Tony D

The Z really only needs a properly ducted 4x28” slit across the front to cool it. Keeping excess air getting in helps stability and aerodynamics. cutting three inch holes under the battery and brake master cylinder has been proven to be extremely effective venting position (low pressure area opposed to high pressure area at cowl) people put thermostatic controlled fans on the exhaust side to force flow through / out in stop and go traffic. no need to go through the upper firewall except to duct inlet air to your intake… you would be surprised what kind of static pressure exists there even at highway speeds… especially compared to behind the wheels in the left and right fender area! vent high pressure to low, and you use/require less open area to accomplish the same exhaust flow…

OK, now let’s mirror-image this Beyatch, size it for 50mm’s and hang it on the Right Side of the Datsunworks DOHC (which since it’s CrossFlow can use plastic additive machining to knock it up and prevent heat soak…) Thank God the bore spacing remained the same! My Necropost for 2022…

I wonder where they come up with the "1965 Prototype" designation, as at that time development of the concept car was farmed out to Yamaha...

Parts bought out of the Nissan "Yellow Book"! Ahhhh, the good old days! I remember when Nismo was birthed. Long after the S30 was out of production, that's for sure!

As I said, this is mischaracterization of poor engineering on the builder's side, and anybody reproducing it with the intent of using it for 'high performance usage'. The characterization of the stock head having "a problem" is incorrect. The characterization of the JMC having the same identical problem WOULD be a 'design flaw' as the issue is known, as is the solution! The L-Head as was on the cars stock was not intended for more than around 220bhp, and even then they blanked internal bypasses and ran 2bar radiator caps. They ran those heads in production car categories. Where the rules permitted, they ran the LY head, or FIA head which was intended for sustained 220bhp+ production. It's like the breakpoint for applying the R200 in a chassis compared with the R180. It's curious Subaru who also uses the Fuji produced differential seems to follow the exact same application for intended horsepower and torque that Datsun/Nissan did back 45 years ago.

"One?"

No, really it's logical. The head is altered and likely is just as illegal to run in any sanctioned events as the DW head. If I'm plunking down $10 Large + for a head to be done up... I'm not getting one limited to maybe 250 cfm. On a good day. With huge lift and all the buggery that entails. Truthfully the DOHC would be easier and is the logically-minded next step in the engine evolution. Now, if they reproduced the FIA L6 Head.... THEN we might have some competition. The L6 FIA head already HAD 'equal exhaust ports' but then people would whine about their existing headers not fitting, or that they couldn't buy and fit $149.95 Thunderbird Headers on it and had to pay money for custom speed parts... The "Rent, Baby Milk and Daipers Crowd" as John Coffey used to say! And besides, the Datsunworks head is a brilliant adaptation of modern port theory and combustion chamber design mated with modern production techniques that make previously impossible things possible at an affordable price! Whomever thought up that whole scheme and put it into production is absolutely Enstein-ly Brilliant! True L-Godz! All should supplicate themselves at their feet and pay homage...

Run the stock build engine and spend your money on porting, polishing, camshaft and EMS along with a properly sized turbo. An all stock L28 at stock compression ratio of 8.5 will run 350hp without anything but be somewhat of a boring ride IMO (see end for why.) A bone stock L28 N42/N42 bottom end with a ported, polished, cammed and fuel injected (Now, was blow through mikunis) EMS can make upwards of 450HP at 17psi with a GT35R strapped to it.... And that's limited to under 7,000 rpms. Once you get all that sorted, and are satisfied with your build THEN buy your pistons and retune as you deem necessary. By that time you will know what you are doing, and breaking the pistons will not break your bank. I know someone who did not listen to this device and spent upwards of $6000 on engine 'refreshes' before he listened, put a stock bottom end under his head and bolt-ons and then blew those pistons three more times before getting it all right. But those pistons and rings only cost him $200-300 a set (ITM off eBay) and he learned that after the Fel Pro Gasket blows three times, likely the pistons are shot... All those failures on the stock bottom end didn't add up to the costs of ONE refresh of his forged piston built engine. He was mildly annoyed that a stock bottom end ended up besting his 'first generation forged piston' build by some 25 odd horsepower and at only 17psi instead of 30! Spend your time on fuel delivery and airflow, same as an N/A. Then worry about durability. You WILL blow up your engine tuning it if you're going after big numbers, and even if you're not clogged injectors can sink your setup at 8psi as spark knock at 30psi. I'd never put a MLS head gasket or Forged Pistons in a Boosted Build unless all major tuning is over and I was satisfied with the results to 7,000 and only had 7,000+ left to tune. Even then, I'd keep a Fel Pro Gasket in there for a 'safety valve' in case detonation occurred. Blowing a $50 head gasket is better than sinking the rings on 5 of your cylinders because a fuel filter decided to explode and clogged all your injectors! Identify your power goals in advance, and work to them. Don't get greedy and make components do something they aren't capable or suited to doing. Under 400HP cast pistons will do just fine unless you want the engine to ACT like an L-Series and pull to 8,000... then you will need forged pistons and woo wheee will it be fun to drive compared to a big boost low-flow setup which will basically be a Boring Big Block Corvette setup. Sell the Z in that case and buy the Vette...

Not really, until the valve head is away from the seat more than a given ratio to it's diameter, it represents a flow impediment. On a ported head capable of flowing more, the further away that valve head needs to be to not impeded the inward rush of airflow. Since the valves are relatively large, compared to a DOHC Valve and do not tilt inward away from the cylinder walls like a Pent-Roof DOHC again... it represents a "shrouding" of the valve. This is why people cut the heads combustion chamber in the area of the valves... it 'unshrouds' the valve at low lifts and represents a considerable amount of flow increase (ESPECIALLY on Turbocharged/Supercharged builds) given the assymetric nature of the cam profiles used on Nissans and their time spent 'just off seat'. If he's got large ports, it only stands to reason that higher lift gives more flow. If the porting is conservative, you will hit a wall and not flow more regardless. Even at that, you can still use a higher lift cam as it will spend more time "under the curve" at the peak flow number with no restriction at all than if you used a cam that only lifted to the max your head was capable of flowing.

Fitting Liners is the way it was always done for big engines. You can muck about trying to find a block that might take a boring (and that usually is an L28 Block) but overseas where block casting numbers as well as stamps are checked for compliance with national inspection criteria, people have been making 3.2 liter L20A's since the early 80's when I was in Japan. This obsession with boring on OE metal and aversion to Liners is just laughable to me. How many Keith Black Hemis are there that don't run Sleeves? Different animal altogether I understand, and different maintenance routine for sure... but if they'll handle over 1,000 HP per hole, I think a liner will be just fine in any L-Block... just mind the head stud clearance as that's the OD Max Limit... Or IS it? Mowhahahahhaha!

When you call Ron at Isky and tell him you want an "all out performance cam" after all these years he realizes there are two kinds of people out there, and his first question is "do you mind cutting your pistons?" If the answer is yes... ohhhh the wonderful things he has for you!

Now, you want to discuss an SOHC head that SHOULD have been reproduced? For $6K? FIA Group 4 Six Cylinder SIGN ME UP NOW! For the money given the JMC current offering? I'd buy a Datsunworks.

Guys, this is not a "5/6 Problem"! You're trying to make a silk purse out of a sow's ear and blaming the OEM for incompetent and uninformed aftermarket engineering when increasing performance! Look at the Nissan L6 FIA Group 4 Head, the LY Head, and the S20 Head - all Nissan "HIGH SPECIFIC OUTPUT" heads and you will find they have a SIGNIFICANTLY different way of handling water flow through the head, and all of them handle it almost identically! And unfortunately without an external water manifold to remove the "flow knife" action of cylinders closer to the water pump obstructing flow back along the exhaust side to the front of the head to take it off to the radiator. The solution to this is simple: take water off the top of the cylinder to an external manifold which can be designed like an exhaust header with subsequent cylinders creating a pulling effect on the downstream cylinder to promote flow out of the head. The knowledge of this "issue" has been known over 50 years! It was decided at Nissan that there were high specific output heads which addressed the issue, and cheap to make production heads for the millions of vehicles they planned on selling with the head in it. It's not "addressed" because most people aren't making over 220hp (which is where Nissan started using those heads...) and because people think a $5,000 bare head is somehow 'unrealistic' for purchase. And $35,000 for a bare vintage FIA Group 4 or LY head is absolutely out of the question. Note the aftermarket heads use the "take it off each cylinder" model, either integrated, or external.