Lazeum

I would not have expected a header to bring such changes. Your story about oxygenated gas makes sense also. Now I'm waiting for AFR analysis to see exactly where you stand It makes also me feel my library of jets might not even be complete also My engine is in rebuild stage but as soon as it would be back in my car, I'll have to start again from scratch since I'll change the chokes with bigger units.

I've heard good stuffs about Acura Integra rubber. The point is to have a long enough piece you can trim. My advice would be to target cars with big doors (coupe, minivan?) You can either have one 90° corner or a straight piece. If you have a straight piece, you can trim the rubber at 45° and close the weatherstrip at the top of the door As far as I'm concerned, I'm in Europe, we also do have our donor cars for weatherstriping that works very well. They are pinched type instead of glued, profile is hollow (=extruded) instead of plain which make them thicker in free state but easier to compress. It means doors are sealed and I don't need to slam the doors as I used to with previous seal. They're no difference in effort to close the door from my DD Ford Focus and my Z. In europe, fyi, I have Renault Twingo seals.

The car definitely sounds quite healthy. I'm surprised how big are the mains! Since I started to post of this thread I moved from stock N42 head with mild off the shelf cam (schneider) to P79 head port/polished with Rebello Street cam. At first, I did not change anything on my carbs (40DCOE also), venturi/chokes are 32 - way too small. As a result, I had to move from 140 with the N42 to 120 with P79 and the engine still ran super rich (11:1 AFR) Since your setup looks nowhere near like mine, it would be hard to compare but the effect of the new head/cam was quite interesting, I have much more vaccum at idle with the more extrem setup Regarding Air jets, they are also huge. Is it because of AFR being rich at high RPM? If such, it seems too small carbs (= out of air at high RPM) still push gas inside engine without sufficient air coming. This is what happens with mine. I'm the first one to state 40DCOE are NOT too small for L28 applications even if 45DCOE seems more suitable as soon as you start changing stuffs. In europe, I see 45DCOE being sold by pair for 400€ everyday - very tempting I have to admit but I need to tweak the intake manifold to do it properly since intake runners are Ø40mm (there's material to be removed anyway).

Maybe a stupid idea but have you check for leaks? you might have some air going thru the engine at some point. 14.2:1 seems very lean to me as well, I would expect at WOT around 12.5 at Max torque & 11.5 at redline as a baseline.

I agree with Tony. I had a L28 combo made with off the shelf parts: stock overbore flat top pistons (0.5mm), N42 head giving me a CR around 10:1 with “stage 2†MSA cam (Schneider 274°/274°). I ran 40DCOE Weber with 32mm chokes tuned with O2 WB sensor showing good AFR. Engine was running good but timing wasn’t so good due to poor part matching. I decided to trust head builder so I’ve changed the head and the cam on my setup, CR has been decreased to almost 9:1. Head is ported and unshrouded. Cam is a custom grind to meet my engine specs and especially my needs; I wanted a fat torque curve over peak HP. It’s amazing the difference it makes. Engine torque has increased very significantly whereas displacement remains the same, CR has been decreased and engine is not even tuned yet. Timing can now be setup as it should without fearing ping; it means also you should be able to play with timing to get what you're after. I’m now limited to my Carb chokes, 32mm is definitely too small – they don’t match my setup. Something as well to bring to the discussions is the feeling. With Triple carbs or ITB and a good exhaust, I believe car feels also much quicker than it really is; noise becomes really nice, you’ll get addicted very quickly. With same HP but more torque than your RSX, the Z will feel way quicker and rewarding.

You're right, we can find L28 but cars that go with L28 are rare. So no way you'll find a motor at the junkyard. So the only way is to get a car with the engine it. Then it is impossible to part the car out. It happened once or twice somebody would have got 2 cars to make one, then an engine would be available... In Europe, s30 & s130 are quite expensive. A good 240z is worth 15,000 / 20,000 € and a 280zx NA 2+2 around 8,000 € whereas a 280zx rusty shell would be aorund 2,000€.

I'll also add that setup could be of interest in Europe since we do have some classic rally races. People are bored with 911's and start to think about alternatives. Z's are nice choices, this engine could meet Group 4 specifications and make wealthy racers happy as long as you've got all the data that goes with such motors. On the other hand, it is not so easy to find a L28 in Europe to make a turbo engine so it could become a challenge to build a cheap setup. The target you're trying to reach with turbo setup seems also out of range with NA (or close to be). So if it is really what you want, I would advice selling this combo. So keep it and enjoy or go turbo! I don't know who build this engine for you but there's definitely some support for Datsun in UK or France if you like to build such setup

When you torque the head bolts, you clamp them to 60/80 lbs.ft depending on bolt type/lube, etc. if you'd check the load created with such torque, you would see that load for each bolt is around 50,000N. That's 5 tons per bolt Does it answer your question?

I've thought about how to do it. I've already done this kind of work on brakes during my studies (NVH engineering) We would need to take the signal, cut it into pieces, transform the piece of signal with Fourier transformation (to translate the signal from being "Noise amplitude in dB" = f (time) to "Noise amplitude in dB" = f (frequency) ) and get some measure average done to reduce backgroud noise (white noise) According to engine RPM, you should be able to get noise made by valves with the appropriate frequency & harmonics. All that would have to done with correct sampling frequency, correct filtering options, correct management of samples, etc. No so easy to do if you want to do it right

For your info, my engine had the head removed as well. I lift it up from the engine brackets. It was not balanced so I've used a strap to balance the whole weight. The trans was not part of the engine assembly during this step. It worked quite well but not sure I would do it again this way...

Most of the threads are fine thread on our cars. M10 & M12 are usually going with 1.25mm pitch

I would be surprized too to hear holes in air dam are efficient. I'm also wondering then why air dam suppliers are not proposing air ducts that could be installed. It seems the only way is to make your own parts... I'm trying to but to mold a custom piece that matches the air dam is not so easy. I'm trying with foam to get the form out of the air dam prior to attempt making the ducts with fiberglass. So far, no success on my side but I'll keep trying!

I think it is clear in my mind, thanks Tony It's good to have feedback and knowledge from people with experience

I've got your point My intent was more about avoiding flow restriction because of the step (whatever the flow direction was) than improving flow. The goal was just to make sure I would run with optimal conditions with the head. No point of having a $$$$ cam/head if surrounding components are not able to keep up with it. Here was my basic idea when I first asked the question (intake is obviously on the left, the right part is the head). Vortex would create flow restriction and would avoid to use efficiently the intake system. The question then became: vortex presence < ? > anti reversion effect ...and based on comments, it tends to depend on the application. in "street" mode: vortex presence < anti reversion effect in "race" mode: vortex presence > anti reversion effect

Just to add on more item, here is a picture of the intake with the ports that go to the head. We can see the shape of the gasket and where some material could be potentially removed. Whereas Mikuni manifold is having a some 'extra' material all around, my Cannon manifold is having some only on one side. Not sure what would be the reason: to tilt the flow, cheap design with no reasons? I will leave alone my intake then

I'm more thinking about porting the intake than leaving it alone. However, contradictory advices show my question is not so straight forward. So, madkaw, I have looked for the thread you're talking about and there're a lot of good info in it. If I summarize some of the comments made by Tony and Braap (please forgive me if the meaning has been lost without the full context), here is what I got. I'm not saying Tony & Braap are always right (I have to admit they are most of the time ) but the comments below make sense to me. Actually, Cannon manifold runners are not round, they have a 'eye shape' hole, there's more material than could be 'removed' on the lower side of the runners which tend to go towards Tony's comment above. To get back to the links I've posted above regarding port matching on V8's, Tony made an interesting comment. At the end, Braap also made a comment that goes towards the vortex creation t the step that could help mixing air & fuel together: On this thread I can see TimZ made some comments saying porting the intake could be beneficial. Based on power made with his setup, it can't be wrong... Should I conclude it would depend on the setup? high rpm/power monster (race applications) will benefit from this mod since flow reversion is minimal, intake shape optimized to keep the taper all the way along the runners? whereas street versions would benefit from keeping the intake as it is since flow reversion would be important at low rpm where the engine would be mostly used? I start to be really confused. I might keep the intake the way it is for now since it is easy to get back on it later than adding material in the future if I do a bad move... I'm mostly in the 2500 / 6000 rpm range with my engine. Anyhow, thanks all for your answers

I'm in process of rebuilding my engine. the whole intake is down so it's a good opportunity to perform some mods I should have done already (who said "while I'm at it?" - I've already redone the whole front/rear suspension, steering & brake system while the engine was down ). My setup is 3 Webers 40DCOE with Cannon manifold. this combo goes on a F54 / flat tops with ported P79 head made by Braap with Rebello "street" cam. There's a lot of material to play with on the manifold and I'm wondering what I should do. I mean intake ports are quite small vs. head ports. It would make sense to me to make them as large as the head to improve (or should I say "optimize") flow, at least to avoid steps on the way that could create vortex / turbulences. it's obviously better to have a small (and fast!) flow going thru a big hole than a big flow trying to go thru a small hole and hitting walls but none of those situations seem to work good in my book. First one will slow down flow a lot when going into the large section, the other one would obstruct the flow. I believe also some phenomenon could occur according to RPM making the engine hard to tune; such as rich spots at some RPM range. By doing so I might have a large section becoming big (exit of carbs) then small (middle of the intake) then big again (head port). So pressure will follow the same path, it could create some pressure variation issue also. And what about flow reversion? Is there anything to fear about? A small step could after all be beneficial... By looking at my intake and the shape of the gasket, I might have a much as 3mm of material on one side to be removed around the port which is a lot. The only thing clear so far is to make sure I never get intake ports bigger than head ports. So far, I've only performed the porting between the intake and the carbs. For the record, here are links about the topic, it seems something could be done after all http://www.cartuning...ching-an-engine http://www.torquecar...g-polishing.php I've searched as well HBZ with no luck, I'll be happy to find some talks about it on the board if any (the only threads found were about EFI intake and if it was possible to do; not about the effects...)

I agree with what you just said except for one comment: The limit would be MBT (minimum best timing) not "as much timing as you can". Most likely with high comp L-engine you will ping and never meet MBT but it would mean your engine is not optimized to get the best of it (for NA application). That's why Braap advices to not go further than a limit (for instance around 9.5 with P79/90 head AND correct cams as you've said )

We had some time ago a nice discussion about flat tops with N42 head, you should find your answers in there Attn flat top 2.8 with E31/N42 head guys

Besides firing order and ignition, the reason could also be flooded plugs. It happened on mine right when I got the car. Everybody wanted to hear the triple and the exhaust tone so the car was started many times with chokes on without having the chance to run the car for good. It fooled plugs and I had the same symptoms as the ones you described

I had some issues blowing rear tail lights fuses because of problem in the front. I had to rewire the lights harness however on mine to meet Euro regulations with lights (blinkers on side lights in the front, brake and blinkers on the rear had to be separated) Try disconnecting all the bulbs you can (easy to do) and check again. If you've tried without the switch, without bulb, it remains only wires... If something is smoking under the dash, you might be able to spot the location and see what could be linked with lights... Good luck with your issue, I've lost many weekends dealing with the issue and nice opportunities to drive my Z because of electrical issue, I feel your pain

to clog engine lube system because of RTV would suck Thanksfully, not the problem in my case, all gaskets were installed dry (and no leak!).

If it is an answer to me comment above, indeed, I've removed the plugs from the block. I'm also wondering if I should not get the crankshaft plugs out as well to get a real good clean up I've got great support from Braap and my machinist did the crankshaft of the Renault turbo F1 back in the 80's Hopefully I'll get a perfect motor afterwards, I would freak out as soon as I would hear a noise of the engine once it would be redone. I'd rather do it right! Thanks for your advice though, it's always great to have support to do the right thing

Let us know! As far as I'm concerned, I ended up tearing apart the whole engine since metal flakes were everywhere... my crankshaft needs some polishing on journals at least, the block needs a full cleaning treatment prior to put all the bites together & the head did a round trip between Paris & Oregon to be fixed with fresh new parts from Braap & Rebello . The whole oil system has been upgraded (oil restrictor increased, HF pump, spray bar and internal oiled cam went back in) Engine is waiting for some funds to go to the shop... I have also the "while I'm in it" syndrom so I've got tons of stuffs to do now (front & rear suspension overhaul process but also steering and braking)

Yes, my oil pump is shot and debris when right into it. I had a thread about it, you can check it out. Oil pressure was always showing good number on my gage (stock sender, stock gauge), it was getting low at idle but it has always done it. Regarding oil, after the damage, oil was pouring just fine out of every cam lobes as well. Question for everyone: Something I would try is to remove the cam shaft, clean it with solvant and air (I remove the hood, remove the cam sproket, tilt the engine with a jack and pulled the cam). Then crank the engine with no cam shaft, no spark, no spark plugs to pour oil out of cam tower, you'll have no more restrictions to get debris away from the systems. Can it be done??? The chain will have to go before attempting something like this, so the front cover that holds the oil pump.... A lot of work but it might be worth it if it could save an engine for major failure and full disassembly.