Cam Spec

[240znz]

I have had the cam that came with the car profiled and it as below. The head shop has worked the head also.

So far I have.

E88 head

Compression is 9.5:1

Inlet valves are 44mm

Exhaust valves are 35mm

A bit of porting only in the chamber to match them. No unshrouding done.

Cam spec is 236@50 0.465 lift. 108 degree separation and tappits are .010

That's all the info on the cam that I have. Based on info I have read, this seems like a mild cam at best. Am I right?

Engine size is 2.5 running triple 44PHH's. I wonder if I am wasting my time with rebuilding the triples when the SU's would be OK.

Your thoughts please.

[240ZMan]

You're correct, it's not a "big" cam. But you didn't say what your goals for the engine are, so don't know if that's a good or "bad" thing.

As for triples vs. SUs, you certainly have more carb than you'll need for your engine, but I still think you should go with the triples because you can tune for part throttle and WOT separately. With SUs you'll either have good power at WOT and be rich everywhere else, or the reverse. About the only way to tune with a bigger cam and SUs is to grind your own needles.

And then there's the sound of triples

[240znz]

The car will be used for some weekend driving and the occasional time trial events at the local track.

So what I'm after is a engine that will give me pull and a bit of top end when stomping on the loud pedal.

[jmortensen]

44's should do that for you. I'd probably swap the cam out for a larger one to make full use of them, but they should work reasonably well with the cam you have.

[240znz]

Jon,

The duration looks tiny to me. After visiting various AU and NZ cam profiler websites, common duration is about 260 to 290 for more torque.

The engine is a overbored L24 to L2.5. His arguement is that we aren't chasing compression as I want it to run on pump gas and avoid pinging with our pathetic 95 octane fuel that we get here in NZ. He went on to add that the L24's rev better than the L28 so the setup is for higher rpm without sacrifcing low down torque. I'm not sure that he just hasn't thrown up enough fog so I can't see the reasoning.

I guess I'm doubting his reasoning with this cam with the head work he has done. Maybe I'm a "Doubting Thomas", but I guess I'll just have to see what it's like and if it's not what I like, then change it.

I'm also running headers with a 2.5" pipe. Standard dizzy at this stage and 3.54 diff. Any ideas on what I can expect?

[janaka]

I'm running a Schneider cam- .460 valve lift, 270 intake duration, 280 exhaust duration with dual SU's, header, 2.5 MSA full exhuast and I put down 162RWHP and 162Ft/lb torque this spring. that was with a P79 head 3angle job and new hardware all around. its got a nice idle and still gets decent milage

[jmortensen]

Jon,

The duration looks tiny to me. After visiting various AU and NZ cam profiler websites, common duration is about 260 to 290 for more torque.

The engine is a overbored L24 to L2.5. His arguement is that we aren't chasing compression as I want it to run on pump gas and avoid pinging with our pathetic 95 octane fuel that we get here in NZ. He went on to add that the L24's rev better than the L28 so the setup is for higher rpm without sacrifcing low down torque. I'm not sure that he just hasn't thrown up enough fog so I can't see the reasoning.

I guess I'm doubting his reasoning with this cam with the head work he has done. Maybe I'm a "Doubting Thomas", but I guess I'll just have to see what it's like and if it's not what I like, then change it.

I'm also running headers with a 2.5" pipe. Standard dizzy at this stage and 3.54 diff. Any ideas on what I can expect?

Your cam has the duration rated differently. Yours has it listed at .050" lift or better. The ones that you're seeing with 290 duration are giving you the full duration to .001" lift. The theory is that the .050" lift is the more accurate at describing what the actual cam will perform like, but the logic is a bit flawed because it assumes equal profile cams, not assymetric like most Z cams are. Being that the cam is only .465 lift, I'd expect something between 260 to 280 duration if it were listed in the more traditional way.

A larger cam will make it less likely to ping, and will also give you more top end at the expense of bottom end and midrange power. If you're building for top end power, I feel that a bigger cam is in order. When you go to a larger cam than about .470 or .480 lift, you run into several problems.

Coil bind on valvesprings happens right around in this area for one, and requires aftermarket valvesprings to fix. Valve spring retainers hit the valve stem seals. Ford makes a viton valve stem seal that fits right on and is much shorter, and very commonly available here in the states anyway. I know I've linked to the Hybrid Z thread in the past. You can also use the Nissan A series valve stem seal, but here they're a lot harder to come by.

At some point the pistons need to be notched for valve clearance. I don't know that there is a hard fast rule for this, since the head thickness and gasket thickness is variable. I am running a .490 lift cam with a slightly shaved head and have not had any issues, but I've heard that a .520 lift cam requires notching the pistons. I think the only way to really know for sure is to assemble it and check the clearance with modeling clay.

The chambers on your head look decently polished out and valves unshrouded, that's a lot of work so that's nice to have done for you.

I'd suggest a 5 speed swap and 4.11 gears to make the most of the triples.

[240znz]

Thanks Jon. Thanks for explaining that, it makes more sense now.

I got the 5 speed rebuilt last year and I'm about to pull the spare diff I have in the parts car. That car had the triples on it with L28, some suspension mods and relocated battery. So I'm keeping my fingers crossed for a 3.9 or 4.11 in there.

I compared the head work with the E31 and N42 I have, yes, big differences all round. The valve size is huge. Now I just need my car back to put it all in.