Technical Carb & ignition for an ex-TBI CSB350 -89?

A friend has a 350 CSB TBI engine out of a 1989 van, 200hp if I remember correctly. For simplicity (and to go better with the 1965 european GM car it's moving into) he wants to retire the TBI system and replace it with a carburettor and ignition system - simple, reliable stuff, nothing fancy.

What carburettors, intake manifolds and ignition systems are suitable for a ~200hp CSB 350? Preferably stuff that is easy to find second hand (and things that can give descent mileage, since gas costs equal to $6,46 per gallon here).

 

>>> gas costs equal to $6,46 per gallon>>>

I think your friend should use it as is for simplicity, reliability, nothing fanciful, easiness & decent mileage. Jack E/NJ

 

There is also a matter of getting a line saying "Engine modified" in the title when the car is registered with the V8. If you don't have that you need a bone stock engine and any major changes might be easy to find during vehicle inspection. With that line in the papers and no more specification than it being a CSB 350 with so-and-so many horesepower you can sneak quite a bit of tuning under their radar. Just looking at it, noone can say for sure if its 200, 300 or 400hp...

 

I agree.

Ben

 

The center four intake manifold bolts changed angle in 1987, so if you use an old carb manifold, you will need to do some mill/drill work to make the bolts fit. Some of the 87-95 engines have a hole for a fuel pump push rod, some do not. If there is a cover blocking the fuel pump mounting area, then it will probably have a hole, and you just need to add a pushrod and a plate and the mechanical fuel pump. A 1975-1980 HEI distributor (or most any other distributor with an advance mechanism and no computer control) will work.

That is about all there is to it.

I got better mileage with a TBI 350 by putting it in a lighter truck, and switching to carb. The fuel system doesn't really make much difference for mileage, but the vehicle it is installed in will make a big difference. Lighter weight, less air resistance, longer gearing, will all help.

 

No TBI roller cam engine that I have worked on had a mechanical fuel pump eccentric on the cam.

Not sure about the flat tappet truck ones.

 

other than the fuel pump previously mentioned, that 89 short block will take all the appropriate earlier pre-TBI stuff...heads, intake, water pump (to get rid of the serpentine belt setup) and HEI or even older points type distributor...I don't know how closely the inspectors will scrutinize what your friend is doing, but it's easy enough to fab up an adapter to fit a 2bbl carb in place of the throttle body, swap out an earlier non-computer dependent distributor and just run it that way...I did it. It worked. Wasn't really pretty but it DID get the old car moving...and it wasn't a gas hog.

I didn't keep the setup for long, but it would have worked just fine...

 

Just helped a friend do the exact same conversion on a 3500 series truck . Used an old Qjet intake and hogged the center holes out. Used a big cap HEI and done.

 

The truck motors with flat tappet cams do have the fuel pump lobe.

 

Thanks, great info!
So, if I understand correctly:
Any old CSB distributor will fit, HEI units are preferable but anything with mechanical advance (and no computer control) should do the job.
The older styles intake will fit after some basic modification of four bolt holes. (Or a two port carb can be adapted to the TBI intake.)

But what carburetor would be suitable? I have thought the quadrajet would be good, car manufacturers generally use good and reliable parts (although not always suitable for performance applications), but we have been looking for those and none has come up for sale for a while. Holleys and other aftermarket carbs turn up more often, what size should we keep an eye out for?

 

A quadrajet would be good. A non Quadrajet will probably have a square bore base and won't fit the old factory intake. So you will probably want to get a matching intake, if you get a Holley or Edelbrock carb. 600-650 CFM is suitable for a stock 350.

 

An intake from an '80s pickup will work well, and a q jet. I don't remember which heads the '89 motor has but if its got the Vortech style heads you just elongate the center holes.

A distributer from any SBC will work, someone is going to say an HEI but I don't care for them so I won't say that. LOL

 

Accel or Mr Gasket used to sell beveled washers that kept the inner 4 bolts flush after elongating the holes on the older manifolds, I'm sure if you can't buy them anymore, they'ed be easy enough to fab up.

 

They still had Mr Gasket beveled washers that last time I looked ( about a year or so back).

 

Those are just centerbolt heads.

Vortec heads did not appear until the 1996 model year, in V8's.

 

Sort of....the term "vortec" is an advertising word, it really doesn't describe much about an engine except that it's a Chevy truck engine. LS motors in trucks say "vortec" right on them, for example.

 

Nope. It describes a specific combustion chamber shape.

Vortec is a specific thing, not just a word.

 

"Starting in 1996 on several GM Trucks and Vans, the L31 Vortec heads came on the scene. Not just a modification of existing heads, but complete redesign using the 1996 Caprice/Impala SS LT1 cast-iron head castings as a base. The biggest change GM made in the new design was revising the water jacket so the new Vortec heads could be used on conventionally cooled small blocks. The idea of using the 1996 LT1 cast iron head as a starting point for a new performance stock head came from the fact that it was the highest flowing LT head used by GM. The 1996 Caprice/Impala heads outflowed the Corvette Aluminum LT1 heads by as much as 20 cfm on the intake side. The cast iron Vortec head was in development six months longer than the aluminum head, and during that time, GM engineers tweaked the intake and exhaust ports for additional flow. The cast iron Vortec heads was one of the first to purposely integrate tumble instead of large swirl numbers in the design."

 

Intake and carb wise it might come down to what your friend can find that fits and is available locally. That is probably a Quadrajet intake and a 70's/80's pre computer quadrajet. I'd go with the HEI distributor, they may be a bit ugly but they work, are rather simple and put out enough spark to fire up an engine in a Swedish winter. Made a big difference on a 350 powered rig I own.
Or make and adapter for a two barrel carb, install a non computer Hei and stick a big stock looking aircleaner on the two barrel. At least until after it gets past inspection.

 

It's not the chamber, they called the engines with heads with a lump in the intake port Vortecs, also (starting with the 4.3 in the mid 80s)

Since you can get a Vortec straight 4, straight 5, V6, small block, big block, or LS type engine, it really doesn't tell us much about which head it is, does it?

But I do understand that many folks consider the 1995-99 small block V8 head to be the one and only "vortec" head. Which is a rather selective way to apply a much more universal name.

 

You can call a pig a duck. Good luck getting it to quack.

Irrespective of what GM did with the name later on, centerbolt heads on a V8, pre-1996, are not Vortec heads.

This is directly out of GM literature. I am not guessing.

 

So the 1985-up Vortec engines had some other kind of head? Chevy started calling them Vortec when they first introduced the concept of swirl, by blocking off one side of the intake port.

I would not have a problem with this if folks specified the year and engine size when discussing Vortec heads. But most guys seem to have forgot that there is more than one Vortec engine.

Direct from Chevy literature:

 

I had a set of late 80's TBI pickup heads, they had a large vane in the intake runner, supposedly to promote swirl at lower RPMs.

 

A V6 is NOT a V8.

I have benched both. The 90° V6 heads have that chamber.

 

It appears second hand parts aren't as easily available around here as we thought. At least not in the middle of the winter. So, new stuff then!

Would this distributor be a good choice? Good price, just a bit unsure about if it has the correct gear.
https://www.summitracing.com/int/parts/sum-850001r/overview/

Carburettor and intake seems harder. I can't figure out what carburetors goes with what intake, and on top of that they have to be suitable for a stock 350, and have jets etc. for adjusting easily available... and the webshop is sloooooooooooow when I try to look around.
Any suggestions, preferably from the same place? Perhaps a kit with carb and intake, if there is something suitable there..

 

Get an Edelbrock Performer manifold (2104), and, if you are keeping the cam stock, a 600cfm carburetor (1400), with an electric choke, a mechanical fuel pump, pump plate, and pushrod.

That distributor is fine, as long as you don't have a roller cam. You should have a flat tapped "truck" cam, but you are across-the-pond, and who knows just what happened there. If you have a roller cam, the distributor gear would need to be changed for it to be compatible (and you would need an electric fuel pump).

 

The intake manifold vs carb selection thing....there are two basic designs, square bore and spread bore.

The manifold suggested above works with either design, but it includes an "adapter" plate that helps seal the flange when using a square bore carb. Be sure you use this plate.

also, you probably want to use stock replacement intake manifold gaskets, instead of the Edelbrock gaskets. The Edelbrock gaskets have rather large ports, compared to the heads, and don't seem to have enough sealing area.

 

That's Edelbrock 2732.

 

How do those lump intake port heads perform? Is the idea to induce swirl, or better atomize the fuel? Seems like having to make the turn and pass the valve and seat would diminish the effect. Better done in the chamber?

What makes the Vortec (95 up) engines perform so well? Is the the chamber, the roller cam, the fuel injection, or a combination thereof?

My daily has a well running '79 305 with an SP2P, Q-jet and headers. Gets 13-14mpg in a 4,000 lb. brick and slower than a DMV line. I've thought about Vortec heads but I believe at 58cc my heads have less volume. Maybe add a cam, but by then might as well get the whole Vortec enchilada.

Maybe I'll just get a Tornado.