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PostPosted: Mon Aug 06, 2018 6:19 pm 
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Joined: Fri Oct 27, 2017 9:12 pm
Posts: 18
Location: Nampa, Id
Background: I have a 70 351-4V in a 31 Model A coupe, originally built around 1985. Hydraulic cam from SSI with Rhoades lifters, screw in studs and guide plates. After sitting for 15+ years, I dug in to it last year to basically do an in-frame refresh. New rod bearings, rings, and S/S valves. All done in the garage. Got it running good enough last month to go ahead and insure and register so I can do some test drives. Had a few issues with carb, and got cleaned out and floats set and idle mixture good. Took it to H.D. a couple weeks ago, (3 mi one way) and it seemed to do OK. Decided to take to my Dr Appt today, about same distance. Got about a 1/4 mile from house, and it started making a popping noise. I have heard similar noises in the past with a couple of FE engines when a rocker arm broke, or a push rod got bent. It was worse when accelerating, but was barely noticeable at a steady speed; which in the city was barely more than an idle. Kept it at low RPM to the office and back to baby it home. Just as I made the final turn on my street it went away. Totally. I gunned it the last 100 yds and it ran fine. I'm getting ready to pull the rocker covers, but I doubt I'll find anything broken. What else causes this noise ? To me, the popping noise of a valve not opening is very distinctive.

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Mike - Nampa, Id., via Reno/Sparks, Nv, Lawrenceville, Ga., Albuquerque, NM, and Terre Haute, In
31 Model A coupe w/ 351C- 4V & FMX
69 Triumph TR6 w/ 289 W & C4.


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PostPosted: Mon Aug 06, 2018 6:44 pm 
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Joined: Mon Oct 29, 2012 9:05 am
Posts: 2328
Trash in the fuel/carb?

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Brent Lykins, Lykins Motorsports
www.lykinsmotorsports.com
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PostPosted: Mon Aug 06, 2018 7:02 pm 
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Joined: Fri Oct 27, 2017 9:12 pm
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Location: Nampa, Id
Not saying impossible, but I put in a new fuel tank, new line to a new filter before the rebuilt Holley electric fuel pump, new lines to the carb with another new filter just before the carb (Holley 3310-2)--- within the last 6 mos.---

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Mike - Nampa, Id., via Reno/Sparks, Nv, Lawrenceville, Ga., Albuquerque, NM, and Terre Haute, In
31 Model A coupe w/ 351C- 4V & FMX
69 Triumph TR6 w/ 289 W & C4.


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PostPosted: Tue Aug 07, 2018 12:20 pm 
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Joined: Mon Oct 29, 2012 1:52 pm
Posts: 467
I'd bet on a flat exhaust lobe on the cam. It was popping whenever the intake valve was opened against cylinder pressure. This creates a VERY high load and usually bends a pushrod. When this happens that intake valve no longer opens and the popping stops. The engine sometimes sounds ok but runs as a V7.


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PostPosted: Tue Aug 07, 2018 12:43 pm 
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Joined: Fri Oct 27, 2017 9:12 pm
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Location: Nampa, Id
So I guess I'll pull the rockers and check the push rods. I'll report back. (Simultaneously on hold with the DMV....) :x

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Mike - Nampa, Id., via Reno/Sparks, Nv, Lawrenceville, Ga., Albuquerque, NM, and Terre Haute, In
31 Model A coupe w/ 351C- 4V & FMX
69 Triumph TR6 w/ 289 W & C4.


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PostPosted: Tue Aug 07, 2018 1:07 pm 
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Joined: Fri Oct 27, 2017 9:12 pm
Posts: 18
Location: Nampa, Id
Yep. Both rockers on #4 were very loose, and push rod on intake has about 1/16" deflection. I'm sure it's more under load. I don't have a dial indicator, but I'll see what I can rig up to check cam lift.

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Mike - Nampa, Id., via Reno/Sparks, Nv, Lawrenceville, Ga., Albuquerque, NM, and Terre Haute, In
31 Model A coupe w/ 351C- 4V & FMX
69 Triumph TR6 w/ 289 W & C4.


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PostPosted: Tue Aug 07, 2018 1:11 pm 
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Joined: Fri Oct 27, 2017 9:12 pm
Posts: 18
Location: Nampa, Id
and there was a lot of wear on the push rod in the area of the guide plate.

---still on hold---- :-(

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Mike - Nampa, Id., via Reno/Sparks, Nv, Lawrenceville, Ga., Albuquerque, NM, and Terre Haute, In
31 Model A coupe w/ 351C- 4V & FMX
69 Triumph TR6 w/ 289 W & C4.


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PostPosted: Wed Aug 08, 2018 2:41 pm 
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Joined: Fri Oct 27, 2017 9:12 pm
Posts: 18
Location: Nampa, Id
Cam lift appears to be OK. I'm assuming my error at this point in not having rocker arms nuts locked in tight enough. I'll replace both pushrods on that cylinder and see what happens.

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Mike - Nampa, Id., via Reno/Sparks, Nv, Lawrenceville, Ga., Albuquerque, NM, and Terre Haute, In
31 Model A coupe w/ 351C- 4V & FMX
69 Triumph TR6 w/ 289 W & C4.


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PostPosted: Wed Aug 08, 2018 3:40 pm 
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Joined: Mon Oct 29, 2012 1:52 pm
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Good.


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PostPosted: Wed Aug 08, 2018 4:38 pm 
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Joined: Fri Oct 27, 2017 9:12 pm
Posts: 18
Location: Nampa, Id
I've read a lot of recommendations for case hardened pushrods. Is that the same as heat treated? Summit has a great price on their brand, as does Alexsparts. This would be a good time to possibly upgrade at a low price. (I don't remember what I bought 30+ yrs ago...) Any feedback ?

https://www.summitracing.com/parts/sum-g6415/overview/

https://www.alexsparts.com/hardened-bla ... 6-x-8-408/

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Mike - Nampa, Id., via Reno/Sparks, Nv, Lawrenceville, Ga., Albuquerque, NM, and Terre Haute, In
31 Model A coupe w/ 351C- 4V & FMX
69 Triumph TR6 w/ 289 W & C4.


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