Has anyone ported their manifold opening from the pair of holes to one big oval? It seems that by opening up the opening and grinding down the wall separating the two sides, the air fuel mixture from both injectors would be available to each half of the engine. And yet I also wonder if it would matter at all since the amount of fuel as dispensed by the 'puter is the same as before. Hmmm. Anyone, Bueller?

Dan - '91 RS no mods yet, still working on basic tune and 160K mile replacement stuff.

 

I think you might run into a water jacket trying to do that.

 

Howdy Dan..

As for going into a water jacket. Uhh what the **** you smoking? The only water jack on the manifold is where the t-stat is..

As for opening the hole up to an oval all that you would be doing is shortening the runners a bit since the manifold is of a dual plane design. I dont think that their would be much of a benefit todo that.

Kat

note from Tas:
**bypassing the banned word filter is a no no.**

 

Howdy yourself, it looks like you're just around the corner. Based on a quickee google search of Upland,PA gives zip 19013. I'm in 19014 right behind Wawa corp.

I was actually thinking along the lines of a semi-single plane manifold. For a carb, there is advantage because then each set of runners can access the capacity of the whole carb. However, the carb being vacuum driven will increase the fuel flow to the level asked for by the engine. The throttle body only sends as much as the computer tells it and so I'm not sure if there'd be an advantage or not. Perhaps anyone running a single plane manifold with an adapter could shed a little light on the subject.

Da

 

Wow I thought that was Media still out that way. Yeah I live up the street from Crozer Hospital and the zip code here is actually 19015

Still you could be right tho on what you are thinking. I havent heard of anyone running a single plane intake on TBI (then again I dont follow TBI cars too much).

Kat

 

Are you sure about this or are you just guessing. My oem intake has water jackets running all arround the TB. I tried to drill it to two inches and hit one. You could probably get a figure 8 shape at most.

 

Yup I know this for a fact. I've worked on more of these cars than most of you combined


Kat

 

All the serious members with TBI are running single plane intakes. Fuel injection on a single plane intake doesn't lose the traditional bottom end, like a carb.

I've contacted machine shops about boring my stock intake from 1 11/16" to 2" and they all explained to me that it couldn't be done without encountering water jackets. I'm not sure, I've never tried opening the holes myself.

Sure with the Carb'd intake manifolds the water crossover sits just in the front and doesn't go near the carb. But this isn't a carb.

 

How can you have worked on these cars more than most of us combined and not follow TBI too much? The car we are talking about is a TBI car, right? But seriously you cant make an oval hole in the intake without hitting a water jacket. You can drill it to two inches if you are lucky, I was not. All of your work must have ben done at a car wash for you to say something as stupid as the intake only has a water jacket arround the thermostat.

 

youd probably increase the top end breathing some youd essentially make a larger plenum. The stock tbi manifold allready has a window connecting the two plenums I had thought of opening up the stock window further as that might have a positive effect aswell. If i were you though Id just get an aftermarket manifold though they are rediculously cheap (a carb manifold with tBI adapted on top that is) single plane or dual... a mild dual plane and you might get away with the stock chip but i personally am partial to single planes for what we do (drag race) and that will require tuning.

 

Amazing because I just went outside to check my spare L03 manifold and sure enough, water runs throughout the entire manifold, not just the front like your typical carb manifold. You can clearly see where the water runs and when you feel your way in the front water jacket, you can see coolant goes straight towards the TB. When I picked it up, water spilled outta the back holes that are usually blocked off on carb intakes (don't remember the name, maybe you could help me out remembering since you know so much about our manifolds).

 

I'm pretty sure the TBI stock manifold has coolant flow throughout the manifold. This is to keep the manifold at temp in order to prevent fuel condensation to the cylinders around the curves. This is a necessary thing due to the TBI setup not being dependant on vacuum to flow fuel into the engine rather as you should know the TBI force feeding under pressure the engine its fuel.

 

oh my my intake mainfold is broken i put water in were the t stat is and it came out the back guess its usless now

 

Thats a really good picture to clearly show the paths where the water flows in the manifold.

 

So I've been proven wrong. Most of the other intakes (carb TPI aftermarket) do not have that coolant flow under the intake like stock TBI manifold does.. Learn something new.

Umm Yeah umm I've been working on these cars for err 7-8 years now

I am willing to bet that I still know more than you about them..

Kat

 

well as for me i sure as hell hope so i only have one year under my belt and before that i have never even touched a bolt on a engine and am learning something new every day just about and consider my self pretty knowledgeable form were i stand. BUT i don’t really see the point of saying that i am always right and that i am more knowledgeable than every one else and then get proven wrong and your come back is i still bet i am more knowledgeable than all of u. the stupidity of this, so 7-8 years makes you G0d in the automotive world? I pity you

 

Nope just in general thirdgen knowledge I'-ve worked on aleast 50 if not more of them by now... Most of them been TPI (well lately) TTA's and carbed ones.

As for TBI motors I just do general maintence on them thats it.. They are just like any other SBC exceot with the TBI on top and a funky manifold. Every other damn SBC (or BBC for that matter) I've ever worked on has never had something like that stock TBI manifold does. I know why they did it looking at now. Its kinda stupid I think.. Personally I'd find a way to bypass it and pick up a few ponies from it..

Eh

Kat

 

I'm getting familiarized with TBI myself, but I have 6 years of SBC experience and 8 years of street rod building . I learn something new everyday on this board.

 

There are TBI spacers that combine the bores. Its probably easier to put one on than modifying the manifold.

 

If anyone still wants to bore and enlarge the manafold let me know and I will chop one up so the water jackets can be seen. Despite what Kat claims to know you still can only get a figure 8 pattern, an oval is simply out of the question. The hole that connects the two sides can be enlarged quite a bit. If you have a 6'' carbide cutter and a die grinder alot of work can be done to the manifold.