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Falls on face above 2500

2K views 21 replies 10 participants last post by  MoreBassXD 
#1 ·
As the title states my car falls on its face when above 2500 rpm.
It's a 302 with a summit carb. Set timing to 8* (don't know how to set total) Floats were adjusted and idle air speed is set.

The car idles great but the second you get into the throttle it falls flat on its face almost stalling. I can't seem to figure out why. Did some reading and some people suggest putting the timing to 10-14 (as long as you don't ping) and you need to adjust the total timing at WOT but I'm not sure how you go about doing that.

I bought the car today it is an 1968 coupe (second one of these) and my last one was a stock 302 and would rip through first and chirp 2nd and 3rd so I know these stock 302s have some power but I can't seem to dial this one in.
 
#4 ·
For checking the timing, set your timing light up and rev it up until timing stops advancing. Max advance for most small block fords is between 28 and 36 degrees. Yours is likely the higher of that range. The amount of timing advance will vary in model and if it is functioning properly. Some tune to max advance and let the idle timing be where it ends up.

Is your fuel pump up to task?
 
#6 ·
My first guess is accelerator pump, check to see that you're getting a shot of fuel when you hit the gas (With the car off!). When you say fall on its face... Is it sputtering? Backfiring? Just dying?

From there, start with the basics. Fresh fuel filter? Fuel line clogged? Condition of the plugs and wires?

For timing, get your timing light on and slowly increase the RPM while checking the readings. The highest number you get is your total timing. (That's a simplified version)

Get a buddy in the car to check what RPM the timing maxes out at. Here's a little write up I did for checking timing: How To Set Ignition Timing | Save Classic Cars

It does sound like a fuel related issue, though.
 
G
#8 ·
The accelerator pump only supplies a squirt for a fraction of a second before the power system kicks in. That causes a momentary stumble, not an engine that has no power over 2500 rpms. I would look into the timing advance. If that solves nothing, then your carb may have a problem with the power circuit and need a rebuild and careful cleaning.
 
#10 ·
A new power valve will change when the valve turns on but not how much fuel is dumped. Do you know the size of the new and old power valve? Power valves controlled by manifold vacuum. Manifold vacuum divided by 2 and if you land on an even number subtract .5. So if you have 12 inches of vacuum at idle divided by 2 is 6, subtract .5 is 5.5. If you have 13 inches divided by 2 is 6.5. You should install a 6.5. I think you are on the right track with power valve and timing.
 
#11 ·
Going back to a previous question, when it "falls on its face" does it simply cut out, sputter or chug, backfire or _____________? Do you have a vacuum gauge available to record the readings at idle and when you intentionally get it to "fall on its face"?
 
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