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| Stupid question about O-rings... https://slantsix.org/forum/viewtopic.php?t=65526 |
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| Author: | SpaceFrank [ Mon Nov 02, 2020 10:38 am ] |
| Post subject: | Stupid question about O-rings... |
Maybe I should've looked at the injectors I was planning to use a little sooner. It turns out that LS3 injectors use a larger lower O-ring where they seat into the intake manifold (~15.4 mm) than most older injectors (~14.5 mm). Anyone know where to find conversion O-rings that allow an LS3 injector to go into an older 14 mm (LS1, etc.) injector bore? All the threads I see on ls1tech and elsewhere talking about this swap mention that you need the smaller bottom O-rings, but I can't seem to find these O-rings listed anywhere. The diameter on the body of the LS3 injector is slightly larger where the lower O-ring goes (8.59 vs. 7.77 mm), so I can't just slap new LS1-sized (or LS3 upper) O-rings onto the bottom because the OD still ends up slightly too large. They fit in my injector bosses, but it's so tight I feel like I'm going to break something. So I basically need O-rings with an LS3 ID (~8.5 mm) and an LS1 OD (14.5ish mm). I can try ordering something from McMaster, but I'd be a lot more confident getting this for the specific application rather than trusting my measurements and guesses at durometer rating. |
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| Author: | Greg Ondayko [ Mon Nov 02, 2020 11:52 am ] |
| Post subject: | Re: Stupid question about O-rings... |
is it just the OD of the O ring that's different? or is it the machined ring on the injector that is a different Ø as well? I would try and see if the smaller o rings will work on your injector.. I mean you just hafta to roll 'em on there and maybe a wee bit of lube when installing them into the rail. Greg |
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| Author: | SpaceFrank [ Mon Nov 02, 2020 12:20 pm ] |
| Post subject: | Re: Stupid question about O-rings... |
The machined ring on the injector is fine; it's just the O-rings giving me trouble. So for reference, the Gill Welding fuel rail I bought has an injector bore ID of about 13.6 mm. The injector bungs I made may be just a hair smaller at 13.5 mm. The smaller blue O-rings from the top of these LS3 injectors (which I believe are the same size used on the bottom of LS1 and other earlier Bosch-style injectors) have an ID of 7.6 mm and an OD of 14.3 mm. When installed on the top of the injector which has a 7.7 mm OD, the O-ring OD expands slightly to about 14.4 mm. This fits easily in either the fuel rail or (upside down) in the manifold-side injector bung. Just a few pounds of force required, as long as the O-ring is lubricated. The bottoms of these LS3 injectors use a larger red O-ring with an ID of 8.6 mm and an OD of 15.5 mm. This would never seat into my fuel rail or manifold, full stop. If I install the blue O-ring onto the bottom of the injector which has a ~8.7 mm OD, the blue O-ring OD expands to about 14.9 mm. Even lubricated, this takes a significant portion of my body weight to seat into the manifold bungs. But it can be done, and they can be removed without apparent damage to the O-rings. I did chamfer the tops of the bungs and sanded all the edges smooth. Maybe I'm overthinking this. If it works, then tighter is probably better, right? |
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| Author: | Greg Ondayko [ Mon Nov 02, 2020 1:47 pm ] |
| Post subject: | Re: Stupid question about O-rings... |
I think they are tight if my memory is correct. Greg |
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| Author: | SpaceFrank [ Tue Apr 27, 2021 7:22 am ] |
| Post subject: | Re: Stupid question about O-rings... |
Just for future reference, I ended up ordering a pack of these O-rings from McMaster-Carr, which are 8.5mm ID and 3mm thick, for an OD of 14.5mm. Putting these on the bottom of my LS3 injectors allowed me to insert them into the intake bungs with a lot less force, and nothing leaked when pressurized or running. |
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| Author: | Greg Ondayko [ Fri Apr 30, 2021 10:27 am ] |
| Post subject: | Re: Stupid question about O-rings... |
Quote: Just for future reference, I ended up ordering a pack of these O-rings from McMaster-Carr, which are 8.5mm ID and 3mm thick, for an OD of 14.5mm. Putting these on the bottom of my LS3 injectors allowed me to insert them into the intake bungs with a lot less force, and nothing leaked when pressurized or running.
Awesome - Good to know Frank! Greg |
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