on the chamber side of a closed head. Kind of like this.

 

Though I'm sure I should just probably go the L18 piston route on an open head... If I cant find the Z20e rods and Z22e pistons

That's a neat idea. How much are you talking about machining? There's not a lot of meat on the top of those pistons. A small offset dish to help quench the gasses wouldn't need to be that deep.

[bajango]

Its probably be more like a valve relief CC amount of dish to be honest. You're right that there's not a whole

Lot of material there. It's not a new idea by any means. Chevy did it before, but then the hemi-head idea left it to be shelved until pretty much the LS engine. I've only just now understood the concept. A good aircooled VW friend of mine came across the thread for the idea. We have a cool friendship of working on eachother's piles of junk and researching. Anyway, I think it'd be great if I could get 5 or more CC of dish though.

http://forums.hybridz.org/topic/63444-l6-squish-discussion-the-battle-against-detonation/

[datzenmike]

Here's my L20B slugs...

 

 

 

It would HAVE to be L18 pistons. That would suck having L20b pistons in there. Anyway, I too like blasting my L16 to 6k+. Although I'm sure I'm not getting anywhere faster on the rock stock engine. I still like the idea of L28 flat tops and machining a little bit of a dish on the piston on the chamber side of a closed head. Kind of like this.


Though I'm sure I should just probably go the L18 piston route on an open head... If I cant find the Z20e rods and Z22e pistons

 

 

L16 with L28 flattops. This would require the L16 to be over bored 3mm.... uuuuh I think that is too close to the limit. But for the hell of it...

 

That's a 1,712cc engine.

Open chamber head.....................  9.21

Closed chamber head................... 9.9

Stock L16 head............................ 10.42

 

For breathing run the larger valve U67 head and unshroud the shit out of it to increase the combustion chamber to get the CR down. If you could remove about 4ccs from each chamber the compression would be much better at 8.6.

[bajango]

Sorry mike, I was agreeing that I like to romp on my engines. I'm still talking about building my L20 donor. But man,. These engines must just HATE compression. Cuz all I've ever seen is peeps talking about CRs under 9.

[datzenmike]

Higher compression increases engine efficiency, it makes more with less. Higher compression risks pinging or detonation. Gas octane reduces the ability of fuel to self ignite. Gas today is crap compared to the leaded type in the early '70s. These old engines don't have the electronics for knock sensors and ignition retard to safe guard them. Pinging is not good for them and slight pinging is not good over the long term. You can do some thing to lower the risk ... higher octane gas? Well if you gain enough mileage through improved efficiency to pay for the extra cost (or close) then that's the way to go.

 

Say you get 27 MPG with regular and timing maxed at 8 degrees to prevent pinging and with 91 or whatever passes for high octane gas today to get say 30 PMG with the timing set at 10 degrees. On 10 gallon tank you get 30 miles extra. A tank of $2.20 and $2.50 is $22 and $25 for 10 gallons you paid $3.00 more and went 30 extra miles or saved one gallon worth $2.50. In this case you paid $3.00 to save $2.50 in gas. This is not always the case.

[bajango]

But then more smiles per gallon too ☺️. I run premium anyway, which isn't saying much. This Oregon has is kinda sucky

[bajango]

Could I benefit from a spray bar and if so, how can I get one?

[datzenmike]

Spray bars benefit after market cams with monster lift and stresses running at extreme RPMs. Otherwise the stock L series valve trail is marvelously engineered and long lasting.

 

If you want to do your cam a favor don't run the oils they have today. Year by year they are reducing the levels of a critical anti scuff additive called ZDDP. There are no engines made to day that need it in the formulas of the 60s and 70s. Those engines had flat lifters and needed extra scuff protection. In addition it clogs the new catalytic converters and ends up in the environment. Oil makers have cut the ZDDP levels to about half and say that the level is still good enough to protect our older flat lifter engines because the original amount was too high to begin with. Well this is one Datsun owner who isn't buying it. What I do is run a light diesel oil that still has the same level of ZDDP as the old gas engine oils. Then there is no risk of premature wear.

 

Oil? Chevron Delo 400 or Shell Rotella T in 15w40. In a pinch if you are away from home and need to top up, and can't find this, a qt. of anything will still be fine. Not the end of the world, but return to the Chevron or Shell for the next one.

[bajango]

I like to run the Vr1 racing oil by valvoline. It's competitively priced vs some of the expensive stuff like joe Gibbs racing. It has additive in it. I don't know how much, but at $6.30 I'm not overly critical about it. I can get delo easily, but there's just something about the number combination of 10w-30 that makes me happy.

[flatcat19]

Wow.

[bajango]

Wow.

???

[DanielC]

I just picked up some Valvoline VR-1 30 weight at Knects auto parts for $5.19 a quart.

[bajango]

I just picked up some Valvoline VR-1 30 weight at Knects auto parts for $5.19 a quart.

I might have to start shopping there... ☺️

[Lockleaf]

Delo comes in 10w30 now...

[Stoffregen Motorsports]

Straight 30 wt really turns me on.

[Lockleaf]

There's just something about engines that really calms me down