Sanchez Posted April 2, 2013 Share Posted April 2, 2013 So I'm getting around to actually building an L28 for my 240z and I have a dilemma. I have access to any engine parts possible, from an E31 to a P90A and all block combinations. I dont want to make a race engine with streetibility. I would like to stay with the square ports exhaust and compression from 9.0:1 to 9.5:1. I would also like to keep machining and extra work to a minimum. So if you wouldn't mind telling me what combination you use and what mods are necessary, I also want to run SU's Thank you, If you have any more questions let me know. Quote Link to comment Share on other sites More sharing options...
OldAndyAndTheSea Posted April 3, 2013 Share Posted April 3, 2013 (edited) I had pretty much the exact setup you described when I first bought my car. Just l24... E31 port and polished- mild cam l24 with .030 flat tops SU's Was 9.5:1 compression with a felpro, and a very fun motor I might add! Edited April 3, 2013 by OldAndyAndTheSea Quote Link to comment Share on other sites More sharing options...
BluDestiny Posted April 3, 2013 Share Posted April 3, 2013 You say you have access to everything, but want to use square ports and carbs. That in itself is limiting. From this there are two roads you can go that will get you around that compression. N42 block (dished pistons) with a slightly shaved N42 head (small enough shave to not need shims) or F54 with flaptops and a shaved p90. Personally I'd go with a p90 since it has a better chamber design. I'd go off this website: http://datsunzgarage.com/p90/ Quote Link to comment Share on other sites More sharing options...
Sanchez Posted April 3, 2013 Author Share Posted April 3, 2013 (edited) I like the sound of the E31 its just that I am looking for something along the lines of simple yet sporty. I am concerned about doing any cutting into the wiring due to all of the hard-wires a previous owner did and the bad quality of the harness overall, so I would like to stick to SU's with the option of Weber's. I'm leaning towards the F54 Flattops and a P90 because it has decent CR and a freeflowing design. I would like to know the possible ways to boost CR on the P90 F54 setup, and possibly how much I can sell my E31 for? Edit: I did however just see an interesting concept about creating a "poser-stroker" engine that yields roughly a 3.0L engine without and LD28 crank, the one thing I cannot get my hands on and one thing I would probably not even buy if I could. It envolves the KA24E Flat-top pistons on an l28 overbored 3mm, l24 connecting rods and the l28 crank; all with an E31 head. It sounds very interesting and I would like to give it a try, anybody done this? Edited April 3, 2013 by Sanchez Quote Link to comment Share on other sites More sharing options...
Tony D Posted April 3, 2013 Share Posted April 3, 2013 Just ran across a non USA, 1984 Carburetted E88 head on a Nissan Laurel here in Brunei...original owner since new... Now working the angles... I want to see those chambers! Quote Link to comment Share on other sites More sharing options...
BluDestiny Posted April 3, 2013 Share Posted April 3, 2013 E31, if its a solid base and has not been messed with and is uncracked, no broken studs etc, should go for $150 easy, and that is a low price. I know a store that is holding onto about 3 of them, and asking $300 a head. They know the price will just go up on them. As for upping the CR did you even open the link? You can get away with a certain amount before you need to use shims, but you would need to know the total head height to make sure you don't take too much off. Quote Link to comment Share on other sites More sharing options...
Lazeum Posted April 3, 2013 Share Posted April 3, 2013 (edited) Not sure why you'd like to keep square exhaust port but I've asked the same question to Braap and we end up with the combo I've got in my Z: F54 / flat top & P79 that could be switched with P90 if you really want square ports. What has been done however was a street porting (ie. improving flow without making the port bigger), valve unshrouding, etc. Install a properly designed cam (Rebello street cam with tight lash) that match the rest of the engine with surrounding components such as springs & retainers, lash pads. head has been milled by 0.020" to bring compression around 9.5, towers had to be shimmed in the process, pistons have been milled also to make sure quench clearance was spot on. In the process we also revised oil system with bigger restrictor in block (ID = 3mm), turbo oil pump, internally oiled cam + spray bar. Edited April 3, 2013 by Lazeum Quote Link to comment Share on other sites More sharing options...
BluDestiny Posted April 3, 2013 Share Posted April 3, 2013 I'm assuming he has some square port headers that he wants to use. It is possible to run square port headers on a round exhaust port though. Quote Link to comment Share on other sites More sharing options...
Lazeum Posted April 3, 2013 Share Posted April 3, 2013 This is what I'm running. Quote Link to comment Share on other sites More sharing options...
Sanchez Posted April 3, 2013 Author Share Posted April 3, 2013 Well I heard that the square exhaust flows better cause it doesn't have emissions stuff on it... plus I can set it up to get the compression I want, 9.5:1 and a 2949cc displacement... and a valve job will solve the flow issues Quote Link to comment Share on other sites More sharing options...
madkaw Posted April 3, 2013 Share Posted April 3, 2013 Flow issues?? Quote Link to comment Share on other sites More sharing options...
Xnke Posted April 3, 2013 Share Posted April 3, 2013 Stock for stock, there is no difference in a round port or a square port head. None. Nada. Nothing. As for the rest of your questions, it's your choice. All the build threads and information you could ask for are in the archives of this website. Quote Link to comment Share on other sites More sharing options...
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