Which head should I shroud

[circinus]

I have a n42 head that got all fubbed up when a valve broke. I thought it was just junk aluminum until the other day. My dad came over and started dinking around with it and shrouded it out and said there ya go now you can use it again. Well it got me to thinking, if I'm going to spend my time on finish shrouding out a head, I've got 3 and which one would be my better choice to spend my time on. Heres what the engine plan is for the car.

 

I have a stock 81' f54/p79 engine right now together.

 

I plan on installing a turbo w/ megasquirt, 2mm head gasket. Now I planned on just p/p the p79 and call it a day and be done. Now I'm thinking if I'm going to spend the time shrouding the n42 would that be the better head, or I have the a n47 and should I spend my time doing that one or the p79? Or is it not worth all the efforts to shroud any of them. I've been wearing out my search bar for days now and not finding much of anything on this certain topic. Alot of p90 info out there. So I guess question is If these are my head choices for my flattop turbo and I am going to spend the time shrouding and p/p them which one would be the best choice for what I'm building. Btw this isn't a daily driver so I plan on it being as much of a beast as it can be up to the point I'm not busting rear-ends and cv's. Its my 10yr sbc z project that went a whole diff direction 6 mths ago. Stupid turbo's

[circinus]

Should I repost this in the turbo section? Head work is head work no matter which way you look at it and thats why I put it here.

[skib]

if your going to go threw all the work of doing a head and planning to go turbo Id just pick up a P90

[leftover z]

if your going to go threw all the work of doing a head and planning to go turbo Id just pick up a P90

 

Yeah, according to Fastdadd, Skib is the expert on head.

[circinus]

I would do a p90 if I could find one cheap and thats not happing for me right now. I've been looking. I already have those 3 heads and since its so cold outside here in ohio I can do one of those heads in my free time in my basement. I will get one down the road but for now I was focused on doing up one that I already have.

[Xnke]

You are going to end up spending the money anyway, to unshroud a head.

(BTW, you're UNshrouding a cylinder head...)

 

If you are going to put in the money and time to do headwork, do it correctly or spend more money to fix it later.

 

It took me three cylinder heads before I was able to make few enough imperfections to call it good. I have one other that is "usable" and one that is "garbage/practice/let's chop it up and take a peek inside"

 

Headwork, even repair work, takes time and practice to get it correct, and if you take shortcuts you can end up with WORSE performance than if you had left it alone!

 

If you take some time to search the forums and read the stickies that BRAAP has posted here, you'll find he's given out some AWESOME information on head porting for the L6, with photos and everything. He's a professional, and it's rare that you'll get that kind of information for free.

 

But If it was me...

 

I'd take the N42 head, weld it up, and port/unshroud it to be exactly what I wanted it to be. Failing that, I'd go get a P90 and work it over to be what I wanted. If you can't weld it up, then be very careful how much you increase the chamber size, and be even carefuller how much damage you do to the gasket sealing surface, you don't want to mill too much off, with the flat-top pistons in that block. Compression ratio is getting to be a problem, with a 1mm headgasket, you'll get about 10-10.5:1 on a flattop block with an N42 head, with a 2mm you'll see about 9:1 compression....pretty high for an L28ET.

 

If you are running a P90 and a 2mm headgasket, you might as well not bother running a P90, you're giving up a lot of the advantage there. You've got a flat top engine, so I'd run the stock thickness headgasket, flattop pistons, and a ported P90 head to go turbo. ESPECIALLY if it's a megasquirted street car, and you are planning on moderate (15lbs or so) boost.

 

Now, there are other schools of thought out there, and you'll probably hear from them as well, but that's how I'd do it.

 

(currently have a N42/N42 engine, dished pistons and a ported/unshrouded/chamber resized N42 head in my car, at 9.5:1 compression N/A, going turbo in the future. I'll have to get a 2mm headgasket, which on my engine will drop CR to 8.5:1, highish, but turbo-friendly, for the L28ET.)

[circinus]

Thanks xkne. I didnt know if I opened up any of those heads It would give me good enough flow where p90 wasnt needed. Its one of those things where between the wife, kids, and everything else when I found some free time here and there I would try to go to town and go thru one of those heads while its cold out and nothing can be done on the car because of that. When I threw that post up i typed first ran out the door and read it when I got home so It didnt even realize the shroud/unshroud. I grew up always hearing shroud out the head. But I think 75% of the terminalogy I grew up hearing is prob wrong. I have enough exp. to not think twice about digging in on a head but not enough where I'd go out and start a buissness doing it. And your right about Braap. I've had my car since 1990 and up until around 2000ish I didnt know jack about turboing my car or even upgrasdes exp. for your oldies sbc,stroker,p/p, and gasket matching. Thats when I started going to the library and used the computers and found this site and got educated on my z real quick. And he's one of the big ones who schooled me well. So I Finally got my own computer somewhere around 2005-2006 and I finnaly got to have my own login here. And the car became one of those projects where everythings there to do it , now I just have to do it. Not really into welding up the head. I have the resources to do it but thats starts getting into more than here and there nights in the basement. It seems like the n42 being a sweet head for n/a isn't going to give me any advantages with that high of comp. I was really hoping to read yeah open up the one of the heads and it makes the perfect turbo head. Looks like that head is the p90.