Which head will yield streetable compression?

[280zipper]

Im looking for around 10:1 on 91 octane. can this be made possible with the stock n42 block, crank, flat top pistons (possibly overbored, havent got the word from the machine shop) and a shaved head?

 

will i have problems with this CR without the use of a aftermarket cam? if yes what duration/lift would be best for my application?

 

Finally is the CR im looking for possibly by mixing and matching different oem heads/piston combos?

 

keep in mind im 17 and i dont have the cash to shell out on tons of machining and such so im purly out to find the cheapest most cost effective way to raise the compression and squeeze just a little bit more out of my NA l28.

 

also does anyone know what head came on a fuel injected 280z in 1976? this bit of info might come in handy for further research...

[hoov100]

It would be easiest to find a decent head and deck the hell out of it. One question though, what do you plan on doing for your fuel setup?

[skib]

toss on an E31

[blue72]

Here's a timeline of L6 heads for 'ya.

 

http://datsunzgarage.com/heads/index.htm

 

You can find L-series engine calculators on the internet that allow you to throw together different combinations with a reasonable calculation of the static compression ratio too.

Edited August 24, 2010 by blue72

[Bahraini240z]

Here's a timeline of L6 heads for 'ya.

 

http://datsunzgarage.com/heads/index.htm

 

You can find L-series engine calculators on the internet that allow you to throw together different combinations with a reasonable calculation of the static compression ratio too.

Thanks for sharing

[Challenger]

Would it be best for him to throw on a set of carbs if hes gonna go that high of compression with a cam?

[hoov100]

Would it be best for him to throw on a set of carbs if hes gonna go that high of compression with a carb

 

Yes, about the only way he is going to get some decent power out of of a high compression motor is with a bigger/long cam.

[JMortensen]

Consider the effect of the compression on total hp and the cost to a 17 year old to bump it up by changing heads, not to mention the cost of 91 octane (or mixing with race gas if you go too high and find that it won't run on 91). This topic has been discussed quite a bit, even just a few weeks ago. I think it's a bit foolish to try and get that last hp with compression when you can get so much more via headwork and cam and not have to worry about being on the ragged edge all the time, wondering if you're going to put a hole in a piston via detonation.

 

I warn you of this as a guy who put an E31 on an L28 flat top block, did a few mods like changing valves and going with valves that didn't have a dish in the face, and then found out that I needed 95 octane to keep it from pinging.

[Bahraini240z]

So, what do you think a good compression to run on 91 oct? Coz an N42 head with flat pistons should get u around 10.5:1 compression, right?

[JMortensen]

Flat tops and N42 is pushing it. Really pushing it. IMO, I'd try for 9.5:1 or less, and I wouldn't get it by putting a 2mm headgasket on. I'd go with a different head, preferably one with better quench. I like the P90 head but it gives about 8.3:1 if I recall. Shave it a bit if you feel the point in compression is worth it, or run it at the lower compression with 87 octane if you don't. Like I said though, this has all been gone over even very recently, so a bit of searching will prevent having the same ol argument again and again.

[Bahraini240z]

Sorry for my ignorance, but what would the compression be for an E88 with flat tops?

[BRAAP]

Sorry for my ignorance, but what would the compression be for an E88 with flat tops?

 

Same as the N42 with flat tops.

[Challenger]

Just in case someone asks what the compression on a n42 with flat tops would be, itll be the same as an e88 with flat tops. hehe..

[Bahraini240z]

just FYI guys... the compression of those 2 heads with flat tops is the same

[blue72]

And just in case anyone out there is curious, the compression ratio of an early E88 (not a late E88 with 3.1cc larger chambers) or an N42 would be the same as throwing an N47 on this theoretical flat top engine.

[dhartig]

It is always fun to compare:

 

http://www.ozdat.com/ozdatonline/enginedesign/

[Bahraini240z]

It is always fun to compare:

 

http://www.ozdat.com/ozdatonline/enginedesign/

Another useful link... Thanks