Guys I really need some help. My autocross car has a problem of banging or cutting out at 4000-6000 RPM. It seems to be OK up to 4000 RPM and will pull easily at 6500-7000 RPM. I THOUGHT it was a carb problem. I figured I was having a transition problem from the primary to the secondary. I finally got my Sterling Carb in today and figured this would be the end to my problems.............WRONG!!

The new carb acts the same as the old carb. Still banging out at the same RPM.

I now think possibly ignition.

OK, I have a new cap, rotor, Magnecore wires, plugs, two new MSD coils. I have swapped my leading and trailing ignitors around......same thing!!

Car idles perfect, starts perfect and pulls at 7000 rpm!

HELP!

 

if ur still running the stock pump, that's probably ur problem. stock pump is like, what, 2.5-3 lbs?

 

that or check your timing when you run a modified carb you should prolly advance your timing 5 degrees, or you might be off by a few teeth on your dizzy

 

Well I thought it could be fuel related. I have an aftermarket fuel pump. I had to use a regulator to bring down the fuel pressure. If it was fuel pressure related, it would not pull OK at 7000 RPM.

When you are putt putting around...your fuel bowls are full....when you deck it...hit 4000 RPM and my car starts banging out...you have NOT ran out of fuel yet.

I really am starting to think it is something other than fuel.........but I am not ruling out fuel yet!

 

I thought about this also.. When I first got the car it did not run. When I got it running, it really ran shitty. I ran my timing light and found the front pully 1/4 turn off.

I adjusted the pully, set the timing and it now is running..well better and at least I can see the timing marks where they belong.

I tried advancing a little...still banged out at 4000.....retarded a little....still banging out..

Could I be 180 degree out??? How do I REALLY check to see where my distributor should be??

 

this is what you do unbolt your dizzy pulldizzy up just alittle tell the teeth are free and and turn it one tooth clockwise, be gentle, repeat if needed, if that dont help..... just thought of something, whens the last time you did a tune up?, plugs cap dizzy rotor, wires etc, that was my problem onec upon a time , let me know what happens

 

New cap, rotor, wires, plugs, coils....just checked the TDC per instructions of forum...skinny part of flywheel = TDC and all looked OK. Checked with the pully at the top timing marks= rotor on dizzy = L1...All looked OK.

 

Any other ideas folks??? I am trying to get this car running right for an Autocross race this weekend.

 

Have you checked the clearance between the reluctor wheel and the pickup coils in the dizzy?

Do the bushings in the distributor allow too much side play or end play?

If you are using the vacuum advance on the dizzy, are you connected to the right vacuum sources? Are the advance diaphragms working right, or maybe binding/reacting slowly?

& can you translate "banging out?" I'm not sure what that means, exactly...

 

Banging out= missing badly, cutting out, making no power during this RPM.

I have not checked the clearance, but will check it tonight.

 

This is a strange one. Drops out at 4k but once over 7k she starts pulling again? Just plain weird!

Do you have another dizzy you can throw in there? Otherwise, clean all connections for ignitors and associated wires, also battery connections in case you have a weak ground. I don't know what else to tell you. Maybe run some Seafoam through the tank just for ***** and giggles?

 

I dont have another dizzy.. I am getting an MSD with harness to fit the stock pickup and two MSD coils to fire directly. I am getting this today and hopefully this will eliminate some problems.

 

Does this happen at the same RPM range no matter how rapidly or slowly you advance the throttle, or does it only happen when you make rapid RPM changes... or slow ones?

Does it happen only when RPM is increasing, or does it also happen under deceleration?

Does load on the engine seem to be a factor, or does the problem show up both under load and when out of gear?

(looking for anything significant, here, that might help us narrow down systems)

 

Seems the worse when you are under load... Not really sure if it misses just cruising at 4000+ rpm... I will check and find out.

If i cant fix it with the MSD 6a, I will video tape the problem and let you guys see.

 

Well I installed an MSD 6A and 2 MSD high vibration coils, new MSD wires. Install went very well and was very straight forward.

It did NOT fix my problem of sputtering on acceleration!!! NADA, zippo, nothing!! Car acted exactly the same as before.

What I did find was I was running too rich and this was causing the sputtering on acceleration!!

I installed a low pressure Holley regulator inline to my carb and presto.....this repaired the problem.

WOW...now I can move on to the next thing to repair!!

Thanks for all the advice guys....

BTW, the car now really runs great with the MSD ignition installed...

 

Huh? What fuel pump are you running? For some reason I thought you were running a fpr already. Anyway, yeah. That would do it. You'll probably find that changes of even 1/8 psi can have a noticeable effect on the power band and smooth running. Which is why you need a pressure gauge that is able to read accurately at that low of a pressure, and there aren't many of them out there....

 

Well my bad....I really did not understand the importance of running a FPR on these cars. I "thought" my fuel pump put out about 4 psi. I am now running a holley FPR and am running about 2.5 psi. It is happy now.

My fuel pump is a Facet Cube. here is a link, scroll down to the cube one.
http://www.facet-purolator.com/index...Itemid=48#cube