Is a rear fuel rail cross over nessesary? I am running an -8 an line between the front of the rails, and have -6 an going from the rail to the regulator, and then -6 an from the regulator to the factory 5/16 hard line. The pressure line is -8 an from the rail to the 3/8 hard line back to the tank.

I currently have a rear -8 an crossover line, but it will be pretty close to the distributor. I would hate to see what happens if I spring a leak. A fine mist of fuel and 30,000 volts probably wouldn't behave very nicely together

My thoughts are to just plug the rear openings in the lines for now, and monitor inlet pressure on both rails for a while.

I'll link a couple pics of how it is right now to give a better idea of what is going on here. Just keep two things in mind:

1. Yes, I know my room is a mess. I've been short on time lately.

2. It is not a final assembly. I still have some minor port/polish work to do, and then cleaning/polishing to do on the exterior. I am also undecided on the regulator. I think I can make the stock one pretty enough to keep, and I know I can make it adjustable.

I would also like to do a little filling in on the intake ports themselves to try and redirect some air and fill some gaps. I was using JBweld last time, but I'm not so sure I liked how it held up to the heat cycling. It seemed very brittle as I was taking it apart. Like brittle to the point where an intake backfire could take a chunk down the runner into the combustion chamber. Any recommendations on something that can take the heat, fuel vapor, possible oil and coolant vapor (worst case scenario), and the constant heat cycling?

Any thoughts? This should be the manifold's final incarnation, I'd like to get it perfect as possible right off the bat this time.

 

Here's a small list of things I'm doing different this time:

-No hard line on the manifold, it's all braided stainless.

-Much smaller plenum volume. Just utilizing what edelbrock designed into the manifold, plus the volume of the spacer.

- 70mm monoblade TB, positioned vertical right over the plenum. This, combined with the small plenum volume should give me much better throttle response and an even cylinder fill. Might provide a slightly worse idle quality, but I'm sure I can tune for it.

-using actual injector bungs. Got tired of the old aluminum tubing not sealing properly. Hated even more having to use silicone to seal them. Looked like a hack job...

-Injectors are on a 90* plane now. Before they were angled inwards.

-also wanted to comment on the quality of the stock rail extrusions. It is excellent, to say the least. All I needed to do was trim the ends of the rails, and tap them for my -AN adapters, and I was good to go. Next step is to sand them smooth and polish them. Also want to sand the manifold casting smooth and polish it.

-minor cleaning up on my rail mounts, then paint or powder coat. Any idea how much it would cost to powdercoat just those 4 brackets?

I'll keep an update going on the thread, feel free to throw in any comments as they come.

EDIT: For all the guys upgrading the rails for better flow, here's the cause.

For what ever reason, GM decided to install this restrictor at the inlet line into the driver's side rail. The actual ID of the fuel rail is 9/16" at it's smallest point, and nearly 3/4" at it's widest.

 

Yes, you want the system to be self purging, ie doesn't allow any air to accumulate. With all that goes on in fuel system, cavitation, and percolation can occur, and the air bubbles that accumulate have to go some where. You have your choice of thur an injector, and have a momentary leanness, or have the fuel lines so they self purge.

 

That large of monoblade, is getting to where the volume *above* it is, part of the plenum. Look at Lingenfelter's last Cavalier for an classic example of that concept.

I've run a 70 on my lil 231 V6, and had to bolster up the AE with the VE Table, at lower RPM. There was just no way to get enough low TPS AE, for off idle, and then having a nice slow speed characteristics.

YMMV

 

That looks to be the outlet for the cold start injector. It comes out of the rear of the drivers side rail on my 87 setup.
Your setup looks neat. Good luck with it.

 

I would say your -8 crossover tube should be perfectly acceptable the way you have it. If you look at Edelbrocks multi-point efi systems for trucks they use the exact same arrangement you have in the front .Looks good to me.

 

I'll second the motion to keep the rail crossflow. Deadheading can cause pressure pulsations also, kind of like a water hammer (although less significant on large diameter tubing).

On the note of AE fuel, I'm thinking about implimenting a current MAP multiplier to TPS AE, where from low MAP, TPS AE is large, but less if starting from higher MAPs (for our new EFI system). Right now our new transient algorithm is all percent based, but it takes a LOT of % to get that tip in fuel good, and only a few percent under sustained throttle movement (rolling in), even with the same dTPS. This is all just avoiding going to a model based transient algorithm (we have the means and the code has been converted from equations, but sometimes we like to wait for things to bite us (not my philosophy)).

Powdercoating is cheap or free for small stuff if you have connections. Shouldn't be too much if you aren't very picky about the color.

I too wonder what epoxy is good on aluminum and inside manifolds/ports. I buggered up on an Edelbrock head (near the pushrod slot) and used some QwikSteel? I think. I haven't had the ambition to put them on yet, and am thinking about some better heads now that I have a gripload of cash from working in Chiner. Welding would have been a better choice in retrospect.

I can't see the pictures for some reason, but I'm visualizing a 70mm monoblade on a carb manifold. I think that would actually have terrible part throttle airflow imbalance. And as Grumpy says, the TPS AE is going to be t-r-icky, unless you can train your foot to always slowly roll into it (which will probably feel like good throttle response, just because small openings will have high flow). My definition of good throttle response is almost purely based on the fueling, if that isn't right, then there's no way to get good response.

 

Thanks for all the replies fellas. So the braided stainless is reliable enough where I shouldn't have to worry about springing a pinhole leak somewhere down the road?

That's also interesting about the TB becoming part of the plenum. I'll have to look into that cavalier you mentioned. As far as tuning goes, my thoughts were to just dump a bunch of AE enrichment at first, and lean it out from there.

Even though it is a return style system, I would still have to worry about cavitation and air contamination?

I am not to concerned with color of the powdercoat, I could even paint them afterwards. I am really just looking to prevent electrolosys since everything on the manifold is aluminum and the brackets are steel.

That restriction is 100% on the inlet of the rail. The outlet for the CSI uses a threaded fitting, this one is pressed into the front of the rail and has the inlet line integrated into it. I can snap a pic of the other side of it if you're really interested

Would there be a downside to sanding off all the fins on the rails? It seems that they would serve as a heatsink, but for what I don't know. The fuel in the rails is much cooler than the ambient temp in the engine bay...

 

I always thought you ran the inlet fuel line into one rail, then ran a line over to the other rail and put the regulator on the end of that rail which pressurerised everything on that end of the world and just bypassed the extra fuel to the tank, so the fuel would flow through both rails and you wouldn't have to worry about air being trapped.

I've only messed with TBI setups so I'm not familiar with how the TPI regulators work, it does look like the LT-1's use this style of regulator though.

 

The 58 code uses a AE multiplier vs RPM, AE vs dTPS, and AE vs dMAP.
Adding a MAP enabled PE enrichment also helped.

 

Ours has the same, plus dTPS decay vs Ctemp, dMAP decay vs Ctemp, Overall ECT multiplier, and overall IAT multiplier, and dTPS trigger threshold vs TPS, and dMAP threshold. Also have fast and slow filters for both, which the difference between fast and slow is d*. We're going for Euro 3 soon, so we're going to disable PE for the first 20 minutes on this engine.

It's just that on those quick opening rates from Low MAP, as you know, it takes a lot of fuel, and with a percent of a small PW going in, it takes more from there, but if you trigger the same dTPS from a high PW, the same % becomes a big fuel change, almost the opposite of what you need. I'm just trying to find a way to counter act that without starting from scratch. I didn't design this algorithm, but I'm stuck tuning it, and small changes like this can be done in an hour (C code, star12 processor).

I'd recommend Open loop if it gets too difficult, and run the mid to high MAP at low RPM at fairly rich if it came down to it.

Fins on the rail serve no practical purpose, other than grip for installers. They may have provided a tad more rigidity with some material savings, but theres no bending forces on it in a normal engine bay, so do what you want with them.

 

I really like the continuous dialing in of the feedback system for daily driving, so I won't run O/L unless it's completely nessesary. I guess I won't decide for sure until I get it going and see how it runs.

What is euro 3?

I'm also curious how much my tune is going to be off now. I gasket matched the heads, did extensive bowl work, smoothed and polished the bowls and runners on the exhaust side, and removed any casting flash on the intake side of the runners. I also gasket matched the manifold, which was more than 1/4" off in some spots

I was also over cammed before, so I'm going with a comp grind with 20* less duration. Lift is about the same, and I have slightly more overlap. I wasn't getting power until roughly 3000 rpm before, then it would throw you back in the seat. This cam should do that from right off idle.

 

Grumpy, you wouldn't happen to have any pics of that cavalier engine, would you? I searched around and could only find distance shots of the one he wrecked in.