Datsun Roadster Forum-311s.org

I have a B cam on a spare head. The cam looks good. Wondering if my stock rebuild would allow me to simply drop it in. I still have the stock manifold and SUs on the car...69 2000. What adjustments would I have to make? What characteristics would change on the car. Assuming rougher idle and less predictable starts. Would the power band change? I can post some pics to support the post soon.

thanks,

-ccb

Lots of people would advise you to have the B-cam checked for all the basic faults and possible wear and then if you still wanted to swap it out with your present camshaft, then you should have the rocker arms reground/resurfaced, which if they are the 2-piece type, this can be done without damaging them (if they are the one-piece variety, then don't attempt it--you really ought to search this site THOROUGHLY about the rocker arm question, because In my opinion, they could be re-used no matter what type they are, but that's just IMHO)--OR just use the rocker arms from the donor cylinder head (AND KEEP THEM IN ORDER). The only truly assured method when swapping camshafts, is to remove the cylinder head, put in on a bench, tear it down, change the camshaft and reassemble it, then hand-rotate it in order to check the wipe profile of each rocker arm using machinist's blue. If everything looks good (cam lobes are contacting mostly on the center portion of the rocker arm wipe pads), then the geometry is good and it should work ///// At this point I will stop my sermon and leave it UP TO YOU...because I have never tried this (in a Roadster); I have however, done this very same thing with my Z-Car's L-series engine. Both cars being close cousins, I wouldn't presume it would be much different, results-wise. if it were my car, Roadster or Z, after what was just described having been done, I would be inclined to reinstall the entire assembly and let 'er rip.
I can't help you with an answer about the change in characteristics. The B-cam being a factory grind profile isn't a radical one even for pre-smog, but would probably induce a slightly rougher idle and better top end, but with SU carbs it could be a zero-sum gain since they don't flow as much as Solexes do. You may not even notice it. I hope those with better knowledge than myself can speak to actual experience and confirm that's likely.

I tried it two weeks ago in my car using new rocker arms. I was very methodical and patient and all went well. I did the run-in procedure using SU carbs, before swapping those out for Solexes. The car likes the B-cam a lot. Sounds great, idles fine, no complaints.

I need to echoe here that you can't go wrong when using Nissan-designed hardware in any power/performance-adding upgrade

bakerjf wrote:I tried it two weeks ago in my car using new rocker arms. I was very methodical and patient and all went well. I did the run-in procedure using SU carbs, before swapping those out for Solexes. The car likes the B-cam a lot. Sounds great, idles fine, no complaints.

How was the carburetor swap, difficulty-wise? That can't be easy especially if the engine is still in the car. Either you've done this before, or you're very adept in tight spaces---my hat's off to you nevertheless!

SDkvrd wrote:

bakerjf wrote:I tried it two weeks ago in my car using new rocker arms. I was very methodical and patient and all went well. I did the run-in procedure using SU carbs, before swapping those out for Solexes. The car likes the B-cam a lot. Sounds great, idles fine, no complaints.

How was the carburetor swap, difficulty-wise? That can't be easy especially if the engine is still in the car. Either you've done this before, or you're very adept in tight spaces---my hat's off to you nevertheless!

Haha - my hands are just starting to heal up now. I spent a lot of time trying to figure out "the tricks" to getting to certain spots, e.g. the Solex heatshield. The manifold is always a lot of fun of course, whether SU or Solex. I spent the first ten years out of high school working on some not-maintenance-friendly airplanes in the Navy. I guess I picked up some skills there.

My roadster had a U20 with SUs and B-cam. Noticeably "lumpy" idle but no problems starting or running. You can hear it rev out in this video:




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According to Bob2, mine is a B cam reground toward a C cam with SU's. Starts easilly, good power and keeps up with Solex cars. I do have almost zero vacuum at idle, which makes it hard to adjust and confuses the SU's, so idle is very lumpy under 900 rpm, but performance is fine. I do need to adjust the valves, which might help idle a bit.

I reused the original 2-piece rockers after polishing the surfaces along with original lash pads. Idles just fine with great mid-top end. Rebello grind close to B-Cam specs, tad less duration with tad greater lift. 270/450. Really wakes it up! Do not even think of smoothing out 1-piece rockers, way too soft. Good luck, you will have fun

That video from Alvin was too cool...the sound, the sound! Amazing. No cars sound like that now.

Thanks everyone. Bottom line, I need more planning. I have the cam on a spare head, so might make sense to do all the work independently of what's installed. Then when I get the bug, I swap out. I had heard a rumor that the dizzy needs a new cam as well when you swap out. Thoughts about that?

Dizzie does not need a new cam, unless it is still running the smog set up. If a smog set-up then yes, I recommend recurving the distributor or going EI.

Best to go electronic ignition. I prefer Crank fire with computer controlled advance.
Rebuilding your Distributor and updating to a non-smog advance curve.