L24 Engine Build, Head / Camshaft Suggestions

[ksmithgall 0]

I recently picked up a non-running ’73 240Z with 160k miles that was sitting for years. The original engine has been pulled and disassembled and now I’m trying to come up with a rebuild plan for it. I know that the cheapest way to increase power is to buy and swap in an L28, but for right now I want to rebuild and get the original engine running with possibly some performance improvements. Generally I would want to reuse the original block, rods, and crank. Primary use would be street driving with an occasional autocross or track day.

 

I have already acquired some round top SU’s and a ZX distributor with an E12-80 module that will be incorporated in the overhaul.

Right now I’m considering two options.

Option 1: Rebuild Like Stock ~8.8:1 CR

Block: bore and hone 0.020” oversize, line hone main caps

Pistons: ITM RY6335-020  From this thread I saw that the ’73 pistons were different: https://www.classiczcars.com/forums/topic/59242-interesting-1973-e88-240z-head-info/?tab=comments#comment-538427

I emailed ITM to check compression height, and they said the compression height of the RY6335 is 38.8mm matching the ’73 pistons that were originally in it so they should be an identical replacement.

Rods: Hone and add ARP rod bolts, and re-use original L24 rods

Crank: Polish and re-use L24 crankshaft

Head: Rebuild ‘73 E88 head, replace bronze intake valve seats with hardened ones. New valves, valve springs, resurface original rocker arms

Head gasket: Fel-Pro or equivalent

Camshaft: ? The original “Japan” casting camshaft has a heavy wear pattern and would need to be re-ground. Would a more radical camshaft profile be a benefit given the rest of the build, or should the camshaft be re-ground/resurface to stock?

 

Option 2: Maxima N47 Head ~9.5 CR

Bottom end would be the same as Option 1, but notch block for larger valves or bore to 0.040”?

Head gasket: 2mm HKS

Head: find a Maxima N47 head, valve job, new springs, resurface original rocker arms

Camshaft: Any recommendations for a camshaft that would suit this build and take advantage of a higher compression ratio?

 

Is there an option 3 that should be considered?

Overall has anyone gone put a Maxima N47 head on a Z L24, and what was it like, was it worth it?

 

Thanks,

Kurt

[Zed Head 2,203]

@Diseazdand @siteunseen and others have done some rebuilds, performance and stock.

I think that E88 head is going to be a question mark.  There are several variations, as I understand things.  Not positive though.

The Maxima head is used to raise CR.  Wouldn't make sense to use a 2mm head gasket with it.  Defeats the purpose.  @madkaw has done a Maxima head, I think.

Good luck.  I'd just put a cam in it and some new rings myself.  Have you measured the bores?  Does it need boring?  If not, save the money, the Datsun blocks are tough.  Don't forget that with a new cam you'll need new or reground rocker arms.  Nickels and dimes will add up.

[siteunseen 3,445 5 Vehicles]

I rebuilt my original 2.4 with the early E88 head. The 2.4s are a little more costly to get parts for but I like the higher rev of the smaller motor. The '73 will have bigger rods but the pistons should be the same size, 83mm, as the earlier 240s. I did mine for about $1,000 total but that includes a MSA header and premium exhaust. You'll end up using a lot of 280 parts, they just don't make the 240 stuff anymore. The best money I spent was for an aluminum flywheel. It weighs about 10lbs and revs up like crazy. 

Here's some info to read over when you can.

https://www.google.com/search?q=2.4+engine+builds+classiczcars.com&rlz=1C1BOFA_enUS494US494&oq=2.4+engine+builds+classiczcars.com&aqs=chrome..69i57.17799j0j7&sourceid=chrome&ie=UTF-8

[madkaw 542]

Many options !

MN47 head is a great alternative to a late E-88 head . It already has the good seats and a 35mm exhaust valve . If I had my rathers - I’d invest in a MN head . Drilled cam is better than spray bar . Closed chamber head - better for detonation . Smaller chamber for CR . Go with 44 mm intake valves 
L24 block can go with L28 pistons if you find the right machinist to check wall thickness . If not - go 1mm over on the bore .

camshaft ! ISKY cam 490/290 or Steve Bonk cam 530 lift . I think the aftermarket pistons come with reliefs , so a little more room for valves . 

[ksmithgall 0]

Some good suggestions from everyone, thanks.

I'll throw a lightened flywheel on the build list. For the time being, my plan is to sort out the head first and then tweak the bottom end as needed to support the head. Despite reading the saga of @madkaw's build thread I think I'll take on a MN 47 head. Seems like a great performance option for the L24 I have now (with bore notching for valve clearance), and would be easy to bolt onto an L28 block down the road for even more power. Let the search for a buildable core begin!

A couple further questions based on @madkaw's build. Did you use the severe - duty Manley valves, P/N 11679-6, 11678-6, or something else? Any concerns about valve train wear from the increased seat pressure of the Isky valve springs? For the camshaft I could send my "Nissan" casting to Isky to regrind, but it's externally oiled. Which would be worse, externally oiled good metal, or newer internally oiled billet which may not wear as well?

[madkaw 542]

MN head is a good choice , might be a bit harder to obtain . Try the used car parts websites that search salvage yards . Someone has one laying on a shelf . Bribe someone out west to pull one off of a Maxima .

Probably about the best upgrade for an older second gen E-88. No seats to change . Has the bigger exhaust valve . Put the bigger intake valve , do a little port work and vroom . Liners flow just fine . Better casting then the older heads .

Isky springs are fine . Don’t need Manley valves , just Nissan intake valves at 15$ each new . 
Get a new spray bar