Slant Six Forum :: Engine hiccups at higher revs at freeway speeds

Hi, I am having a bit of an issue. The car runs great at all other times except when I am trying to get it to pull at higher revs . For lack of better terms it seems to hiccup. like vroom put vroom put vroom put, until I lay off the gas and feather back to current speed and then runs great again. 60-70 mph passes are awesome but the car wont go past 80.
My set up:
1972 225
Clifford intake
Weber 38 electric choke
Clifford headers to dual 2.25
Pertronics II
ignitor II coil
ZFR5N Plugs
new carter mechanical fuel pump through rerouted fuel line with redline regulator to carb

Any Ideas? Am I running out of gas?

What is your rear gear ratio, and tire size?

Not sure of gear ratio, but tires are 195/70/14

What is fuel regulator set at?

I think it is 3psi

Dose engine falter when going up long steep hill at lower speeds with large throttle opening?

Have not encountered this driving condition yet

I suspect that engine is fuel starved at high load conditions such as pushing to 80 mph.

Quote:

I am dealing with other issues all together with 38DGES swap... I had similar problems earlier today and corrected with jetting. I have S6 intake, Ignitor II, Flame II, Magnecore wires, 3.5 regulated PSI, 5/16 fuel lines, adn have corrected high rpm/mph hiccups by jetting as follows...
50 IA
145 MAIN
170 AC
9 deg timing
NGK V-power stock gap
87 Oct fuel

Author:	matt71vh [ Wed Aug 21, 2013 6:47 pm ]
Post subject:	Engine hiccups at higher revs at freeway speeds
Hi, I am having a bit of an issue. The car runs great at all other times except when I am trying to get it to pull at higher revs . For lack of better terms it seems to hiccup. like vroom put vroom put vroom put, until I lay off the gas and feather back to current speed and then runs great again. 60-70 mph passes are awesome but the car wont go past 80. My set up: 1972 225 Clifford intake Weber 38 electric choke Clifford headers to dual 2.25 Pertronics II ignitor II coil ZFR5N Plugs new carter mechanical fuel pump through rerouted fuel line with redline regulator to carb Any Ideas? Am I running out of gas?

Author:	wjajr [ Thu Aug 22, 2013 5:11 am ]
Post subject:
What is your rear gear ratio, and tire size? What is fuel regulator set at? Dose engine falter when going up long steep hill at lower speeds with large throttle opening? I suspect that engine is fuel starved at high load conditions such as pushing to 80 mph.

Author:	Aggressive Ted [ Thu Aug 22, 2013 2:11 pm ]
Post subject:
Good points......I vote for lack of fuel and in combination with lots of timing. With better fuel lines and new fuel hoses at the tank, pump and carb mine will easily go 90 mph with a near stock cam. I test it from time to time on the freeway on ramps. If I can hit 90 mph at the end of the ramp, I am happy.

Author:	DCFAB.US [ Thu Aug 22, 2013 5:46 pm ]
Post subject:	Re: Engine hiccups at higher revs at freeway speeds
Quote: Hi, I am having a bit of an issue. The car runs great at all other times except when I am trying to get it to pull at higher revs . For lack of better terms it seems to hiccup. like vroom put vroom put vroom put, until I lay off the gas and feather back to current speed and then runs great again. 60-70 mph passes are awesome but the car wont go past 80. My set up: 1972 225 Clifford intake Weber 38 electric choke Clifford headers to dual 2.25 Pertronics II ignitor II coil ZFR5N Plugs new carter mechanical fuel pump through rerouted fuel line with redline regulator to carb Any Ideas? Am I running out of gas? I am dealing with other issues all together with 38DGES swap... I had similar problems earlier today and corrected with jetting. I have S6 intake, Ignitor II, Flame II, Magnecore wires, 3.5 regulated PSI, 5/16 fuel lines, adn have corrected high rpm/mph hiccups by jetting as follows... 50 IA 145 MAIN 170 AC 9 deg timing NGK V-power stock gap 87 Oct fuel

Author:	matt71vh [ Fri Aug 23, 2013 4:45 pm ]
Post subject:
Quote: What is your rear gear ratio, and tire size? Not sure of gear ratio, but tires are 195/70/14 What is fuel regulator set at? I think it is 3psi Dose engine falter when going up long steep hill at lower speeds with large throttle opening? Have not encountered this driving condition yet I suspect that engine is fuel starved at high load conditions such as pushing to 80 mph. My buddy thinks it is the fuel pump, but that does not seem likely to me.

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Author:	matt71vh [ Fri Aug 23, 2013 4:52 pm ]
Post subject:	Re: Engine hiccups at higher revs at freeway speeds
Quote: Quote: Hi, I am having a bit of an issue. The car runs great at all other times except when I am trying to get it to pull at higher revs . For lack of better terms it seems to hiccup. like vroom put vroom put vroom put, until I lay off the gas and feather back to current speed and then runs great again. 60-70 mph passes are awesome but the car wont go past 80. My set up: 1972 225 Clifford intake Weber 38 electric choke Clifford headers to dual 2.25 Pertronics II ignitor II coil ZFR5N Plugs new carter mechanical fuel pump through rerouted fuel line with redline regulator to carb Any Ideas? Am I running out of gas? I am dealing with other issues all together with 38DGES swap... I had similar problems earlier today and corrected with jetting. I have S6 intake, Ignitor II, Flame II, Magnecore wires, 3.5 regulated PSI, 5/16 fuel lines, adn have corrected high rpm/mph hiccups by jetting as follows... 50 IA 145 MAIN 170 AC 9 deg timing NGK V-power stock gap 87 Oct fuel Thanks for the advise

Author:	matt71vh [ Sat Aug 24, 2013 3:42 pm ]
Post subject:	I think I nailed it
I started farting around with the fuel regulator and though I don't have a pressure gauge, which I think I will get, I increased the pressure just a little at first then tested and got positive results so I increased just a tad more and after a couple of on ramp blasts I had not one hiccup which I am sure I would have had before, not to mention the engine runs stronger and smoother at all revs now needless to say I am very pleased. Thank you to everyone that chimed in with suggestions and advice I always appreciate those of you that try to help.

Author:	Louise76 [ Mon Aug 26, 2013 6:35 pm ]
Post subject:
I had the same thing happen on a stock 75 with the 1945 carb. Inside the carb. top, found the power enrichment valve retainer bushing had fallen out (normally staked in position), allowing the valve assembly to wobble around. Engine ran great at everything except high "passing' RPM. When I relaxed a little on the pedal it smoothed out. Found the surge happened at only high RPM- passing in "Drive" or romping on it in "Drive 2". No problems after re-staking the valve into position. (904 trans)

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