Datsun Roadster Forum-311s.org

So I have a question that I can't seam to find the answer I'm looking for. So I'm rebuilding a r16 that is going to be a casual car show/weekend auto cross car. (I know the r16 is kinda a dog unless it's stroked) but it is basically completely stock engine with a heavily decked head, headers, and im still running the su carbs but will be rebuild and have some work done by keith out here in vegas, so now my question is what one of deans cams would work the best for some midrange power he lists them as

Performance #1 - G15 / R16 grind - 420 Lift at the valve / 260 degrees duration. For SAE camshaft Order by PART# 1497ABS

For METRIC camshaft Order by PART# 1497ABM

Performance #2 - R16 motor - 442 Lift at the valve / 270 Duration. Order by PART#1497DBS

Or is there any other regrind by isky or anyone that would work for what with what im looking for Any help would be greatly appreciated and sorry for the rambling in the beginning.

Christian - Are you planning on just a cam swap, or are you looking at (now or down the road) doing some head and bottom-end work to go with it? Either way, you should have a read through these two threads if you haven’t already done so. I think it will help with your decision:

viewtopic.php?p=130421#p130421

viewtopic.php?p=201222#p201222


… and delete your duplicate post on this subject so things don’t get too confusing.

Thank you very much and I do plan on down the road going with more head work and possibly stroking the engine

I'm analyzing this myself right now for my U20 and have been doing some research. I literally just pulled my cam as I've decided that I'm running too much lift and I have a Racer Brown pattern that will work really well (at least on paper). Anyway, you mentioned the head is cut... any idea what kind of compression you're going to run? For a cam, duration tells the engine where in the rpm band it will make power but also helps it breath better at higher rpms, so adding duration can improve things at higher rpms but will loose power at lower rpms due to overlap between the intake and exhaust valves. Aso an aside, if you're going to compare cams from different companies you need to know what the duration is at "50 thousands." In a U20, a "B" cam is listed at 280 but it's about 248 at 50 thousands. The engine really starts getting happy at about 3200 rpms in a U20 and hits peak torque at about 4600-4800 rpm (this is in MY motor, which is high compression, see upcoming point). In contrast, below about 3600 rpm a stock U20 with an A cam (less duration) will make more torque and be more responsive/quicker than a B cam engine. BUT here is where higher compression can make a big difference. What they have found is that increased compression makes up for the lost torque and matches the lower duration cam's torque down low. So, knowing what your compression ratio is going to be is important. That may help you decide on what duration to try. Compression has to be at least 10 to 1 vs the original 9 to 1, 10.5 would be better. Now, increasing lift will help most everywhere... to a point. From what I've been recently able to find, a good guide regarding lift is to go at 25% of valve diameter. I think a stock R intake valve is 42mm, so 25% of 42 is 10.5 x .0394 (to convert to inches)= .4137. Another way to estimate lift was to go with "percentage of cylinder bore." The two engine share the same bore (87mm). Â good guide is somewhere around 12% to a max of 15%... 12% calculates out to .411; 12.5% .428; 13% .445; 13.5% .462 (B cam lift); 14% .479 (C cam lift); 14.5% .497, 15% .514; 15.5% .531; 16% .548. [As an aside, my Isky cam is 278 (246 at 50 thousands) but has a lift of .531 (15.5%). Unfortunately what can happen is that too much lift can cause "air separation", so I've decided to back it down to the same 280 or so duration but a .478 lift (14%). So I'm going to run a B cam/C cam hybrid.]

So... from all that I'd go with the first choice... 260 duration .420 lift, especially if your compression is up. That's like an A cam, so peak torque will probably be at 4400 vs 4000 stock R16 and it should breath well. Some port and valve seat work to improve flow would be money well spent... it's all a system and it's only as good as its worst restriction.

Improve the ignition system via an EI dizzy or consider a 123 programmable dizzy. The EI is one of the best drop in mods you can do.

That's my opinion, but I'm no engine specialist etc.... just my own research and experience, and not without mistakes!

Thank you so much for that break down...that helps out a shit load

Isn't NV, inspections on the stringent side emissions wise
I'd bet laser exhaust fumes checks are coming back . The state looses fed road $ when it get too bad

I've never had a issue with it and neither has anyone ive known out here ....now they are trying to pass a bunch of rules like even classic cars have to pass smog now somehow but I don't see how that's gonna work out ...and if I absolutely have to then it will just become a registered antique with limited mileage or a full blown race car and I won't register it lol

If anyone is interested I had Delta Cams print out the factory specs for the R16 cams when I had my cam ground.
One thing this verifies as we found before is you can put either cam in either engine. The SAE cam has better numbers.

https://kendo-usa.org/datsun/r16_sae_fa ... m_spec.pdf

https://kendo-usa.org/datsun/r16_metric ... m_spec.pdf

Curtis wrote: Tue Sep 13, 2022 2:45 pm If anyone is interested I had Delta Cams print out the factory specs for the R16 cams when I had my cam ground.
One thing this verifies as we found before is you can put either cam in either engine. The SAE cam has better numbers.

https://kendo-usa.org/datsun/r16_sae_fa ... m_spec.pdf

https://kendo-usa.org/datsun/r16_metric ... m_spec.pdf

Great baseline reference there Curtis.

Thanks

So from what I can tell a stock R16 cam is 196 duration at 50 thousands and .354 total valve lift with a 1.5 rocker ratio. As noted, it's important to know what your rocker arms ratio is for total valve lift. My Isky listed as .499 valve lift on the cam spec sheet that comes with it, but that's based on a rocker ratio of 1.3, and a U20 rocker is 1.4, which equals .531.

Irrelephant