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Discussion Starter #1
I am about to completely rebuild my motor, this is the setup I have... I have been told it will work, then some say I am nutz... Please help!! I want to send all the parts in this weekend to have them cleaned, surfaced and ported. The combo I have is.....

N42 Intake Plenum (The one without metal between the runners)
N47 Head with larger valves and ISKY cam
F54 Flat-top block
Centerforce Clutch
Stock Injectors + High Pressure Fuel Regulator (@50lbs)
Larger Fuel Pump

All of this will be assembled after the entire lower-end is completely balanced internally.

Pistons

Rods

Crank

Pulleys

Harmonic Balancer

Flywheel
The head will be surfaced and a 3way valve job done.
Now this is where the confusion is, I am currently running a F54 block with a N42 head. I kept blowing gaskets out of it. I then read up and found out this setup produces 10.8-1 compression. I was running 89 gas. So If I rebuild this motor with the N47 (same as N42 but with steel seats rather than brass) and get new Turbo pistons and rings. Will it work or will I be driving a timebomb? Anything I missed I can fill in, I will be on the board for the next 8 hours looking for help so PLEASE!!! respond.

Bean Bandit
 

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> I am about to completely rebuild my motor,
> this is the setup I have... I have been told
> it will work, then some say I am nutz...
> Please help!! I want to send all the parts
> in this weekend to have them cleaned,
> surfaced and ported. The combo I have
> is.....

> N42 Intake Plenum (The one without metal
> between the runners)
> N47 Head with larger valves and ISKY cam
> F54 Flat-top block
> Centerforce Clutch
> Stock Injectors + High Pressure Fuel
> Regulator (@50lbs)
> Larger Fuel Pump

> All of this will be assembled after the
> entire lower-end is completely balanced
> internally.

> Pistons

> Rods

> Crank

> Pulleys

> Harmonic Balancer

> Flywheel
> The head will be surfaced and a 3way valve
> job done.
> Now this is where the confusion is, I am
> currently running a F54 block with a N42
> head. I kept blowing gaskets out of it. I
> then read up and found out this setup
> produces 10.8-1 compression. I was running
> 89 gas. So If I rebuild this motor with the
> N47 (same as N42 but with steel seats rather
> than brass) and get new Turbo pistons and
> rings. Will it work or will I be driving a
> timebomb? Anything I missed I can fill in, I
> will be on the board for the next 8 hours
> looking for help so PLEASE!!! respond.

> Bean Bandit
You should have the block O-ringed as well. That will make blown head gaskets a less likely occurence. Also start using at least 91 octane. 89 isnt really enough for 10.8:1. If you can find a place that will sell race fuel that would work better. It would be cost prohibitive if you drove it every day though. I bought a 55 gallon drum of 100 oct and split it with a friend. NICE difference.
 

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Discussion Starter #3
Small Update...

I will not be using Turbo pistons due to the fact it will drop compression to 7.6-1 I DON'T want that...I plan ro run HiOct pump gas...What to do...
 

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Re: Small Update...

Don't worry. If you run turbo pistons with the N42 or N47, you will only be dropping compression to 8.3:1, creating a standard 280z motor.
The only time you get comp. in the 7's is when you use dished pistons with a P79/90, those heads had much larger chambers to work with the flattops .
So if you use turbo pistons with the N42/N47, expect 8.3:1.

But running a hot cam on a motor with 8.3 comp is going to kill the bottom end torque. My vote would be to stay with the flattops and find a way to get the compression above 9.

My 10:1 comp L28 with flattops and ported P79 runs perfectly on 93 octane, but pings like there are marbles inside the block when using 89.

My Vote:
Keep the flattops/N42, keep timing stock at 8btd, and use the best gas you possibly can.

Bryan
The Datsun Z Garage
 
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