dogboy

I went to the track the other day and maually shifted my 350 auto through the 1/4. The first run I was shifting at 5k, but the second and third runs I wasn't able to get past 4800 rpm. The tack was bouncing around between 4600- 4800. I thought valve float but the springs have only 23,000 miles. They are the stock springs. I have the comp 260 H came. . I'm thinking ignition or fuel? I have a crappy carb for sure . Old fuel pump also.I have a 2 yr old coil, cap, &wires ; plugs are 1 year old. Today I got on the entrance ramp and gunned it in 2nd and was bouncing around in the 4500 rpm range so it may be getting worse. What should I be looking for?

GrandSportC3

Get a nice HEI Ignition, Accel 8.8mm RACE Wires and a Carter 120 GPH fuel pump and your problem should be gone...

Robert N

Sound advice. There doesn't sound like there is enough spark.

GrandSportC3

I personally converted all my C3's to HEI Ignition.. The difference to regular ignition is unbelievable...

:cheers:

Olivier

dogboy

I have an HEI.

jackson

Before he beat me to it ... I was gonna say dogboy's 77 probably has OE HEI ... but maybe it needs attention/repair. Beyond that, I'd also look to fuel starvation ... maybe fuel pump ... trash in carb.

GrandSportC3

Get the PROFORM 50000 Volt coil... It's not too expensive and works great..

:cheers:

Olivier

Marks69BB

Just a thought: Have you checked to make sure your throttle linkage is allowing the secondaries to open completely. Have someone check this while another sits in the car and works the gas pedal. Your gas pedal bracket could be bent which has happened to others on this forum. Good luck w/finding the problem.

Justin79-L-82

I had a similar problem where my tach would bounch between 4500 and 5000 and it was having a hard time shifting gears and woul dreally hesitate... It happened to be the fuel pump. It was the original one that came from 79 :lol: I'd check that out!

nunus79

Other than your fuel pump problems, how's the engine running with the new 260H cam? Low end improved? Cylinder pressure (cranking compression) go up? 165ish range?

redwingvette

Does it back fire at all? You might have a bad plug wire or maybe one came loose from the plug or cap. You also may want to check the Vacuum advance and make sure it is working.

my74ls4

I had a similar problem with an 81 Z28 I restored. I had a new fuel pump,plugs,wires,carb,and engine. According to the tach the engine would not go past 5200-5300rpm. After changing timing and checking other things out, I got out my old dwell meter and connected the tach to the diustributor. Found out the electronic tach was off by 800rpm on the low side. Replaced the tach and alls well now but I sure racked my brain figuring that one out. Good luck.

Jvette73

Good points made above. However, I recomend that before you spend any money to check your ignition timing. If its too far advanced it can kill yur top end. Cut it back a few degrees and take a test drive. :D

Jvette73

Also, what carb are you running?

dogboy

Jvette73
Running stock q jet.
Timing idea is good. I'll test that tomm. when it gets a little warmer down here. I was having problems with the advance a short time ago and loosened up the rust siezed condition that it had developed. I'm running an accel cap & 50k coil with 8mm wires. I 'm running the initial timing at 12 btdc with total of about 52 btdc. I also installed an adjustable vac advance along with recurve springs & weights. I'm not pleased with my timing as it does tend to wander a little. I'm not sure if its the timing light or the advance sticking.
I have no idea as to how to test the fuel pump at high rpm,s. That to me is a hit & miss item. The carb was never good but didn't effect rpm's before so I tend to think that this may not be the problem. I guess I'll start with ignition first & of course the timing and go to fuel supply next. If I can get a carb I'll do that after as it could use a good q jet replacment. Very expensive though.

Oh yea to earlier post; I like the cam and I did pick up more low end. quite a difference from the stock cam. It pulls great in hwy traffic with the 3:08 rear but a higher ratio would help bottom end more than anything at this point. 3:73 rear would be awesome but the gas mileage will suffer.

Jvette73

If you installed lighter advance springs they could be causing the timing to wander at idle. If the springs are too light they can actually cause the weights to begin thier advance even at idle. Try heavier dist springs and test to see if still wandering. Test for total timing with vacuum advance dis-connected. You do not want more than 36 total, which would be the sum of initial and mechanical combined. My timing was to far advanced once before and my engine ran flat at 5000rpm. Retarding 2 or 3 degrees brought it back and it reved beyond 5500rpm pulling hard still.

On yur q-jet: Check the filter in the inlet. Some of these q-jet filters have a plastic check valve in them. They can cause fuel restriction. Remove the filter and look at the end with the rubber gasket. Pull the rubber gasket out and you might find this plastic check valve and spring contained within the gasket. If its there, remove the check valve and spring then put the gasket back into the filter and re-install. Ive cured the problem you describe on more than one other vehicle in the past by removing these check valves from the filter.

These are just a couple of things to fiddle with and could help without spending any money. One of the more satisfying ways to fix a car....without spending $


[Modified by Jvette73, 5:19 AM 1/25/2003]

mrvette

Try the FUEL FILTER FIRST before anything else...good test is pop the thing out of there, drain the gas, and blow through it...better pass air VERY easy...if it don't....replace it....3/8 filter you should be able to huff very easy through.....NO back pressure....

second off has been mentioned....make sure carb secondaries are being allowed to open under full acceleration, that means the choke is openint up ALL THE WAY< THAT PRIMARY FLAPPER HAS TO BE 100% VERTICAL...look at the linkage really close on the pass side of the carb....ANY hint of it not being open all the way there is a lever that stops the secondaries from opening...the cross bar of the secondary flapper on bottom of carb base....

that air valve ofcourse has to be allowed to open too.....lotsa adjustment there...be careful to not go too hog wild in this department...look and examine the functions carefully....think before acting.....

it's complicated, but not impossible to figger out....

pumps and such are seldom the problem,,l...IMO......

GENE

mrvette

OH, uh, yess....leave the stock ignition alone in i'ts weight/spring department...just make usre the vacuum advance is working, also that the weights/spings are free to move as necessary....that the shaft if not all full of dried grease/corrosion so the weights can actully function...that i's NOT frozen in the advance mode, and then the timing readjusted to retard it...and there fore no advance is possible.....sometimes its a good idea to just pull the damn thing, clamp it into a vice, and examint it's functions one at a time....suck on the vacuum hose to see if the vac advance is workig right....
play with springs, weights, shafts to see they are not all locked up with corrosion....but leave the stock stuff in place.....MOST engine anywhere near stock will not respond well to loose springs and or custom weights....beleive me.....

GENE