Hi guys new on the forum. Have finally purchased a 300zx TT 2 seater manual..needs abit of work. when i was doing some work on it i saw that its running N/A heads instead of the TT(30p marking on the heads). The guy i bought the car off said he recently done the heads, head gasket etc... I know that it will have some power drop but i was wondering whether it will have any other effects on the motor, or any suggestions, Trying to get away with not taking apart anything yet... Sorry if this is a noob question but new in the z game. Thanks in advance
Z1MotorSports did a NA/TT differences doc some time ago, here is what they say about the heads. http://www.z1motorsports.com/PDFs/NATTconversion.pdf
mmmm very weird this z has bigger turbos, os giken twin plate clutch( which I took out cause it makes a noise only to find out that they make rattling sound when disengaged and already bought new clutch.), bigger intercoolers, aftermarket fuel pump, ems ecu and..... na heads... *head scratch*. Thanks for your responses ..
With that sort of shopping list, I would suggest the na heads were just blanks that someone's played with. Wouldn't be surprised if they've not been ported.
the valves are made of different material in the TT's. to do with heat resistance i think. Then NA ones may not survive aslong/as well when used in a TT application.
Ignore the heads. You wont notice the difference. Inconel alloy is desireable as a valve material but nowhere near necessary as legions of high boost engines seem to survive with plain old *whatever material* exhaust valves at stupid rpm and boost levels. Drive on M8 and enjoy your car rather than taxing yourself over insignificant details that dont matter at the end of the day. E
I don't think the the ports are actually smaller but possibly port shape/angles slightly different. They stamped them with different numbers for a reason .. could only be to distinguish them on production line for the different valves that went in . All someone has to do is flow test them to kill the myth not rocket science .
According to Z1 website the valves are the same size but ports are smaller to the point that porting them out to TT size would be a significant undertaking. Dunno if that's true or not but no reason to disbelieve it.
I've seen another independent test by an engine builder that says the port runners are the same . Who do you believe? I have every reason to question it for all the mis information I've seen on our cars like our cranks being nitrided.etc Like I said all I have to see are flow charts .. Simples Until then its the usual he said ..she said . .
Intake ports are much smaller volume on NA heads. That's not hearsay or Internet "truth", that's fact. You show me this independent test that disputes that, and I will provide you cc numbers.
Smaller? So what? Port size isnt everything and is not tied that closely to flow. Too many uninformed are fixated on "bigger must be best" syndrome when in fact thats rarely the case. The important factor here is port shape and gasflow entry angle and its relationship with the valves and their angle and bearing all that in mind, it seems that the NA heads are a better choice to begin with. I submit that one engine fitted with NA heads and another fitted with TT heads, same boost and subjectively driven around would reveal insignificant differences. Get over the size thing. E
Probably -but if you're running higher boost/bigger turbos etc id be willing to bet the motor with the NA heads will hit a ceiling sooner. My only point above being that it sounds like someone threw this motor together from spare parts rather than making a point of using the "right" heads.
PLEASE DO ! Would love to see some real numbers and GET SOME REAL FACTS ! I'll find what I read and post it up . .
The thing is, and this is where a lot of men get confused and not see the big picture. Its not the port size thats the limiting factor. Its the area around the valve seat. THAT is where the restrictions happen. Secondly and importantly, low lift flow, as in at the early and late stages of the valve opening event is far more important that open port flow figures!!!! Full open valve opening time is pretty short in comparison to limited lift flow. lastly, high lift does not always increase flow. in one of my race engines, an extra .050" lift results in no increase of flow and further lift actually reduces flow..... Once you get your head around such things, big ports might not seem so wonderful afterall. All is not as it first appears!!!!!!!! E
Agree with everything you said Evan, but the vg heads do respond very well to an experienced porter, plenty of room for improvement. The major difference in the 2 heads is the NA has a much longer port divider on the intake than TT, no doubt because those clowns at Nissan knew bigger isn't always better too and wanted to keep air speed up at the back of the valve to get a healthy 220hp out of the little 3 ltr asthmatic lung. The snazzy whirly bird fed version doesnt care too much about a little less volume or a longer runner, itll jam whatever it can down there. It's a pity they let the team down in the machine and casting shop and gave us misaligned port to intake seat as well as overly chunky guide bosses. The biggest improvement comes from grinding away that guide boss flush and throating behind the seat, straighten out the short turn, give the rest a once over to clean up any flash with a cartridge and your done on the intake side. Exhaust takes a little more to get it within a healthy flow % of the intake but that's a lesson for another day.
