I thought I read somewhere that the manifolds that come on the 3.4l flow better then the 2.8 and 3.1's???

Also thought I read somewhere that their is something that I can grind away in them to make them flow better??



Reason I ask is I have the manifolds of this 3.4l thats going into the truck, and might put them on the camaro if they are better. Don't have the funds to do the headers and y-pipe.

 

I have no idea about flowing better, but you can use a dremel or whatever to port them just like heads or an intake.

 

better hope it has a provision for a distributor

 

I dunno if he's asking about the plenum or the actual intake manifold......but if he's asking about the manifold, there is a hole for the distributor but there ISN'T a vacuum port for the PCV valve.

 

oops i thought he was talking exhaust manifolds

 

$hit, maybe he was talking about exhaust. Post was too vague........

 

Yes, sorry, the exhaust manifolds.

 

yeah you can port those.

 

There's not much restriction in my 2.8 manifolds that I could see. There are spots that poke out a bit, but that's also where the casting is thin, so don't go too crazy on 'em!

What I found was that the little cast iron donuts between the manifold outlets and the y-pipe inlets have a removable restriction in the center. Looks like GM took a boring machine to these things, and bored one small hole thru the y-pipe side of the donut, and then a larger hole through the other side (manifold side). At any rate, there's a very prominant ridge right in the center. The ridge seems to block exhaust gas from getting into the y-pipe.

First I took my air grinder to the ridge, but it was taking forever. After my circuit breaker blew for the second time (oops!), I brought it to the bench, and used a coarse round metal (as opposed to meant for wood) file on the ridge- that worked nice and fast. I angled the ridge so it'd make a smooth transition between the holes, and then, I felt frisky, so I continued filing, and hogged the thing out a bit wider than stock. Then I used my air grinder to polish out all the deep scratches from the file. Put everything back on, and I actually felt an improvement; I was shocked... didn't think I was going to.

Just be careful loosening the manifold-to-y-pipe bolts; they're metric, and if you strip the nut or snap the stud, you'll be in trouble (happened to me, oops, luckily I had a spare manifold in the basement). Spray those nuts up good with some penetrant for a week or so before working on them; just be careful and don't spray the liquid wrench on a hot manifold; not only could the steam get into your eyes and really hurt, but the stuff is flammable, and might catch fire after you close your hood and walk away!

 

ok tomp

I will have to take some pics and post for you to modify them

Show me how to modify these babys.

I'm hoping for a dremel for x-mas, and have several similer tools for the oversized air compressor we have

 

LOL! I tried taking pics of the manifold donuts (is there a technical name for these suckers?!?!?) with my camera but they came out like crap. I should try them with my digital pencam instaed.

 

if getting rid of those donuts makes that much of a difference, imagine what those headers will do...

 

I got a very decent camera, If you dont mind drawing on my pics, to explain, It would be much appreciated. This way, anyone else who wants to modify theirs can see also. send them in to the site to put on the "list of mods" type stuff.



I would love headers, but dont think the mrs, or my cash flow would go for it.


I'm doing this since I have extra parts, and rem reading a post. I put both together, and make it work. Hell, the parts will turn into scrap steal if I dont put them to use.

 

Ok tom, here they are. Please "draw" on this and show me what needs to me ground away. IMO they look like they got good flow anyway.

 

They're known as head pipe seals.

Also, Tom, I'm not positive but I believe the 3.4 manifolds used a different type of seal. They might not have the ridge you speak of.

 

3.4 manifolds virtually identical except for the O2 senosr per maifold exhaust log.
Tom, the pic Dale posted is exactly what I saw upon checking my exhaust doughnuts.
I got Fel Pro & no ridge at all.
What brand did you get?
Exhaust manifolds are fragile.
Don't touch them, modify the "Y" Pipe for better flow.

 

Wait; you can't separate the donuts from the manifold? That's different than my '86... I gotta go dig up my MS Office CD so I can load my picture editor, when I do, I'll edit that pic. Maybe tonight I'll look for the cruddy pic I took of mine...

 

That would be great tom. No hurry. PM me when you modify it.

 

Tom, they are different. The seals can be removed though. You just need to get a chisel and pound them off.

 

i have to start learning to read the entire post first lol

 

Yeah, see, on mine, the donut seals don't press fit onto anything. They're just -there-, sitting between the manifold and the y-pipe. In fact if the y-pipe nuts loosen up, the donut starts to rattle around. I'll try to get a pic this weekend; school's kicking my butt this week. I hate the last week of classes. Everything's due!! Then the next week, finals! Dammit!!

 

No prob tom. It will be a few weeks before I get time to do/attempt the swap.