 914 Popping and backfiring out exhaust, Need help! |
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| SolarRT99 |
 May 13 2017, 07:02 PM
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#1
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Newbie  Group: Members Posts: 6 Joined: 10-April 14 From: Minneapolis Member No.: 17,238 Region Association: Upper MidWest  |
I'm at my wits end with this. Background on car. Originally a 74 1.8 car. Now has a 1.7 engine block with an A&A 1911cc piston kit. All new bearings, scat c45 cam with new scat lifters. Rebuilt 1.7 heads with hp springs, shims and elephant feet adjusters. Pertronix ignition with flamethrower coil. Dual Weber 40's. SS 2.0 Heat exchangers with Sebring exhaust. New cap, rotor, plugs, and wires. I have set the valves 3 times and it still has a pop out the exhaust at idle. Carbs were rebuilt last year. I think 3 and 4 aren't firing completely even though it idles fairly well. I crawled underneath with my nc temp gun and 1 and 2 are at 500+ degrees at the exhaust pipe right off the engine, 3 is right around 350 degrees and 4 is around 220. Could it be a bad carb? I tried new plugs and wires and nothing changed. Any thoughts or ideas appreciated.
Thanks pics here https://drive.google.com/drive/folders/0Byp...d28?usp=sharing |
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| iankarr |
May 13 2017, 08:44 PM
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The wrencher formerly known as Cuddy_K Group: Members Posts: 2,595 Joined: 22-May 15 From: Heber City, UT Member No.: 18,749 Region Association: Intermountain Region 
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Just watched the videos. scared the hell out of me that you were under the car while it was running!
Tough to tell from the clips, but the valve train sounds loud and the pop almost seems like a timing miss. Are all barrels breathing equally and in sync? If so, I'd try making the mixture a bit richer on the popping side and see if that has an effect. Popping can also be from an exhaust leak. I'm sure you'll get lots of suggestions here. Good luck and be safe. |
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| SolarRT99 |
May 14 2017, 01:12 PM
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#3
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Newbie Group: Members Posts: 6 Joined: 10-April 14 From: Minneapolis Member No.: 17,238 Region Association: Upper MidWest |
QUOTE(cuddyk @ May 13 2017, 09:44 PM)  Just watched the videos. scared the hell out of me that you were under the car while it was running! Tough to tell from the clips, but the valve train sounds loud and the pop almost seems like a timing miss. Are all barrels breathing equally and in sync? If so, I'd try making the mixture a bit richer on the popping side and see if that has an effect. Popping can also be from an exhaust leak. I'm sure you'll get lots of suggestions here. Good luck and be safe. Car was up on 2 jackstands and 2 floor jacks, was nice and steady! Thanks for your concern though. |
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Posts in this topic
SolarRT99 914 Popping and backfiring out exhaust May 13 2017, 07:02 PM
McLovin Don't know much about those carbs, but maybe y... May 13 2017, 08:52 PM SolarRT99 So I pulled off the 3/4 carb today. After I pulled... May 14 2017, 01:16 PM cuddyk Glad it's running better. IMHO the car is neve... May 14 2017, 01:52 PM
SolarRT99 Well after a 10 minute jaunt around the neighborho... May 14 2017, 04:48 PM |
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