Swapping Nissan L6 Cams?

[skirkland1980]

Stock springs bind over .460" lift. Isky doesn't have a grind that small. You'll have to send it elsewhere to keep it within stock spring limits. A .460" will be an enormous improvement over the stock cam, and much cheaper.

[deuce8ernerozero]

"It is a common misconception that the 280ZX's L28 engine is less powerful than the L24 engine of the 1970 240Z; the difference is due to Nissan adopting the SAE net standard of power measurement, which resulted in lower power ratings than the earlier gross figures and added emissions". http://en.m.wikipedia.org/wiki/Nissan_S130

[Connor280ZX]

All I really want is a good power curve starting at about 3000 out to 6500 with a stock cam. But If I'm getting a re-ground cam I'd want to spin to at least 7000. Is that possible on an otherwise stock engine with just a cam?.

I wouldn't push the engine over 7K with a stock bottom end. From what I know, the stock cast

pistons can break over 7K.

[osirus9]

I wouldn't push the engine over 7K with a stock bottom end. From what I know, the stock cast

pistons can break over 7K.

 

I wasn't going to go over 7k, I want to go TO 7k.

 

So what I'm hearing is either go balls deep and re-do the valvetrain to get a cam over .460 or just stay with a stock cam. Well I can always re-do the whole head and valvetrain later after I decide 325 rwhp isn't enough and my wallet actually agrees with me for once.

[Tony D]

The issue will be where the power peak is, and with a turbo engine so many people mindlessly throw boost at it they turn their car into a SBC conversion with less reliability...

 

The earlier camshaft has a higher power peak, make your boost threshold below where the cam "comes on" and you get a nice linear response...

[osirus9]

The issue will be where the power peak is, and with a turbo engine so many people mindlessly throw boost at it they turn their car into a SBC conversion with less reliability...

 

The earlier camshaft has a higher power peak, make your boost threshold below where the cam "comes on" and you get a nice linear response...

 

The only thing I don't understand about this logic is that, according to here: http://www.atlanticz.ca/zclub/techtips/cam/   The L24 and the L28 both used the same "A" Cam? So by later, are you referring to the L28e which used an "F" cam vs the L24?

 

Sorry, just a bit confused here, and I want to make sure I use the cam with the higher peak power.

[Tony D]

look at the dyno charts... camshafts react differently to different displacements.What's hot on a little motor is mild on a larger one.

The power peak on the L28 is unmistakable though, it's done by 53-5500. That's how it's geared.

Compare that with the L24 curve. Either published by nissan, or by anybody posting the dyno run of their stock car...

 

Frankly, you're wasting your time with a stock one. The only thing a stock cam is good for is a core for regrinding. Delta can regrind a copy of an Isky L475 (higher lift than stock same duration for L24, Higher lift but shorter duration for L26/28), L480 (Higher lift than stock and 10 deg more duration L24, same duration as an L26/28 but higher lift), or L490 grind (Hihger lift and 20 degrees more duration L24, and  higher lift and 10 degrees more duration than stock L26/28) with the requisite 0.465" Valve lift...and a slight lobe center change so it minimizes overlap. Its turbocharged so you play with opening events to minimize reversion, and put in as much lift as you can. Look at the charts for stock ports and flow and it tells you when more lift is not doing anything for you. Then you are left with as much duration as you can use with minimal overlap....and Boost.

 

It's wasting time playing with the stock cams. Get something that has duration and lift.Lift is good. Lift means flow. Even the stock valve events with maximized lift will be very satisfying when boosted.

 

The thing is, the bigger your engine, the bigger your cam has to be  to make it pull up top. And that just isn't going to be with a stock cam!

[osirus9]

Ok thanks for explaining that Tony.

 

So People use the "A" cam because it is the biggest stock cam, but its still pretty small for a boosted L28. By biggest I mean highest lift and second longest duration.

 

I think I will have to stick with the stock cam for a while and see what I like and don't like about it before re-doing the valvetrain for a bigger and more properly sized cam. Head porting and whatnot would also happen then. 

 

Its interesting, but not surprising I guess, that the exact same cam moves the power curve lower between the L24 and L28 engines. It is cool to see how everything works as a system.

[osirus9]

Stock springs bind over .460" lift. Isky doesn't have a grind that small. You'll have to send it elsewhere to keep it within stock spring limits. A .460" will be an enormous improvement over the stock cam, and much cheaper.

 

Hmmmmm... Depending on the price I would love to have the cam re-ground to fit with the stock valvetrain. Know a place that I could call about this?

 

Also I was on MSA's site and their stage 1 cam is .460 lift 260 duration. Is this ok to run on the stock valvetrain? I know people say you can't go OVER .460, but is that lift ok to run without risking binding the springs? I am assuming yes, otherwise their site would say so, but I just want to be sure.

 

They also have a stage 1 turbo cam that is has less exhaust lift/duration but the same intake lift/duration as their N/A cam and says its only for the p90 head. This seems weird to me since the cams are all interchangeable as far as I know. Not sure why decreasing the exhaust valve lift/duration would be better for a turbo...?

 

I apologize again for my ignorance on the subject of cams, thanks again for your helpful knowledge on the subject guys!

[Connor280ZX]

Depending upon the condition of your rocker arms, you might be able to run that cam with the stock springs. however you will probably get valve float sooner due to more lift/duration, and you might not be satisfied with how high you'll be able to rev the engine. But on the safe side, I would get new rocker arms with a new cam, or else you can risk damaging it due to the wipe pattern. (My amateur opinion)

Edited November 19, 2013 by Connor280ZX

[Tony D]

We had a regrind by a hole in the wall outfit (under $100) for our N/A LeMons car.... We maximized duration, ran lift to the point of 0.005" away from coil bind and carried a BOX of matched valve springs to the track and changed them all overnight. That car with MS ran scarily well being all stock otherwise.

 

The thing is this: if you are committed to STOCK parts....you have to discount the cams. You can get a regrind done cheap to maximize the lift---even if it's the stock duration, you want as much lift as you can ESPECIALLY on a boosted engine. The numbers for flow off the seat (0.050" lift) seem small when flow-tested on a ported head on a flow bench, but when you cram even as little as 3 psi onto it flows massive air. So that lift gets to that flowing point as quickly as possible---meaning a big bump in torque over the exact same cam with stock height.

 

If you add some duration, then you can start breathing up higher in the rpm range. Like I said, for all the hassle you would go through, even on stock ports, a cam reground to give you 460" lift will perform VERY STRONGLY compared to a stock one especially when boosted. Isky really throws lift at the boosted grinds, and his power doesn't lie. It's not my discovery, I'm not to proud to steal ideas from the best out there.... you may not necessarily 'need' a huge cam and ported head, but again....look at 1FastZ's stock port comparison and realize the flow possible at given valve lifts. EVEN on STOCK ports, they will show a flow increase at higher lifts. So that means, you can increase lift to get more flow without the downside of lumpiness and all those things associated with duration and overlap. YES, this means your cam has faster ramps, this could mean valvetrain instability, but at the RPM's we are talking about it's not going to be an issue.

 

For the money, a stock duration l28 Grind 460" cam, is a VERY good choice for someone who doesn't want to port the head.

 

The cam - to - displacement relationship is very well known in the VW Air Cooled Circles. An Engle W110 cam is 'the standard' for first time builds. These numbers are changed when you run 1.25 rockers (another first time build standard hop-up) This works really well in a 1600 CC engine, but for something like a 1835 or 2110....it's really not worth the effort it's WAY too mild to try. The general cams available in the USA discount the L20A SU Cam, which outdoes them all! More lift and more duration....  To get the same power ratios from smaller engines, you got to be more and more aggressive with the camshafts. Here's a list of the Engle Cams which progress logically according to grind so you can see the relationship. The limit is how far you can push the lifter into the case and in some cases clearancing the lobes is required to clear crankshaft counterweights...when you quickly hit the lift limit, you start adding duration. The difference can roughly be stated that a 2110 with a 125 will have similar characteristics as a 1600 with a 110 or 100. The use of 1.25 rockers can lead to instability on the bigger cams, but I hope you see what passes for "STAGE SIX" on a 1600CC pushrod engine lift wise (460 valve lift) is basically 'Stage 1' for our cars... that 274 duration at 0.050 is not that big relatively speaking, while stock on ours is around 245??? In fact, the Engle 110 is very close to a stock Z Cam specification wise (245 duration, 430 lift.) something like that. The commonalities and progression on the cam (since most everything else is the same) becomes clearer looking at the below comparison table. Oh yeah, and any of these cams is like $84.... and you wonder why I started on VW's? The Engle 110 used to be $19.95!

 

The Engle W100 Classic VW Bug camshaft grind is designed for 1.1 or 1.25 rockers, and it's specs are .383" Cam Lift, .420" Valve Lift (1.1 Rockers), 276 degrees of advertised duration, and 236 degrees of duration at .050", on a 108 Lobe Center.

The Engle W110 Classic VW Bug camshaft grind is designed for 1.1 or 1.25 rockers, and it's specs are .392" Cam Lift, .430" Valve Lift (1.1 Rockers), 284 degrees of advertised duration, and 247 degrees of duration at .050", on a 108 Lobe Center.

The Engle W120 is a Hot Street VW Bug camshaft grind is designed for 1.1 or 1.25 rockers, and it's specs are .397" Cam Lift, .435" Valve Lift (1.1 Rockers), 294 degrees of advertised duration, and 253 degrees of duration at .050", on a 108 Lobe Center.

The Engle W125 VW Bug camshaft grind is designed for 1.1 or 1.25 rockers, and it's specs are .418" Cam Lift, .460" Valve Lift (1.1 Rockers), 301 degrees of advertised duration, and 262 degrees of duration at .050", on a 108 Lobe Center.

The Engle W130 VW Bug camshaft grind is designed for 1.1 or 1.25 rockers, and it's specs are .419" Cam Lift, .460" Valve Lift (1.1 Rockers), 308 degrees of advertised duration, and 267 degrees of duration at .050", on a 108 Lobe Center.

The Engle W140 VW Bug camshaft grind is designed for 1.1 or 1.25 rockers, and it's specs are .419" Cam Lift, .460" Valve Lift (1.1 Rockers), 313 degrees of advertised duration, and 274 degrees of duration at .050", on a 108 Lobe Center.

[Tony D]

For comparison, some of the more 'radical' cams, and what they say about them  note the 'STUMP PULLER' specs, this is what you would like for a Turbo Cam.... note the lift compared to everything else, and compare it to the duration!!!:

 

The Engle FK7 is a classic VW Cam for milder engines. It is designed for 1.4-1.5 rockers, and it's specs are .357" Cam Lift, .500" Valve Lift (1.4 Rockers) 288 degrees of advertised duration, and 244 degrees of duration at .050", on a 108 Lobe Center. This is a much milder behaving cam than many people think it is, because it lifts .500". If you want a lopey idle, get the FK8 or bigger!

 

The Engle FK8 is a classic VW Cam for milder engines. It is designed for 1.4-1.5 rockers, and it's specs are .382" Cam Lift, .534" Valve Lift (1.4 Rockers) 298 degrees of advertised duration, and 258 degrees of duration at .050", on a 108 Lobe Center.

 

The Engle FK10 is a classic VW Cam for serious engines. It is designed for 1.4-1.5 rockers, and it's specs are .385" Cam Lift, .539" Valve Lift (1.4 Rockers) 310 degrees of advertised duration, and 266 degrees of duration at .050", on a 108 Lobe Center

 

The Engle VZ14 is a Stump Pulling cam for Off-Road engines. It is designed for 1.1 rockers ONLY. Specs are .420" Cam Lift, .462" Valve Lift (1.1 Rockers) 274 degrees of advertised duration, and 242 degrees of duration at .050", on a 108 Lobe Center.

[osirus9]

ok, so I'm getting that for a turbo cam you want more intake duration than exhaust, and also not as much duration as a crazy N/A cam, but as much lift as possible.

 

So the MSA stage 1 turbo cam is actually looking pretty good. Its got as much lift as you can get out of the stock valvetrain, and a little more intake duration but basically stock exhaust duration.

 

It just seems odd to me that you would want less exhaust duration? I get having maximum lift, and I get not wanting much overlap because the turbo pressure seems like it would try to blow air through the intake valve and then straight out the exhaust valve. Is that why the exhaust duration is shorter? To prevent overlap?

 

Sorry for all the questions, I'd just rather understand why I'm doing something rather than just do it because people tell me its a good idea.

 

One other thing. Is there any good reason to replace the rocker arms if they are in spec? People like to replace valvetrain parts, but I don't see the paint if they are working properly?

[Tony D]

WHEN the valve opens is as important as how long. If you open that exhaust valve earlier so it 'pops' the scavenging and also the turbo gets more energy.

 

Actually what happens with turbos is the opposite of what you theorize: the overlap, because the exhaust pressure (in the old days) was usually higher than intake pressure, would cause exhaust REVERSION (a reversal of flow into the intake) and kill cylinder filling.

 

JeffP checked his build some time ago, and was shocked to find that his exhaust manifold pressure was identical to his intake pressure at 7,000 rpms.... meaning he was not in any danger of reversion, and not long ago, that would have been unthinkable on a street turbo car, only something in F1!

 

The reason for maximising intake lift and duration is simply 'cylinder filling' the more time it's open, the lower boost you will have to run for the same power. Split duration cams are nice as they have better manners than 'straight up' cams. 

 

Kind of a disjointed response, it's late here....

 

the key in minimizing overlap is to get your cyllinder filled and no chance of dilution by any residual exhaust gasses... Opening the exhaust at the right time gives a nice, concentrated pulse and then it's closed. That's what you want.

[Tony D]

Now, if you had a roller cam setup so you could run radical ramps to maximize time at full lift, you could RADICALLY decrease overlap, and increase duration without any degrading of idle quality or vacuum....

 

See how it all starts to work together?

 

More lift doesn't cause the vacuum drop that more duration does. But because we have assymetric cam events the cam is ground pretty screwy to make it linear opening. 

 

JeffP's cam idles at maybe 900 rpms, but has only 10" Hg Vacuum at idle. It would be what you would call a bit on the sporty side. But it idles BETTER than the prior cam he had, with less duration and quite a bit more lift than the last. (0.575" I believe...)

[osirus9]

Thanks Tony, That's really interesting that the pressure on the exhaust side is usually higher or equal to the intake side. Definitely not what I was expecting!

 

I'm going to go ahead and call Isky and see what they would charge for a regrind of one of the stock cams I have to the same profile as the MSA stage 1 turbo cam. If they can do it for under $250 (MSA's price for the cam) then I'm sold. Maybe I can even talk to them about more radical ramps to get more time at max lift like you mentioned. I'm not shooting for insane power here, but if regrinding the cam will get me to my goal with less boost then that sounds like a great way to prolong engine life!

 

They should also be able to tell me if I need to replace other valvetrain parts, which is something I'm curious about because if I have to replace rocker arms and springs and stuff anyway, then why not just replace it with a bigger cam in mind? I only say this because on the MSA site they will only warranty a cam if you replace your entire valvetrain, which seems unnecessary to me... 

 

Plus when I get bored and turn up the boost there will be more power there... ahahaha.

Edited November 20, 2013 by osirus9

[Xnke]

Yes, you do need to replace the rocker arms with new or reground ones. You wouldn't re-use flat-tappet lifters in a Ford or a Chevy, don't do it on your Nissan either. They need to have the proper radius, surface finish, and "blank" wear pattern or you risk very rapid cam destruction, and by virtue of oil circulation, total engine failure.

 

That sounds scary enough, I think it will get the point across nicely.

[osirus9]

Yes, you do need to replace the rocker arms with new or reground ones. You wouldn't re-use flat-tappet lifters in a Ford or a Chevy, don't do it on your Nissan either. They need to have the proper radius, surface finish, and "blank" wear pattern or you risk very rapid cam destruction, and by virtue of oil circulation, total engine failure.

 

That sounds scary enough, I think it will get the point across nicely.

 

point taken... 

 

So no matter what cam I use, if it is not the one that the rocker arms were used with, they will need to be replaced or reground... 

any other vlalvetrain parts that must be replaced as I start assembling my hybrid motor? what is a good place to get rocker arms reground?

 

I was looking at delta cams since Isky doesn't list a cam profile that will work with the stock springs. I was hoping I could just swap in a different cam and be done, but it looks like even changing to another stock cam will be a pain in the ass and the wallet...

[Xnke]

I use delta camshaft for rocker regrinding. the "480/280" grind I got from them was only 0.455" lift, works with stock springs and required 170 thou thick lash pads. this thickness pad is NLA though Nissan, Isky has them and you can have thicker pads ground down.

[Tony D]

" I only say this because on the MSA site they will only warranty a cam if you replace your entire valvetrain, which seems unnecessary to me... "

 

This is the typical customer response. You want them to cover all the risk with minimum investment on your part. They want to minimize their exposure by making sure everything is the way it's supposed to be. If you don't want to do it YOU ASSUME THE RISK...just don't whine about something being un-necessary. Wear patterns are wear patterns, it's all a matter of risk tolerance. As a manufacturer selling these things by the hundred their exposure to multiple failure liability is quite a bit higher than yours. Put six new rockers on, and six used ones. If six lobes wreck, and six aren't wrecked it costs you the same either way...for saving the cost of six rockers. In all the excitement of reassembling the engine, maybe you forgot.... "did I replace all 12 rockers, or only 11?" Well, being it's well know Datsun OHC's have an appetite for cam lobes when things aren't just right you gotta ask yourself a question: "Do I feel lucky?" Well, do you feel lucky? By the sounds of it, you think you are.... So maybe you will be Mustafa at the Bank who takes the chance, and not Scorpio on the Dock...

 

Why do you CARE about the warranty anyway? Please go watch "Tommy Boy" with David Spade and Chris Farley to get a real perspective on a guarantee/warranty:

 

Tommy: Let's think about this for a sec, Ted. Why would somebody put a guarantee on a box? Hmmm, very interesting.

Ted Nelson, Customer: Go on, I'm listening.

Tommy: Here's the way I see it, Ted. Guy puts a fancy guarantee on a box 'cause he wants you to feel all warm and toasty inside.

Ted Nelson, Customer: Yeah, makes a man feel good.

Tommy: 'Course it does. Why shouldn't it? Ya figure you put that little box under your pillow at night, the Guarantee Fairy might come by and leave a quarter, am I right, Ted?

[chuckles until he sees that Ted is not laughing]

Ted Nelson, Customer: [impatiently] What's your point?

Tommy: The point is, how do you know the fairy isn't a crazy glue sniffer? "Building model airplanes" says the little fairy; well, we're not buying it. He sneaks into your house once, that's all it takes. The next thing you know, there's money missing off the dresser, and your daughter's knocked up. I seen it a hundred times.

Ted Nelson, Customer: But why do they put a guarantee on the box?

Tommy: Because they know all they sold ya was a guaranteed piece of s hit. That's all it is, isn't it? Hey, if you want me to take a dump in a box and mark it guaranteed, I will. I got spare time. But for now, for your customer's sake, for your daughter's sake, ya might wanna think about buying a quality product from me.