Hello, I have an Rx7 1rst gen 1984 with a 1991 13B 6 port stock, running a 6al direct fire on the leading with 600 cfm holley carb 1850. header and RB muffler, holley blue pump with holley regulator running 6 psi. 63 jets 0n the primaries , and #6 secondaries plate with vacuum secondaries , with the screw trick on the secondaries.
also running the stock full line from the pump to the carb wish I believe to be 1/4". Ok now to problem I'm having. I really appreciate all the inputs I can get. I have read several threads on this forum but I can find the problem I'm having. Wish is, the car runs beautifully and strong when cruising and respond great on the high way but when I want to really open up the car, I bring the car to 8000 rpm on first gear and shift full throttle to second gear the car leans out at 6000 rpm this also repeats when I shift to 3rd, also I'm running 4:87 gear ratio on the differential wish make my gear shifting short but it gives me great power on my 4th and 5th gear cruising at 4000 rpm 65 mph on 5th. Thank you for any imputs and all the help.

 

Your engine is starving for gas.

 

Did you check your fuel delivery to the carb? Is the fuel filter new and the fuel pump putting out the required flow?

 

Why do you rev it to 8k?

 

I have not check the filter because it runs good when cruising but I will change it this upcoming weekend , and I just rev as high as I can before shifting, I'm trying to get the car ready to take it to the track and find out my 1/4 mile timing. but like wackyracer said I'm starving for gas and I can find out Why.

 

Is there any other ideas other than the fuel filter? I like to look into them all this weekend coming up, Thank you.

 

When you run up to 8k, your E=shaft will tend to bend and cause your rotors to hit against the housings, causing chattering/chatter marks. Really really bad for your engine. If it is stock, why run it past 7? You will not be making any more power after then.

 

Also, when you change the fuel filter, take off the fuel line to the carburetor and blow in it and see how much (if any) garbage comes out. Could be starting to clog.

 

Jeezus Thank you for the rev tip, I did not know that.

 

Prove it!!!!

 

prove what?

 

 

Does it have the same symptoms with a full tank of gas?

 

Yes it does, I'm thinking I need to up the pressure on the regulator but I dont know how much more than 6 psi the carb will handle with plastic floats. Or maybe a regulator that self adjust with vacuum.

Here is a pic after my GSL SE suspension upgrade.

 

how do you know that you're running lean?
maybe you're not lean.

 

I don't know for sure but it feels like is running out of gas. what other problem wold you suggest do to the symptoms?

 

what exactly it's doing at high RPM?

 

like I said only when I shift at high rpms from 1rs to 2 nd i can go past 6000 rpm and it start to bug out, but if I'm cruising on second gear and I decide to punch the pedal it will go to 8k and then the problem comes back on 3rd.

 

what do u mean "bug out"
is it back firing or hesitation or...

 

check the float level and make sure they are adjusted correctly. you should be able to see the gas dribble out of the float site on the float bowls when you remove the site screw.

 

I get hesitation, I check the float levels and I do get a little drip of the holes.

 

You need to change you secondary spring out for a lighter one . It would probably be a good idea the get the secondary quick change kit, that way you can experiment with the lighter springs. When you are that high in the rpm range, your engine does not pull enough vacuum to keep the secondarys open. Hence your leaning out condition.

 

Your car is running out of fuel.

Couple of issues that I see.

1. Fuel pressure should be 7PSI not 6PSI at the carb. Set the pressure higher and then reset the float level so that the fuel is even with the bottom of the sight hole.

2. Take the screw out of the secondary linkage and let the vacuum diapham do what it is supposed to do. Your car is falling on it's face at high RPM in 3rd and 4th because the secondaries are open but there is no enrichment - no extra fuel. You have a lean condition. You don't notice it as much in 1st and 2nd because of your gearing but the problem is there in those gears too.

Here is the deal, you should never "feel" the secondaries open on a Holley 4bbl with vacuum secondaries. When "you" feel a surge in speed at high RPM what you are feeling is the fuel metering signal "catch up" with the increase in air volume, not the fact that the secondary butterflys just opened. In reality they have been open a long time and were causing a lean condition that was slowing you down.

A properly tuned vacuum secondary carb will open the secondaries when the engine demands it. Opening is controlled by the secondary spring. You can install a softer spring for an earlier opening point or a stiffer spring for a later opening point. My guess is you will need a later opening point. The spring that came in the carb would be a good starting point. Holley sells a kit with different color codes springs - get one. By the way, don't shorten these springs because it makes them stiffer.

Another useful addition is 3150 kit that includes a secondary metering and a longer transfer tube. This will allow you to change jetting in the secondary side just like the primary side. I would keep the side hung floats that came with your carb beacuse they orient the pivot of the foats so they swing fore and aft. This will help you avoid fuel starvation in corners.

I have no idea if you primary jetting is correct and you didn't specify the opening point of your power vlave. Others may be able to help you with that.

Get a Holley tuning book, they are invaluable.

 

Wheres the baby supras?

 

Thank you for the input on the spring, is time to take the screw of the secondaries, I was told by people that I look up to that this wont have any effect, I now realized they were wrong, Thank you