3500 LIM, fuel rail issues

[AleroB888]

Using a 3500 LIM with 3400 UIM and 3400 fuel rails:

The 3400 fuel rails are too narrowly spaced apart, which points the injectors slightly outward. And the installed height at the brackets is about 1/4-3/8 inch too tall, where the bracket bolts mount to the 3500 LIM (therefore the rails sit higher). I did not have this issue installing various injectors on the 3400 LIM. The only route seems to be UIM spacers, but the slight angling outward would remain.

[Guest]

What?

I'm using an LA1 fuel on my LX9 with an LA1 UIM just fine.

The LA1 fuel rail will actually sit lower on the LX9 LIM, because the mount bosses are lower (relative to the lower injector holes). I have used a small washer and 2 small washers between the LA1 rail and the LX9 LIM. I currently use only one, and only because it feels like without any washer the rail is putting a fair amount of pressure on the injector.

If there is any increased angle of the injector it doesn't cause any issues.

[AleroB888]

I had the GM 36 lb injectors in there, and now I'm trying a set of RC 35 lb units. I think they fit better, but we'll see.

[Xnke]

The LA1 rail doesn't really fit well, IMO. Yes, it fits, but using standard length Bosch D3 type injectors (the GTP 36lb/hr units) the angles are not particularly kind to the injector seals, upper or lower.

I used a pair of LS1 coil pack studs to raise the rail up to make the angles less severe, and had to clearance the upper intake manifold to make it not hit the fuel rail mounting nuts. I am considering welding the injector ports completely closed, re-porting the intake manifold, and re-drilling the injector ports at a more favorable angle.

[2fast4u88]

I run gtp injectors, 3500 lower/upper and 3400 rail without a issue with the rail spaced up like 3/8 inch. No clearance work besides the tab that holds the regulator was ground down to clear the 3500 upper throat.

[Forgotten User]

Think I heard the 99 3400s have a slightly different fuel rail bracket that better accommodate's the GTP injectors

[AleroB888]

I put some 1/8 thick cork gaskets on there, with the 35lb RC Engineering injectors. There seems to be just enough clearance over the rails now, and alignment appears to be OK.
edit: used with washers to raise up the rail brackets.

[ericjon262]

3400 rail is working fine with my 3500 lim and uim. I'm running siemens 60 lb injectors though.