Rare E31 head 1970 240z

[240zguy240]

Hey guys,

My dad and I bought a project 240z with the E31 head on it. Since this car is 23 years older than I am, could some of you maybe give me some insight of the pros and cons of this head? One site (http://datsunzgarage.com/heads/) says they are hard to come by these days...anything would help!

thanks guys

[Montezuma]

They are great high compression heads and I would highly recommend it for a L24. Looks fresh in the picture.

[240zguy240]

the guy we got it from said it had been recently rebuilt

[26th-Z]

Looks to me like the head that belongs on that engine. The web site you refer describes the E31 correctly if not generally. Let's see pictures of your project car!

[madkaw]

It's not only a higher compression, it has a good high quench area which makes good use of the compression. It does have the smaller valves, but that is easily fixed to improve flow. They have had issues with corrosion around the coolant passages and also cracking around the exhaust valves. The fact that it is rebuilt is good because the valve guides and seats have probably been upgraded, which it would need because of unleaded gas.

I would make sure that the oil spray bar has been replaced-they are prone to breaking and then say goodbye to your cam. I would also recommend running some zinc additive to your oil now and then which is helpful to our solid lifter cams.

I run an early e88 head, which for all purposes is identical to the e-31. It is a great running head and I have no issues with detonation running more then stock timing.

[240zguy240]

http://www.classiczcars.com/forums/album.php?albumid=520 heres all the ones i have so far. the car is completely stripped down and being slowly attacked with bondo.

[Walter Moore]

I have the original E31 head on my engine. When you rebuild an E31 head you basically have to upgrade the intake valves to the larger L28 size because the orignal intake seats are brass and have to be cut out. The hardened steel intake seats that are required for unleaded gas are much easier to replace I am told.

I got lucky and accidentally kept the standard, smaller diameter, exhaust valves, thereby preventing the interferrence with the cylinder wall issue that occurs when you go to larger exhaust valves. (I didn't "eyebrow" the cylinder walls because I didn't know that you were supposed to...) For an L24 I doubt that an increase in exhaust valve diameter buys much. Now if you were running an L28 it might help.

Anyway, if the head has already been rebuilt, and the engine runs OK I would say keep what you have. Spend your restoration money on the other things that need work.

[Carl Beck]

Hey guys,

My dad and I bought a project 240z with the E31 head on it. Since this car is 23 years older than I am, could some of you maybe give me some insight of the pros and cons of this head? One site (http://datsunzgarage.com/heads/) says they are hard to come by these days...anything would help!

thanks guys

Looks like you have started with a pretty solid car and it should be a great project ahead - enjoy every minute of it..

The main "Pro" to the E31 for you - is that it is the correct head for anyone that wants to keep their 70/71 240Z looking stock/original.

If there is a "con" - it might be that the E31's have a tendency to crack around the exhaust valve seat. Also - if they have to be milled to straighten out any warpage - there isn't much more that can be removed without driving compression ratio's too high for pump gas today.

I would agree that finding good, unmolested, un-cut E31's is pretty hard to do today. For that matter the late 71 & 72 E88's, as well as the N42's are all getting hard to find in good condition. You have to be very careful when buying any of them used - as many are no longer really useable without significant rework, repair etc.

- The E31 is an uncommon, desirable head that came on many 1970 240's. It's chambers were high-quench designs, however the valves were smaller than the 260 and 280 heads. Probably about 10,000 were made

Actually the E31's come stock on 70 & 71 Model Year 240Z's.{up to about 07/71} Not 10,000 but more like 43,000+ 240Z's were equipped with them. Only the exhaust valve was larger on the 260Z - 35mm vs 33 mm. Both the exhaust and intake valves were larger on the 280Z heads 44 mm vs 42 and 35 mm vs 33.

FWIW,

Carl B.

[LeonV]

I have the original E31 head on my engine. When you rebuild an E31 head you basically have to upgrade the intake valves to the larger L28 size because the orignal intake seats are brass and have to be cut out. The hardened steel intake seats that are required for unleaded gas are much easier to replace I am told.

I got lucky and accidentally kept the standard, smaller diameter, exhaust valves, thereby preventing the interferrence with the cylinder wall issue that occurs when you go to larger exhaust valves. (I didn't "eyebrow" the cylinder walls because I didn't know that you were supposed to...) For an L24 I doubt that an increase in exhaust valve diameter buys much. Now if you were running an L28 it might help.

Anyway, if the head has already been rebuilt, and the engine runs OK I would say keep what you have. Spend your restoration money on the other things that need work.

FWIW, it's the larger intake valves that may require clearancing the block, not the exhaust valves. You're lucky in that there was no interference with your block, although the valves seem to clearance themselves when there is slight interference. Larger intake valves will be more shrouded on an L24 than L28.

[Carl Beck]

Also no need to eyebrow the L24 block if it has had a 5mm or larger overbore.

FWIW,

Carl B.

[240zguy240]

we are definitely enjoying the car itself! just not the body work that we're putting into it...it'll be worth it in the end!

[Holly Pitters]

Hi, Not sure if anyone is still posting to this thread - but I'm trying to figure out if my 1970 240z has the original E31 engine.  I think not but I'd like to know how to tell for sure?  Is there an engine model or ID number on there somewhere I can look for?  Mine says Nissan OHC on the top and I think the E31 said something else.

 

Thanks