Hello to the Thirdgen.org forum!

I've been lurking around on this forum for a couple years because it's a goldmine of information about not just F-bodies, but many other '80's and early-'90's GM vehicles. So far I've been doing pretty good at finding information myself via searching (or sometimes just getting lucky and happening to see it at the right time!) but this time I've come to a dead end.

I'm looking to do a TBI swap on my '86 Monte Carlo (yeah, I know it's not a 3rd gen, but from what I've seen, you guys are the guru's of TBI, and that's what I need help with). The engine is only a stock 305, but when I do the swap I'm planning to use some mildly ported 416 heads, and maybe some headers if the budget allows. It's only a daily driver, and I'm wanting to get away from the Edelbrock carb in favor of some better fuel mileage.

When I do the TBI swap, I want to save some $$$ and keep my Performer intake (spreadbore) by using an adapter plate, but I'm not sure which one to get.

This one mounts the throttle body to the back of the plate, while this one mounts it to the front. This one mounts in the center, but is "open" in the middle compared to the other two. What I'm curious about is what are the pros and cons of each? I'm wondering if, for example, I got the rear-mount plate...Would I risk starving the front cylinders of fuel (or vise-versa)? Is that only something I would even need to worry about on a virtually stock engine?

Thanks for any help you all could give me.

 

Welcome to TGO (and Marry XMAS)

Regarding adapters - you have to do a bit of mock up before selecting the plate. What this means - remove your carb and place TB on a TB adapter cardboard mock-up. Now - take a look at TB fuel lines and TV cable. Make sure that TB fuel lines can clear the back side of your Q-jet intake without excessive bending. Similarly, your TV cable end should reach TB TV post.
On a personal note I try to avoid adapter plates due to inherent problems - vacuum leaks. Before final installation verify that TB to plate bolts do not interfere with Q-jet flange (this happens when bolt is too long). If the adapter kit uses studs (or counter sunk head machine bolts) to secure TB to the plate put some RTV on the threads (or around the head of the bolt) going into adapter plate - this will prevent vacuum leak. Do not over torque as some of these plates are rather thin and will warp resulting in a vacuum leak.

//RF

 

Alright then, I'll probably do that tomorrow. I'm not too concerned about the fuel lines because I'll have to custom bend my own. Thanks for the heads up about potential vacuum leaks, I'll definitely have to use some sealer on the bolts when I put it all together.

Hope you had a wonderful Christmas!

 

Two things, some guy's who have tried using the thin adapters say DON'T, (I use a Holly). And are you sure that there isn't a square bore or even a 2300flange manifold that you would like to use?

 

I'd love to use a TBI specific manifold, but with my current financial situation, if I can save $200 here or there and still do the job decent (not a hack type job), I'd rather go that route.