Attn flat top 2.8 with E31/N42 head guys

[Mycarispurty]

I'm looking for some personal stories on the feel and power of a flat top motor (f54) with one of the high compression E31, E88, N42 heads to help me decide what direction I'm going to go. I've never driven a Z with a higher compression motor like that and just looking to see what you guys can share. Also if anyone has dynoed their stock level motors with this combo, feel free to throw some numbers at me.

[fhptom]

I have a f54 2.8L block with N42 head. Started off with dual SUs dyno showed 165 rwhp.

Switched to Triple S&K 45mm carbs and jumped to 187 rwhp. Have to run high test fuel to keep detonation down.

Have 3.1L stroker bottom end ready to switch to .

 

Tom

[Mycarispurty]

No problem with high test, I'm used to it with my SC400. So you say with a stock bottom end and stock N42, it dynoed that much hp? That's not too shabby for an old car thats lightweight. Did you have any other mods or anything? Probably all I'd have is my headers and exhaust. And a cam more than likely, but not a very big one.

[ozconnection]

I have a f54 2.8L block with N42 head. Started off with dual SUs dyno showed 165 rwhp.

 

Wow, that's impressive! Stock cam? Stock head? Stock exhaust? Stock ignition? Manual trans I guess?

 

To quote a rear wheel power figure and help this guy out ya gotta be more thorough in your description. What you've supplied if so thin, its worth basically F.A.!! Hell, I wanna know too how you got your power, so do tell.....all.

 

I worked hard to get over 135 rwhp on my auto trans L28. Head, cam, exhaust, ignition, induction...all systems were modified, so you can see how surprised I was to read your figures without qualification.

[Lazeum]

I currently have:

F54, N42, flat tops, MSA stage II (scheinder 274/274), 6-2-1 header, 2.5" exhaust, 3 weber 40DCOE, electronic ignition.

Comp ratio is around 10.3

Timing had to be backed up a LOT to make no knock with 92-93 pump gas (28° total which is lame).

 

To increase whp but also streetability, 2 choices:

- To go with bigger cam to lower dynamic compression

- To change the head with less compression and/or better chambers

 

Both of those changes will alow you to increase timing since you'll delay knock threshold.

 

I've chosen the 2nd solution It still have to be installed.

 

for your info, car is nice to drive and feels good (plenty of torque). power starts to be smooth at 2500rpm but it falls down quite fast at 5500rpm. It is nice BUT it can be much better... and it will, I'm sure

To reach 100mph on open road is easy. I estimate the power to around 200hp at the crank when I compare with my DD (same weight - 140hp) but I did not dyno it (would it make sense anyway since you cannot really compare dyno # from different dynos?!?!)

 

I'm planning to change the head around Xmas if the weather is not too cold, I'll post some updates if any are available

[ozconnection]

I currently have:

F54, N42, flat tops, MSA stage II (scheinder 274/274), 6-2-1 header, 2.5" exhaust, 3 weber 40DCOE, electronic ignition.

Comp ratio is around 10.3

Timing had to be backed up a LOT to make no knock with 92-93 pump gas (28° total which is lame).

 

To increase whp but also streetability, 2 choices:

- To go with bigger cam to lower dynamic compression

- To change the head with less compression and/or better chambers

 

Both of those changes will alow you to increase timing since you'll delay knock threshold.

 

I've chosen the 2nd solution It still have to be installed.

 

for your info, car is nice to drive and feels good (plenty of torque). power starts to be smooth at 2500rpm but it falls down quite fast at 5500rpm. It is nice BUT it can be much better... and it will, I'm sure

To reach 100mph on open road is easy. I estimate the power to around 200hp at the crank when I compare with my DD (same weight - 140hp) but I did not dyno it (would it make sense anyway since you cannot really compare dyno # from different dynos?!?!)

 

I'm planning to change the head around Xmas if the weather is not too cold, I'll post some updates if any are available

 

Excellent summary!

 

You said you're going to change heads. Which head are you going to use and what will be your resultant compression ratio?

 

To get your engine to rev harder at the top end, a bigger cam would theoretically work (and to rid your engine of that pesky ping). Knowing how much bigger is the trick here. We can all work out what will/won't happen if the wrong cam or a too small one is selected. The other issue of low rpm response raises a concern if there is to be any of it left after the bigger cam is put in. Some people don't mind this trade off though.

 

I'd just like to add something here that may be of interest. I recently was experimenting with my induction system. Changing manifold/carbs brought about pinging on my engine that I didn't have before the experimenting began. No other changes were made to my engine other than to change some of the bolt on hardware. Once the engine started to ping, I tried lots of things to try and eliminate it, without success. As soon as I installed my original hardware, the pinging ceased immediately!

In retrospect, the only reasonable explanation was that maybe the engine didn't need more than 28 degrees total advance...that was my total advance on a 8.3:1 comp motor, the experimental induction system so efficient, craming in the air/fuel, it was the ignition curve for that combination that was all wrong. I guess you've seen diagrams of the ignition curves of EFI engines...they look like the mountain peaks of the Andes rather than the slopes and plataeu's of the Sahara. Maybe more work should be given to the ignition setup before abandoning the idea of higher compression and installing a head or bigger camshaft that will give less static and dynamic compression.

 

What are high performance street guys running 10.5 or more compression doing about this problem?

[skib]

subscribed

 

Im working on a high CR L28 as well

[johnc]

I worked hard to get over 135 rwhp on my auto trans L28. Head, cam, exhaust, ignition, induction...all systems were modified, so you can see how surprised I was to read your figures without qualification.

 

The auto is probably giving you the low hp number you've listed.

 

I ran a stock internals L28 built to SCCA IT specs (9 to 1 CR) with SUs. 185 hp on the engine dyno and 163 at the wheels. I know of a couple L24s built to the same IT specs with 9.5 to 1 CR and they made 208hp on the engine dyno. Again, stock internals (pistons, cam, etc.) on SUs. Just hundreds of hours in labor making sure everything was perfect inside the engine.

[RedNeckZ]

I have a L-28 w/E-31 head that has been ported/polished (Heads by Paul, Denver, CO) and has bigger valves in it. It also has a bigger cam (Schneider stage III 270-80f) in it and a header (6 into 1) with a 2 1/2 inch exhaust and triple 45mm Weber carbs. It has a five speed and r200 rearend (3:54) in it. The only thing that is wrong with it is that it has dished pistons in it now. Getting it ready to put 40 over flat tops in it. The last time we put it on the machine it only showed 180 hp. They think with the bigger size bore and flat tops I should be able to see above 200 hp. Drivability with it was easy. It even got good gas mileage if you didn't put your foot into it. Loved the sound it made when you put your foot into it! Also had a 3:90 rearend in it, good for speed and bad for mileage. Had to change it out. We also have run a Sig Erson cam (290AS) (had this cam in it for the test) in it. We flat lobed the cam, racing it. The engine has never gone above 7,500 rpm. Good Luck, Rich. Edited December 4, 2009 by RedNeckZ
spelling

[BluDestiny]

Getting it ready to put 40mm over flat tops in it.

 

that's like would be one hell of a stroke, lol but we all know you meant .04 over.

[drzed]

The 240Z in my sig has the following:

Stock bore and stroke flat top piston (late) L28

E31 head (unported but cleaned up) with larger 280Z valves

Colt cam - 510 lift 280 duration advertised

Nissan Motorsport? header

2.5" exhaust

45mm Webbers

recurved 280ZX distributor

10.6 to 1 compression

 

Engine runs very strong up to 7000 RPM. Good fuel economy (considering 45mm webbers and 4:38 gears).

The bottom end had over 200K KM on it and I still reused the old pistons. By using my weight and my trap speed at the track you get 190-195WHP. I love the power and the sound but if my choice was this or a turbo it would be a tough decision. The turbo power is VERY addictive. My 260Z traps 20MPH higher even with the auto and loose convertor.

As for fuel we get 94 at the pump here so I just manage to get by on this with 34-36 degrees of total timing depending on the weather.

[drzed]

Oh by the way I just thought I'd add that I used to run the same top end on the earlier 280Z dished piston block and the power difference was huge. Now the engine pulls way harder, starts making power earlier and traps way better at the track. I don't remember what the old trap speed was but the absolute best time was 13.999 - I remember that as all I wanted to do was break into the 13's and it seemed like all the car would do was 14.0's. Anyway as you can see at the bottom it will now run 13.44@101.

 

My point is that a cam with 510/280 wants way more compression than the 9.0:1 that I had. With the 10.6:1 bottom end it idles better, runs better, starts better and pulls way better. BTW the new combo reads 190-195 on the compression guage.

[Lazeum]

Excellent summary!

 

You said you're going to change heads. Which head are you going to use and what will be your resultant compression ratio?

 

To get your engine to rev harder at the top end, a bigger cam would theoretically work (and to rid your engine of that pesky ping). Knowing how much bigger is the trick here. We can all work out what will/won't happen if the wrong cam or a too small one is selected. The other issue of low rpm response raises a concern if there is to be any of it left after the bigger cam is put in. Some people don't mind this trade off though.

 

I'm going with a "street" ported/polished P79 made by Braap with adviced Rebello cam. The new comp ratio should be around 9.0-9.3.

[ozconnection]

The auto is probably giving you the low hp number you've listed.

 

 

Yes, auto's do suck up quite a bit of power, about 10% from what I've read and seen. My engines were never built for outright power, more of a bias towards torque for my heavy car and auto trans as it turns out.

 

For what it is, still goes alright....

[Mycarispurty]

I did some calculating the other day with online converters. If the guy up top said he got 187whp with a setup not too far off from what I will have, that converted to roughly 225hp crank hp. I also took a LT1 Trans Am, as I used to have one and would have something to compare it to. Their hp is 275 crank hp, which equaled out to roughly 263whp I think it was. I did a power to weight ratio, and the Trans Am had .0625 while the 240Z had .09. Even though the Trans Am might feel like it is faster (to me) because of all the torque and that nasty LT1 sounding like a beast (at least the one I had did), according to the math, the Z should be a little bit quicker. So I figure if I can hit near 187whp like that guy figures, and some of you do, I should have one hell of a quick car

[fhptom]

Sorry about not listing everything I forgot how much you guys are knowledge hungry. It has flat top pistons with block bored .04 at last rebuild 1999. I also have the MSA Stage III cam with stock valves & springs and the N42 head has been shaved quite a bit over the years and guessing comp is over10.5:1. I only run race gas 105 or higher and have a 5 speed out of a 280. I only do track days so my main concern is lap times so I don't think too much about one thing I have done to the car but every change I make.

[SHADY280]

i have a 10.8:1 motor, p79 decked .080" ( i know not on the list) i run 94 octane and stock efi ecu and injectors. motor is bored .040 over and has 60mm tb and raised fuel pressure. i can keep up, and just barely loose to a 07 stang gt with his traction control turned on thru 3rd gear. needless to say im swapping to tripples soon. drzed, good to see your still alive!! his yellow car is impressive to say he least, here it is

 

[z-ya]

L28 (1mm over), flat tops

N47 head - no head work - just intake port matching

Stock head gasket

Comp cams 280 dur., .460 lift cam

Round port 6:1 header, 2.5" exhaust, glass pack

Megasquirt EFI

EDIS ignition

26 deg full advance

 

Solid plot is dual SU throttle bodies:

 

Dotted plot is stock L6 intake

 

 

[JMortensen]

Had a dished piston .020" over L28 with E31, 280 valves, .490/280 cam, triples, light flywheeel, MSD, 2.5" exhaust. It was pretty strong, and I liked it. I ended up wasting the ZX harmonic balancer and building a flat top bottom end, not bored, shaved the head a bit, installed new valves which had almost no dish, and compression was up around 11:1. This WOULD NOT run on pump gas, even with the timing cranked WAY back. It required about 95 octane to keep from pinging. As drzed says, the flat top bottom end was a lot stronger and idled better.

 

I would much rather lose a point of compression and be able to run the ignition for best performance than have to dial back the ignition on a higher compression motor. There is a lot of HP to be had in the last few degrees of timing.

 

Video of the dished piston motor just after installing the 44's (read carbs not tuned):

http://videos.streetfire.net/video/2000-autox-indisde-and-outside-I-think-my_8051.htm

 

I'd still like to see what Pete's motor would do with either enough octane to run optimal advance or a bigger cam so that he could run optimal advance.

[BRAAP]

I as many other have noticed with the L-6, it is highly sensitive to detonation. With an aluminum head, it should be able to handle 10.5:1 compression ratio N/A on premium pump with no rattling, (many Chevy, Toyota, and other valve designs do just fine), but far more often than not, the Datsun L-6 will rattle at anything above 9.5:1 comp ratio on prmeium pump gas! Why? I have my theories and I firmly believe it is rooted it eh coolant through the head which this thread address. Again, just my theory...

http://forums.hybridz.org/showthread.php?t=125186

 

L28 (1mm over), flat tops

N47 head - no head work - just intake port matching

Stock head gasket

Comp cams 280 dur., .460 lift cam

Round port 6:1 header, 2.5" exhaust, glass pack

Megasquirt EFI

EDIS ignition

26 deg full advance

 

Sorry to pick you on ya Pete, but your example is perfect.

 

Too common for the L-6 to have to back off ignition timing due to the compression ratio. I have been preaching for some time that the power lost due to the retarded ignition timing to keep it from rattling is far greater than the power gained by the bump in compression ratio. Gain of maybe 7-10 HP max for the compression ratio bump over the paltry 8.3:1, but over 20+ HP lost in retarded ignition timing! open chamber L-6 heads, (E88, N42, N47), have their optimum non octane limited spark advance in the 38-42 degree range. If you can't get 38 degrees total ignition advance above 3500 RPM at WOT, (N/A), with E-88, N42 or N47 head because it is rattling, you are leaving HP on the table.

I'm not saying that 10.4:1 comp ration can't be done successfully and still have adequate ignition advance, it has been done, only by a few with no info on what makes theirs able to run ideal ignition advance without rattling vs the many others that cant run that advance. Most of those combinations rattle and can't run full ideal ignition advance which is leaving power on the table.

 

 

One specific example I dealt with first hand;

… One of my customers, (now a great family friend and HBZ member, Mike Hintz) had a shop build hi-po L-28, their recipe was an L-28 with flat top pistons and Z car N-47 head, stock EFI and Schneider stage 2 cam. With 92 octane super unleaded he had detonation issues that could be heard at higher RPMS outside of the car WOT and also showed up very audibly on the while it was optimally tuned for power on the dyno at Torque Freaks. After many discussions back and forth I convinced him to let me build him a P-79 head and go back to a stock cam. He agreed and wanted back to back dyno com and after putting it all together and re-tuning the EFI and ign advance for this combo. He couldn’t be more happy, maybe he’ll chime in. The engine ran WAY smoother, pulled harder everywhere in the RPM band, took it back to the same dyno and the lower compression stock cammed combination gave 10ft lbs increase across the entire RPM range over the previous big cam high compression combination with a solid 15 HP increase at peak, and best of all, no more detonation. He has since switched over to standalone EFI and are considering installing an aftermarket cam now that he as fuel control to take advantage of the aftermarket cam.

 

…

 

 

In short, I do not endorse L28 builds with flat top pistons and E88, N42 N47 heads for ANY street application unless a thicker head gasket is used to drop the compression down to below 9.7:1 or so. If flat tops are is on your must have list, then I recommend the P79 or P90 head.