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Discussion Starter · #1 ·
Tinkering with my car yesterday I noticed that a fuel inlet fitting was loose where it screws into the carb. It wouldn't tighten up and I presume the bowl threads are stripped. Not sure why, although I either partially stripped it many years ago during instsallation, or over those years the weight of the fuel line rocking back and forth under vibration stripped the threads. Maybe some of both.

Looks like the P/N for a replacement bowl is 134-101, but I notice they also sell an aluminum bowl, P/N 134-76C. Holley doesn't say much other thna there's a weight savings, but I'm wondering if it stronger and will hold up better than the zinc based bowl. Any thoughts?

Below is a picture of my installation:

 

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Discussion Starter · #6 ·
T-Y for all the replies. There is no evidence of leaking as this was an older picture. The teflon tape is yellow, commonly used with propane. Looking into it at the time I found it is also gasoline proof. I always had a slight leak there because the fuel log (Summit) doesn't have very good flares on the ends. They look almost cast. I doubt they are, but it didn't look good for cutting them off and re-flaring. After using the tape, no more leaks. Oh, and I did the original install back in 1996, although I had it out once since then.... maybe 15 years ago.

I htink there are repair kits, but one has to be accurate using them and keep the fitting perpendicular to the inlet hole. It turns out that a new float bowl may be not much more than a kit. I intend to look into that some more, but at this point a new bowl seems like the best solution.

I need to take things apart. It may be that the float bowl input fitting boss cracked underneath. I noticed it the other day when my hand brushed the fuel log and it moved. The fitting moves up and down and when I tried to tighten it, it just kept turning.

I was really wondering if the aluminum float bowl was stronger and less susceptible to having the threads strip.
 

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Discussion Starter · #8 ·
Now that's a good idea. Thanks for posting about it.

It seemed familiar so I looked in one of my books and found this:



I just now checked the fitting and carb and the fitting is fine, but the carb is stripped. No cracks that I could see. In the pic below you can see the stripped threads (from me continuing to turn it when I thought it was only loose).

You can see the stripped area and good threads further in.



At first I thought that if the fitting was longer, it would be stronger, but if it was any longer it would cover up the transer tube. That's the funny looking gray area to the lower right of the good threads.

 

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Discussion Starter · #12 ·
Thank-you for the link. I checked a few things and their prices went from quite cheaper to "way" cheaper. Good to know. T-Y.

I've done a bit of research and it appears cast zinc is stronger than aluminum, but I couldn't find anything on thread strength, although is does relate to shear strength which is stronger for the zinc. On the other hand, aluminum sort of "smooshes" over when stripped. The zinc threads fracture and came out looking like fingernail clippings. In the end, I don't think it matters much about the material.

If the inlet fitting worked back and forth after years of vibration (and then stripped when I tried to tighten it), one answer might be to use blue loctite on the threads when installing it. That might also help when tightening the compression fitting as holding a wrench on the inlet fitting without letting it move is touchy when you torque the compression fitting down.

One Youtube video demonstrates that subsituting the inlet fitting for one with a AN-6 male fitting solves a lot of leakage problems. My issue with that is finding an AN fuel rail that is adjustable as they all seem to be the length that suits a single carb with inlets on both the primary and secondary float bowls. I have a greater distance to span with the two carbs. I could make something up but my flare tool is for 45deg, not 37deg. I'll keep looking.
 

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Discussion Starter · #15 ·
I now have a plan. In fact two plans.

1/ New bowl(s) and new inlet fittings. The ones I have were used when I originally installed them. New ones with fresh threads and a good inverted flare might be wise.

2/ If I get leaks, I can go to AN fittings. See the picture below. Just cut the flares off my existing fuel log.

One other issue is the vibration of the fuel line and log. I used to use ty-wraps to support the fuel line to the overflow tank bracket where the line crosses over the engine before dropping down to the fuel pump. When I switched from a copper line to a steel line and added silicone tubing to stop vapour lock (which it did 100%) I didn't replace the ty-wraps. I'll add them again.

If I continue to get leaks from vibration and probably metal fatigue, I'll have to go to flexible hose for a fuel log.

I think I better carry a fire extinguisher too!

 
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