What head to use?

[Chad Hack]

I have a L28 with flat top pistons and stock boar. I also have mikuni triple dues carbs. Does anyone know what head i should use? I would like to keep the compression down so i can drive it on the street and use high test gas. It also has a mild cam (witch i don't have to use). Also the header ports are square that matched the n42 head exhaust ports that met its demise by the last owner. I also don't know if i can use those headers on say a p79 with round exhaust ports. Any help would be appreciated.

[Pop's Z]

Hi Chad,

Look at my signature. F 54 w/ N 42, stage 2 Delta cam, 10.5-1 compression. ZTherapy Hitachis. ZX distributor, 91 octane. No knocking at 5,000+ feet of altitude. P 79 and P 90 will require major modification to obtain high CR. They have to be shaved and the cam towers shimmed up to match among other things. N 42 is a bolt-on. Just clean it up, and have your machine shop replace the valve seats with steel (if stock they are bronze), do a valve job, and put in new valve guides and seals. You will be good to go and believe me the power is really good AND streetable. Good luck.

Cheers, Mike

[Jeff G 78]

I have one Z with a flat top/N47 engine and my race Z has a flat top/shaved P79 engine.  Both work great, but I chose to use the P79 for my race car.  I did not change valves or shim the towers.  There is another way to build it without major mods.  Pretty simple actually.  I only run about 9.5:1 CR on that engine, but it makes great power.

[Zed Head]

7 hours ago, Chad Hack said:

I have a L28 with flat top pistons and stock boar. I also have mikuni triple dues carbs. Does anyone know what head i should use? I would like to keep the compression down so i can drive it on the street and use high test gas. It also has a mild cam (witch i don't have to use). Also the header ports are square that matched the n42 head exhaust ports that met its demise by the last owner. I also don't know if i can use those headers on say a p79 with round exhaust ports. Any help would be appreciated.

The head has the cam, not the block.  If you move the cam over to your new head make sure you do it right.  Several ways to go wrong.

People say that the square port headers work fine on round port heads, but not vice versa.

The question is "what is most important to you?"  Getting the engine running quickly and easily. or putting together an engine with more power than stock.  You could buy a complete head with cam and rocker arms and install it and be up and running pretty quick.  Or you could buy a bare head and use the parts from your damaged N42 head.  Many different ways you can go, but you need to define some things.

What, exactly, happened to the old N42 head?  Maybe it's salvageable.

[Chad Hack]

The last owner must have floated the valves, and the exhaust valves tapped the pistons. It must have happened early in the 3k miles that was put on the newly built motor, because carbon was already over the marks it made on the pistons. Any way, the bottom of the n42 was straight so i put new exhaust valves in the head. I went to put the cam back in, and it would not go through the last cam tower. Found out the top of head is warped. I have been contemplating shimming the tower because everything else is good.