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which is best mod to do first?

679 Views 27 Replies 13 Participants Last post by  orange260z
i have a 1980 n/a 280zx. It has the dished pistons & n47 head. i currently have the head off to replace headgasket. While it's apart should i do a perf. camshaft? i was thinking about doing headers but i read in the archives that it won't gain much on a stock engine. I also read that a perf. camshaft doesn't help a lot without raising compression (i think that's what i read)?

maybe i should just take the plunge and get the f54 block from the junkyard & put my n47 head on it....

what do you all think?
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I'd "take the plunge". Theres not much as far as bolt ons go that will give you any appreciable power gains. Best way is to change cams and raise your compression. Or turbo.
port the heck out of the head, raise the compression to about 10 to 1 and change the cam and stick a header on it.
Does the l28 not respond to mods like old v8's cause it already has effecient spark burning, heads, intake, fuel injection, etc?
Essentially yes. The domestic V8's, even todays, still respond much better to mods than most imports do. For a current mustang you can generaly get 10+hp from exhuast alone but on an import 6 cylinder you are lucky to get 5 unless you are running a turbo. Back to the older cars, my girl friends Ford 302 gained much more hp and dropped more in the 1/4 mile from basic bolt ons than my 280z did; lucky for me I'm still faster due to her gears. But in a sense yes, the L28's set up is pretty good stock. It has it's weak points such as the intake manifold and head but you won't really notice it until you start adding other mods.
Ha Ha. Watch a re-run of the History Channel "Full Throttle" to see what V8 type mods will do for you on a Datsun L-series engine.

The F54 block will not make any difference, at all, zero.

Either you will have to build up the engine from scratch an get 160hp, or go turbo and start with 180HP out-of-the-box that can be tweaked up to 200hp really easily.

For the heavier ZX, turbo is a nice way to go quicker.

An f-54 will make a big difference, contrary to what hybrid says above, because it IS a big difference! The flat top pistons in the f-54 will raise your compression ratio with the n-47 head nicely and will run much stronger that your stock motor.
If you are buying the whole engine, get an f-54 with a p-79 head, and put your n-47 on it and have fun while you take that p-79 head and port it, polish it, shave it, and build it with a new cam and valves. The combustion chamber shape of a p-79 head is more modern. If you are buying just a block, just make sure the pistons are flat tops.
as for the efficiency of our motors, they are choked by their own heads and EFI intake manifolds. Our heads' design is old. But porting, polishing, and bowl work will make a big difference, and either using a custom efi manifold or switching to carbs will help too.
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The BLOCK does NOT make a difference, the PISTONS do.
I say again, the BLOCK does not make any difference AT ALL. Stay with what you have and swap pistons since the block differences are irrelevant.
Piston sets show up here all the time for $50-$75 bucks and will simply drop into your block.


On top of that "cheap price" for piston-rod assemblies thatr "just drop into your current block" you neglect to add in the cost of honing the big ends round after you have the ARP rod bolts installed (another cost), or to add the cost of NEW rod bolts period.

You are not going to re-use a stretch bolt on a reciprocating assembly in a 'high performance' application when the factory says to NOT re-use them for a STOCK application, are you?

Therefore, swapping an F54 block assembly will probably be AS CHEAP as PROPERLY swapping the pistons into the bolck he currently has
(not to mention mismatched rings requiring honing to reseat, if not new rings altogether, etc etc etc)

A matched set of worn in rings,pistons, and undisturbed 180,000 mile F54 parts is a better bet than a junkyard abortion swaporama any day.

So I would say get the "block assmebly" as in "shortbolck assembly"...

Don't go parts-swappin, it never works out as cheap as everyone theorizes it will...
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But if you get a junkyard engine, you will need to recondition it anyway and use new rings, bearings, bolts, etc, etc. No such thing a s a free lunch.

Swapping in a set of flat tops while the head is off is also easier than a complete engine pull. If you want to pull the engine and you want an F54 assembly, you might as well go all the way to turbo.


Post Edited (Nov 15, 11:11am)

"But if you get a junkyard engine, you will need to recondition it anyway and use new rings, bearings, bolts, etc, etc."


The bottom end on an L-Engine is good for WELL over 200K! WELL OVER!!!

The assumption that a bottom end needs all this "reconditioning" is a total load of BULL$HIT!

NONE of my cars has LESS than 150K on the bottom end! My 75 currently has a donor engine that was installed from an 81ZX 2+2 with 186K miles on it, it now has 225+ on it. NOTHING BUT VALVE SEALS!

The 74 260Z I have has had nothing but a HEAD GASKET AND VALVE SEALS in it's 225+K mile life!

A Junkyard bottom end if running well has ABSOLUTELY NO REASON to be opened up and screwed with! You will CAUSE more problems that you will SOLVE!

At most, you put a turbo oil pump on it if you have the need for the flow, but the bottom ends are bullet-proof, and people here are requilding stuff that does not need it!

If you have compression at stock levels (my 75 is 185psi... it was at 186K miles, and STILL is at 225+) there is ABSLOUTELY NO REASON TO DISTURB THE BOTTOM END.

You do the math: I have driven almost 40K HARD MILES (ask anyone how I dirve the Z...) with nothing done!

This is a parrotting of DOMESTIC PARADIGM and is simply NOT APPLICABLE to a street driven and occasionally raced L-Engine! Swapping pistons in-car is a hassle, and if you are removing one engine mount, you may as well go the whole way!

MISMATCHED parts will not work out well, but a complete matched, mated, and run-in-together shortblock will OUTPERFORM THE MIX-Y-MATCHY block from day one and for the next 40K miles for a minimum.

And IF your mix-y-matchy parts finally do seat fully around 30K you MIGHT be up to the HP you got from a stock unmolested shortblock. But that is a BIG IF! There is no warranty that every cent you spent on rings bolts, etc will pay one dividend if it doesn't properly seat, and you have to do it all over agin! If the short block doesn't work in 30K miles, you can get another for $225, and do it again, having a spare to do PROPERLY, and not mix-y-matchy...

No, I would not scramble an engine. I would take the entire shortblock and go from there. Tehre will be less hassles in the swap. And in 40K miles, (if you keep the car that long) you can reevaluate. But by then, I expect mine to have close to 100K on it, so what will become of the theory then?

L-Engines need HEAD WORK, spend your money on that. Once the bolck is assembled, LEAVE IT ALONE! UNless you are going to spend the FULL BOAT MONEY and do it PROPERLY, you are better off with an unmolested factory-assemble short block with a reqorked head than ANY mix-y-matchy abortion riding under it!

This goes abck to the "Four Avreage Readers of the forum" contention. You simply don't "bolt on horsepower". A poor match of parts is asking for trouble. Put a good head on a worn-in block and run it. But you put a head on a set of mismatched used parts from three engines and half-ass it, you are LOOKING for trouble!
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Yes, that is a good plan!

Yes, that will probably work well if you want the raised compression of the flat-tops. Use an F54 Short Block as an ASSEMBLY ,and bolt your head onto it after spending money on the porting, cam, and proper setup of the head.
L-Engines wear out the heads well before the blocks.

If at all possible, do a compression check on the F54 before you buy it. That will tell you if you are getting a good one. Better yet, buy the WHOLE CAR if it's a runner! Beat dogs of ZX's are all over here for well under $500, and cheaper if non-runninng. YOu get a diffy that you want, a block, and parts to sell like the tranny, etc...

Horsepower is in the head on an L-Engine. Spend your money for valve seals, and head work, and you will be far better off.

Especailly if you F54 has less miles than your current engine!

And now you have a spare engien to really get busy with!

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Gotta Ask "WHY"

Have you ever torn down a 200K mile or 275K mile L-Engine and actually LOOKED at the bearings?

I have...they look like new in MOST CASES. If the engien is running, chances are the bearings are FINE.
Same with everything else inside.

If ind it humorous how so much needs to be "reconditioned"when it was running fine and making HP....

The fine are of an actual "rebuild" where items are miked and evaluated individually, and not "shotgun parts attacked" is becoming a lost art, I'm afraid...

So sad...
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Tony, you TRUST an unknown engine from a yard for a high horsepower application?

Not me. As long as it's out, it would be stupid NOT to pull it apart, dip it, inspect it, and throw in a set of bearings. Dip it to clear out the oil passages and cooling areas, inspect it for previous work(since it's history is totally unknown) and replace things with new bearings since they are cheap. God knows what you'll find in a junkyard Z engine, from years of abuse to corrosion.

There is nothing mix-y-matchy in using flat tops as a "best mod first". Once the internals are good, then you can work on other mods like exhaust, fuel, cam, etc.
OK BOYS, we all agree that ANY performance engine needs a good free flowing exhaust system, so start with that. Get the MSA aluminized Superturbo 2.5" system for around $200. Next, if you already have your head removed, have a good import machine shop do a "performance" 3 angle valve job and porting. Have the valve guides all replaced as well. You could go ahead and put a mild cam in while a professional is working on it, but until some other supporting peices are in place, you won't feel the full effect. Remember, the key to high performance is "GOOD AIR IN, BAD AIR OUT".
Where did he say "high performance"?

he mentioned a mild cam for a street-driven engine.

Apparently you don't trust the integrity of the Japanese, but after over 20 years of buying Junkyard L-Engines, I have not had a problem in a street-strip dual use vehicle YET!

I do not do stupid things, and that leads to my success.

If you are going to build a PROPER high-performance bottom end, you sure as **** aren't going to use OLD pistons that cost $75 a set, either!

The guy asked what would be a good way to go about this, and IMHO, and from my experience, a junkyard shortblock will be LOADS better than ANY mixy-matchy gob job someone scabs together on the cheap!

So, YES< I would trust the Japanese Assemblyline technicians with the proper tools and keep a good running mated assembly untouched for use rather than disturbing it.

It ain't a Chebby or a Ferd, it's a Datsun, and the bottom ends are bulletproof.

Just as a measure and gauge, my engine in the black car was in OUTSIDE STORAGE in the tropics for FIVE YEARS before it went into the engine bay of the car. This included numerous typhoons, etc etc etc. When I drained the "oil" out of it, it was almost a five gallon bucket! MOSTLY WATER, adn "chocolate mousse" was the rest.
I pulled and regasketted the head, cleaned the tops of the pistons with lacquer thinner, and cleaned the bottom end out, BUT DID NOT DISTURB THE FASTENERS, PISTONS, OR ANY BEARING CAPS!

I had a stuck ring for about 10K miles which was freed up after an extended run at 17+ psi boost. This engine has been through **** and back with a triple blow-through Mikuini Turbosystem, revving to 7K and blowing the guts out of too many alternators to count...

So with THAT experience, along with scads of other engines buiult similarly that had NO PROBLEMS WHATSOEVER, I would say, unqualifiedly YES! I TRUST THE DATSUN ASSEMBLY LINE ASSEMBLY AND WOULD NOT DISTURB IT UNLESS I WAS PLANNING ON A $5000 BOTTOM END BUILDUP!

Short of a total racing or serious ITS effort, I would skip any bottom end work whatsoever unless you have a lot of extra money.

Yeah, you may think it's stupid, but pi$$ing away moneyu you don't NEED to could also be viewed as stupid...
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actually, Iwould have normally recommended he start with a TUNE UP, but since people were baggin on Datsun's assembly techniques, I went in that direction defending the Datsun Name, and tryuing to break the "FULL THROTTLE PARADIGM" prevalent in some postings here...
But if you get a junkyard engine, you will need to recondition it anyway and use new rings, bearings, bolts, etc, etc.


LOL, I'm using a junkyard F54 engine in my Z and rev it to 7000 regularly. The cheapass parts most people put in a rebuild are no where near as good as 100,000 mile old original stuff.

Also "porting the heck out of the head" is a TOTAL waste of time if he's using the stock EFI.

Best route to cheap/easy power: get an F54 bottom end, get a pair of early SU's, throw a mildly "ported" (just clean up the area between the valve seats and the ports) N47 head with a 274/274 schnieder cam and a header w/ 2.25-2.5" exhaust. This will make very close to the power a -stock- turbo engine with no where near the hassles.

If you want to keep the stock EFI, I'd go down one step on the cam to the 260deg one and use the same mix of engine parts, just don't expect much power over 5500RPM. The P79 head is a better choice but requires a major mill (.080") and valve swap, shims etc to get the compression to the same place the N47 is.
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Funny How it works that way, huh Steve?

Two guys, with 40+ cumulative years experience working on Datsuns BOTH seem to believe in running unmolested Junkyard Blocks and bottom ends for just about everything short of a full-race application or where serious competition is involved.

What is it with us? Why are we so deranged? Why don't we believe in the Dominant Domestic Paradigm of "freshen it up"?

Probably because it's UNNECESSARY!

I totally agree on the "cheap parts used in rebuilds" not being as good as STOCK PARTS...

I almost always harvest the bearings out of EVERY engine I snag a crankshaft from, simply to have the mated parts.

I had an LD28 I pieced out, and at 275,989miles, the bearings were **** AND SPAN! The crank journals miked NEW on SPC equipment! When you have proper bearing clearances, and they are already mated WHY ON EARTH would you screw with it? "New Bearings"--WHY What exactly WEARS? If the clearance is there, and it's spinning freely, DON'T MESS WITH IT!

We agree on this, too Steve.

Oh, and BTW, the guy we hired in Fla just quit. For some reason he got in some To-Do with the people at the Rome GA plant, so they asked for me to come in next year. If I am scheduled to do that job, we gotta get together. I want to come down and see the shop when I have the time after the Rome Job is done...
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Well, most Z's I see in the yard down here look like they have had 5 owners and the last one was a kid that ran it so hard that it ended up in the junkyard. I never see engines that I would swap in without cleaning up, measuring and putting in a set of new parts while they were open.

Where the heck are you guys finding pristine engines these days? Maybe location will determine the course of action.
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