I'm considering a possible (distant) future upgrade to a hotter camshaft for my Z and was wondering if anyone is running the Isky L490 in a street driven Z, and more importantly would you choose it again? I'm running a Compcams 252S now, which is a good daily driving cam, but doesn't really come on strong. Very stockish. I'm looking to make my ride a bit more exciting/interesting but I'm not wanting to make driving under normal circumstances (town/traffic) a struggle or frustrating. I prefer driving on twisty country roads and that's where I want her to shine.

Combo would be L26 (stock head) with early 5 speed and 3.9 rear.

Thoughts?

Jay

I run the .490" lift / 290* duration Isky cam with a titanium valvetrain in my .20" over L-28 (now an "L-29"). It's certainly a change-up from the rebuilt L-28 engine. Whereas the stock L28 Datsun cam would idle at 650-700rpm the Isky will hear none of that. It needs 1,000 rpm to stay alive and really wants 1,500rpm to be happy. Not much happens below 2,500 but the cam comes on furiously at 2,800 for the next 3,000 rpm. Highest torque peaks for me btwn 4,000-5,000 rpm and sounds awesome. With my gears I can run @4500 in the power range in 4th gear at 65-75mph. 3rd and 4th gears will push me back into the seat at any speed; how it develops all that torque at higher speeds is beyond me. The overdrive 5th gear isn't that much fun and is reserved for long-distance. A very little increase in rpm makes a big difference in road speed with this cam in 5th gear.

This is the cam which Vinny Bedini prefers and recommends for a hot street Z which still has to haul groceries occasionally. I told him I wanted him to rebuild my engine to no more than 220hp and this cam was the very first thing he mentioned.

After discussing head options, I used an E88 shaved on In/Ex side and milled on the face, combustion chambers completely filled then drilled out to 41.8 ccs for 10.3:1 compression over flat top pistons, Nissan stainless valves (35mm Ex/43mm Int), Isky titanium competition valve springs and retainers. I have a set of 3x2 40mm Webers and the cam would handle those, but I stayed with the SUs. I'm left with the triple Webers, a spare P90, a rebuilt E88 and the E31 which is still on my original L-24 engine. The Isky .490" cam should run about $200, maybe more by now.

Frank

_________________
1970 240Z

You run a delivery service now ?

_________________
W.Karl Walton
Somers CT



75' - 280Z - HLS30203249 - #304 Gold Metallic (stockish)
96' - 300zx TT - JN1CZ24d3TX960293 - Black on Black (enhanced)

PiZZa, with capital Zs.
Guaranteed to reach you hot, even if your neighbors complain.

_________________
1970 240Z

_________________
W.Karl Walton
Somers CT



75' - 280Z - HLS30203249 - #304 Gold Metallic (stockish)
96' - 300zx TT - JN1CZ24d3TX960293 - Black on Black (enhanced)

Yes, Vinny is the one who recommended that cam to me, really before I even asked about performance recommendations. Looking the specs over on Isky's site (and admitting that I'm not knowledgeable enough to confidently select a cam and know I'm getting what I'm after) I would have immediately dismissed that one as too large for the street. It's around 244 or so degrees duration @.050, which just seems really high. I've also read extremely good things about the Isky profiles for our Datsun engines.

On the other hand I put alot of stock into what Vinny says as his experience building these engines is decades long. If he says it will be good I'm sure it will.

Also Frank, that is one heck of alot of custom work you've got into your engine. It must be an absolute blast to drive! Mine is great fun and it's very mild by comparison. I still didn't get to hear it as I got derailed on my way over at the picnic. Next time.

So are you satisfied with that grind now that you have lived with it for awhile, or would you have taken it down a notch? Or up? Also, what does the Shaving on the intake/exhaust side do for it? Or was that just a cleanup?

Jay

I'm having fun with this engine; it's the most horsepower this car has ever had. But I sent the original L24 engine to Vinny to be rebuilt (and maybe pumped up a little) because I want to keep the car as original as possible (I received it back modified when I bought it the second time, so there's only so much I can do about that). Since I will eventually replace this "L29" engine with the rebuilt L-24 original anyway, I will live with it for now and enjoy it for as long as it takes to rebuild the original.

I feel happier if my SPORTSCAR engine idles down closer to 600rpm. Sportscars are not intended to be hotrods and, while my car clearly isn't one, this cam and magic head has taken it several steps toward that. I don't mean to imply that I get a dragster "thump thump thump" at idle, but I would prefer it idled maybe 800-900rpm slower. I guess that's a confusing way of saying I like the power of this engine setup, but I wouldn't want to live with it indefinitely.

Since I have so many "spare" heads and cams now, I might consider just swapping this hot head onto my L24 when it's finished, and maybe install a lighter cam. The E88 heads did not come with the very early 1970 Zs, but this one out-performs the E31 in every category. I'm very proud of the head. The cam is ever so slightly hotter than I think I need for the way I drive. But I will say this: It's a lot of fun passing everybody uphill in 5th gear without trying hard.

Shaving the exhaust/intake side of the head ensures the manifold and header can sit on a perfectly flat (not warped) surface so there are no airleaks or wavy surfaces which try to be an airleak.

Milling the bottom of the head reduces the volume of the combustion chambers (thus increasing the compression ratio) and ensures the head gasket is working with a completely flat surface above and below it. Putting uniform torque on the intake manifold and exhaust headers when the surface is warped, results in uneven tightening and gaps for potential leaks around any of the gaskets.

However much you mill off the bottom of the head, you must add to the height of the camshaft towers. (e.g. if you lower the head by milling it 0.10", you must shim up the cam towers 0.10" taller in order to keep the timing chain tight).

_________________
1970 240Z

Oh I see. Yes my head was milled on "all" 3 sides when I had it rebuilt, my block was decked also. Only for cleanup and flatness, not for compression.

Since I have the 260z I've read they are slightly more prone to detonation due to their combustion chambers. I'm sure some of Vinny's magic work could cure that but I'm sure I probably can't afford that haha.

So what kind of lighter can are you considering Frank? L470, L480? You'd love my cam for it's idle, probably not for its power though.

Jay

Unsure at this point, far too premature to think about it. Probably stick with Isky or Duntov, tho, just something slightly milder than this one.

The next cam will be going into the rebuilt L24 (if Vinny ever gets around to rebuilding the L24) so the whole existing "L29" will be coming out as a lump. I'll just continue to enjoy it until then. Strange, despite all I spent on this engine, it was never intended as a permanent replacement.

Never heard that about the L26 pre-ignition problem. Several things can cause that and they are all fairly easily overcome.

_________________
1970 240Z

What I'd read was that the shape of the late E88 cylinder head combustion chamber was more prone to detonation than the other versions of it. I don't know why that is, or if it is even true to be honest.

I know mine didn't care for that gas I bought on the way to the fall outing. That's the only time mine ever pinged on me. Backing off on the ignition timing by turning back the distributor got me home without issue, but she was certainly not running her best that way. I have since advanced her back to the old setting and she feels spunky again. Amazing what a difference there can be with fuel and timing settings. I'm planning a trip to Vinny's for some proper tuning in the spring, my guess is I'll leave there amazed at how well my car can run.

I also have read that a closed high quench design combustion chamber is preferred over a flat top piston. That must not have been common knowledge in 1974.

It's funny that you went so crazy on a temporary motor. Most people would consider that build their ultimate one. I would.

I would have hung the triples on it too though.

Jay

Triples intimidate me.
And I have to pay for the fuel I use.

I have tried in past years to find someone to fabricate a custom manifold which would allow me to run TWO dual-throat Webers instead of three. That would double my carburation instead of tripling it.

I am also trying to get on the list for a set of the "new" SU DU-6 dual-throat replicas when they get released. They are very late already; supposed to have been available this year. I would hang a pair of those on my Z in a heartbeat, doubling my carb flow. This cam would handle them, too. DU-6s were big among racers back in the late 1950s and very early '60s, mostly on 4-cylinder sportscar engines (Lotus, Minis, Alphas, etc). They didn't have chokes on them so they were almost unstreetabe back then. The new ones are being designed to modern standards but nobody alive at Burlen Industries today is even old enough to remember the originals, and they're having trouble making them work correctly. I hope I live long enough for them to get it right!

_________________
1970 240Z

Completely understood Frank. You're a very technically savvy person though, you could handle triples I'm sure. The increased fuel consumption is a factor for sure, but as I understand it big cams eat more too?

I don't really get to drive mine enough to worry about that. At best an hour or two a week for me in summer. I care more for the performance but definitely understand the economy concerns as well.

Those dial SUs are awesome looking carbs! I've never seen those before but they would be wild looking on your Z engine for sure!

I'm a big fan of the SU setup we run, the triples just have a bigger presence visually. Not really a great reason to switch. I don't see myself actually ever running them.

My SUs are leaking badly at the throttle shafts though, and I am going to be sending them to ZTherapy to be rebushed this winter. I want to give Vinny every advantage he can for the tuning session this spring!

Jay

Before the Mercedes Benz cars led the world away from carburetors and into fuel injection, several British cars (Aston, Jag, Healey) put triple SUs on their big 6 cylinder engines. One of our members here in CT built a custom manifold and mounted triple SUs on his Z engine (I forget which siZe the engine was). He had a terrible time making the float bowls clear each other and ultimately had to mount one carb backward so they would all fit (something like that). He was never happy with the result so his Frankenstein SU carb setup rests in his garage, mounted to his spare Z engine.

I'm rawtha afraid of that happening to me. Building a custom manifold and throttle linkage for dual Webers or DU-6s won't be cheap, and if they don't work when I finish them I will be stuck with the attempt; nobody else will want to buy them.

Reminds me of an old American racer who tried mounting three (or four?) 4-Bbls on a single manifold. Didn't work but looked monstrous. Stuck with the freaky mess which had cost him thousands of 1960s dollars, he brought the setup to each race and just laid it on the bench in his pits. Other team mechanics would drift by, spy the mess and inquire about it. He would brush them off and tell them that was "for later if we need it". The other guys went nuts trying to duplicate his effort, fearful that he was actually going to mount that thing on his car someday and sweep the track. I'll try to remember who that was and post a picture of his creation.

Ahh, found it:

_________________
1970 240Z

Sorry I feel the need to comment. I love cams. Absolutely love it. Jay I would say you might actually have lost top end power using that cam from comp. You certainly gained low and mid range, up to 4500 RPM's. Comp for some odd reason loves 110 degree lope separations and relatively early intake lobe center lines 104 is the usual. Great street cam. They do tend to decrease actual compression at slow speeds if you measure it. Regular compression test. With this design / strategy I feel you would loose a lot of character of the stock L6 motor, mainly that they carry the revs. Below is a good link to the stock cam specs. The stock 109 center line, even with stock small duration will put peak hp pretty high into the revs around 6,000 and kinda kills low end torques. Like stock.


http://atlanticz.ca/zclub/techtips/cam/index.htm

_________________
Bruce - Early 260Z - 305 Light Blue Metallic