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Engine heads how they flow


Gav240z

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Well i thought i should write up about what I've been up to with my Z lately. Since the site has been down for a little.

I was originally going to install a new camshaft and engine head ontop of the existing block. However after pulling it apart and discovering the lash pads weren't wearing quite right and the camshaft was a bit rough they had filed down the square parts on the cam you can use a shifter to turn it from. For what reason I don't know. I decided I'd pull my P90 engine head off and compare the two.

Here is the part some might find interesting.

I have 3 motors:-

Motor 1(Specs)

F54 Block , 72 E88 Head, N42 Valves, Port work, Mild Cam. Pretty sure flat tops from comp reading (In Car).

It goes fine sounds great but is burning oil which could either be valve stem seals or blow by. Still unsure on that 1.

Motor 2(Specs)

P90 head, F54 Block , Flat Top Pistons, Decent size valves(Appear to be stock but are quite large compared with others we had), Port work unsure.

The motor was going ok but started to play up right before the car it was in was written off. Found water had been leaking into combustion chamber and carbon build up everywhere.

Motor 3(specs)

N42 Block, Dished Pistons, E88(73) head, 76 Degree cam , n42 valves, port work etc..

Apparently was pulling 120rwkw with tripples(webber) on it.

Ok so for now I get motor 2 and 3 tested for flowing capabilities and guess what the P90 is much better. The E88 did not flow that well the port work could have been done better last owner said he pumped $1200 into port work.

I bought the motor for $400 but have realised it's a bit of a waste.

So if your still with me to this point, I am going to build the P90 get a 76 degree camshaft made up that is internally oiling the other head i bought the cam was a squirter bar type and I'm not fond of those. I've had my distributor mapped and it will now rev to 9000rpm if i want. We are going to do some port work on her(p90) , get a 3 angle valve job done. Then once the head is ready try putting it on depending on comp ratio to the block in the motor if she burns oil still I'll build a bottom end(which I will anyway) but quicker and I'll go the Diesel crank and bore her to 3.1ltr.

So basically I have reconfirmed the issue that the P90 is the best engine head for a Z by means of a flow bench test. As a result I am now building a new motor for my Z slowly and properly and I'll let everyone know how it turns out :)

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The dizzy may rev to 9k, but surely the valves would start bouncing, and the bottom end falling apart well before then, assuming its fairly stock? Just curious but what did it rev to originally before things all went to $^!#?

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