Olds Intake modification?

[SRD art]

Apparently Olds 307s have exhaust dumped into the intake below the carb?? Wow, that's something I've never heard of, seems a little counter productive for performance, no?

I just watched a youtube video about a guy that removed the exhaust injection tubes in the intake and plugged them with brass plugs to increse performance. Anyone else do this? Just want to make sure it's legit before I do it too. Thanks for any insight.

Here's that video, you can skip to around 5:40 where he talks about it.

 

[ELCAM]

It is not done for performance this is done for emissions and to make the engine warm up faster and to help atomize the fuel when it is cold. A cold engine pollutes much more than a warm one.

This also provides the exhaust gas for the EGR and heat for the choke stove or hot air setup.

Plugging these passages is commonly done on race engines in classes where you have to run stock parts.

 

[slow 442]

Edelbrock makes or made plugs that fit into the head or manifold. Not sure where they go as it's been awhile,that block off the crossover port. Like Elcam stated you will lose the hot air choke and egr Port. I have also blocked them with thin stainless steel sheet between the gasket and head. If the heads are disassembled it was common practice to melt an old aluminum piston into the port to completely block the heat in an all out application.

 

[olds307 and 403]

Yeah, the Edelbrock plugs need ground down and pounded into the head. Yes, the tubes in the intake are done as you mentioned. There is also long tubes that go into the exhaust that can be removed if the air injection is also removed. Guys have drilled small holes when using flat stainless steel to keep the hot air choke. Electric choke is not a hard conversion as well.

 

[403Olds]

I did the plugs in the heat crossover tube. Can't really tell you if it made a big difference, at the same time, I had made the "header clips" for the exhaust side, and milled the plenum divider down 1/2". But overall for a summer car, blocking off the heat crossover is fine.

 

[SRD art]

Thanks everyone for your input. I was mostly being sarcastic about the performance thing, I'm sure that set up has some decent negative effect on it. To save time and a few bucks I was trying to avoid removing the intake on this engine and I don't mind the heat crossover for the egr valve and choke so I'm not too concerned about blocking the cross over.

The thing I'm more focused on is blowing hot exhaust directly onto the carb base and diluting the intake charge so I'd like to block those tubes under the carb. I'm wondering if it's as simple as removing the tubes and plugging the holes with brass plugs? The guy in the video mentioned tapping the intake so I'm wondering if they're threaded or pressed in?

The car ran 21 seconds in the 1/4 mile as it was right after buying it. Removing the cat and running a single 3" exhaust got it down into the 19s. I've removed the air pump system and am doing some other minor changes in the engine bay plus replacing the 2.14 gears with 3.42s, I'm hoping the car will be in the 16s somewhere with those upgrades. My last daily driver G-body ran mid 13s so 16s is no big deal as far as performance goes but it's 5 seconds quicker than 21, lol. A healthy 406 SBC is in the plan for next year so I'm not going to spend much $ on the 307 to try to go much faster. Just focusing on the cheap easy things for now.

 

[78Delta88]

Just curious, how did you make out? Ever get the 406 in there or stay with 307?

 

[SRD art]

In this case plugging the intake heat ports was super easy, so I did that and painted and regasketed the engine. It's still on the stand as I later had a 454 Chevy fall into my lap and I did a bunch of research to find I can make about a solid 475 hp and 550 ft lbs with some basic port work on the peanut truck heads and a fairly mildish street cam. Then ... (with my builds there's always a then...) I started doing more research and found a solid game plan to make 650 hp and over 600 ft lbs with a pair of cheap ebay turbos on a low boost stock bottom end 454. That's where we're headed with Grandpa, although I hate to just dump all my work on that lowish mileage 307. I'm debating putting the 307 back in temporarily to just drive the car while I build the big block. That almost makes sense.

But... (there's also always a but as well, two in this case...) I still need a front body clip for the car, the fenders I had were rougher than I thought so I need fenders and a nose. I was chatting with a fellow that had some for sale but we lost contact, not sure but I haven't heard back from him in a while. I'm a little stuck on needing that.

The second but is figuring it'll still be a bit before I get Grandpa back on the road I picked up a low mileage 85 GMC S15 to putt around in. Got all the BellTech drop stuff and was going to call that good but then some pro touring handling suspension parts fell into my lap and I'm half way through the suspension upgrade. Then a 5.3 LS and 5 speed collecting dust in the corner of my garage started yelling at me saying it needed to be put in the S15 and I need to take it to LS fest in the spring. Soooo.... that's what's happening there. I started a thread on Gary the truck, here's the link, but I haven't updated it in a while. Got lots done to it now but lots left to do still. free time has been scarce but I have a bunch of pics and will update the build thread as soon as I can focus on it. https://gbodyforum.com/threads/g-body-cousin-s-truck-barn-find.83174/

 

[78Delta88]

Good work engine looks good, like the paint schemes.

I'm same with 454, got one 92 TBI unit, needs crank. Debating on putting the 89 wagon it has 307 now. Cam and duals sounds tough but reality is can't do much with 307.

Keep checking IAAI and Copart, Georgia site had 2 up for auction the one was totaled in rear so front clip was good.

Tucson area has lots of rust free pieces, one issue I Ran into is hard to get titles on abandoned cars. There are a few just sitting around. Owners passed leaving no paperwork.

I havnt done LS swap yet, was planned for the 86 but it went to the back burner.

 

[78Delta88]

Good work engine looks good, like the paint schemes.

I'm same with 454, got one 92 TBI unit, needs crank. Debating on putting the 89 wagon it has 307 now. Cam and duals sounds tough but reality is can't do much with 307.

Keep checking IAAI and Copart, Georgia site had 2 up for auction the one was totaled in rear so front clip was good.

Tucson area has lots of rust free pieces, one issue I Ran into is hard to get titles on abandoned cars. There are a few just sitting around. Owners passed leaving no paperwork.

I havnt done LS swap yet, was planned for the 86 but it went to the back burner.

Just did casual fly by on DVAP, dvap.com. they have front clips.

If I'm available, I can trailer out to you. Right now working on 91 Caprice for road car, small v8 700r4 class 3 hitch....