TBI vacuum leak at manifold

[CDeeZ]

Looks as good as the powercharger. But you made it so it's better!

[Daveo91]

Looks as good as the powercharger. But you made it so it's better!

Agreed, that's pretty cool. Do you have an outlet for the PCV system, or do you just use a breather mounted on the valve cover?

So I'll definitely consider that mod, but I first need to figure out this sucking air problem. I've had the adapter out four times now with different gaskets and/or light coating of grease, but nothing helps. I can actually hear the leak now and can change the sound of it by touching the part of the gasket that overhangs in front. I've come to the conclusion that the 454 adapter I'm trying to use does not bear correctly on the GMPP intake. I don't really see why, but I have no other explanation, the adapter is not warped or gouged. Fortunately I have another option. I also have this aftermarket adapter and I'm going to switch to it. I didn't use it originally because the OEM one has a vacuum port that I was using for my brake booster and there's also a coolant passage to aid in cold weather operation. But it's running fine in cold weather without heat and I'll use the port on the manifold for brakes.

[Kitch]

I looked at trying to add a hose from the salad bowl to the rocker cover but in the end I just fitted a breather into the rocker cover.

[Daveo91]

I looked at trying to add a hose from the salad bowl to the rocker cover but in the end I just fitted a breather into the rocker cover.

Cool, thanks. Yeah, I'd probably go that way too. Looks like you're using the GMPP TBI-specific intake for Vortec? Happy with it? I wish I would have gone that way even though they seem to be a lot more expensive. I wouldn't be having the vacuum leak problems I'm having now.

[Kitch]

The manifold seems okay, I'd have liked something a little more high rise but the GMPP manifold is the only one I know of with the factory style water passage that links the front of the heads to the back of the heads. It was expensive and then I had to get it bored out for a 46mm TBI unit and block off the EGR ports.
I also decided to block the EGR ports in the bottom of the runners because I thought fuel might pool in there.

[Daveo91]

The manifold seems okay, I'd have liked something a little more high rise but the GMPP manifold is the only one I know of with the factory style water passage that links the front of the heads to the back of the heads. It was expensive and then I had to get it bored out for a 46mm TBI unit and block off the EGR ports.
I also decided to block the EGR ports in the bottom of the runners because I thought fuel might pool in there.

Yeah, the q-jet manifold for Vortec is easier to find used. I've bought two now, both only slightly used for about $150 each. Mine has EGR provisions as well, and I'm not using it. I've got a block off plate where the valve goes, but I didn't do anything with the ports in the runners. You've got me a little nervous now - when I had everything off tonight I could see a small amount of fuel down those holes. What did you use to block them?

[Kitch]

I got my engine machinist to tap the two holes and put Allen head grub screws in there, then he staked around them so they wouldn't come out.
I don't now how critical it really is, it just looked like it made sense to me.
I bought the plate to block off the EGR and also had to block off the hole on the opposite side that also looked related to EGR, you can buy a genuine part to block it off but once again for that particular part the shipping to NZ was quite a lot so I go the machinist to make something, I suspect I didn't save much in the end.

[Fast355]

I looked at trying to add a hose from the salad bowl to the rocker cover but in the end I just fitted a breather into the rocker cover.

Not to get too off topic, but I went a little different way with mine back in the day. Running a mass air flow sensor on the TBI and used a Caddy intake bonnet that had a built in power bowl.

[Kitch]

In the photo it looks like you're running the PCV valve off the housing above the TBI unit?

[tayto]

PCV is hooked onto the adapter plate (manifold vac). The line off the air cleaner/bonnet generally goes to the other valve cover.

[Daveo91]

I built mine today and got it installed. There's a store called Tuesday Morning near us that sells discount home goods - set of four metal mixing bowls for $11.99. I got the second biggest one and my wife got the other three. The one I used nested perfectly under one of the ring insets of the OEM air cleaner's base. And I cut out the overhang of the base so the transition is smooth and I have the biggest opening possible into the mixing bowl. I went ahead and drilled a hole for the PCV breather tube in the mixing bowl. I had all the parts to do that and I would have had to go buy a valve cover breather so I thought I might as well. And I cut the bottom flange off the choke ring, leaving about 1/8" to 1/4" of the ring, and then installed that into the base of the mixing bowl, in the hole that I had cut out. Gave the something to rest on at the TB and also gave it rigidity, it was pretty flimsy with its bottom cut out!

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