EFI Throttle Body Spacer Size

[Later-A-body]

I am currently swapping my 466 Pontiac to EFI. I need help on one point. I have to run at least a 1.5” spacer under the throttle body in order to get the TB linkage to not make contact with the fuel rails. If I run a 2” spacer instead, will this have any negative affect on performance? I have room under the hood. The other option is to run a 1.5” spacer under the TB, and a 1/2” spacer under the air cleaner. The ½” spacer under the air cleaner will be needed in order to allow the factory air cleaner to clear the fuel rails. I am running an Edelbrock Torker II EFI manifold. Thanks.

[Hammered]

What TB are you running? Also, are you running the pico injectors or a taller set?

I did the same thing and only had minor (compared to you) clearance issues.

[Later-A-body]

I am running a 1200 CFM TB. The injectors are Ford 42 pound, not the Pico injectors. That is why the rails sit up higher. Hood clearance is not an issue though. I'm hoping a 2" will not have a negative affect on bottom end, or throttle response. The plenum and runners have been ported by Dave at SD Performance in order to flow the 310 CFM my E-Heads do.

[Hammered]

Most of what I've read in general for 455ish + Pontiacs is that a 4 hole, 1' spacer helps the low end and peak HP/TQ. An open spacer helps the peak numbers more, but takes away from the bottom end. I haven't read too much about using taller spacers.

You might as well try the 1.5" if that fixes your problem. If it doesn't, you can always swap in a set of 44lb picos to make it work.

My heads and intake are also ported the same and I've got way more low end than my tires can handle. I wish I had gone with a shorter TB and a 3/4" spacer.