L28 Build Questions

[Zguy91]

Ok so I'm looking at using an F54 flat top l28 and a N42 head with a reground cam electronic ignition 6 to 1 header SU carbs lightened flywheel close ratio 5 speed and 3.90 R200. Should make a pretty quick car considering the light weight of the 71. My question is is the CR going to be ok with the F54/N42 combo and what cam specs would you recommend. Z-Engine Calculator says that N42 on a flat top motor with felpro 1mm headgasket should be 9.97:1 CR. Sounds like it would be okay to me but there are many of you with more L series experience than me.

[steve91tt]

It sounds like you are building a great combination. 9.97:1 should be fine. I'm running 10.3:1 CR on 93 octane without issue. I'm biased towards a big cam in these engines but it's a personal preference. If you do a search I don't think you will find many folks who regret a big cam but I bet you find a bunch that regret buying one that was too small. Having said that, I suspect the powerband of your cam will be limited by the ability of your SU's to supply enough air to the L28 on the top end. The lift you can run may also be limited by your valve springs unless you plan to change them. If it were me I would give Dave Rebello a call and see what he suggests for your setup. Dave should be able to match a cam grind to your setup. Good luck with the build and keep us updated with your progress!

[Zguy91]

Sounds good thanks for the help! Ive got the cylinder head I'm just looking for a good F54 short block right now.

[Zguy91]

Do you know if the N42 head has a spot for a mechanical fuel pump?

[Travel'n Man]

Do you know if the N42 head has a spot for a mechanical fuel pump?

It does.

[Lazeum]

Your combo has been discussed a lot of time with very knowledgeable people on many forums.

It was also my setup some years ago, I've changed it and I'm not looking backward

Car was running ok but at the cost of low timing to avoid ping. I have a adjustable distributor so it was possible to change initial & total advance but hardly transition (it's a Mallory Unilite).

I could have avoided ping by having a bigger cam to ease things up or by changing ignition system to get a more versatile setup (MSD 6AL-2 or Megajolt could be the answers).

So bottom line is that it can be run but you have to be careful about the setup as a whole, otherwise it would ping. I support the advice about calling Rebello to plan ahead for a proper setup & to avoid potential frustrations.

I went with P79 head, ported/polished/unshrouded, milled a bit with appropriate cam & springs, the car is a lot more powerful than it was with the N42.

Edited February 23, 2012 by Lazeum

[Zguy91]

Yeah I have heard the quench on the N42 isnt as good so its more prone to knocking. Do you think I would be better of using my E31 head off of my L24 and installing 280z valves? Does anyone have an idea of what that might run me? What did it cost you to work your P79 head over

[Travel'n Man]

Call Dave Rebello - he is into these engines more than anybody else.......his knowledge is excellent and the end results are even better;)

Let us know your findings.

http://www.rebelloracing.com/

[Zguy91]

Ive actually spoken to dave before. He did recommend the N42 over the E31 but didnt get to much in detail other than that. Ill give him a call again. Im not trying to spend a whole hell of alot on the build just because if i was gonna spend alot of money on an l series i would just go ls1 but with that said I do want a decent set up that has a little more go than a stock 240z and is fun to drive

[steve91tt]

Lazeum makes a good point about the distributor curve. Dave coached me that with higher compression it was best to use about 17°-20° initial, 33 total and all in about 5500rpm. Flatting out the spark curve like this keeps the timing a little lower around 4000RPM where these motors tend to ping. I'm sure the best spark curve is a function of a given engine setup but in my case following Dave's recommendation with my Mallory Unilite provided a ping free 10.3:1 compression pump gas motor.

[madkaw]

I'm suprised Dave went with the 42 head over the e-31, but the e-31 might be too much compression and would require more money to make it work.

Of course all you have to make your determinations by, are what folks on here say run well. Not much in dyno results. So is it better to give up timing advance for more compression?-only dyno comparisons would say.

Running high compression and running only 30 degrees total advance seems self defeating.

In the end I guess Dave from rebello would know better than anyone else

Edited February 24, 2012 by madkaw

[Lazeum]

Dave made an engine for a friend (Rebello 3.2L engine) dyno'ed at 310 crank HP which is quite torquey with mild cam. The head used for this engine is a E31. Speech from my friend is that head looks quite stock (but it isn't of course), modifications looks quite subtle.

As far as I'm concerned, my head was made by Rusch Motorsport (Braap on HBZ), overall cost is around 2k with very good support. Cost includes new valves, new Rebello cam made specifically for my head work, new springs, new lash pads, new retainers, dual lubrification (cam + spray bar), milling/port/polish operations, cam tower shimmed, etc

Regarding timing, I would choose the MSD 6AL2 box since it could be setup very easily with a computer instead of the mallory unilite that needs some more work to be setup right.

Edited February 24, 2012 by Lazeum