Head Swapping

[Ed]

I'm in the planning stages of rebuilding my L-28. I already have 71 round tops with a K&N. 6-1 headers with a 2 1/2 exhaust. I want to do some head work and I'm planning on putting in a mild cam and having some port work done. I currently have a N42 head that needs work. I was considering a E-31 head for the higher compression but heard it has smaller valves than the N-42. Any suggestions?

[2ManyZs]

You are right, the E-31 has the smaller valves as do the E-88's. However the 280 valves can be put into these heads.

For the best info on heads I would suggest looking at the Datsun Garage web-site in the web-links section. There is a lot of good info on the different heads and there pluses and minuses of each head. There is no head that is really bad, just a couple that are better than the rest.

BTW, the web-site is number four in the top ten web-links for a reason. It is packed with good info, not only on heads but the whole drivetrain.

[Ed]

I can't find the Datsun Garage web site.

Any help?

[240znz]

Try http://www.geocities.com/zgarage2001/z.html

Zed not Zee

[Phacade]

A couple of thoughts. You have the headers already. Are they square or round port exhaust? This will pretty much determine the head that will mount to them. If for example you went with a P79 head, you would probably need a new set of headers since both heads you mentioned are square port exhaust heads. There is really no bad choice, just a few better choices. Personally I liked my P79 head, much better than my N42 head I have now. After the head work and mated to my F54 block, Z therapy SU carbs and MSA 6-1 headers, I have an unbeatable combination. A couple of things you have to ask yourself. What do you intend to use your Z for. Racing? Autocross? Daily driver -w- attitude? While most of us would like to build out engines to race, few of use actually will. N42 heads tend to make good racers but poor drivers. Again this is my opinion form personally experience, please feel free to flame me if you like. Another idea on the Datsun garage web site was to use a P90 head. It has the square exhaust ports the will match your headers but is very free flowing. Should make a nice compromise between racing and everyday driving. Again, just a thought.

[Ed]

The exhaust ports are square. I intend to keep the car as close to "Daily Driver" as possible. My advantage is that I have a 24 mile commute (one way). Seven of which are on a lonely country road with lots of curves. The rest is all freeway. My freeway has about 10-15 cars in 17 miles. And I've only seen 2 cops in the last 6 years. So there have been many an opportunity to let her go.

I do want to increase horsepower without loosing the ability to drive into town and have to deal with 100 degree stop and go traffic. :mad: In other words I need to beat that Acura Integra! I already have the N42 head on it now but I can tell that the valve seals are gone. I'm really checking out my options for some more horsepower. Oh yea, did I forget to mention that new cam is going to go in at the same time (not sure which one though?).

[jcdozier]

A California freeway with "...about 10-15 cars in 17 miles."??

What time of the night do you commute to work?

JIM DOZIER

[Royce]

Ed,

You don't mention, or I didn't see it, what car you have or more importantly what block you have. If you have a N42 L28 block under the N42 head, going to a P79 or P90 head will drop your compression to below 8 which would be low even for a turbo application. Also, the P79 or P90 take a lot of modification, or you would have to change your pistons, to get that much a good compression ratio with those heads. If you modify your N42 head now and decide you want to go faster in the future just find a good F54 block and put it under that N42 head and you will be close the the max compression that allows you to still be able to use pump gas, close to 10.5. I think anything you do to your existing head will be good use of $$$ because it could be used in either setup. I wouldn't bother with the E31, you really can do a lot for your $$ with a N42. If you decide to change heads I would be happy to take the N42 off your hands!

Good things to do to the head:

- going to hardened steel valve seats (just to eliminate needing lead in the gas).

- porting (and port matching the intake manifold).

- upgrading cam.

Also, keep in mind that if you do decide to race or autocross having a modified setup can put you in a "faster" catagory. But again this depends on the club.

Have fun!

[Ed]

I have a 73Z with the N42 block. I do have an F54 available. I guess that's what I'll use. I also heard that the 260z intake allows better air flow good enough for some extra HP? Thanks for all the good info.

Jim, I leave the house at 10p. And I drive away from the city.

[jcdozier]

ED:

10pm sounds like the "graveyard" shift. I did that years ago when I lived in SF - north over the Golden Gate through Marin and over the Richmond-San Rafael bridge to the Richmond refinery. Going to work was a breeze (more than 10-15 cars, though) but the ride home with all of the folks commuting into SF was a whole 'nother experience.

Good luck with the engine.

JIM DOZIER

[Royce]

One more thing about the F54 block, there are two different pistons that came in them. The "turbo" motor came with dished pistons which leave you with a 8.?? compression ratio then there is the "non-turbo" motor that came with flat top pistons which would put the compression ratio up in the 10.?? range.

[Ed]

No turbo. I took the 5 speed out of an 81 280zx and put that in my 73, I guess I should have taken the engine while I was at it. Oh well, it will give me something to do next week.