L18 Pistons

[brodster]

Okay I have held out and researched for as long as I can, but I can’t find a solid answer. Currently, I have a L20b with a U67 head. I am trying to push the CR up a bit, but nothing crazy. The L28 flattops would work but I am afraid for a street driven engine, this may be a poor choice because of detonation. I don’t want to run octane boost, but I am okay with Supreme. My current plan is to use the L18 pistons with the ~4cc dish. Considering all the variables, this should put the CR at ~9.5:1.

 

The problem is I am going nuts trying to find a L18 piston (30 over) with a VERIFIED 4cc dish. Kb-silvolite has the 9048 and 9071. The 9048 from my rough calculations and talking to Hainz is pretty much a stock L20b piston with 11cc dish. The 9071, from my rough calc has a bowl of approximately 18-19cc. Who knows what that was intended for? Turbo? ITM/Repco offers a L18 1770cc piston for the 610,620 710: RY2656. However, it also lists this as compatible with the L20b, which considering bore size, etc. is true. Unfortunately I found another website that lists the RY2656 with a 3mm deep bowl. And from pictures of NOS repco RY2656 pistons on Ebay, it sure looks like a stock L20b dish. The other L20b piston from ITM is RY6102. Not sure what the difference is. Federal Mogul has some pistons too, but again I cannot verify the dish on them.

 

Right now I am trying to find the OEM L18 + 1mm pistons (12010-A8706). Nissanparts.cc lists them at 58.48 a piece. If they are not NLA, I would be willing to cough that up, but the compatible rings per the How to Modify book list part number 12038-A8702 for the compatible OEM rings. Price 98.46. I hope that is not per piston, but I am not sure how else they would list it. Right now I have one of their customer service people looking into the parts.

 

Does anyone know of any verified 4cc dish L18 pistons?? Anyone running the L28 flattops with a U67 head on street gas? (I think that one has been discussed before).

 

Thanks

 

 

[banzai510(hainz)]

run stock pistons and get closed chamber head to pump to close to 9 cr and better detonation on closed chamber head.

 

If you want to run the U67 head you have cuase its good just run the stock piston. spend moeny on head,cam duel carbs or turbo.

 

that part# I gave you for the Sealed Power could have been Fed Mogel also 12159P as it is a L18 4cc dished piston.

[brodster]

run stock pistons and get closed chamber head to pump to close to 9 cr and better detonation on closed chamber head.

 

If you want to run the U67 head you have cuase its good just run the stock piston. spend moeny on head,cam duel carbs or turbo.

 

that part# I gave you for the Sealed Power could have been Fed Mogel also 12159P as it is a L18 4cc dished piston.

 

I do have access to a W53 head that needs to be gone through, but I got a smokin deal on a U67 that is completely rebuilt with match porting and regrind street cam.

 

So I searched your part number on Summit and got the following: http://www.summitracing.com/parts/SLP-12159P-75MM/

 

When I go through the drop-down menus and looked for Sealed power pistons on a 1770cc L4 Nissan I get the following: http://www.summitracing.com/parts/FEM-12159P75MM/

 

I am assuming here that Federal Mogul= Sealed Power = Sterling? I am not sure why there is a price difference.

 

I did a rough calc on the dish specs on the latter part number and it came out to <5.5cc. That is the right piston. Thanks!

 

BTW, in your experience, how does Federal Mogul compare to say ITM pistons, etc.?

[maredlin1@hotmail.com]

I've found you canot get a straight answer on this site! Good luck.

[bilzbobaggins]

^ huh?

[ggzilla]

Does anyone know of any verified 4cc dish L18 pistons?

that part# I gave you for the Sealed Power could have been Fed Mogel also 12159P as it is a L18 4cc dished piston.

Which part number?

[DanielC]

"I've found you canot get a straight answer on this site! Good luck."

  

Sometime the answer to an exact question is not there.  But there is useful information.  If the question has been answered several times, it kind of proves you did not bother to search for an answer first, and we tend not to spoon feed you.

 

If you really need -4 cc dish pistons in an odd sized overbore, maybe you need to get a burette, and measure that yourself.

 

I know this seems odd to many people, but when looking for Datsun parts, you would be surprised what is still available at Nissan dealers.

[banzai510(hainz)]

I have these 12159P in my stash soemwhere . and yes its 44cc dished.

I got them from a website that now is defuckt.

[maredlin1@hotmail.com]

I'm like Brodster, waiting to be spoon fed, what 4cc dish 86 mm piston fits a L20b ?

[Doctor510]

Stock early 280Z, stock for the Z , .040" (1mm) over for the L20B

[datzenmike]

I've found you canot get a straight answer on this site! Good luck.

 

Not seeing where you did not get a straight answer.

 

Maybe your question wasn't straight either. Here are all the topics you started

 

 

 

Was the 0.773 fifth gear ever factory installed in the old style case having the two ear muffler hangers and the speedo bolt at 12 o'clock position ?

 

 

 

No.

 

It was only on the later 1980 280zx for the one year.

 

 

 

 

I am going to put a 1980 280zx 5 speed into a 1978 620 pickup. my question is will the 1980 280zx flywheel bolt up to my 620? I heard the 280zx flywheel is lighter (which is what I want). Also if it fits, what throw out arm, throw out bearing, collar and clutch assembly do I use? Or is it even worth the effort.

 

 

 

Sorry if I offended you, but I am a Nicky New Guy to the site.(actually sort of confusing). I am going to use the 5 speed transmission from a 1980zx. I still have not got a response to my questions (it's a daily driver like a car)

1

Is the flywheel lighter ?

Yes, about 21 pounds down from 29 pounds.

 

 

2

Will it bolt up to my 78 l20b 620 pickup ?

Yes it will bolt right on to your L20B engine. However you will find that taking off from a start will require slightly more revving and clutch slipping now and even more if carrying a load. This is because a lighter flywheel stores less kinetic energy to get a heavy truck off to a start. If you do a lot of in town stopping and going this is annoying. A lighter flywheel isn't going to turn your truck into a race car.

 

 

3

Would I use a 280zx clutch assembly or a 1978 l20b 620 assembly (I believe they are the same)

 

You could use either but I recommend the 620 one as you have the matching release collar or sleeve for it already. If you have the zx sleeve then you could us the zx clutch...

 

4

What throw out bearing, clutch fork, and what sleeve to use ?

All throwout bearings are the same

Use the truck fork, it's the same as the zx fork.

The sleeve is covered in 3 above

 

http://community.ratsun.net/topic/65700-cylinder-head-exchange-or-rebuild/?do=findComment&comment=1220008 answered.

 

http://community.ratsun.net/topic/65788-l28-pistons-in-l20b-620/ also answered

 

http://community.ratsun.net/topic/65903-1980-l20b-installed-valve-stem-height/ also answered.

[Stoffregen Motorsports]

I've found you canot get a straight answer on this site! Good luck.

Somebody's got sand in their vagina.

[Stoffregen Motorsports]

Price 98.46. I hope that is not per piston, but I am not sure how else they would list it. Right now I have one of their customer service people looking into the parts.

 

 

Custom pistons cost little more than that.

 

I wouldn't be afraid of running 10:1 CR. With the right cam and proper distributor curve 10:1 is perfectly fine on the street.

 

And also, as mentioned above, a burette and a bit of engine math will get you your answers far quicker than the internet.

[scooter]

Throw the flat tops in it and TUNE IT

[ggzilla]

10:1 is best with common Premium gasoline, use flatttop pistons and closed chamber head.

 

If you use dished piston you need to lower the compression ratio to avoid detonation. Quench only works with flattops.