Comments & Suggestions Please

[onemore240]

This is what I plan on running in my 70 240Z autocross / street car

L28 block

E88 head + 280 valves + port & polish + milled gasket

Triple 38mm Webers or dual SUs from www.ztherapy.com

Bored to 2.9L

10:1 comp pistons

shot peened rods

2 3/4 inch header w/ 2 3/4 inch piping all the way back

5 speed w/ R200 w/ a 3.90

Lightened flywheel

I was thinking about the E31 head but its aquisition is quite difficult isn't it? If anyone knows where to find one for a relatively good price (sub $700US) I'd greatly appreciate it. Also, what about an N42 head with dual SUs? Also, a cam suggestion would be awesome...cant seem to find something I like.

[2ManyZs]

You seem to have a pretty good plan so far. Only a couple things to think about before you do it though.

First is your choice of a 2 3/4 exhaust pipe. If you lower your car with lowering springs or coil-overs you might have some problems with the pipe being a bit too large and giving up ground clearance. You might be better of to get a 2 1/2 exhaust and make sure it is tucked up tightly especially around the front diff mount, which is where you will normally grind the exhaust on a lowered car.

Either of the heads you have picked are a good choice. The N-42 is a bit better in that it will already have the larger 280 valves in place. Might be a bit easier to find a good N-42 due to the larger numers of 280's imported versus the 240's and 260's with the E-88.

I'd stay with the ZTherapy SU's only because they would end up being cheaper to buy intially, and a bit easier to synchronize.

Try to find an F-54 L-28 block out of a later 280ZX as they have more webbing in the cylinder area and should already have flat top pistons to boot. With a light shave on the cylinder head and a thinner headgasket you should be able to come close to your target of 10:1 without buying custom pistons. Look in the downloads section here for the L engine calculator and you can play around and pick the best parts to give you what you are looking for. Pick the ones that give you what you want, with parts that are the cheapest and easiest to find...

Cam choice will depend on where in the rpm range you want the best power and where your car will spend the majority of its time. If it were me, I'd go for a cam with the best power under 6500rpms down to a low of 2500-3000. A lot will depend on your rear gear too.

If you can find a 3:90 R-180 you would save 20 pounds or more over the R-200 and not have to change the mustache bar or rear control arm crossmember. R-180's will hold up to almost anything a good L-28 will dish out, the R-200 is better only if you go to a turbo or V-8 conversion.

Hope that helps a little, and yes, unfortunately E-31's are getting harder to find in good condition.

[onemore240]

The Z will double as an autocross/daily car...so I need to find a cam that is balanced between drivability and all out performance.

If I was doing a drag car on the other hand. like a weekend driver/strip car I'd just go with a LT1 block with LT4 intake manifold & ported LT4 head with a HOT cam and shorty header to make a good 400 NA hp...but since its autocross I tried to find a good mix of factory parts inorder to reach my hp goal of 275 rwhp...I could always save and slap individual throttles on it and use a larger choke for more high end power..but for an autocross i'd have to use a midsize choke for good low/mid...

jeez...its soooo hard to build an autox car --- I figured if use the early E88 head that came with the 70 240 and put it on the L28 block and equip it with 280 valves and deshroud/port the head...i'd give me higher compression than a N-42 ...this comparison i used the LT1 vs LT4 head comparison...almost the same square port etc., except the LT4 head flows better and is thicker & machined better..not to mention aluminum ...

Also what if I was to run a 260Z cam...I've heard of peopel doing this...but a cam that is good from lowrange to 6500 RPM sounds extremly enticing...any recommendations for dur/lift ?...

My transmission choice..81-83 N/A ZX 5 speed is accredited to the fact that it already comes with an 3.90 R200...what cars did R180 3.90s come in? I figure for my hp goal 3.90 would be the best gearing..what about 3.54?

[onemore240]

I also looked in the download section and couldn't find the L engine calculator..maybe I'm just blind but would it be to much to ask if you could provide me with a link?

[2ManyZs]

Oops, I got the transmission calculator mixed up with the engine calculator. The transmission calculator is in the web-links under tech info if you are interested in that.

Now I can't remember where I downloaded the engine calculator from, perhaps it was from a post on the site. Let me look again.

:stupid:

Take a look at this post and you can download it. I knew it was here somewhere....

http://www.classiczcars.com/forums/showthread.php?s=&threadid=1292&highlight=Z+engine+calculator

[onemore240]

Thanks a lot for the calculator...it seems my setup would give me exactly what I wanted. I decided to run a 268/.472 advertised cam and pick up some rebello valve springs. @ $4.50 each seems like a pretty good deal.

I've also chosen my suspension setup but need to choose a springrate. I've chosen to go with Ground Control coilovers, Eibach springs, and KYB GR2 shocks which are #7 in the Ground-Control application guide. Also, are there any adjustable camber plates and pillowball upper mounts offered for the 71 240Zs?

[2ManyZs]

Ground Control offers camber plates for both the front and rear. They can set you up with a complete set to go with their coil-overs as I believe they use different top mounts.

Not sure what you are referring to as to the body numbers. If you are looking for spring rates GC should be able to tell you a close estimate for what you will need when you tell them what you are going to do.

I know road racing and autox'ing is different as far as spring rates so you will need someone like John Coffey to give you ideas on that. I mainly did road racing with a 75 280 so what I used will not be the same as what you will need.

[onemore240]

Yeah, i posted before I read....the 1234 and 7 are shock options...I'm going to go with #7 which are KYB GR2s... I don't know why they have the application key at the bottom with different lablings at the top of their application table....