Over on the 510 forum there is a saying..... If you think it's fuel, it's electrical and if you think it's electrical, it's fuel........

Oh, and a question if I may..... Why do the needles get adjusted up and down rather than the nozzle which is all about adjustment? I don't think this is the first time I've heard of this being done on here. Needles move an RCH where the nozzles adjust a half mile up and down so to speak.

Over on the 510 forum there is a saying..... If you think it's fuel, it's electrical and if you think it's electrical, it's fuel........

Oh, and a question if I may..... Why do the needles get adjusted up and down rather than the nozzle which is all about adjustment? I don't think this is the first time I've heard of this being done on here. Needles move an RCH where the nozzles adjust a half mile up and down so to speak.

Bruce, the needle adjustment was a trackside test just to see what it would do. I didn't really expect it to fix anything, but I wanted to see what direction it took us.

As for electrical vs. fuel, I certainly agree, but I have tried three different distributors and three different coils. In every combination, the symptoms didn't change at all. I will add another ground strap, but I don't think that is a problem either.

Randalla, I have read about fuel lines sucking air elsewhere as well. All of the hoses are new and the hard lines are in good condition, but I will verify once I get a big gauge connected that I can watch. You must be talking about Guernsey Farms Dairy. I live within walking distance of it and go there often in the summer for ice cream.

What electric pump does everybody recommend? And don't say get an RX7 pump from a JY because I haven't seen a JY RX7 in these parts for decades. I'll probably look for a 3 -4 psi Facet cube pump, but I want to find something local if possible to save time.

Okay, I'll throw in my thoughts. You haven't said-or I missed -what theplugs look like-carboned, lean??

Check your float bowl hoses. I bought some from Bruce-sorry Bruce- that collapsed or kinked, which shut off fuel obviously. They could be kinking and unkinking under heat conditions.

Float bowl adjustments-does the car bog under hard acceleration before it gets to this wall at 5k? If NOT, I would go in there and tweek those floats to maximize fuel. You'll know if you tweeked too much. It could still be running your bowls dry-been there!

Sorry I was so late on suggestions-I guess i have been sulking in my own misery here lately.

Edited September 27, 201113 yr by madkaw

Carter Fuel Pump

Holley 12-804 Fuel Regulator

Holley 162-551 Fuel Filter

I forgot to ask, why aren't you using a thermostat. I would want one in there to regulate temp. You don't want a cold engine.

I forgot to ask, why aren't you using a thermostat. I would want one in there to regulate temp. You don't want a cold engine.

The T stat is gutted simply to avoid a stuck thermostat and an overheating condition in race conditions. I can certainly put one back in. That was on my radar as a possible problem, but I figured it wouldn't be an instantaneous cutout, but rather a general running problem.

As for the plugs, I didn't have a chance to shut the car off during a stumble to check them at that moment, but after a session and cool down lap, the plugs are a perfect light tan color.

I can't say if it bogged prior to hitting the wall, but I don't believe so. I think it's fine and then terrible.

I am running new hoses from Bruce. When I installed them, I made sure they were straight and they show no signs of kinking, but how can I tell? Is there any evidence to look for of them collapsing?

Mitchell, thanks for the pump suggestion, but I need to find something local due to time constraints and the only thing I have found is a Facet 1.5 - 4 psi cube pump from Napa. I just talked to Bruce and he thinks that will work fine. The low end of the pressure range scared me a bit, but ??? They also have a 4 - 7 psi Facet cube pump, but Bruce is worried that the pressure will puke fuel out the vents.

Thanks all for the help and keep the suggestions coming. IF I ever fix the problem, I'll be sure to report my findings.

Just as important as the pump is the fuel pressure regulator - you really need to control that fuel flow! Get Bruce's idea on what PSI should be ran for your application with your engine set up and racing requirements - he would know the best! Most of all - keep that fire extinguisher handy for your first race!

As far as the hoses, mine were brand new and would kink. I can't quite remember how I discovered this, but I believe I was just checking that the nozzles were flush after closing the choke.

I would run a quality thermostat-IMHO

The point i was making about the bogging is that even if the float bowls were lean, you would probably see decent acceleration until they emptied out. If they were lean you would definitely hit that wall after at WOT for a while. Mine are adjusted beyond factory specs.

It would be nice if you had a wideband to see what the mixture is doing. I had SM needles in my Z and took them out and put OEM back in. The OE needles supplied enough for my mods.

Hi jeff I believe i have a ome 83 rx7 carb fuel pump around somewhere .

Let me know if you want it i will look for it.

Only 70,000 mi on it.

Bill

I had the problem with new hoses on my carbs as well. I went back to the old ones which were more rigid.

Do you have a spare set of carbs that you could swap in just for sh#Ts & grins? That could at least remove one variable.

I don't have a clue about the stress of racing but...

Maybe you've got two problems going on. I understand your not wanting a stuck thermostat to toast your engine, but seriously, even with a malfunctioning gauge, if the thermostat stuck, I think you'd pit because the engine would start running badly before any great damage occurred. If the engine is too cold, and you've tuned the carbs for the cold running engine -- wait, I just read a thread on the effect of temperature and altitude on carb tuning. Running 50 -- 60 degrees below normal might not have a one to one correspondence with the effect of air temperature on mixture, but surely it must have some effect, would 1:2 be an unreasonable guess? That would give you an unusually dense air-fuel mixture.

Combine that with your first post describing the effect of RPMs on the engine, which sounds very similar to my experiences when I adjusted (another word, beginning with "f" might better describe the entire process of my first attempt) float levels. My first attempt had fuel running out the air cleaner. I decided that lowering the float bowl level was appropriate. Car would run fine around town, even accelerate normally up to and cruise at 70 mph. But run it through the gears hard and fast, hack, ack, ack or drop into 4th and run it from 70 (~3600 rpm) it would make it to about 95, then start hacking and be unable to hold speed. Might not be the bowl levels, but I'm thinking an unusually heavy fuel demand caused by low engine temp and some sort of fuel delivery problem might well be the problem.

My not even two cents.

Chris

One more long shot, but worth considering. Do you notice any difference when the gas tank is topped off vs. 1/2 tank or less? If so you may want to check the fuel pick up tube in the tank. I don't know if this has actually happened or not but it was something we looked at on Duffman's car since he had recently had the tank boiled out and we suspected the chemicals may have perforated the tube, thereby allowing air to be sucked into the system. Admittedly this is a real long shot. You know of course, that when you find out what's causing all your problems it will be some little detail we have all missed so far.