Smith

Went to the drags about 2 weeks ago and on the second run the car started to miss in 3rd and 4th gear. It is not the kind of miss where it falls flat but it feels like it just stops making power. The mph was down the rest of the day from about 112 to 105. The car was about .5 to 1.0 off in ET. 13.3' vs 12.3's.

I have checked the following.

Compression is good 210 to 230 in all cylinders.
I was using points because the petronix quite but they sent me a new one so I tried that. No difference.
Inspected distributor and everything seems ok.
Dwell with points very stable at 25.
New cap and rotor.
Disconnected the MSD 6al box. No difference.
Checked plug wires 50 to 80 OHMS resistance.
Put in new spark Plugs. No difference.
Fuel pressure is 7 PSI and it will fill a 12oz coke can in 13 seconds.
Float level fine.
Took apart the carb everything looks fine. Cleaned all parts. No difference.
Voltage to coil with engine running at all rpms 11.5 volts.
Switched coils. No difference.
Vacum is normal for this motor about 11 at 1000 rpms.
Ran car with gas cap off in case of vapor lock. No difference.


The only thing that seems a little weird besides the miss and lack of power at higher rpms is when I check the timing it is hard to get a reading, almost like the light is firing twice. The car really does not run that poorly at lower RPMs.


Any thoughts would be helpfull.

Thanks members.




[Modified by Smith, 7:42 PM 11/19/2001]

1LE

Had a problem similar to yours in my Autox-Camaro a while back. Car would run fine at idle and normal speeds, but would loose power above 4500 rpm. Checked everything like you did. It finally turned out to be plug wires, There was one that was cracked where it went through the wire loom. Car ran fine after replacing the wires.

Alwyn678

Wow I would have guessed it was the Pertronix ignition....Mine crapped out on me within 2500 miles

Smith

I will put new plug wires on it this evening. I can't believe that it will fix the problem but it is about the last thing to do before I drive it off a cliff.

Ganey

You need to keep the wires separated esp. well for 5 & 7 ! This is well known on Chevys. Bought a SS running on 6, took it home & replaced 2 wires & rerouted to fix quick- guess which 2. Then did not need to check the others.
Have not run points in a long time, seems dwell should be around 30. Moroso Blue Max are good wires.

:cool:

QuickVet

sounds kinda like my car. two weeks ago i ran four staight runs at the drag strip that were 12.91-12.94 at 105.9x mph. then on the last run it ran a 13.0 at 100. then the next week i ran the car three runs. the first a 13.2 at 102. and the last two were 13.55 at 96 mph! i was and still am like WTF :eek: i put a new fuel gauge on the outside of the car and that doesnt seem to be the problem either. i dont what im gonna do. let me know if you figure something out. i will change my wires tommarrow and see if there is any differnce. :sad:

LAvetteman

I Think I have the same problem. Engine starts to shake and loose a little power around 3000 rpm. I hadn't figured it out yet.

Smith

Replaced the plug wires tonight with MSD 8.5 mm and guess what---No difference. The problem is the same. I am going to take the car in and see what some others say. I think it might be the carb but I can't understand what is going on. :cry


[Modified by Smith, 11:03 PM 11/19/2001]

71coupe

Try checking all of the ground points - engine, frame, etc.
Too bad you don't have a spare carb to throw on it to check your double pumper.
Pull the mufflers off & see what happens. :chevy

Matt Gruber

1st thought is weak valve spring(s),...
Fuel: Did u say 13 seconds to fill a coke can? LOL sounds low; check out an A/F meter, see my article: http://community.webtv.net/MATTGRU/AFtesting



[Modified by drives61, 7:09 AM 11/20/2001]

micks69

Dwell sounds kinda low at 25? maybe 29 or 30. Also I had a similar problem and when a friend checked Dwell it was at 17 set it two days prior to 30. The diference was he used a digital DM and I used an analog from the 1970 sears catalog! Check it again before you go banannas and rip every thing apart! :smash:

Smith

ttt :cry

QuickVet

i change my wires today and there doesnt seem to be a difference yet either. i know how you feel :cry

lars

Your dwell is way off. 25 degrees will not get you adequate coil saturation at elevated rpm. Get the dwell up to 30-31, and then re-check your timing (every degree change in dwell changes timing one degree). 25 degree dwell will cause the problems you're describing.

Vetterodder

I'm with Lars, dwell is off. Why would it become off in between rounds? Your symtoms are also consistant with a broken valve spring (though a broken valve spring should be noticable in lower gears also). A close look might be a good idea.

Smith

Thanks for the help.

I do not think it is the dwell because the problem is the same with a new petronix as it is with the points. I took off the valve covers and inspected all the springs and they looked good.

I took it in to a guy I know and the only thing he could think of is that the coil is not getting the correct power. I will run a jumper from the battery to the coil today and see what that does.

QuickVet

what is dwell and how do you check it? :confused:

could i have the same problem? :confused: