Going from turbo to N/A. Need help with choosing parts/setup!! Please chime in!

[pjo046]

Hi!

Well, it's been a REALLY long time since I last posted. To make a long story short, it turned out to be a real hassle trying to get my build aproved by the vehicle-authorities here in norway (L28ET in 240Z). Furthermore they were negative to the Modern Motorsport coilovers as I didn't have any test-lab papers on them. Also, I haven't had time for my Z because of studies and house-renovation. Now my father and I have decided to go the N/A route instead of turbo.

 

I have sold my custom P90 head, but still have the F54 block. It has forged JE flat-tops (they have a small dish, but are nearly flat-tops. They were spec'ed to give a 8.5:1 CR in conjunction with a 1mm HKS gasket and a stock P90 head on a stock bore F54), and I also have the 1mm HKS headgasket.

 

What head is suitable for this bottom end?

Also, what can I expect the engine to put out? We are not going to make a stroker or bore it since the bottom end is already complete with lots of money spent. We want to use carburettors and some sort of upgraded ignition. (what's recommended here if one wants to use something better than a 280ZXT distributor?)

 

We might be able to buy a L24 for cheap that has tripple 40mm dellorto carburettors, 6-1 headers, E88 head with a stage 3 Schneider cam (.460 lift and 280/270 dur. Makes good power from 2500-6500 rpm).

Is this head+cam usable for our bottom end? How about the carburetors? I only know that tripple webers is a good thing, but I am not familiar with dellortos.

 

IF we go that way, what sort of output can we expect? If it is not advisable to use that head/cam, what do you recommend?

I still have the Borg Warner T5-transmission (280ZXT) that I bought earlier on. Can this be used with a N/A setup or will the ratios be wrong? I guess my 3.54:1 R200 isn't suitable? 3.9:1 og 4.11 would be best? I also have the R180 that came with the car (1970 modell US 240Z, not sure what ration it has). Is this usable, or will it be too weak? How about the stock 240Z half-shafts and stub axles?

 

I appreciate all input on this!

[pjo046]

Btw, I still have the L24 that came with the car. The head on this engine is

the E31. Are the valves on this head too small for it to be suited in it's stock form?

[naviathan]

Do some searching for info on the E31. It is a sought after head for the N/A L28 builders. It enables a high compression and I believe has a nice quench pattern. The valves may need to be increased, but a decent machine shop should be able to handle that with no problems.

[Daeron]

Do some searching for info on the E31. It is a sought after head for the N/A L28 builders. It enables a high compression and I believe has a nice quench pattern. The valves may need to be increased, but a decent machine shop should be able to handle that with no problems.

 

+1000, I was going to suggest the same thing.

 

Have the E31 head taken to a machine shop, have larger valves and hardened seats installed, and have that head prepped. Despite my post count or any other impression to the contrary, I am not exactly that hands-on experienced, so I use this engine calculator as a crutch and let it do all my thinking for me:

http://www.ozdat.com/ozdatonline/enginedesign/

 

I can not certify it is dead accurate, but according to that a piston with zero dish/dome yields just under 8.5:1 on a stock P90.. and a zero volume piston equals 10.1:1 compression on a stock E31 head.

 

If that is a little high for your tastes (sounds just about sweet to me, if you find the right cam and put a nice distributorless ignition on it but I don't know what you really want to bother with) then you can always have a little meat taken out of the piston, but I would recommend doing that not in a circular, symmmetrical fashion, but rather offset to the valve side of the piston. This gives you a 3-dimensional "peanut" shaped combustion chamber that ought to work, just fantastic.

 

Whatever you do, the E31 is probably your best bet for an easy, high performance NA head. The biggest reason it isn't talked about so much these days is because they aren't incredibly easy to find, and alot of the heads that ARE available fetch a slight premium because they are useful in 240Z class restricted racecars. In other words, the E31 head is only ever written off because its hard to find; if you have one, then its a GREAT head to work with once you get it to breathe with some larger valves and appropriate port massaging.

[pjo046]

Thanks for the replies guys! The engine that was for sale turned out to be located on the other side of the country, so the shipping would be too expensive. I think we'll go for the E31 then.

 

I definately don't want to start altering the pistons. We will install a proper cam suited for the raised CR, along with a high rpm valvetrain.

For ignition we were thinking along the lines of a distributorless setup, but not until after we have shown the car to the local car-authorities and gotten it registered/approved with the larger displacement engine.

 

But, if we are to go distributorless etc, the question arises whether we should opt for FI instead of carburetors? I do like the old school look/feel of carbs. If we stick with carburetors, how big a difference is there between properly set up round top SU's with 260Z manifolds vs tripple webers/dellortos/mikunis? From what I gather here: http://datsunzgarage.com/engine/ the advantage with going tripple isn't THAT big compared to the extra complexity when tuning them. But the sound is sweeter!! The question is, is it necessary?

 

What about the drivetrain? We'll stick with the T5 tranny and the Spec stage 2+ 240mm clutch. We'll also get a 240mm Fidanza flywheel.

Will an R180 do, or do we need the R200? Are stock 240Z half shafts strong enough for the torque this engine will produce?

[cockerstar]

FI is only going to add to the flexibility and performance of your engine if you get everything set up right with something like MSII. It gives you the ability to tune specific parameters from your computer, and record data for comparison. However, you do lose the look/feel/sound/nostalgia of carbs, but in the long run the price is comparable to a top-end triples set-up with adequate jetting for tuning. If you do go with the FI set up, it does afford you the room to be able to swap heads and go turbo later on down the road after you have had your vehicle inspected and approved if you so chose.

Personally, I would be going with a standalone FI system for your build. It isn't necessary by any means, but it will get the job done for a comparable price and allow more flexibility down the road.

 

It sounds like you're going down the right road with the BW tranny and 240mm flywheel! It should be able to hold whatever you would likely throw at it in n/a trim. I think that your r180 should hold up just fine (again, staying n/a) if everything is in good condition, but if you already have the r200, why not swap that into place? In my mind it's kind of like going with EFI over carbs. It sets you up to be able to push more power down the road. I'm not sure on the 3.54 gearing. It would be great if someone could chime in on the topic.

 

The stock half shafts are going to be the weak link in your drivetrain. If they're in decent shape I think they will do fine for you if you stay n/a, but if you do run into issues, you will have option to upgrade to CVs then.

 

It would be a good idea to look around and see what the general power level half shafts start giving out at. I know that the way you drive the car (launching vs feathering) makes a huge difference.

 

If anyone sees anything wrong with what I've said, please point it out! I don't want to accidentally put any misleading info out >.<

I think everything is accurate, but I'm always reading and learning.

Hope this helps!