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Can somebody please explain the difference in heads for Z's. I see the lingo on this site all the time. What does it mean to me? My Z has a P79 head. Is that a good thing?
 

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Can't vouch for the 240-260 heads but 280 z is as follows; '75-'76 N42 some say the best head to mod (bolt onto the flattop block presto,10:1 comp!),'77-78 n47 practically the same plus the exaust liners to reduce emission.(some say a VERY bad thing:) same result with the flattop. '79-83NA P79 the OTHER BEST head to mod.
'81-'83Turbo p90, p90a (hydraulic lifters) by the way, visited the junk yard ,saw an zx with the n47 head , go figure.
Stan
P.S. check the datsun workshop site for complete info.
 

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> Can't vouch for the 240-260 heads but 280 z
> is as follows; '75-'76 N42 some say the best
> head to mod (bolt onto the flattop block
> presto,10:1 comp!),'77-78 n47 practically
> the same plus the exaust liners to reduce
> emission.(some say a VERY bad thing:) same
> result with the flattop. '79-83NA P79 the
> OTHER BEST head to mod.
> '81-'83Turbo p90, p90a (hydraulic lifters)
> by the way, visited the junk yard ,saw an zx
> with the n47 head , go figure.
> Stan
> P.S. check the datsun workshop site for
> complete info.

Is p90a supposed to mean it has hydralic lifters?, Mine has a p90a with mech. lifters.
 

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Good Info On Z Heads

> Can somebody please explain the difference
> in heads for Z's. I see the lingo on this
> site all the time. What does it mean to me?
> My Z has a P79 head. Is that a good thing?

A guy's kept up a web page you'll find interesting. It gives good info on Z heads. Find it at:

<A HREF=http://www.geocities.com/MotorCity/2824>http://www.geocities.com/MotorCity/2824</A>/

-Rob
 

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> Is p90a supposed to mean it has hydralic
> lifters?, Mine has a p90a with mech.
> lifters.

Leslie,
No it doesn't. Externally, they are almost identical in appearance to the mechanical lifters. The only way to tell is by looking at the boss if you will, or the part that the rocker pivots on. On a mechanical head, there are three nuts, one for the whole boss, and two adjusting nuts, one to move it up and down, and one to lock it down. The hydraulic heads don't have the lock down nut. They appear to have the adjustable nut, but it is just an integrated part. The only real difference is internal, besides being physically larger than the mech. units, they have a check ball and resevior inside. when put under pressure, the check ball locks up, and the lifter won't depress. anyways, I originally thought mine was a mechancial head as well, but was wrong. if it says p-90a, it is hydraulic.
-bob hanvey
 

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> Leslie,
> No it doesn't. Externally, they are almost
> identical in appearance to the mechanical
> lifters. The only way to tell is by looking
> at the boss if you will, or the
> part that the rocker pivots on. On a
> mechanical head, there are three nuts, one
> for the whole boss, and two adjusting nuts,
> one to move it up and down, and one to lock
> it down. The hydraulic heads don't have the
> lock down nut. They appear to have the
> adjustable nut, but it is just an integrated
> part. The only real difference is internal,
> besides being physically larger than the
> mech. units, they have a check ball and
> resevior inside. when put under pressure,
> the check ball locks up, and the lifter
> won't depress. anyways, I originally thought
> mine was a mechancial head as well, but was
> wrong. if it says p-90a, it is hydraulic.
> -bob hanvey

I have to disagree with you Bob. I have adjusted mine many times using a feeler guage. And I know I was able to change the clearance. Hydralic lifters can't be adjusted as far as I understand. Mine has the three nuts on it. I just checked to make sure it is a p90a. Could it possibly have been modified?
 

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> I have to disagree with you Bob. I have
> adjusted mine many times using a feeler
> guage. And I know I was able to change the
> clearance. Hydralic lifters can't be
> adjusted as far as I understand. Mine has
> the three nuts on it. I just checked to make
> sure it is a p90a. Could it possibly have
> been modified?

yes, they can be modified. but it is a rather involved process. the boss if you will, is physically larger than the non-hydrauilc, so an insert must be made to make it fit. it has been done, but it is not cost effective, for the p-90 head by itself is available. beyond that, you are where i don't have expertiese. i would say that it is remotely, i mean very remotely possible that you have a freak head. i would say it is more likely that someone along the line had the lifters wear out, and their machine shop just made inserts to utilize the non-hydraulic bosses. i have heard of it before, but again, it is not that cost effective. i guess in the long run, you avoid the cost of replacing the hydraulic lifters every time they wear out, from 60-100K+ miles.
-bob hanvey
 
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