My Motor

[KGL]

Hi All: New member love the site. I'm currently rebuilding my l24. The bottom end is to remain the same, only bored if need be. I will not be changing to an L28. Now to the head: it is an e31 which I will be keeping, the car is to be used as an every day driver but as always am looking for as much performance without sacrificing to much. I plan to change out the cam, and am wondering if I should increase the valve size to the 280z valve size. Will I have to grind the block some to occomadate the larger valve size. Any suggestions on what cam to use. Will this combination work well and what will my compression ratio be. Also I need new head bolts where can I get them. Sorry for the long post. All help is much appreciated.

[Bambikiller240]

If you are rebuilding an L24, I recommend "How to Rebuild Your Nissan/Datsun OHC Engine". It will be the best $20 you ever spent and will answer all of your questions. MSA sells the headbolts also.

http://www.zcarparts.com/store/merchant.mvc?Screen=PROD&Product_Code=70-1041

[KGL]

Thanks Bambi: I have the book your quite right it is helpfull. My question was in response to being told that contrary to the book someone at msa told me that if I'm keeping the L24 and the E31 I wouldn't notice any difference with the larger valves and to just go with the cam modification. So what is the right cam to use for my requirments as listed before? Thanks

[Bambikiller240]

I don't think that a hotter cam is going to get you very much more performance if the E31 head doesn't breathe better (bigger valves). Just my opinion.

I can't really advise on a cam, as I've stuck with the stock grind, although I wouldn't go too radical if you plan to use the car as a daily driver.

Some of the people at MSA have good advice, and others don't; in my experience. I would tend to believe the book over almost anyone (except Rebello Racing or Sunbelt Racing)

[zguitar71]

If you go to larger valves with your set up (L24 block) you will have to "eyebrow" the sides of the cylinders or the valves will hit the cylinder walls and be destroted. An overbore might solve the problem but I do not know how much.

If you change the cam you shuold, IMO, go to larger valves and port and polish the head. The cam will not perform to its potential if you do not rework the entire head. A cam will move the power higher in the RPMs, the small valves would counter act what the cam is trying to do. Bigger valves will allow more air to come in and go out. You will need to change the needels in your SU's too, (SM or custome grind) to take full advantage of the increased air intake and ability to make power at higher revs or go to triples. The stock needels do not flow enough in the higher rpms. Talk to Rebello or other reputable Zcar builder, they should be able to explain everything better than I can. Your compression will change if you overbore the block, shave the head, change head gasket thickness, put in different shaped pistons, ect... Those are all things you should get with an engine builder and talk about. I would not go beyond 10.5:1 CR for pump gas or use a cam larger than the MSA stage 3. Most of the builders like rebello or Sunbelt will use a custome grind and make the cam to suit your needs (best way to go). I was quoted $1800-$2400 from Rebello to have my E31 head completely reworked to my specs. That is a lot of money but absolutly no corners would be cut (a lot of man hours).

You could get by fine with out doing all that but the power gains from a changed cam with out the other work will probably not be worth while. I think you should be able to get 190 maby 200 HP (crank) from a 2.4 and still be streetable. The BRE team got over 240HP from their's but of course it had a huge cam and would suck as a daily driver.

[KGL]

Thanks for your reply guitar: I am building the motor my self, but won't be doing the head work. Head shop seems good enough and will do what ever I say but doesn't want the responibilty of saying what I should do and what the package should be. The same with the guys at msa. If I run fast I can be at thier counter in 8 min. thats how close I am to them. But honestly I think they suck.... but they got the parts. I just need an answer as to the correct cam to use that will run like a stripped as* ape on 92 fuel idle smooth and I'll be pleased with. With the cam package at about 540.00 and the valves about 250 plus the machineing I'm tapped out. I still have to finish the rest of the car ...two master clyinders,alt. hoses rad ect. interior and suspension tire ect is done. The port and polish will have to wait till I win lotto. Any additional sugg. appreciated.....kgl