pjo046 Posted January 10, 2009 Share Posted January 10, 2009 So, I am going to use my E31 head on the F54 block I have built. (stock stroke and bore, flattop pistons, 1mm HKS headgasket, a CR around 10.5:1). We will be using either twin roundtop SU's with a N36 manifold, or tripple webers/mikunis/dellortos. This will be in combination with headers, 2,5" straight through exhaust and distributorless crank-fire ignition (Unless an electronic ignition from a 280ZX is good enough?). The camshaft will be a relatively mild grind (stage 3 or so) so that we keep good driveability in the lower rpms. It won't be a racetrack-car, only for spirited driving on the streets, and maybe an occasional trackday. What do we need to do with the E31 to get the most out of this engine-combo/get it to work well? Is it enough to lightly port it and install hardened valve seats? Or do we "HAVE" to install larger valves in it? Will the valves be the one thing restricting power and flow if we keep the stock size? Quote Link to comment Share on other sites More sharing options...
katman Posted January 10, 2009 Share Posted January 10, 2009 If it was me I'd go with the bigger valves, or start with an N42 head. After that, money spent on dyno tuning will far outperform any head work you do, epecially with a carb setup. Just my 02c. Quote Link to comment Share on other sites More sharing options...
2fast2Z Posted January 10, 2009 Share Posted January 10, 2009 I'm lurking here, i'm considering the same build just with a E30 head. Chris Quote Link to comment Share on other sites More sharing options...
Xnke Posted January 11, 2009 Share Posted January 11, 2009 If you really don't want to upsize the valves, at least do the exhaust valve. you do not have to replace the seat to go with the bigger exhaust valve, but you should get the bronze intake seats replaced anyway. Might as well go with the bigger valves. By the way, L series valves are only about 7-8$ each new, from many suppliers. Or get a set from an N42 or N47 and use those. Quote Link to comment Share on other sites More sharing options...
Daeron Posted January 11, 2009 Share Posted January 11, 2009 you pretty well want to put the larger valves in. The E31 head was designed for a stock level performance 2.4 liter, and the valves are sized appropriately. My dad has an early E88 (virtually identical to the E31) that he put the larger exhaust valves in only, and he has ALWAYS loved and used that head, (on his 2.8 powered by rebuilt and re-needled SUs and later, a four barrel; the head also has had port work and a camshaft installed) so you might look into just that side but staying with the stock valves is definitely a hindrance. Quote Link to comment Share on other sites More sharing options...
ozconnection Posted January 11, 2009 Share Posted January 11, 2009 I wouldn't make the ports any larger. Good gas velocity through the ports is very important for a streeter. Sure, do the usual cleanup around the bowls etc but don't hog out the holes! Good luck. Quote Link to comment Share on other sites More sharing options...
pjo046 Posted January 11, 2009 Author Share Posted January 11, 2009 Yeah, my plan was to just clean up the ports. Smooth out the intake ports, and go all the way and polish the exhaust ports and the chambers/bowl area. I have never performed major head work before, only gasket matched some manifolds and turbos etc. So I don't know all the specifics when it comes to head-rebuilding. But if I understand you guys right, installing bigger valves is as easy as just slapping in a new one? (once I have installed hardened seats) If someone could explain the specifics that would be great. Arizonazcar sells ss-valves. Are these suitable? Quote Link to comment Share on other sites More sharing options...
RedNeckZ Posted January 11, 2009 Share Posted January 11, 2009 To make the head work, you need to have it ported and polished. Install bigger valves with harden seats. This will involve cutting into the head (machine work) and pressing the seats into the head. Then get a three angle valve job for it. If you want to, you can weld the bowl area (again machine work) and have it reshaped to something better. Make sure you shave the head to make sure it is flat. I had ny head done by Heads by Paul in Denver, CO. Good Luck, Rich. Quote Link to comment Share on other sites More sharing options...
Tony D Posted January 11, 2009 Share Posted January 11, 2009 The operation of installing the seats is what determines what valve you use. Simply buying L28 seats (hardened) and having them installed already gives you the larger valve seating area you want anway. By using stock parts you get the 'performance upgrade' for the exact same price of installing something you were going to have to install anyway! In other words, since you are replacing the seats with hardened units anyway, you may as well install the larger seats for the L28 valves and get the increased dividend of better flow at the same time. The only associated cost is buying different valves. And if you are installing NEW seats, it's false economy to try and re-use old valves! They would be getting new items installed anyway, regardless of which size seat you chose... Porting would be affected by which seats you chose as well, as larger seats allow for more bowl work. Check your head closely for corrosion. Nothing sucks more than having a head ruined by a corrosion perforation into a chamber or port after 95% of the work is done to it... Then you end up finding a heliarc welder and getting really friendly with it's operator to salvage all the money you put into the head. E31's are old, and usually the most corroded of the cores out there. Check VERY closely. The E88 is a popular alternative if you have one available. They were available new (bare) till a few years ago, so corrosion is not an issue on them. One day Paul...one day I'll scan those receipts and send them to you... I know where they are. Honest! Quote Link to comment Share on other sites More sharing options...
JMortensen Posted January 11, 2009 Share Posted January 11, 2009 I would do what the E Production racers do. Or, if you want to go all out, send your head to Sunbelt and tell them to do what they did to Zredbaron's head. Quote Link to comment Share on other sites More sharing options...
pjo046 Posted January 11, 2009 Author Share Posted January 11, 2009 One day Paul...one day I'll scan those receipts and send them to you... I know where they are. Honest! Haha, glad you remember it still. I haven't been around here the last few years. I was worried you wouldn't reply to my threads any longer because of the money I owe you. I was gonna ask about it now that I have started visiting the forum once again, it came to mind the minute I set foot here again. If you just tell me how much I owe you, I'll paypal it to you straight away. Jmortensen: Because I live in Norway, the cost of sending the head to the US and back again would be quite expensive. So I'd like to avoid that. But, I bet no machine shop here in Norway knows the Datsun OHC heads.... Unshrouding of the valves, this is something that can be done by myself right? But when I install hardened seats and larger valves, do I need to have a valve-job performed as well? (3/5 angle or radius cut) Another thing, I can get my hands on a set of Dellorto carburetors. They are Dellorto DHLA 40's. 3 twin 40 mm carburetors. But the thing is, these have been used together with a turbo on a push through setup, thus I don't know if they can be used on a N/A-engine without modification? Quote Link to comment Share on other sites More sharing options...
Daeron Posted January 12, 2009 Share Posted January 12, 2009 I do not think that you would need to modify the carbs, beyond making sure that the jets and whatnot were all correct.. BUT 40mm is a little small for a big, brutish L28. It *works* but you might want to consider upping the ante to 44mm bores. The Dellorto's don't have as good a reputation as the Webers, anyhow, and Webers are MUCH easier to get jets and air bleeds for. Quote Link to comment Share on other sites More sharing options...
Tony D Posted January 12, 2009 Share Posted January 12, 2009 The DHLA's likely have the turbo shaft seals and emulsion tubes. The emulsion tubes richen under boost. It's all standard parts that can be had easily enough. The 40DHLA's were good enough for OEM Fittment in Blowthrough Turboservice for the early Maserati BiTurbo. But as Daeron says, for an N/A the 40's may be a bit small. 45's would likely be better, though for a street engine and if you aren't concerned with total horsepower output, they would work nicely for around town driving with nice throttle response. They will just fall off in HP above a set RPM range. You can upsize the chokes and get fairly close to the HP you would get with a street setup with 45's... It's a tossup, really. If it's what you can get, it's what you can get! Quote Link to comment Share on other sites More sharing options...
Daeron Posted January 12, 2009 Share Posted January 12, 2009 thank you for finishing what I was trying to say Tony; not having the hands-on experience with all the carb stuff, I couldn't quite make the comparison detailed enough. Quote Link to comment Share on other sites More sharing options...
RIP260Z Posted January 12, 2009 Share Posted January 12, 2009 pjo046, Just because you live in Norway, does not mean you can't have someone do your cylinder head work. Braap done mine and shipped it via FedEx (a bit under $200), and instead of sending yours, ask the person you decide to do the work to source you one in the US... Quote Link to comment Share on other sites More sharing options...
pjo046 Posted January 12, 2009 Author Share Posted January 12, 2009 So what you are saying is that the Dellortos can be used as is? (with regards to them being set up for turbo vs N/A) The reason these carbs are interesting is because I can get them cheap from the person who bought my unused T3/T04B turbo and Lonewolf Performance intake manifold since I gave him a good deal on those parts. We haven't settled on a price yet, but probably somewhere around 300-400$. They will probably need some tlc. (what price am I looking at for a set of decent tripple webers/mikunis?) The alternative will probably be roundtop SU's with a N36 manifold. So, how do these two options compare? I know the SU's are much easier to tune etc, so that's a good reason for going with those. But, will the dellortos offer much better power despite them only being 40mm? If you guys were to give a ballpark guesstimate, where would we be power- and torque-wise with these dellortos (or the SU's), L28, flat tops, street cam (typical stage 3 grind), E31 with the bigger valves installed, headers and a crank-fire ignition? Quote Link to comment Share on other sites More sharing options...
pjo046 Posted January 12, 2009 Author Share Posted January 12, 2009 pjo046, Just because you live in Norway, does not mean you can't have someone do your cylinder head work. Braap done mine and shipped it via FedEx (a bit under $200), and instead of sending yours, ask the person you decide to do the work to source you one in the US... Yes, I know. I actually did just that with the P90 head I had built for my turbo-project. I bought a good core from ebay and had it sent to lonewolf performance. But this time, if I am going to alter the E31 I have, the shipping charges will be at least 400$ if not more for shipping it both ways. It's a rare head, so it will be hard to find one in the US at a reasonable price. Furthermore, I doubt we will do anything more to the head than install hardened seats and larger valves, and smooth out the ports and the chamber. Hopefully someone nearby will be able to perform those tasks. But I'll send Braap a PM and ask him how much he would charge for such a job. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted January 12, 2009 Share Posted January 12, 2009 street cam (typical stage 3 grind), MSA's Stage III is the third stage of wussiness. Go bigger on the cam. I'd go bigger than their Stage IV for an aggressive street motor. I don't think there is a lot of love here for guessing power outputs with a given combo, but I've had pretty much that combo with 44 Mikunis and it put down mid 240's whp. Quote Link to comment Share on other sites More sharing options...
pjo046 Posted January 12, 2009 Author Share Posted January 12, 2009 I know, people are negative to such estimates. All I need to know is if we will be able to pass 200 whp, I guess we would be satisfied with anything above. We won't go too radical on the cam as we want good driveability. It will be a cruiser for the most part, perhaps the odd trackday every other year. I found out today that the R180 I have is 3.36:1. Which sucks. And the R200 is 3.54:1. How hard is it to change gears, and do most R200 gears fit in the R200 that originates from the 280ZXT? I see that many gears are available from Japan on ebay. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted January 12, 2009 Share Posted January 12, 2009 I know, people are negative to such estimates. All I need to know is if we will be able to pass 200 whp, I guess we would be satisfied with anything above. We won't go too radical on the cam as we want good driveability. It will be a cruiser for the most part, perhaps the odd trackday every other year. I found out today that the R180 I have is 3.36:1. Which sucks. And the R200 is 3.54:1. How hard is it to change gears, and do most R200 gears fit in the R200 that originates from the 280ZXT? I see that many gears are available from Japan on ebay. Changing gears is a real PITA. I'd suggest if you were going to order gears from Japan that you just order a whole diff instead. I hope more people offer cam opinions for you. I know several people who installed that Stage III and then took it out and installed a larger one later because it really is a small cam and too small for a performance oriented engine. In my opinion if it weren't for the crappy FI systems, that would be a Stage I. But since the crappy FI can't handle a larger cam than stock, they made two other even smaller cams so that people could think they were really stepping up to the Stage III. I drove mine which is similar to a Stage IV in bumper to bumper traffic every day with a light flywheel and Mikunis and it was no problem at all, in fact I should have gone bigger. Quote Link to comment Share on other sites More sharing options...
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