O ring cylinder head

[DAT240Z]

I'm in the process of building a N/A engine for my 240Z. The engine is an m42 block and a N42 head combination. The head I bought came off an old race car the head has copper rings around each of the combustion Chambers and has been ported on polished. What I would like to know is can I run the head with a stock head gasket, or do I special gasket thanks for your help

Edited April 17, 2016 by DAT240Z

[TimZ]

I'm in the process of building a N/A engine for my 240Z. The engine is an m42 block and a N42 head combination. The head I bought came off an old race car the head has copper rings around each of the combustion Chambers and has been ported on polished. What I would like to know is can I run the head with a stock head gasket, or do I special gasket thanks for your help

If I'm interpreting this correctly, the type of o-ring you have is intended to be used with a stock gasket and adds some "crush" to the gasket around the chambers.  This should _not_ be used with an MLS gasket.  

[DAT240Z]

Tim,

Do you know what the benefits of having the rings. I have a picture on my phone but they can to upload it

[NewZed]

I'd set your head gasket over the rings and make sure the gasket sealing ring matches the o-ring.  Today's generic one-size-fits-all head gaskets might not work with an old race engine.

 

Get on the interweb to see about the o-ring's purpose.  They're used on all makes, not just Nissan.  There's a ton out there.

[madkaw]

I saw the pics of this head and its just a stock 42 chamber. I thought it was curious that it had this copper sealing on a basically stock chamber. Maybe had high CR pistons and was running race gas?

[DAT240Z]

I had the Machine Shop check the CC on the head they told me is 47.5 but I don't understand how you go about figure out the compression ratio here is some specifics on my build.

 

N42 block .20

N42 head

Flat top pistons

Port and Polished head

Robello racing tight lash cam kit

SU carburetors with reworked needles by Robello

Edited April 17, 2016 by DAT240Z

[Tony D]

Given it's an unwelded N42 and open chamber with signs of detonation damage in several cylinders, my thoughts are as old-school builds go you O-Ringed the cylinders to keep head gaskets lasting through a race.

 

This is a detonation monster, and has peaky, uncontrolled cylinder pressures so they o-ringed it to keep the gaskets in, rather than welding the chambers and getting a quench-head faster-burning, less detonation-prone setup.

[DAT240Z]

Tony if I'm reading your post correctly are you saying that this head may not be the best for my setup as it's is prone to detonation.

Is there anything I can do to prevent detonation if I use this head.

Edited April 18, 2016 by DAT240Z

[Tony D]

Weld it and get your combustion chamber mirrored in the piston tops to give the CR you want.

 

Everybody welds up that open chamber N42. It's just pingmonster if you don't.

[WhitleyTune]

'Everybody' welds the open chamber N42 is a bit misleading isn't it Tony? Yes it is common on big money builds, especially in Japan. But not everybody has that money to throw at a head! It isn't a simple task. 

 

Lots of N42's with flat tops around without issue. Yes it won't make the power and will have a slower burn than a nice closed chamber but you shouldn't really have issue if it is tuned properly and you run good gas at a reasonable CR. 

 

With 47.5cc chamber and flat tops it will be around 10:1. Try to pop the pistons out the bore to set squish clearance to 1mm, it will help with combustion. 

[NewZed]

I'd set a head gasket on the bores and if the metal sealing ring of the gasket covers the o-ring grooves, just put it together and run it.  Unless you're building a race engine that you plan to use and abuse.

 

Why'd you show a picture of the head and not the o-ring grooves?

[DAT240Z]

"Why'd you show a picture of the head and not the o-ring grooves?"

 

Here's some pictures of the rings that helps. I'm not building a race just the hot street car. I did lay the head gasket on the head yesterday. The o rings sits on top of the Rings in the head gasket I'm running it as is and see what happens

[NewZed]

My mistake.  I was thinking of the o-ringed block only.  In that vein though, you could go all the way and do the block.  Either way, I think that you're supposed to use a certain thickness of ring, depending on if you use both grooves or just one.  If yours is too thick, designed for two grooves, it could stand up the other sealing surfaces.  Better check.

 

Some say head OR block, some say head AND block.

 

 http://www.bhjproducts.com/bhj_content/products/blocktooling/org.php

 

http://www.hotrod.com/how-to/engine/mopp-0108-isky-groove-o-matic/

[NewZed]

Based on further research I withdraw my comment about just using a stock gasket and running it. Unless you pull the ring from the groove, or the ring is flattened in to the groove.  Fraught with peril...

[TimZ]

"Why'd you show a picture of the head and not the o-ring grooves?"

 

Here's some pictures of the rings that helps. I'm not building a race just the hot street car. I did lay the head gasket on the head yesterday. The o rings sits on top of the Rings in the head gasket I'm running it as is and see what happens

I think you'll probably be fine, but I would recommend a couple of things - first, the o-rings can make it more difficult for the gasket's oil and water passages to seal properly, so you might consider using using hylomar or copper seal on the gasket.  

Second, since you are using the o-ring to add extra crush to the gasket, you should re-torque it after a few heat cycles on the engine, as the gasket will likely settle a bit.  I would do this two or three times while breaking the engine in.

Edited April 22, 2016 by TimZ

[Tony D]

Nope, I don't think it's misleading at all. You can do it right, or take half measures.

 

Pistons and rings are cheap, right?

[Xnke]

The N42 isn't a "ping monster" in 90% of street builds...I've run it at 9.5:1 with zero issues. However, that's with a dished piston and controlled timing advance too.

 

Run it higher/hotter/harder than that, and yes, it will ping. But welding the head isn't always the answer.

[Tony D]

The N42 isn't a "ping monster" in 90% of street builds...I've run it at 9.5:1 with zero issues. However, that's with a dished piston and controlled timing advance too.

 

Run it higher/hotter/harder than that, and yes, it will ping. But welding the head isn't always the answer.

 

That's nothing I'd give my wife to go get groceries with.. Basically a stock build then, and even then using controlled timing.

 

If you can't run proper spark  advance at only 9.5 on regular, much less CA91 Octane....I'd call that a 'pingmonster'!

 

For the stated claim of the engine to be a 'racer' I think my characterization is spot on why they O-Ringed it! It kept blowing head gaskets and it was cheaper to o-ring it than have it welded.... and pistons are cheap, change them out every couple of races anyway, right?

 

For my money, I'd pick a different head, or simply do it right.

 

If I can make 375 turbocharged horsepower on an N42 that in the good old days could run on CA87 up to 12 psi.... I think that's not a bad testimony to how well an N42 or any L-Head will work when you get the right chamber in there in terms of detonation resistance.

[Xnke]

36* of timing advance at 9.5:1 compression? I think that's full advance...

 

By controlled, I mean having control of the timing curve, Tony...even you won't run that kind of advance without it. That engine easily ran on 87octane, even with 8PSI of boost on it later.

[Tony D]

That wasn't stated up front, duplicity can drag it out forever. Yeah that's full advance. How much does it "need" with the closed chamber on it?