U20 EFI Stroker build (Scarlett's new heart)

[Pjackb]

Spyder, do you have the cam card for the Z-196?

On the Isky website it only provides total lift and doesn't give rocker ratio. On my Z-197 card it specifies 1.3 rocker and has a total lift of .499, but when using the Roadster 1.4 it's. 537. Mine was measured at Delta Cam after it was polished due to a rocker issue and it was .531 total. For all this time I assumed an L-series was 1.3 based on the assumption that the 196 was for a L-series so maybe the 197 was too... guess wrong! As I think about it now, I do recall reading somewhere that this grind was also for a Lotus, but which one I've not heard.

Interesting, so it sounds like the 197 is a little different idea... a bit more lobe separation, not as much duration as a 196 or a "C" cam (though we seem to have some questions regarding these specs being apple to apple... any thought on what my duration might be? Peak torque has been at 4800, suggesting "B" cam territory) and high (highest? Too high?) lift. Well, we're covering the bases eh?

Greg I searched extensively and I haven’t been able to locate any information on an Isky Z-197 cam for Datsun outside of you mentioning it which leads me to believe it’s likely a custom grind that uses that nomenclature.

Now regarding the 1.3 rocker ratio on the card you’ve piqued my curiosity, and I enjoy investigating things like this!
After some digging, I believe I’ve found the answer: it’s probably a typo.

Here’s why:
1. Isky did make a Z-197-08 camshaft, but it was for a VW/Porsche Type 4 engine, which, as it happens, had a 1.3:1 rocker ratio. However, timing events for VW air-cooled engines are totally different from those of Datsun high-revving cams, so they would not directly copy the VW design for a Datsun engine.

2. What I suspect happened is that you have a custom grind camshaft, possibly using some of the same tools or dies they used for VW cams. They labeled it as Z-197, and during documentation, they mistakenly noted the 1.3 rocker ratio, carrying over the VW application specs. The VW cam is listed at 0.499” valve lift with a 1.3:1 rocker ratio by the way.

3. Supporting this theory: I came across Spyder’s old post about his cam card, which showed a 0.386” cam lift instead of the 0.353” seen on the Z-196 cams for LSeries . This suggests that Isky ground the cam specifically for Spyder’s U20 engine, retaining the same valve lift by adjusting the cam profile for the U20s 1.4:1 rocker ratio.

So, in summary, I think your Z-197 camshaft is a custom grind for your U20 engine, inspired by the VW Z-197-08 camshaft but adjusted for the Datsun’s higher rocker ratio. The 1.3 rocker ratio on your cam card was simply a typo, likely a carryover from the VW/Porsche specs.

[spyder]

Spyder, do you have the cam card for the Z-196?

[tangoterje]

Have you measured the piston protrusion above the block surface yet?

Also, I agree with the need to measure a cam properly. My B cam has EXACTLY the same lobe lift as a C cam a friend of mine measured last year. They seem to vary a bit, so be careful. Luckily it´s very easy to measure lobe lift.

[Pjackb]

Have you measured the piston protrusion above the block surface yet?

One of the first thing we did to get estimated CR
I'm 0.6mm below deck for 4cc

Also, I agree with the need to measure a cam properly. My B cam has EXACTLY the same lobe lift as a C cam a friend of mine measured last year. They seem to vary a bit, so be careful. Luckily it´s very easy to measure lobe lift.

Yeah did some digging and I believe Will Campbell posted something like 6 version of the B cam , I expect to be similar for the C ,
I can tell you the B cam I have is right at .460 but the C cam I have is closer to .465 so yeah almost equal

[Pjackb]

So the Nissan L series rocker has a 1.45 ratio and the U20 has a 1.4 ratio per the Nissan comp catalog. However it is important to remember that the lift that is advertised is at zero valve lash, so depending on how tight or loose you set the lash will determine the actual lift. Duration is also a bit tricky as it too is measured with zero lash and depending on what standard is followed you can see different durations. In the United States you measure duration starting at and ending at.050 of valve lift. In most of the rest of the world they use .040 lift or 1 mm, so depending on the standard you use you could see a different duration. R16 engines also have a ratio, so again you would need to calculate your actual lift by measuring the cam and applying the ratio. So the math is simple take the cam lift off .353 and multiply it by a 1.4 ratio and you then had valve lift of .494 at zero lash. The same lift with the L series ratio of 1.45 and you would have a .512 lift. All of this said now I will totally mess with this, the ratio is only truly valid when the rocker has been set up correctly and wipes through the center of the wipe pad.
Dave

I.48 for L series Dave
I've been having this discussion with a few people ever since I was clued in on it , Most cam manufacturer are giving duration numbers a tappet/lobe with zero lash but not all of them so I always ask where measurement is taken and if Zero lash ,
I always use cam lift as a reference when comparing cams

[Pjackb]

Progress has been a bit slower over the past few weeks, but I’ve managed to make some headway on a few critical items.

Trigger Wheel Update

As mentioned earlier, spark timing will be handled by the ECU using a trigger wheel. Since there isn’t an off-the-shelf solution available, I collaborated with a friend to design one from scratch and had it laser-cut. (ill have a couple extra to sell)
After much consideration, I opted for a 60-2 configuration to ensure greater accuracy ,

Very happy with the results , If you’re wondering why the trigger wheel doesn’t have any missing teeth yet, it’s intentional.
The plan is to assemble everything first, determine the optimal sensor placement, and then remove the required teeth accordingly.



Due to the damper’s shape, machining was necessary to create a flat surface for the trigger wheel to mount securely



Once we finalize the placement of the sensor and measurements to remove the appropriate teeth, the entire assembly will be sent to the crankshaft shop for balancing. Zero balancing is essential to ensure the engine runs smoothly without introducing vibrations or imbalances.

Here’s a preview of what the setup will look like when assembled

[Gregs672000]

Looks good. If this is helpful, my sensor is mounted using the two front cover bolts at the bottom of the drivers side of the engine (alternator on passenger side). The Roadster's stock metal triangle piece used for mounting/supporting the alternator fits there perfectly, and the Ford sensor (magnetic) is bolted to that through some slightly slotted holes that allow for proper alignment and gap to the crank wheel. It has been solid and trouble/vibration free. I don't have a pic, but can take one if desired.

Make sure those mounting bolts don't rub on the cover!

[Pjackb]

Make sure those mounting bolts don't rub on the cover!

Definitely, these are temporary for fit , ill be most using flange bolts with green Loctite (290) to eliminate the need for washer and prevent vibration loosening

Looks good. If this is helpful, my sensor is mounted using the two front cover bolts at the bottom of the drivers side of the engine (alternator on passenger side). The Roadster's stock metal triangle piece used for mounting/supporting the alternator fits there perfectly, and the Ford sensor (magnetic) is bolted to that through some slightly slotted holes that allow for proper alignment and gap to the crank wheel. It has been solid and trouble/vibration free. I don't have a pic, but can take one if desired.

Please share a picture of this , I’m not sure which triangle piece you’re referencing to , I was going to make a custom bracket like this one that I’ve seen from Richard in the Netherlands

IMG_1448.jpeg

IMG_1449.jpeg

[Gregs672000]

I took a few pics. As noted, the triangle is a stock part (often accidently left off when people replace the alternator) and may be the same part used for the smog pump. I'm afraid that I can't get a clearer Pic without disassembly. Not show quality like Richard's part, but I don't have access to machine tools etc... it's just me and a hardware store! What matters most for me is that it works, and it fit the bolt pattern perfectly. "Sinc loss" is an issue that folks experience if their sensor mount vibrates, especially at high rpm, and the gap between the wheel and the sensor is quite small. My wheel was sourced off the internet and the crank pully was machined down as needed to make the teeth prominent. Hope this helps. Looking at this Pic, your mounting bolts will have plenty of clearance! BTW, Daryl has his sensor mounted elsewhere on his R engines and may have other options or suggestions.

[Pjackb]

Thanks , I don't have that piece but i see what it is

[akara]

Great thread, I am interested to do a similar thing to my roadster. thanks for showing us all the details!
I have also been using a Schneider custom grind you might find interesting, I used to live near their shop.

20190825_200649.jpg

its a split profile as you said 284/292 .5/.51 lift, the roadster exhaust port isnt so great when it has to take a sharp 90 degree bend out of the head to the header.

This cam is great for a performance 2 liter engine, it loses some torque under 3000, but I've had it to 8000rpm many times. I do not think a cam with such a large amount of overlap is suitable for a stroker limited to 6500rpm so I will change to a different grind for my engine...

Not to beat a dead horse here, I have a lot of experience building exhaust for motorcycles and dyno testing them, but this is just my opinion. The compression provides the exhaust "signal", that lets the 4-1 design provides strong resonance, and the overlap allows that resonance to do work.

Your two dyno graphs tell me a story: the roadster engine with a short 4-1 header and an A cam has a low resonance, resulting in a smooth torque curve. Meanwhile, the L28, with its overlap and 6-1 header, creates a resonance with three distinct power peaks. Which design accelerates faster ultimately comes down to integrating the area under the curve and gearbox ratios, and as you said, it’s not always straightforward! Personally, I avoid high-resonance exhausts on low-RPM street engines because I often find myself cruising in one of those torque 'valleys,' even if the design offers better peak torque.

I definitely agree—the roadster intake port should not be messed with. If you’re looking to improve your head, one relatively simple but effective modification is blending the seat recession into the head. This area is critical for low-lift flow, and since the valves spend a lot of time in the low-lift range, smoothing it out can make a noticeable difference.

I like to use an old valve with the edges slightly ground down—just enough to protect the valve seat grind. With the old valve in place, I take a Dremel with a small ball-shaped burr and carefully blend the sharp edges around where the valve seat is pressed into the head. It’s a small detail, but I’ve seen it make a real difference. Definitely worth doing if you haven’t already bolted the head on and have some free time.

cylheadblend.jpg

I am looking forwards to your continued progress! Thanks for showing the trigger wheel setup. I think its cool you were able to use the VG pistons.

[Gregs672000]

Akara, you mentioned exhaust development experience and running a cam with a lot of overlap (duration?) with some loss of torque below 3000rpm... any experience with an anti-reversion chamber in the exhaust, or an anti-reversion plate in each exhaust port? It's my understanding that these can improve low and mid torque that allows you to use a higher duration cam without losing so much down low.

Since you're local (Seattle) it would be fun to get together when the weather is a bit warmer!

Pjackb, sorry for the thread hack!

[Pjackb]

I have also been using a Schneider custom grind you might find interesting, I used to live near their shop.

its a split profile as you said 284/292 .5/.51 lift, the roadster exhaust port isnt so great when it has to take a sharp 90 degree bend out of the head to the header.

This cam is great for a performance 2 liter engine, it loses some torque under 3000, but I've had it to 8000rpm many times.

That's actually very close to the specs I wanted but had some clearance concerns because the head has been shaved a lot, so i went slightly lower on the cam lifts , but same durations sa yours
This has to very a very fun cam and would work amazing with EFI

for a stroker limited to 6500rpm

Not sure what you mean , I'm looking for peak power a 6000 around but there's no reasons for my engine not to hit 7500RPM easily

[Pjackb]

Pjackb, sorry for the thread hack!

All good , I've done it too lol

[Pjackb]

Engine Reassembly Begins

It’s been a while, and it’s been a very busy period, but we are continuing to make progress—reassembly of the engine has officially begun!



First off, I like my engines to look as good as they perform. I’m not a fan of the traditional Datsun blue, so I went with GM blue instead, a color I had previously used on another build and absolutely loved. To get the block ready, we properly prepped and painted it, ensuring a clean and durable finish




I also powder-coated a couple of valve covers. Most likely, I will go with the blue one, but I’ll test both options in the engine bay to see which looks best before making a final decision



Next, we assembled the head and block. Other than a broken stud on the thermostat housing—which was an easy fix—everything went together smoothly.




DRP adjustable cam gear looking great


For now, I installed the C cam to make sure everything lines up correctly and to properly align the trigger wheel at TDC before sending it for balancing. However, final assembly will be completed once the Schneider cam arrives.