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Triple Mikuni, CAM option help


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Hey all,

 

First I just wanted to say I’m new but stoked to be part of the Z community. I bought my baby a few months ago. I'm not going to lie; she is and will be for the most part a garage queen. She will only see those prefect weather days for cruises and car shows. In the future I plan to get her into some auto-crossing and track weekend events.

 

Ok, sorry back to the point of the post.

 

I have come into having all the main parts needed for a triple carb setup. I have 3 Mikuni PHH 40mm and Mikuni manifold, all still need to be cleaned and rebuilt. As I'm sure I'm on the younger age side of the community this is my first carbureted car. So right now I am having a huge learning curve. In reading and doing some research I have found on multiple forums people saying in order to take the most advantage of the air flow at the top end of the triple setup to add a mild/performance CAM. All the info I have read makes complete sense and I agree with. Where I'm having some issues is finding info on CAM's that others have used with triple setups. An option I found was a Performance CAM kit (I was thinking Stage III maybe IV) from thezstore website. An really the only other option I have read about is to modified a stock or Japanese made CAM, not really a 100% sure if I have that correct.

 

I am hoping to tap into your guy’s knowledge and see if you guys could help me increase my knowledge and maybecome up with setup that will fit my wants.

 

My wants:

80% street driving/cruising

20% auto-cross and track weekends.

 

I want a setup that is very street-able. I realize with most performance CAM's comes a rougher idle. The more extreme CAM, the rougher the idle will become. I am ok with a mildly rough idle, I'm not looking for extremely anything. As far as HP, I don't really have a set number I want to reach. I just want it to feel alive and be extremely fun to drive.

 

At this point I am still in the research stage; I was thinking about doing everything sometime forwards the end of fall into winter.

 

Any info/experience/recommendation/things to look into you guys could provide would be greatly appreciate. If I have left off any info you need let me know and I can provide.

 

My hope in the end is to have a post that with tons (won’t say all) of info about different CAM options and to have the setups/members experience/recommendation for each.

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I run 40DCOE Webers on a stock 240Z cam. It idles great and has plenty of power up top, and the triples definitely pull better than the old, worn-out SUs! My point is, there is no need to get a "performance cam" especially if you want to be in a suitable autoX class. I plan to do some autocrossing with the SCCA and I have made it a point to read their rules regarding car classes. I plan to run in BSP where induction, exhaust, etc. are unlimited but you must keep the stock cam. Just another consideration...

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Leon, you do make a good point has far class for auto-x. I didn't even consider that. But at the same time I don't see myself going to enough auto-xs to really have to worry about being super competitive. I see myself just going out to have fun and whatever class I fall into, I fall into. I don't want the auto-x classes to determine what modifications I can make.

 

With your setup, do you feel any power fall off up top, if so where does it start. Or does it just continue to pull more and more until you shift?

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My tach works intermittently, but it pulls well from about 3k to 6.5k rpm. Around town drivability is great as well, and as you said, the majority of your driving will be done on the streets. I'm using my Z as a weekend car and occasional autocrosser, so having a "hot cam" in my engine would be more of a conversation piece than a real performance benefit at this point. When I get to the point of further modifications I will dyno the car beforehand to make sure that what I'm doing has a worthwhile benefit.

 

I'm actually planning to make a comparison video of the Z with SUs and then with the Webers, with no other engine changes made. The Z is down right now because I'm rebuilding the suspension but I hope to be done with that in the near future. Trying to prepare for my first autocross!

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Curiously, the Nissan Plan for the Z originally included 40PHH's as the 'performance' option for the car with 175 instead of 150 hp. That meshes nicely with what Mikuini claimed was the bump putting them onto a stock L24 (22% or something like that, emissions compliant to '67 specifications...)

 

A stock cam will work, and it works better in L26 and L24's. The cam timing and events on an L28 is slightly more conservative, and the gains (relative) are slightly less on that engine. If you put in one of the earlier cams into an L28, it keeps you 'SCCA Legal' and makes the L28 have the same rev characteristics as the earlier cars...meaning you're not 'all in' my 53-5500rpms.

 

Mikuinis are a great all-around carburettor. You should be able to get BETTER fuel economy out of them than SU's if you can resist your footfall. I have gotten 28mpg on an L24 with an automatic and 4:11 gearset running 65mph on the highway with Mikuini 40PHH Triples. Really, they are an OEM carb, and drive like an OEM carb. Toyotas used them extensively on their sporting models in the JDM. I think you will be very pleased once you get them cleaned up and installed.

 

You add a dedicated performance cam, and it really starts pulling harder to the redline, usually from 4000 on up to 7000. But for that you will want lower gearing and other things. Before installing a cam, I'd grab a lightened flywheel and spend the time learning to drive the car and getting the suspension back to at least 'firm stock' tune, if not improving it's handling and roadholding capabilities. Really, the last thing these cars need is more power out the gate. But since I consider Mikuini PHH's an OEM fittment....that doesn't count as an "upgrade" in my book, it comes under the same heading as replacing spark plug wires that are bad: "Restoring Intended Baseline Performance Level"! :lol:

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3k to 6.5k is a great range. If remember correctly that is the same range as the Stage III I talked in my original post. From what I was reading, having a mid CAM didn't really change the street-able. To be honest that is one of the main reasons I am even considering it. At the time I have no personal experience and I'm relaying purely on others opinions and experience.

 

If you were to do a mid CAM that had the same power band as your current setup, you would still get a overall power gain. Which would still be very beneficial for auto-xs. Not knowing any HP numbers associated with a triple carb and/or mid CAM , I can't image gaining crazy, car alternating HP just from the mid CAM. And for me also wanting to do track weekend, a little more power over the full band couldn't hurt.

 

But I completely understand from your point of view, your wants/needs wont justify to need to upgrade your CAM.

 

 

On a completely different note, I am interested in what modifications you have and plan on making towards your suspension for a auto-x setup. Would you mind sending me a PM so we could talk about and I didn't want to mix suspension talk into this post.

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Why do you insist on capitalizing 'cam'? Do you think it is an acronym?

"Cam" is short for "Camshaft" nothing else. Unless you are intentionally YELLING everytime you say the word...

 

Suspension mods are covered extensively in the section on the forum devoted to that subject, plenty of FAQ and Stickies there to read.

 

I'll note that on a tight course my bone-stock "Blue Turd" 260Z with a good driver will be suprisingly close to S30 Fast Time of Day considering what usually sets that time has about 100X the money into it as I do in the car. Faster than a lot of other cars with 'far more power' but the same suspension (stock).

 

Things are balanced. And a stock Z is a very well balanced performance oriented vehicle. Standard stepping stones to better handling can be done to make it better, but in almost EVERY case the biggest part of the equation that can be improved is the driver...

 

Improve yourself before you improve the car. Get the car to good stock tune and suspension nick, and you will be amazed how fast you can be in the car...and really how fun it is to drive.

 

THEN move on to suspension 'modifications/improvements' and finally...add a little power.

 

As for me, on this car: not a damn thing (well, maybe, eventually, some day I'll paint it...I guess.) It has poly bushings, stock springs, stock dampers, stock rims and tires (though sticky) and stock engine. It works, starts every day, and goes to an Auto X and makes passes all day long without overheating and with everybody and their brother beating the hell out of it without missing a beat. I can get in and drive it to Florida or some other warm place tomorrow with a fill up of gas and a check of the oil. Why mess with that? I'm faster up and down on/off ramps than most cars as it is now. At most I'll replace the springs because they do sag now so they might be upgraded to a stock height, higher spring rate, and if the dampers ever do wear out I would probably put Tokiko Illuminas in them set on '5' because I like a soft spring, stiff damper combination. Other than that...nuthin' it's rock solid reliable and there are countless witnesses at numerous MSA AutoX events that have been amazed by the performance of a Bone-Stock 260Z! They really are impressive vehicles in stock form...if you can drive them!

 

Now my 73... Oh that is a different story and well beyond the scope of what you intend to do! ;)

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Get a medium-ish cam. If you go with the stock cam, you will get stock-like performance and will leave most of the potential to make hp on the table.. For my money, I'd rather have SU's if you're getting close to stock performance out of the car, they're cheaper and have better bottom end in my experience. If you go bigger than .460 or .470 or so lift on the cam you'll be into valve springs and stem seals. For someone looking to get the most out of the engine these things HAVE to be done, but for your goals I think I'd go just under that and run the biggest cam you can without having to mess with all that crap. A medium cam will still have a nice wide powerband and will take advantage of the carbs better than a stock cam will.

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Tony D

 

Thats great info. I had absolutely no clue Mikuni had been in Nissan's Plan as a OEM performance option for the Z. I knew they were a large in the Toyota world.

 

I also have realized how impressive the 40mm Mikuni are. Everyone talks so highly about them, the best all around carb. I had also found out that the Japanese used the triple 40mm and 44mm setups for years on their Z race cars and had great success with them.

 

Maybe a better option would be to just do the triples for now. Take some time to get use to the significant hp increase and go play at the local auto-x and track weekends this summer. And this winter look into suspension and brakes.

 

So maybe this post wont get to be that post with tons of info and options for different cam as I had such high hopes, lol.

 

Tony D and Leon I appreciate all the info. It has been extremely helpful in deciding the best route for what I want.

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I have Triple webers and am running the stage 4 camshaft. It's a kick in the pants. Streetability sucks, but that's also due to the 6-puck(which is overkill and regret installing :read brag part:) and the fact that the carbs need a good cleaning. Pulls like crazy from 4-7k and could probably do more if my rev limiter was set higher.

 

edit: forgot to add, for the money I spent I could have had a 400hp turbo Lseries. But I regret nothing

Edited by BluDestiny
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A stock cam will work, and it works better in L26 and L24's. The cam timing and events on an L28 is slightly more conservative, and the gains (relative) are slightly less on that engine. If you put in one of the earlier cams into an L28, it keeps you 'SCCA Legal' and makes the L28 have the same rev characteristics as the earlier cars...meaning you're not 'all in' my 53-5500rpms.

 

 

Well maybe. Which L28? According to the much refered to Atlantic Z cam sheet, the L24 and the L28 used the same cam (A) all the way to 8/81. After that date they changed the L28 cam. The L26 of course had a different cam.

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Well maybe. Which L28? According to the much refered to Atlantic Z cam sheet, the L24 and the L28 used the same cam (A) all the way to 8/81. After that date they changed the L28 cam. The L26 of course had a different cam.

 

So then what exactly is the issue with what I posted? Or is yours an attempt at clarification. Most L28's will be out of poop well before 5500rpms. I of course never mention the L20A Dual Carb Spec cam as most people don't have access to them any longer.

 

Would common sense dictate if "A" was in "all" L28's 'to 8/81' that it may not be the "L24" cam referred to? What of "B"and "C" and of course 'others' which may or may not be on an all popularly read sheet? What would your reference be in an 'L28' cam in that instance (those produced after 8/81?

 

"If it came in an L28, you don't want it for performance N/A applications, it restricts the useable RPM range of the engine."---doesn't matter 'which' L28.....'ANY' L28 sux.

 

Clearer now? :rolleyes:

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