Datsun Roadster Forum-311s.org

I finally have the grin off my face from the first drive since the work of the winter has been finished on my '69 2000. The 3.90 rear end and the Keith Williams carbs were an excellent choice to increase "scoot" and driveability. But a couple of questions have come up. I have little or no oil pressure at idle and low rpm's, say 1200rpm or below. When the engine is revved up, pressure builds to 40#s or more. I re-bearinged the engine and am running 20-50 wt oil. Any comments? Also I am going to have a new exhaust system installed. I have Dean's flex pipe but am not sure what muffler to use, turbo style etc. I'm not concerned about staying stock and want a nice tone. Any suggestions. Thanks for any help. Pat Mahoney

Pat,

That is pretty standard with thes cars. The gauges run really low until you crank up the RPMs. I have the same issue with my Z car. I was really skeptical several years ago when I put a rebuilt motor in the Z and the reading was low at idle but fine wth some RPM. I put an atfer market guage in to be sure and it runs around 15-20 on the after market guage but very low on the in dash gauge. I would not be too concerned. As to the exhaust there are all kinds of options. The stock system has two in it. Putting a single muffler right after it comes out the X-frame is fine with a chrome tip of your choice at the end. I have a Flow Master Turbo on mine and it sounds great. Your local shop should be able to help you unless of course you are doing it yourself.

Steve

U20's are very sensitive to exhaust. I used to run a stock manifold through a straight 1-7/8ths pipe to a monza resonator. It was loud but not obnoxious. Then I put a header on it and it was suddenly obnoxious. I added a cheap turbo mufler and discovered it to be a waste of money. significant loss of power with the cheap muffler. At Dennis C's recomdenation I put a Dynomax Ultroflow on it and now it's about as loud as it was to begin with, has a great sound, and power is back to where it should be. Some folks may find what I've done too loud though.

Brian,

How does power with your current setup compare to the stock exhaust setup? I have the full stock exhaust, but if it chokes off a lot of power, I may go a different route...

I've never run the stock set up but I'd have to guess that what I've got now is lots better from a performance stand point. I'd be guessing at power out put in terms of HP but I can tell you that with the cheapy turbo mufler (still 1-7/8th ID) the car simply couldn't build revs as quickly as it could without the muffler. The ultraflow restored the engine's feel back to straight pipe like levels. I'm still a bit off of where it was without any muffler but it's pretty close now and the sound level is livable. Again, don't know exactly how loud but there was a 94dB sound limit at the National Tour in February and I was fine. The CP cars were louder than me but quite a bit so I'd guess that I'm under 92dB at 50ft at WOT.
The big difference is how fast the engine will rev. I noticed a much larger change in ability to build revs from the exhaust than from going to the 16 lbs flywheel.

Brian,

Thanks for the update. I will likely go with the stock stuff since it is here. I am not looking to race anyone in particular, so I will be OK with the stock speeds...

Brian
Not to hijack the thread, but did you have any problems with the exhaust pipe rattling on the frame cross throughs? I have a flex pipe and 1 3/4" tubing. It rattles a lot, I don't mind, but my passengers think they are riding in a some pos. With the work I just finished on the stroker I want to improve the exhaust breathing a little, any help would be appreciated.

Thanks,

I've got a flex pipe between the header and the pipe going through the frame. Since that's there, I mounted the pipe going through the frame solidly. It can move so no rattles. It'll probably wear out the flex pipe more quickly but I think that peice was like $40 so big deal. I'm contemplating fitting some oval pipe through the frame to get a bit more flow but that'll be a next year project.

I'm running a 2 inch pipe (no cutting to make it fit) no rattles. I have a flexpipe, a glasspack ending in a supertrapp with no trapps in it. Some people think it is too loud, some don't. It doesn't really bother me. Pulls hard to redline in 5th (after it gets new rings and has compression again).

Will