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NA 3.1L=>head & camshaft questions. No shortcuts, max

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Wouldn't the duration determine whether or not you need the reliefs, not the lift?

 

EDIT--Dan, did you have to turn your spring retainers down on a lathe so that they didn't hit the stem seals? I recall that you have Schneider springs and retainers, and I had to have mine turned even with my .490 lift cam. Also, did you cut the spring seats flush with the head, or was that not necessary?

 

Jon

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Dan:

 

Thanks for the valve lift details. I'll call Sunbelt again tomorrow.

 

Well, since all L28s were fuel injected from the factory you're not compromising the "purity" of the engine by going with FI. Throttle response has much more to do with reciprocating mass then the fuel system - carbs do not have any advantage over FI. If you build a 300hp NA L6 I think the FUN will be there regardless of the fuel system. Sound is a subjective thing and I agree that a triplet of Webers at full song is beautiful....Regarding fuel injection, you *could* open up your wallet and go with 3x2 50mm throttle bodies and have all of the sound and fury of triple carbs.

 

Okay, Dan. I have to admit that I'm actually toying with the idea knowing that my 40dcoe's are too small. I know nothing about FI, but you say with that setup that it would sound like my webers do? You also say I wouldn't lose any throttle response? If those are both true than I just may go with FI! This 3x2 50mm throttle body setup...are you talking about FIs or DCOEs? How much cash are we talking about?

 

If this is as good as it sounds, I'd also be able to use my Electromotive igntion to its fuller potential. Not to mention tuning based on seasons and climate wouldn't be hard at all.

 

I do have one rule about spending significant amounts of cash regarding something I know nothing about: I make sure others agree.

 

You other NA voices out there agree?

 

Again, thanks so much for your time, guys.

 

-Mark

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Triple TB's are awesome. You can run a 50mm and still get decent low end. Seen 2 Z's with triple TWM's, both REALLY haul @ss. Sound is exactly the same as triple carbs, because you have the same open hole from the air horn to the valve, so you get the same noise. Easier to tune or have tuned too, seems like there are more programmable FI experts than triple carb experts these days...

 

Jon

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Jon,

Sunbelt did the cam setup, they didn't reuse the Schneider stuff. It only now, two years later, occurs to me I should've asked for it BACK, they still have it (or threw it out). When I was running the Schneider kit, I didn't machine anything, just replaced the stock stuff with their stuff. The Schneider cam card listed 0-lash lift as .503", not .490". Weird if they have two L6 cams that close together, huh?

 

One note about Schneider cams, my first one wiped out a lobe just over a year after I bought it. They were great about it and sent me a new one after they got mine back. I checked the dribble holes on the new one, and lo and behold one of them wasn't *quite* drilled all the way through! I only barely caught it. I blew compressed air in to see if it came out at all the dribble holes, which it did, but the air coming out of that one hole felt like just a *tiny* bit less than the others. I'm sure that's what happened to the one lobe that got wiped out on the first cam from them. When using the internally oiled cam, check each dribble hole! Sunbelt set it up for internal and spray-bar oiling, btw.

 

I *think* lift should be as good or a better indicator of whether reliefs are needed, but either way it should be mocked up and the clearances (of intake AND exhaust valves!) checked. When I took the head off and sent it to sunbelt, there were very slight dings from the intake valves on the tops of the pistons. From the .503" cam, and a couple of stuck throttle overrevs to 8k(!). So I guess I'd say .490 is probably getting in the neighborhood of where it needs to be checked for sure.

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I've got the Schneider springs and retainers, but my cam is an American Cams regrind, so that's why my specs are different from yours. Did you reuse the old valves when you installed the Schneider stuff? If so that probably explains why you didn't have to cut the retainers and I did. A new valve sits substantially lower in the head than a valve that's been cut once or twice.

 

Thanks for the info. :D

 

Jon

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Part of the quote you attribute to me is from John. Don't *totally* agree with the part about reciprocating mass affecting throttle response more than carburation or injection. If the carburetion or FI are spot on, throttle response will be good, even if you have large rotational inertia (not the same thing as reciprocating mass, but what I *think* John *means*). Poor carburetion or FI setup and throttle response will suck, even with a formula 1 engine.

 

Back to the main topic:

If you can afford it, and are eager to learn how to tune fuel injection, you should go for it. Carbs are a big compromise. I went with them cuz they were (relatively) cheap, and I didn't have time to figure out FI. I installed the carbs on Thursday, was at the dyno of Friday, and at the track on Sat/Sunday, where the ~30 hp gain was partly responsible for me beating 2nd and 3rd in my class by less than a tenth of a second! The only car faster than the three of us that day was a Formula Ford:)

 

My hp curve sucks, though, and parts are in Japan. I can't just program in a different fuel map.

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I think throttle response will be better with FI because of the method of spraying the fuel. Anyone who has ever played with the accelerator pumps on triples (at least Mikunis) off the car can tell you that if you open the carbs you get 6 nice long pee streams of gas out of them. When port velocity is low there isn't enough turbulence to mix the air and fuel fully.

 

FI doesn't have this problem, so you get much better atomization at low rpms, and better throttle response at low rpms.

 

Jon

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Thanks for the throttle response thoughts.

 

The more I look into this FI stuff, the more confused I get.

 

TWM offers a DCOE manifold conversion where you stick the throttle bodies at the end of your intake manifold where the carbs used to be.

http://www.twminduction.com/ThrottleBody/ThrottleBody-FR.html

I am referring to the 2900 series here.

 

I also see that Top End Performance seems to have put a few of these kits together successfully. However, I am weary of doing business with them again.

http://www.racetep.com/ztripdcoe.html#twmtbod

The picture at the very bottom is what looks to me to be the DCOE replacement.

 

TWM also has manifold/throttle body kit (throttle bodies built into a custom manifold they manufacture) that will be available for L6s later this year. The website says march 2004, but an email I got today said it will be closer to september.

http://www.twminduction.com/ThrottleBody/ThrottleBody-FR.html

I am referring to the 2000 series here. TWM estimates the kit will be ~$3k when it is released. It would include fuel rails, fuel regulators, and injectors.

 

BTW, TWM seemed to think that 48mm would be better for me since I don't plan on pushing 8,000 rpms full time like a road racer would be.

 

Just thought I'd share my internet/email findings thus far. I will make some phone calls tomorrow to get some of my questions answered.

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TEP's stuff is obviously TWM, so why the wait until Sept??? They already have the manifold and the throttle bodies and air horns. All you would need are injectors and SDS or Tec III or MSS or something and you'd be done, which is what TEP has.

 

Ask them what you'd be waiting for that you would get in Sept that you couldn't buy now...

 

Jon

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I have a 3.0L n/a Rebello sitting under the hood using 45MM DCOEs and a TWM manifold. At the time I had the engine built (1997), FI was an option but I wasn't impressed with the complexity and narrow range of choices. TEC-II was the only real option at the time but it was fussy and difficult to program, let alone the fact that not many people really knew what they were doing with it. Since I was already familiar with multiple carb setups and Webers in particular (this harks back to my automotive beginnings working on modified VWs and 911s) I felt comfortable to settle on a set of 45MM DCOEs instead. It's been working well ever since and I have no plans on changing it. It also has the feel of nostalgia which I like and most people are quite impressed to see a set of triple carburetors under the hood of anything on the road these days. Younger people (those less than 30) tend to shrug it off as "old technology" but they have been schooled on a few occasions that old doesn't automatically equal obsolete. :D

 

Fast forward to today, with the myriad of FI setups available, the ease of tuning via a laptop and fancy GUIs makes an ITB FI rather attractive although it is still rather costly. The main benefit of FI is that it has the potential to offer better low-speed drivability due to better fuel metering and atomization. As a case-in-point, I have been in another Rebello 3.0L car that used FI and I can say that the low speed drivability was noticeably better than mine. However, at the top-end there wasn't much difference between the two as they both seemed to pull equally hard. Of course this is just my butt-dyno evaluation but it does make sense given the similarities and differences between the two setups.

 

Which is better? Probably the FI from a purely performance standpoint as you can get great top-end power without sacrificing a ton of low-speed drivability. Coupled with the popularity of FI these days and the ever growing selection of products related to it and it makes even more sense. If, however you already have a set of carbs available there is no reason you couldn't use them. They won't be quite as expensive with regard to initial cost and are rather simple in comparison to FI since you don't have to worry about computers, wires, sensors, high pressure fuel pumps, fuel lines, etc...Ultimately it depends on what you're more comfortable with.

 

Edit - Added gratuitous pic

 

album_pic.php?pic_id=847

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Thanks, Dave.

 

I am one of those younger drivers you are talking about. I got my first 240z when I was 16, I am on my third now at 24 (same one since 18 ).

 

When I started, I didn't even want to go to an L28. I wanted to keep the L24 and overbore it a bit. I eventually decided that I would later regret having the smaller displacement, and I am glad I went with the stroker. I liked the idea of keeping the car as pure as possible, and I loved how carbs looked.

 

However, no one in my family knows anything about cars. Everything I know has been taught third person (which ain't much) . I don't have any friends that know much about cars, just friends that like them.

 

I have had on hell of a time getting my carbs tuned. I managed to accidentally find a mechanic in arkansas (where the car is) who used to run 240s on a track with triple webers back in the 70s. He owns an import repair shop and although he could have tuned them well, he needed jets to play with. I got some jet sizes recommended to me, it ran better, but as my numbers show, not as well as it should be. Again the cause is the head, but the carbs still need better tuning.

 

Every time I go home its a new season and with humidity and temperature changes, it runs different and I have to play with them. I used to just screw them up, but now I get it a *little* better.

 

So for me, having no experience or resources, FI makes more sense. I can let my ignition account for changes in season and elevation. Additionally, I am in the Navy and I see several geographical moves in the next five years. Here to Baltimore, south to Florida, then west to San Diego hopefully. FI gets more and more attractive.

 

But my heart still wants the carbs, Dave. It's too bad. As for the initial cost of everything, even if I would stay with carbs, I would be upgrading them, so I might as well just get what I decide on.

 

I'm still sleeping on it. I'm not in a rush to make the wrong decision...

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Phone calls made.

 

According to TWM, it is well worth the wait for the 2000 series ITB setup over the DCOE replacement series. They expect a much higher midrange power output with the...manifold-like thing. (Well, what do you call it? It's kind of a manifold, kind of not....) Anyways, it's $3k without the injectors.

 

I called Electromotive. My HPV-1 ignition system is not capable of controlling an injection system. They just released the TEC3, which they claim adds 10-40% hp to ANY setup, is $2k.

 

Haha. Side note: he thought I was upgrading to FI from a single carb. I asked his professional opinion if it was really worth the money for just a few ponies. Once I told him I had triple webers: ".........Oh........." Obviously he'd been burned by some trips before, eh?

 

So, I can either tune my webers, possibly upgrade to 45mm or spend $5,000 for some hp and tuneability. Hope this gives the silent readers an idea of what this setup really costs. $5k just for spark and intake is a lot.

 

I'm thinking carbs. Not the Atkins kind. The good ol fashioned atta kid kind.

 

I didn't really like the idea of ditching my carbs anyway. I'll call it a sign.

 

So now I just need to go back to the cam choice.

 

Sounds like the .550 lift and 305 dur cams we were talking about several replies ago are too much for a weekend warrior. I want it barely streetable, but streetable nonetheless. Where is the line where it stops being a car that can idle and park and being a car like johnCs where he just "launches it."

 

.500 lift 290 dur sound about right? Can i push a little higher than that if I go with high compression?

 

Thanks again.

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If you're going really high compression I would think that the .550/305 would work. IIRC Dan drives to events, so that means that it is at least marginally streetable. JohnC has a trailer queen with a flex plate and multi pack clutches, so that certainly wouldn't be streetable even if he had 10:1 compression and 180hp.

 

What I really want, and haven't found, is something like .525 lift and 300 duration. I think that would suit my engine well, and I'd probably be able to run pump gas.

 

If you don't want to change or fly cut the pistons, I know that my .490/280 cam works with no internal mods, but you'd still need the springs and retainers, and if you're unlucky like me, might need the retainers cut to make it all work together. If the compression is 11:1 though, you'll need to mix the gas...

 

Jon

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Just one quick note. There's more to a cam than lift and duration numbers. The amazing thing about the Sunbelt cam is that it can use less spring pressure than stock due to the lobe profile. This is free horsepower. It takes something like 75 hp just to drive a stock cam at 5000 rpm. A roller cam (nee Malvern) or low spring pressure cam like Sunbelt's gives you some of this back.

 

The Schneider and other traditional vendors' cams are very old profiles, often copies of copies of somebody else's. The software for designing cams and simulating the results to the engine is much better today as you might imagine. Dang few people are still developing the old L series motors these days. Sunbelt is one of them.

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JohnC:

Jim Thompson at Sunbelt has a lot of different cam grinds for the L6. My cam has a .534 lift but I don't know (and Jim won't tell me) the duration or the lobe centers.

 

DanBaldwin:

Ditto what JohnC said re Sunbelt. My cam from Sunbelt is something like .550"/305 or 310 duration. Those guys probably know more than anyone else about building up high-perf NA L-series engines at the moment

 

(and btw Dan, I just saw one of your replies that I previously missed from another post--I think you're right, you've helped me with just about every post I've ever put up! Thanks!)

 

Well, this was some time ago that we started this one, eh fellas? At the time Sunbelt was prepping for race season, so I was asked to wait a few weeks before I inquired again. I waited about eight weeks, called today. Chet mentioned only a .550 grind and a .475 grind, but admitted Jim was the man. I need to get back to him with some specs, but his rough ballpark estimate really surprised me. I was thinking the maybe $2k, 1500 for labor and 500 for parts. Guess I was wrong...$3000!?!? :shock: If you don't mind me asking, is that about what you guys put into your heads alone?

 

I know, I've heard it. Put all your money into your head, it's worth every penny. I just wanna get another confirmation. $3k is a lot of money to a kid. You two say go? I've never experienced a change in head, I can only imagine. My head right now is probably worse than stock (I'm only getting 157hp at the wheels, with a stroker, and i do know the block was done right) So obviously my head is a real POS (and the 40mm weber arg, but I think my head is the choke point right now).

 

Side note: dropping in a 4.375 R180 (with a Quaiffe ATB, baby!) made a real difference, lemme tell you! You should have seen the look on my friend's face when his new Vette lost to me (up to about 100mph, im sure I would have been toast seconds later) and showed him the 157.2 rwhp printout. Haha. That diff is hot! You guys may have the fastest NA Zs around, but I might be able to win the fastest ~150hp bracket! haha.... :D

 

(And I'm still deliberating the 3x2 throttle bodies, btw.)

 

Oh, and I'm not sure if my memory serves me right but I think it was John Mortenson who, like me, wanted to find a grind with about .500 lift and around 300 duration.... Sunbelt told me they would custom grind me a cam for whatever they could fit onto my block (this was assuming I would leave the pistons alone), and basically whatever power band I wanted. So there's that option for us, John.

 

Hey this one could have used a bump anyway...

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Jon,

 

I was told almost as a side note, that the cams accounted for $500 of the cost of the head. I'm not sure if that was for the custom-grind or regardless if they had to grind it or not. I do think I remember the custom grind being about a 6 week wait, regardless of time of year. I would think that if you wanted to, they would let you just buy a cam, but I'm not sure. I won't be calling them back until next Monday, as the man I really need to speak to (Jim) won't be back until then.

 

You want me to ask if he'll sell a cam as is? Sounds like Jim has all the knowledge for the L6 motors, it wouldn't be hard to get a little clarification for you. Who knows if the $500 included something else, it did seem a tad high to me...

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Yeah, ask him. Thanks. I'm betting it includes rocker arms at $500. Not a bad deal, but I've got other places to spend $500, since I already have a fairly similar cam now. It would be a small step up for me, but a huge one going from a stock cam.

 

Thanks,

 

Jon

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I'm not a good case study of how to spend money on a head. Jim made three custom cam grinds doing the R&D on my N42 cylinder head. As an example, I'm running valve springs that have 25% less seat pressure then stock Nissan springs but my engine's soft redline is 7,500rpm. I'm not sure if Jim is putting that R&D knowledge into customer cylinder heads yet. You'll know if you have single valve springs on the head you get back from Sunbelt and the 3 & 4 exhaust ports look "funny".

 

I wish my headwork only cost $3K...

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Guest billyzbear

I'm jumping into this thread a little late. I to have had a Z since I was 16 and I'm on my third but I'm 36. I to have a 3.1L with 3 40's an 3.7 lsd in the rear. I used a P90 head which I gave to a friend of a friend to port that does racing heads. When I showed him my N42 head he said the P90 was better. He charged me 1200, ported the hell out of it and matched ported the intake. He also but new swirled valves and went bigger on the exhaust. He took all the metal out around the valve guide and put new ones in. It looked great. He told me it flowed almost twice as much. I put it on my 2.8L at the time to see the differents. It was like 3/4 throttle was full and full throttle was a rush. My old 2.8L put out 240hp, flat tops, N42, 3 40's, Crane Hi-6 and cam 495 lift and 280 duration. It has good power from 2000-6500 rpm. I had a 510 lift and 308 duration cam in it along time ago but wasn't much good for street and had problems with wear. Good power from 3200-8500 maybe even 9000. I use to set the rev limiter at 9000. Never got that one on the dyno.

I just got my Z running again. I kept breaking trannies and stuff. Now I have a t-5 trans hopefully it will stay together. Next, I have some 45mm Webers to put in. I'll update in a few.

One thing that I have found with Z's is heat. I run mine at 160-170. I built a custom heat shield that bolts to the fenderwall and goes under the intake. I put a heat blanket under it and over it. I also lay one on the header which is ceramic coated. I tried wrapping the header but it ruined it in a year but did work. You can get a heat blanket from Summit. Have you ever noticed she runs real good when warm?

I work on cars for a living but if I was you. I'd get a ported P90 head, 3.1L, Total Seal rings, turbo oil pump, 15 pound or so flywheel, Crane or MSD, ZX dist. or better, maybe keep 40's with bigger chokes or 45's get them jetted right and nice big linkage. I would not go crazy with the compression 10.5 or 11 to 1 is fine. Mill the head and shim the cam towers. Pop-up pistons are $ and pain with big cam, forged if you plan on putting it on juice. If a big cam is for you, get a expierenced guy to set it up for you. A medium sized one is easier, less $ to setup, streetable and comes on sooner but ends sooner which is better for more gear. In a quarter mile 3rd will be your best friend. When you get this bad boy in there other things will break. I broke an axle stub a week after putting in my 3.1L, rebuilt 5spd a month later.

Billy

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