Need advice on N47 head with liners removed

[Eddie-G-Force]

I need some help with what to do with a N47 head with the exhaust liners removed. I purchased a co-workers 72 240Z super basket case. Sort of a barn find. He started restoring it 15 years ago and gave up (after totally disassembling everything). The "deal" came with a reworked N47 head with a valve job, the exhaust liners removed, and an interesting porting job was done at some Z performance shop in upstate SC. The intake ports look okay. But the exhaust ports are totally raged where the liners were. Below the valve seat is a 2MM. sharp knife edge wall, I can cut this down but there will be no short side radius. I was thinking of having the valve guides pressed out and smoothing the bottom of the bowl. Take a look at the pictures. Should I salvage the valve train and toss this mess??? I want to build a L28 flat top motor that can run on 93 octane. I also have a used P79 head which I'm thinking about shaving 2mm. and putting the longer N47 valves in Has anyone been successful in building horsepower with a liner-less N47 head?

 

I'm trying to build this car for the Maxton TSC NC event in April 2010, but that's another post. Thanks.

[ozconnection]

Anything can be done if you spend enough money.

 

The exhaust ports were designed with liners. Removed, I'd say it's not worth the money to get them to flow properly. Too much to do.

 

Strip it down, keep the parts and cut it up to look at the water jackets and ports, as suggested in the 'head cooling around 5" sticky.

 

Your call but that's what I'd do.

 

Cheers.

[1 fast z]

Whoever did this did NOT know what they were doing. THis head will never flow as good as it did stock, unless the ports are welded up and started over.

[kolonelklink87]

this is a bit sad to see... from my very limited understanding the focus of home porting on this head should have focused primarily on reshaping the areas on and around the valve guide? I'm messing around with a bit of home porting myself at the moment and this is a great example of a "what not to do".

 

I'd love to hear some reflections on what went wrong and why from people in the know... post mortem?

 

Cheers,

Pete.

[Eddie-G-Force]

Thanks Guys. I pretty much knew the answer before the post, but wanted confirmation. Just to be clear the previous owner paid good money to have this head screwed up by "professionals". Honestly I can't take credit for this one.

 

I hope these pictures prevent someone else from doing the same.

 

I wonder why all the work, and then not smoothing the giant blob on one side of the port. No need to reply on that one.

 

I guess it's on the my P79 shave.

[BRAAP]

The value of that N-47 is going to fluctuate..... As the price of scrap aluminum rises, its value will rise, as it descends, so will its value. If you have the time and resources, strip the head down including removing the valve seats and guides and its value will be higher yet, (clean aluminum brings more money than dirty aluminum at the scrap yard).

 

Noticed you mentioned wanting to build a flat top piston L-28 that will run on pump gas. If you were thinking of using a Z car N-47 such as this, (even if it had the liners), you might want to read this thread first...

http://forums.hybridz.org/showthread.php?t=156953

 

The P-79 in stock trim is definitely a safe bet and will perform well. Shaved .080"?... It might have enough squish at that compression ratio to be friendly enough for pump gas to run the ideal max ignition advance that head prefers... Haven't done one yet so can't say for sure and may look into it a bit further as it is becoming more and more common, at least in forum discussions.

 

 

 

My point is don't get too bent on a couple points in compression that would only yield in the neighborhood of 6- 6 1/2% HP (if producing 180 realistic HP would only be 11-12 HP gain), "IF" you can run full igniton advance which an L-28 with flat tops and either the E88, N42, or N47 head wont be able to on even the best premium pump in this country so you'll be throwing away more power in the retarded ignition timing than you gained with the bump in compression ratio, i.e. going backwards in the quest for more power! Again, this applies to the L-28, not other makes of engines as 10.5:1 is a safe pump gas friendly static compression in most other engines with aluminum heads.