Building A L28 (Na)

[grannyknot]

Thanks a lot for the links, madkaw!

Thanks for the input, Jeff!

Triple Carbs is something I want, rather than something I need. I already have a pair of SU carbs rebuilt by Rebello (Sold along with the motor when I bought it) so I'm already set in that area. TW's is something I'm going to get more down the line.

Thanks for the tip regarding the harmonic balancer! These are things I would like to know regarding the build...things that have been learned through experience. I appreciate you sharing your knowledge! I'll definitely keep that in mind, now.

I messaged someone from HybridZ who is very knowledgeable about L28's and their different builds, and he advised against getting flat-top pistons in an N42 head, and instead, told me to keep the dished ones. He told me that time and time again, he's seen the flat-top swaps done and have seen the effects of detonation in the head. The power gained from the extra compression is therefore lost due to the need to retard the timing. Since I'm keeping the stock valves and aren't planning on boring anything, I think I should heed his advise and keep the dished ones. As I mentioned, power isn't too much of a motivator. Reliability and responsiveness is what I want. A lighter flywheel is up there on the list!

Thanks a lot, again, for all of your help guys! It means a bunch.

I have a F54 block, N42 head that has been heavily worked with flat top pistons.

Compression was 10:1 and I was chasing ping. Tried cooler plugs, higher octane, richer settings, none of it helped. Bought a 1.5mm steel head gasket and the ping is gone and now I can finally use full advance. A longer duration cam will also fix the problem if you do end up with ping.

I'm looking forward to this build.

Chris

[TheCrazySwede]

I have a F54 block, N42 head that has been heavily worked with flat top pistons.

Compression was 10:1 and I was chasing ping. Tried cooler plugs, higher octane, richer settings, none of it helped. Bought a 1.5mm steel head gasket and the ping is gone and now I can finally use full advance. A longer duration cam will also fix the problem if you do end up with ping.

I'm looking forward to this build.

Chris

Thanks for the input, Chris!

I looked into the compression changes due to gasket sizes, too. I wanted to higher the compression with the flat-tops, and then get a slightly thicker gasket, like you, to compensate. I'm in Cali, so I gotta make due with what I've got.

Block still getting bored!

[rbates]

grannyknot - I'm assuming the higher octane (octane boost ?) allowed you to advance your timing ? I'm in a similar place to you, but still debating in my mind the thicker head gasket solution. For me I'm not sure there will be a net Power gain (what you gain in advance you lose in CR). Guess only a Dyno will be able to confirm one way or another.

[grannyknot]

In my case I had a powerful engine that could not use more than 27* advance no matter what I tried, we have 94 octane available here and I was adding booster to it.

I'm very happy with now.

grannyknot - I'm assuming the higher octane (octane boost ?) allowed you to advance your timing ? I'm in a similar place to you, but still debating in my mind the thicker head gasket solution. For me I'm not sure there will be a net Power gain (what you gain in advance you lose in CR). Guess only a Dyno will be able to confirm one way or another.

[LeonV]

grannyknot - I'm assuming the higher octane (octane boost ?) allowed you to advance your timing ? I'm in a similar place to you, but still debating in my mind the thicker head gasket solution. For me I'm not sure there will be a net Power gain (what you gain in advance you lose in CR). Guess only a Dyno will be able to confirm one way or another.

Compression ratio by itself doesn't boost power all that much. Proper spark timing is much more important.

[madkaw]

Combustion chamber design! The N42 head is an open chamber head with no quench pad thus not a great match for flat tops. Pretty sure Nissan knew that so they matched it with dished pistons. If you really study some of the "pundants" of the L engine over at hybridz they sneak out some tid bits of Lagata power formulas. 'Squish'( piston to head clearance/distance) is essential for fighting detonation and there are zones to avoid.

The 42 can be made better with some welding and reworking, but there are better alternatives like the p-79, p90 early Z heads like E31 or early E88.

Then there's timing curves as Leon mentioned. It's all in the details.

I would consider a different head, especially if the one you have needs rebuilt. Spend some money on a different core and rebuild it. Then you can use a stock Nissan sized gasket and not worry so much about pinging.

The CR numbers don't matter much if you can't run aggressive timing.

[grannyknot]

^ "The CR numbers don't matter much if you can't run aggressive timing"

I can't tell you how long it has taken me to learn that lesson.

The right cam (for what you want from the engine), proper valve adjustment,

proper timing. Get those 3 right and your halfway there.

[CG240Z]

My setup is somewhat a mixture of everything. Using a block from a '79, N47 head, flat top pistons, and stage 1 cam. Also it's fuel injected and I can only get 91 octane. Have about 400 miles on it right now. So far so good, engine is smooth and it has an awesome idle with the cam and header. Still tweaking the fuel mixture.

[TheCrazySwede]

Combustion chamber design! The N42 head is an open chamber head with no quench pad thus not a great match for flat tops. Pretty sure Nissan knew that so they matched it with dished pistons. If you really study some of the "pundants" of the L engine over at hybridz they sneak out some tid bits of Lagata power formulas. 'Squish'( piston to head clearance/distance) is essential for fighting detonation and there are zones to avoid.

The 42 can be made better with some welding and reworking, but there are better alternatives like the p-79, p90 early Z heads like E31 or early E88.

Then there's timing curves as Leon mentioned. It's all in the details.

I would consider a different head, especially if the one you have needs rebuilt. Spend some money on a different core and rebuild it. Then you can use a stock Nissan sized gasket and not worry so much about pinging.

The CR numbers don't matter much if you can't run aggressive timing.

So, I haven't started on the head, yet, although I have stripped it apart. So far, just done work on the block. Should I buy another head? I hear a lot of people going with P90 heads. Which one seems to have the best design?

[madkaw]

I don't know if there's a best or just one that might be better. Chamber design got better with the later heads as in the P-79 or P90. It's all in details though. You really need to study some threads over at Hybridz in the FAQ section under drivetrain or engines. Several good threads concerning the different year heads and how to modify them. Look over there and your line of questions will get more specific with more understanding.

[Nite_Grind]

Keep up the good work. I'm doing a oem rebuild/refresh to a l26. My first full engine build ever.

[TheCrazySwede]

So I visited the lads over at Rebello, and they advised against going for the P90, for a couple of reasons.

To start off, he mentioned how the quench pads in the P90 wouldn't leave much piston clearance if I went to flat-tops, and Dave had no idea how these motors made it out the factory.

He also mentioned how building a P90 head is not cost efficient at all, because you end up doing more work for not so much more performance.

What I was recommended was to stick with my N42, use flat-tops, and just compensate with a thicker gasket. I know there are some 2mm gaskets out there, but I can't seem to find one...according to OZDAT, it will give me a compression of 9.1:1.

I'm still debating if that's cutting it too close, running on Cali's pump gas. Would I have to run octane boosters? Do those things even work? Also, if anyone knows where I can find a good 2mm head gasket (getting the block bored .20 over, so I don't know if these things have to be retro-fitted after wards) I'd really appreciate it.