Engine peters out under load
Race Director
Joined: Oct 2008
Posts: 19,178
Likes: 1,668
From: Long Island
Yes
Farmingdale NY, You should come down to the Bagel Factory 9 am Saturday mornings at Airport Plaza. Rain or Shine.
I do all my own work, if you need I can give you a mechanic who owned C3's and just aligned a C1 properly. He is only one I would trust to work on a pre C7 corvette.
do you still have points, if so how old are they as the spring sometimes goes bad..
I'm usually around during the week, if you meet me on Sat we can talk. I may be able to help - will cost you coffee and maybe a bagel.
Farmingdale NY, You should come down to the Bagel Factory 9 am Saturday mornings at Airport Plaza. Rain or Shine.
I do all my own work, if you need I can give you a mechanic who owned C3's and just aligned a C1 properly. He is only one I would trust to work on a pre C7 corvette.
do you still have points, if so how old are they as the spring sometimes goes bad..
I'm usually around during the week, if you meet me on Sat we can talk. I may be able to help - will cost you coffee and maybe a bagel.
Last edited by BLUE1972; Nov 5, 2018 at 05:46 PM. Reason: hate auto spell
Thread Starter
Intermediate
Joined: Jul 2011
Posts: 30
Likes: 1
From: Dix Hills, Long Island NY
I was always concerned that something would break, leaving me on the side of the road waiting for a tow truck.
Guess I'll just have to take that chance and see what happens after it starts to lose acceleration.
Thanks for bringing that issue to me.
Thread Starter
Intermediate
Joined: Jul 2011
Posts: 30
Likes: 1
From: Dix Hills, Long Island NY
Le Mans Master
Joined: Apr 2011
Posts: 6,284
Likes: 1,171
From: Hermosa
If if was the mechanical advance it would perform poorly but would still accelerate. You got your initial and the vac advance still putting in timing.
Is my vette stock?? HAHA
Joined: Oct 2015
Posts: 20,169
Likes: 9,296
From: Im not allowed to tell you
2020 C3 of the Year Finalist - Modified
2020 Corvette of the Year Finalist (performance mods)
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I wonder if youre wiping out the cam itself.
Le Mans Master
Joined: Sep 2003
Posts: 8,812
Likes: 2,029
From: eastern NC
Tom, since you have a '71 (?) it should be safe to assume you don't have a catalytic converter. The symptoms you describe are similar to a failing cat back in the late 70's.
On the other hand, what is the overall condition of your exhaust system? I had a '74 Ford 351C that had true duals, but the outlets had mesh screens about 2" up the tip. I parked the car for a year and when I returned it had difficulty accelerating. The longer I drove it, the slower it got. I parked it and the same thing occurred when I drove it again. With the engine idling, I walked around the car and the exhaust was making a funny sound, so I looked into the tips and they both were blocked by rust scale.
I removed the screens and started the car. When I did, two piles of rust scale blew out the tail pipes. All was well after that.
It's not very likely this is what is occurring with your Corvette, but it's worth eliminating as a problem.
Good luck... GUSTO
On the other hand, what is the overall condition of your exhaust system? I had a '74 Ford 351C that had true duals, but the outlets had mesh screens about 2" up the tip. I parked the car for a year and when I returned it had difficulty accelerating. The longer I drove it, the slower it got. I parked it and the same thing occurred when I drove it again. With the engine idling, I walked around the car and the exhaust was making a funny sound, so I looked into the tips and they both were blocked by rust scale.
I removed the screens and started the car. When I did, two piles of rust scale blew out the tail pipes. All was well after that.
It's not very likely this is what is occurring with your Corvette, but it's worth eliminating as a problem.
Good luck... GUSTO
Thread Starter
Intermediate
Joined: Jul 2011
Posts: 30
Likes: 1
From: Dix Hills, Long Island NY
Tom, since you have a '71 (?) it should be safe to assume you don't have a catalytic converter. The symptoms you describe are similar to a failing cat back in the late 70's.
On the other hand, what is the overall condition of your exhaust system? I had a '74 Ford 351C that had true duals, but the outlets had mesh screens about 2" up the tip. I parked the car for a year and when I returned it had difficulty accelerating. The longer I drove it, the slower it got. I parked it and the same thing occurred when I drove it again. With the engine idling, I walked around the car and the exhaust was making a funny sound, so I looked into the tips and they both were blocked by rust scale.
I removed the screens and started the car. When I did, two piles of rust scale blew out the tail pipes. All was well after that.
It's not very likely this is what is occurring with your Corvette, but it's worth eliminating as a problem.
Good luck... GUSTO
On the other hand, what is the overall condition of your exhaust system? I had a '74 Ford 351C that had true duals, but the outlets had mesh screens about 2" up the tip. I parked the car for a year and when I returned it had difficulty accelerating. The longer I drove it, the slower it got. I parked it and the same thing occurred when I drove it again. With the engine idling, I walked around the car and the exhaust was making a funny sound, so I looked into the tips and they both were blocked by rust scale.
I removed the screens and started the car. When I did, two piles of rust scale blew out the tail pipes. All was well after that.
It's not very likely this is what is occurring with your Corvette, but it's worth eliminating as a problem.
Good luck... GUSTO
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Thread Starter
Intermediate
Joined: Jul 2011
Posts: 30
Likes: 1
From: Dix Hills, Long Island NY
Race Director
Joined: Oct 2008
Posts: 19,178
Likes: 1,668
From: Long Island
NO IT WOULD NOT.
Broken valve springs can also cause the engine symptoms you describe. Don't ask how I know, just don't turn 7500 rpm.
What coil do you have - is it a HELI Distributor or stock / points.
Broken valve springs can also cause the engine symptoms you describe. Don't ask how I know, just don't turn 7500 rpm.
What coil do you have - is it a HELI Distributor or stock / points.
Burning Brakes
Joined: Jul 2016
Posts: 767
Likes: 74
From: Blaine MN
If you're sure you don't have an intake or exhaust restriction, fuel is the most likely candidate. You could plumb a second fuel source to the carb, (electric pump from a gas can). Yes a little scary, but doable and not very expensive.
Racer
Joined: Dec 2016
Posts: 353
Likes: 161
Have you put a vacuum gauge on and read it? If you haven't, it might not be a bad idea. If you haven't used one before, look it up on YouTube or find the chart online. The vacuum gauge may point you in the right direction instead of shot gunning random parts at it that you may not need.
Just a thought
Just a thought
Dr. Detroit
Joined: Mar 2012
Posts: 10,097
Likes: 4,027
From: New Braunfels Texas
Replace the fuel pump.....inspect the fuel tank sock......if you can get RID of that sintered metallic filter if it has one........use paper or inline.
Check timing and curve. You need 36 degrees at 3000 rpm.......without vac advance.
Q-jet has a tiny *** float bowl. Dries up quick when supply is not adequate.
Jebby
Check timing and curve. You need 36 degrees at 3000 rpm.......without vac advance.
Q-jet has a tiny *** float bowl. Dries up quick when supply is not adequate.
Jebby
Thread Starter
Intermediate
Joined: Jul 2011
Posts: 30
Likes: 1
From: Dix Hills, Long Island NY
Thanks very much
Burning Brakes
Joined: Jul 2016
Posts: 767
Likes: 74
From: Blaine MN
Just be super careful, have a helper with a fire extinguisher in hand (I have a 20# CO2 next to the Car anytime I'm doing Air Cleaner off tuning, with the pin pulled). Good hunting
Burning Brakes
Joined: Dec 2005
Posts: 1,153
Likes: 341
I'd start by checking engine vacuum to rule out bent valves, timing chain jumped a tooth, etc. Plenty of Youtube if you not bein' familiar.
Second I'd plumb in a "T" and duck tape a Fuel pressure gauge to the windshield, go for a drive.
Third I'd probably pull out the distributor and examine it, the gears on the bottom, advance mechanism, etc even before I'd bother
to put a timing light on it.
An engine that won't rev ain't getting enough air, fuel or timing advance. For me it's always been #3. From the way you describe it getting worse I'm
thinking the distributor just wasn't clamped down tight enough.
Second I'd plumb in a "T" and duck tape a Fuel pressure gauge to the windshield, go for a drive.
Third I'd probably pull out the distributor and examine it, the gears on the bottom, advance mechanism, etc even before I'd bother
to put a timing light on it.
An engine that won't rev ain't getting enough air, fuel or timing advance. For me it's always been #3. From the way you describe it getting worse I'm
thinking the distributor just wasn't clamped down tight enough.
Is my vette stock?? HAHA
Joined: Oct 2015
Posts: 20,169
Likes: 9,296
From: Im not allowed to tell you
2020 C3 of the Year Finalist - Modified
2020 Corvette of the Year Finalist (performance mods)
2019 C3 of Year Winner (performance mods)
2016 C3 of Year Finalist
IF you pull the fuel pump, pull the pump lifter to see if its worn as well
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,116
From: Crossville TN
Do you know for sure that depressing the accel pedal with your foot actually opens the carb secondaries completely? And before you just answer "Yes" to this question, you should actually check it by looking down into the secondary venturi (hold air valve open) while someone else depresses the pedal.
Note: Actuating the linkage by hand DOES NOT duplicate what happens when you drive the car. Your problem could be in lost motion in the accel pedal, the cable, or the cable retainer. There are too many folks who had this same problem because they installed new floor mats which limited pedal travel. Damaged cable, loose pedal mounting, etc. etc.
If you still have the Q-Jet, it has a secondary lockout lever (right side) which prevents the secondaries from opening, if the choke mechanism is not full open.
Note: Actuating the linkage by hand DOES NOT duplicate what happens when you drive the car. Your problem could be in lost motion in the accel pedal, the cable, or the cable retainer. There are too many folks who had this same problem because they installed new floor mats which limited pedal travel. Damaged cable, loose pedal mounting, etc. etc.
If you still have the Q-Jet, it has a secondary lockout lever (right side) which prevents the secondaries from opening, if the choke mechanism is not full open.