Datsun Roadster Forum-311s.org

Very cool! Whats next on the list?

Tonight I start looking for the culprit on lack of power over 6000, and then replacing the two loaner M/C's when the new ones arrive. Hopefully on to VIR March 9 - 11 for a test day and NC Region race. I'll need that missing power there for sure!

Congrats Al! Glad to hear you went to a SCCA school, it's a great way to get licensed. Now it's time to just sign your retirement accounts over to the racing gods Quite the addictive sport you have entered...

Thanks everyone.

TroyT - Our lead instructor said at the first classroom session that after the weekend we would be wishing we chose the less expensive hobby of cocaine and hookers.

Another update - We got through the spring racing season and are now nationally licensed! Other than a slight misadventure up on two wheels at the Roller Coaster at VIR, we stayed on track the entire time. The car is still not making proper power, so I spent a lot of time watching my mirrors. Those SRF3's will catch an underpowered F/P car in a hurry! During the season I just tinkered around the edges with timing and carb adjustments, but nothing seemed to make a difference. I had hoped to spend more time on the car this summer, but as usual, life wouldn't let me. Now with just over a month to go before my last two race weekends this year, I hope to have at least a little time for the car. One thing I'm considering is to swap the EI dizzy from my street 2L into the race car (1600), which is currently on points. Is this a straight up swap or do I need to do something else? I'm running the bigger bore SU's but there is no vacuum advance to be concerned with. Also, the distributor is turned 180. Is there any advantage/disadvantage to that setup? Thanks for any suggestions.

The EI is a drop in replacement for the points. Being 180 degrees out has no effect whatsoever, as long as it's timed properly. The engine doesn't care where the dizzie is pointed, as long as the firing order and timing is on!

It sort of sounds like you are having a similar issue with your car as I'm having with the #44 Ernie deJacomo car. It hits a wall at 5500 rpm and won't go beyond. I'm told its due to the carb spacers being the solid type and the fuel is percolating due to engine harmonics.

Fixing the distributor being 180 degrees out is easy. You unbolt the distributor stand, note the direction the keyway is sitting, then rotate it 180 degrees. You can also just move the plug wires, but sometimes they won't reach if you do that.

Will

Thanks for the help guys. Will, I saw your post on the FB group looking for the rubber insulators. I have them on the car now, so that may not fix your problem. I was thinking I might be boiling the fuel too as the problem gets a little worse as the car gets hotter. The car has a homemade heat shield from the PO, but it doesn't have the bends at the ends so there is some exposure to the carbs. Basically just a flat piece of aluminum stock. I think I will fab an additional shield with angled ends and rivet to the existing one, with spacer washers at the rivets to get some additional cooling. I'll try a few small things now and I may go for a full rebuild after October. I've been talking with Sam Neave of LNA Engineering about that possibility. It's tough trying to figure out what to do when you have no idea on the engine internals. Car and engine builder are both deceased.

You don't need much of a heat shield if you have ceramic coated headers. Yes, you need something, but the stock one should be ok. I know the heat shield isn't my issue as the 44 car won't rev past 5500 cold (Ok, warm enough to register on the temp gauge.)

You wouldn't happen to have a spare set of those spacers would you?

Will

Header is not ceramic coated. Maybe another off season purchase I need to make. I don't think I have another set, but I'll check the stash this weekend. I think I only have the solids.

Getting the header coated does several things. It keeps heat in the exhaust giving you a higher velocity as it exits creating a bigger vacuum to suck fresh fuel mixture in, it keeps the headers from rusting and always looking good, and last but not least, it keeps the engine bay temps down. All of those are a win in my book. Jet Hot coating works pretty well, but will go dull if you have high exhaust temps. I've heard that Swain Tec (or Tech) is a thicker coating, but doesn't look as nice. Either way its worth doing. Its somewhat tough to make a good larger heat shield for SUs since your throttle return springs attach to it. (it can be done, but its not as simple as bending some sheet stainless steel to work.

Will

Install an O2 air/fuel meter so you can see what the engine is doing at "the wall." How much total advance are you running? Velocity stacks on the carbs? Cam timing issue? What's in there for a cam? There can be many reasons why the engine won't rev or make power where you want it too...

Gregs672000 wrote: Fri Aug 31, 2018 8:57 pm Install an O2 air/fuel meter so you can see what the engine is doing at "the wall." How much total advance are you running? Velocity stacks on the carbs? Cam timing issue? What's in there for a cam? There can be many reasons why the engine won't rev or make power where you want it too...

Its not my car, and the owner doesn't want to spend the $ for an O2 sensor. (I have one sitting in a box here on my desk.) The car has 36 degrees total advance, 50mm full radius velocity stacks. Could be a cam timing issue, the cam is an unknown "custom" cam (The car was sent to the guy who built it with some very trick solid billet custom cams that Ernie deJacomo had made for it. They weren't used, and didn't come back with the car... )

At this point I have it narrowed down to either cam timing (I'm thinking this is less likely) or a harmonics issue that causes the fuel to not flow in that rpm band. Apparently Lou Mondello ran into this very issue on a street car that was brought to him. It took him a year to figure out what was going on. In the end the fix was to run early 1600 rubber carb insulators.

Will

I understand that it's not your car my friend . The sensor is just so darn useful though when it comes to stuff like this, and will pay dividends for months and years to come when it comes to tuning. Not having it is like not having a spark plug socket as far as I'm concerned. Just today I noted that the car has been hesitating off the line a bit, and a quick glance at the meter showed lean. I've also been noting a little lack of smoothness under high rpm demand, and sure enough the meter was showing lean then too. It was noted that there might be some slight Jetting changes needed due to having improved the header scavaging with the heat shielding I have installed. So, based on what the meter was telling me, I bumped up my accelerator jets so they gave a bit more fuel, and dropped my main air corrector jet down from a 210 to a 205 to richen the mains just a bit. Problem solved. Car accelerates smoothly, the hesitation on the top end is gone, the meter shows the ratios that I what it to. There's no guessing. It's either getting fuel or its not. Or its getting fuel but it's not burning it. With the meter you have some way of seeing what your changes produce, whether it's fuel or spark.

Don't under estimate the cam timing issue. BTW, this Isky cam I'm running rocks for my engine. It drives around town and doesn't act like a handful or a bear on hills. That's with a big cam, carbs, head work, bigger valves, aluminum flywheel, and a LSD. I can't believe how docile and easy to drive it is at low rpms, yet it has a wide power band, comes on at 3200 and pulls to 7000 hard. Engine doesn't knock or ping on 92 pump gas at 11.7 to 1 compression.

After all these years, I don't think I could have gotten to this point without the meter (and the megajolt).

Greg,
I wasn't sure if you were responding to Will or me. but we seem to be chasing a similar issue. Cam timing has been suggested to me before also. I've been doing some reading and trying to decide if I can tackle it myself or if I need to find a shop to do it. I'm hesitant to tear into it with only two more race weekends left this year, and the way time seems to disappear on me. One major question I have is, like Will's, I have no specs on the cam as the engine was built when I got the car, so how do I know where to set cam timing? Also, it is my understanding that since the R16 cam gear has only one keyway, I would need to find an offset cam key. Do we know anyone that makes one for the R16? The engine builder and PO are both deceased, so I have no info on my engine internals. Thanks.


Will,
Unfortunately I don't have another set of the rubber spacers. Also, the header is coated, had a brain cramp thinking of another car.