Lukaniuk Posted July 29, 2008 Share Posted July 29, 2008 I searched but couldn't really find much. Has anybody have experience fitting an E31 head on the L28ET block? I've got an E31 (needs a rebuild, but has extensive porting and larger valves) just sitting and not doing anything so I started thinking; "say... I wonder if that would work better than the P90 I have in the car now?" I think would have to get the intake ports cut out for the fuel injection. What else would it take to get it to work? and would it be worth the effort? Quote Link to comment Share on other sites More sharing options...
Daeron Posted July 30, 2008 Share Posted July 30, 2008 I think it would be a screamer personally... The e31 head is beautiful. (BTW, could you possibly post some pretty cylinder head porn for us??? ) The chamber SCREAMS "Drive Me!!" and its only significant drawback is the valve size, which as you say has already been taken care of. There are other things that pile up in the "con" factor when selecting a cylinder head that have, in this day and age, come to give the E31 a bit less of a golden reputation than it once had. For one, since they were the original "performance build" head (before the N42 cars were even rolling off the line) there are not so many heads left untouched, so they are more difficult to find. Secondly, they require the expensive valve enlargment job. Third, the later heads have other significant advantages: The "quench kings" already have a combustion chamber that is tidy and well shaped, and fairly small; and the N42 has a big combustion chamber with lots of room to weld in metal and re-shape to whatever your heart may desire. Finally, the E31 is limited to carb-only use unless you spend to have the injector notches cut. (Incidentally, the E31 is still a VERY desirable performance cylinder head for those limited by class rules in racing to keep a stock head casting on their motor; many if not most ITS and E-production SCCA 240Zs run E31 heads.) So, my point is, the chief reasons that people "avoid the e31 head these days" are either trivial (reasons why there is a tendency towards not bothering with them NOWadays..) or are moot (the real, hard reasons like valve work that your cylinder head already has taken care of.) The chief concern is one that reflects into the extensive early use of the E31 as a racer head. You need to ensure that your cylinder head has not bee excessively machined. Both top and bottom curfaces of the head are areas that get milled to "true" the head, and if it has had a valve job done than it may well have served a long life as a performance cylinder head; as such, it may have seen a knife many times before. Make sure it hasn't been cut down TOO much, because there is a point where it becomes useless. Quote Link to comment Share on other sites More sharing options...
Lukaniuk Posted July 30, 2008 Author Share Posted July 30, 2008 Thanks for the info Daeron. Before I did the turbo swap I was running an L26 with the e31 & triple webbers. It was a blast to drive but it was getting old and was burning lots of oil. I had to rebuild something and I decided to rebuild the turbo motor instead and the L26 has been sitting in the garage the past couple years. Running the e31 might be something fun to try. How much would the compression ratio increase with the swap? Would it oil and cool properly? Also just for interest sake, what's an e31 head worth? Quote Link to comment Share on other sites More sharing options...
Daeron Posted July 30, 2008 Share Posted July 30, 2008 compression ratio, i cannot say for certain because we do not know what has been done to your head.. try this link though http://www.ozdat.com/ozdatonline/enginedesign/ that should get you in the ballpark. Oiling and cooling, I am wholly ignorant of but it should be fine?? thats an excellent question and I go out on a limb saying as much as I did right there.. As for the value, there was a time when a well prepped e31 blank no cams/valves) could fetch a bill or two, but popularity of the head is way down so I couldn't even begin to tell you. The value of the head would probably be maximum with an UNTOUCHED unit, because a piece that had never seen a machine shop is, for a racer's purpose, brand new.. it hasn't been milled on either side, and you KNOW that. Sorry, I tapped out my knowledge hoard in my first post.. but I would love to see you take the leap and do this. It is usually agreed by "the masters" that an E31 would make for a great build, but nobody seems to do the whole L28ET with it because it isn't the well-established solution that the N and P series heads have, and it is a less common piece of hardware. Quote Link to comment Share on other sites More sharing options...
KillerBjt Posted July 30, 2008 Share Posted July 30, 2008 i actualy have 2 E31 heads, one on my 240z and the other in my garage. the one in the garage has a small crack in one cylinder though. im pretty sure bother are stock other then the cam in my 240z. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted July 30, 2008 Share Posted July 30, 2008 The E31 is prized by the ITS and EP guys because they aren't allowed to use heads off of the other L engines. They're stuck with the original L24 heads, and the E31 has the smallest chamber. I think its not a good choice for a turbo. Compression would be too high and needs retrofits for the FI. Porting is less important on a turbo engine since you have pressure cramming the chambers full, but if you were really hung up on it, you could port the P90 and keep the lower compression. In very simplistic terms, high compression turbos are boost limited. Low compression turbos have more lag but also more power potential. Quote Link to comment Share on other sites More sharing options...
Daeron Posted July 30, 2008 Share Posted July 30, 2008 I think its not a good choice for a turbo. Compression would be too high and needs retrofits for the FI. With flat tops, yah, compression comes in at 9.4:1.. but take 10ccs out of the pistons and you get 8.1:1... a small relief mirroring the combustion chamber would be more than adequate to lower the compression into reasonable ranges for a turbocharged engine.... My point is NOT that your comment had no validity; quite the contrary, it is a good "con" to the E31 that I failed to mention in my list. However, it is far from a deal-breaker... I have no idea how well the engine would run with stock dished pistons from an NA l28, but according to the little engine calculator I posted above the stock N42 L28 and the L28E piston dish is just shy of 11 ccs, and brings the comp ratio down to 8:1 flat. The head itself has no fundamental issues. Besides, the "ideal quench pattern" is never achieved with a P90 and flat tops.. it is achieved with a P90 and flat tops, with a relief machined into them that mirrors the combustion chamber in the head. I would reckon that an E31, with large valves, and flat top pistons with MINIMAL clearance and a relief cut in them to match the combustion chamber and lower compression ratio to something acceptable (possibly removal of material on the head as well.. it could use SOME blending and enlarging to match the larger bore of the 2.8) would be one heck of an engine... The reason it doesn't get done is that it has plenty of stalling points, and there are plenty of people who would use the head for a stock 240 for competition. Half of the stalling points (or more) on your cylinder head are taken care of, and are YOU going to be racing an ITS or EP 240Z in SCCA sanctioned events within the predictable future? My point is that there aren't very many good reasons left for YOU, NOT to use your E31 for an L28ET build. Most of the good reasons are gone with the larger valves; the compression ratio is the biggest remaining sticking point (unless someone offers you $350 for the head as is..) Quote Link to comment Share on other sites More sharing options...
katman Posted July 30, 2008 Share Posted July 30, 2008 Jon has it right, E31 not a good choice for a turbo. Not a great combustion chamber (better than a late E88 for sure, but nothing special) but it's biggest downfall for a turbo is volume. When you're cramming air into the combustion chamber more is better. 55cc boosted to 7psi is a whole lot more air/gas/power than 43cc boosted to 7psi. Quote Link to comment Share on other sites More sharing options...
Lukaniuk Posted July 31, 2008 Author Share Posted July 31, 2008 Why would a compression ratio of 8.1:1 be too high? Forgive my ignorance, but what factors does one consider when calculating the ideal compression ratio? Doesn't an RB26dett have a compression ratio of around 8.5:1? Quote Link to comment Share on other sites More sharing options...
Xnke Posted July 31, 2008 Share Posted July 31, 2008 That compression ratio of 8.1:1 only holds (i think) for a 2.4L engine. L28ET implies that you are running a 2.8L engine. Thus, your compression would be something like 10:1 on flat tops, or 8.5:1 on factory dished pistons. Quote Link to comment Share on other sites More sharing options...
Tony D Posted July 31, 2008 Share Posted July 31, 2008 argh... misuse and perpetuation of the 'lag' myth... I won't even try. Quote Link to comment Share on other sites More sharing options...
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