Na mild engine build for pump gas

[silver280zx]

Ok heres what im thinking so far, ive read all the other threads on na builds, and i just cant make up my mind. I have a limited budget, but i have connections when it comes to the machine work, so thats not a big factor. ok now heres my current plan.

 

f54 with .040 flattop overbore

n42 head, ported, polished vlaves

felpro headgasket 1mm

comp cam 280s 460 lift 280 duration

intake with the runners widened and portmatched

60mm tb

larger injectors

 

I currently have:

xr3000 crane cams ignition

silicone wires

NGK iridium plugs

K&N short ram intake

Motorsort header 2 1/2in

2 1/2 inch borla exhaust

i do have a timing gun so i can reset the timing when im done

 

Ok heres the question. Will i get detonation problems on Georgia 93 pump gas? What power range will i be looking at? I run autox so im looking around the 180whp mark. What modifications to my suggested setup do you recomend if its not a good idea? I know about the p90 head shaving and i dont think its worth all the hassle to me. Anyway thanks for your help.

-Tyler-

[1 fast z]

You will get less detonation with a different head. Use a Maxi, or a P series head, for maximum quench. You can run 12-1 compression on 91 octane with 36 degrees full timing with a m, or p series head. I wish we had 93 at the pump on the west coast, grrrrrrrr.

[JMortensen]

Your main limitation as I see it is the stock ECU. I think you should get rid of that before doing anything else. Once you have some sort of aftermarket programmable fuel injection or even SU's or triple carbs, then I'd suggest a slightly larger cam and a different head gasket (go HKS if you want the 1mm gasket for the compression boost). I think you'd do fine with that head on 93 octane.

[SLVRBLLT40]

All the compression math I've done with the N42 head on top of the flat top L28 suggest about 10.1:1 compression with a 1mm head gasket. The N42 is an open chamber design, which I've always understood reduces the chances for pinging. Since the head is also aluminium, you can get away with more compression. Don't turn total advance above 36 or 37 degrees, and don't run static advance above 16 and you'd be fine. If I can run 10.25:1 compression on an ironhead MoPar and be good, you will be too

[JMortensen]

The N42 is an open chamber design, which I've always understood reduces the chances for pinging.

You understood wrong, but let's not get into that one again. Search here or the web at large for "quench" and read for a bit and you'll see that the closed chamber has higher compression but is less likely to detonate.

[silver280zx]

So if i did run a stock ecu and just made it richened the mixture, would it really be that bad? I used to have the cam in it once before, when i was learning about engine building, and i found out what compression was the hard way, but thats another story. back when i did have it in i was retarded and had stock compression, but it always ran rich. would that change when i raise the compression? becasue the cam would be the same. Oh ya i forgot to mention this is a january 1979 s130. So i shouldnt have problems on 93? now and could you explain total and static advance? When i had the cam in, comp sent me the card, and it said to set it at 16 degrees advance for maximum efficiency. The stock one i believe is 4 degrees advanced. The ignition system runs 10 degrees over top dead center stock. Im running 25 degrees right now, i have my distributer turned as far advanced as the adjustment screw will slide, and no pinging. So when you say 35 degrees total advance, what exatly are you reffering to?

[WEBEZEEed]

You will get less detonation with a different head. Use a Maxi, or a P series head, for maximum quench. You can run 12-1 compression on 91 octane with 36 degrees full timing with a m, or p series head. I wish we had 93 at the pump on the west coast, grrrrrrrr.

 

1 fast z.... that 12-1 compression, is that without the modification to the piston?

[1 fast z]

That is with a 100% flat piston, with .023" piston to head clearence.

[JMortensen]

So if i did run a stock ecu and just made it richened the mixture, would it really be that bad? I used to have the cam in it once before, when i was learning about engine building, and i found out what compression was the hard way, but thats another story. back when i did have it in i was retarded and had stock compression, but it always ran rich. would that change when i raise the compression? becasue the cam would be the same. Oh ya i forgot to mention this is a january 1979 s130. So i shouldnt have problems on 93? now and could you explain total and static advance? When i had the cam in, comp sent me the card, and it said to set it at 16 degrees advance for maximum efficiency. The stock one i believe is 4 degrees advanced. The ignition system runs 10 degrees over top dead center stock. Im running 25 degrees right now, i have my distributer turned as far advanced as the adjustment screw will slide, and no pinging. So when you say 35 degrees total advance, what exatly are you reffering to?

It sounds like you're confusing cam timing and ignition timing. Cam timing is often 4 degrees advanced on aftermarket cams, there is a sticky in this forum about degreeing your cam and setting cam timing correctly.

 

Ignition timing should be in the mid 30's at full advance for best power with a normally aspirated engine. The way to check it is to rev the engine to 3000 or 3500 degrees and then check the advance. This is easier to do if you have a timing light with an advance function, you set the light to 35 degrees and then line up the timing mark at 0.

 

There are two lockdowns for the distributor. The obvious one is has the 10mm bolt, but there is also another one on the distributor which uses an 8mm bolt. If both of those don't get you the advance you want then you have to pull the oil pump and move the shaft that connects the distributor to the oil pump one tooth. Moving the shaft is not hard to do but it's easier if you have two people. Get a manual if you don't know what I'm talking about here.

[Pyro]

10:1cr and a compcam 280 should be fine with 93. Especially with alum head and only 36 degrees of timing.

 

I didn't see any mention of valve springs, retainers, rocker arms, or thicker lash pads in your post.

 

Instead of going with bigger injectors, I would just use an adjustable fuel pressure regulator that is vacuum sensitive, (like an aeromotive brand).

 

try 42 psi at idle which should make around 48 psi at wot. 48 psi should be good for 20% more power.

[silver280zx]

ya what size thickness of lash pads should i get? An on the cam card comp sent me, they said to advance the cam timing 16 degrees. Ill check both of those bolts on the distributer, i only moved one.

thanks

[JMortensen]

Read these threads THOROUGHLY. It might also be a good idea to buy the How to Rebuild Your Nissan/Datsun OHC Engine and How to Modify Your Nissan/Datsun OHC Engine books before you proceed farther.

http://forums.hybridz.org/showthread.php?t=111523

http://forums.hybridz.org/showthread.php?t=112184

http://forums.hybridz.org/showthread.php?t=108398

[silver280zx]

I already own it, and am reading it, but its not written to certain after market specs, and it seems to mainly be for race motors. thanks anyway though

[olie05]

You are describing almost exactly the setup I had before I went megasquirt.

 

Basically I have:

flat top pistons in N42 block,

N42 head

STOCK intake

60mm throttle

2.5 inch mandrel exhaust w/ msa header

272/282 .460 cam.

 

I had problems running full timing and not pinging slightly under heavy throttle on 93 octane. But that was with the stock computer, and about 30ish (or more) degrees btdc at full throttle. When I went standalone, i tuned everything to suit my compression and cam combination.

 

It works like a dream with 93 octane.

 

BTW I have never run anything other than 93 on the current engine build.

[silver280zx]

You are describing almost exactly the setup I had before I went megasquirt.

 

Basically I have:

flat top pistons in N42 block,

N42 head

STOCK intake

60mm throttle

2.5 inch mandrel exhaust w/ msa header

272/282 .460 cam.

 

I had problems running full timing and not pinging slightly under heavy throttle on 93 octane. But that was with the stock computer, and about 30ish (or more) degrees btdc at full throttle. When I went standalone, i tuned everything to suit my compression and cam combination.

 

It works like a dream with 93 octane.

 

BTW I have never run anything other than 93 on the current engine build.

Thanks man, thats exactly what i was wanting to hear. Did you do your own maps? or did you get them from somone else?

[olie05]

Mostly tuned it myself. I borrowed from a few others on this forum running similar setups, such as Ed (nismo280zed) to get it running and went from there. I posted my megasquirt map on the map sharing section of the forums if you want to go take a look.

[silver280zx]

Mostly tuned it myself. I borrowed from a few others on this forum running similar setups, such as Ed (nismo280zed) to get it running and went from there. I posted my megasquirt map on the map sharing section of the forums if you want to go take a look.

 

Thanks man. How exactly do you hook mega squirt up? is it a piggy back unit?

[Pyro]

ya what size thickness of lash pads should i get? An on the cam card comp sent me, they said to advance the cam timing 16 degrees. Ill check both of those bolts on the distributer, i only moved one.

thanks

 

The thickness of the lash pad needed will depends on how much compcams ground off to get that duration. Typically the "bigger" the cam, the thicker the lash pad needed.

 

From my experience, a 280 degree cam will need around 0.190" thick lash pads. However, the thickest lash pad a stock retainer can handle is 0.160" (stock is 0.120). Plus a 280 cam will need stronger springs. So, I would recommend a high performance spring/retainer kit. I get my lash pads from Courtesy Nissan in Dallas, Tx for 3.00/each.

 

FYI, running too thin a lash pad can wipe out a cam very quickly and will make the valve train sound like a diesel truck.

 

I also get my rocker arms resurfaced at Delta Cams for 4.00/each. They also do good cam regrinds for 60.00. If you want to use the stock springs and retainers with 0.160" lash pads then get a 260 cam with 0.440" and use a P series head with L28 flat tops (9:1 cr).

 

Longer duration cams do better with more initial ignition timing. 16 to 20 degrees is common for a lopey street cam. Maybe that is what compcams is talking about. I would install your cam "straight up", that is, just install using the factory cam timing location (see repair manual). Or just install on the 2nd position so you can't be too far off (1 position either way).

[JMortensen]

I think guessing at the pad thickness is risky. Is Comp using new cam billets or regrinding? What's the base circle? How do you know if his valves have ever been cut or if his seats are sunk into the head a bit? You might have a vague guess as to what size lash pads are necessary, but it's easy to guess wrong if anything has previously been done to the head. One of the threads I linked to previously has specific instructions about cutting up a feeler gauge and using the pieces to measure what thickness you need so that you can order the correct lash pads the first time.

[silver280zx]

im about 99 % sure it is a re-grind, ill have to go dig up the cam card. The shaft is not quite as thick as stock. When i installed it the first time, i used stock lash pads, and had to re adjust the hieght of the rocker arms to to the manuals specs. but im almost certain its a regrind.