Engine Gurus: Need major help with TPI to Carb conversion

[CobraEatr]

Now before some of you try to kill me for replacing my TPI with a carb setup, please know that I've thought about this for some time now and I really want to do this. I know the disadvantages, but I want a carb. Replacing all the sensors has nickel-and-dimed me to death. I'm ready to tune my car in the garage with a screwdriver instead of having to use a laptop. I've posted a trade in the 'For Sale' section of this board and I think I've found someone to trade me their carb setup for my TPI setup.

My Blazer is a 1984, with a rebuilt 350 V8 from a 1989 Blazer. The TPI is from a 1985 Z28 Camaro. I was told by the previous owner that if I did change back to carb then I would have to use an electric fuel pump instead of a mechanical one because there isn't a place on the block for the mechanical pump due to the block being an '89. I have no idea what he's talking about.

Now, here's my question. What exactly will I need to get from someone in order to make my Blazer run. I'm just a shadetree mechanic that has installed bolt-ons but have never gone internal into the motor. Below is a list of items that I think I need, but please add anything and everything that I'm missing.

1. Lower Intake Manifold
2. Carbuerator
3. Distributor (can I use mine ??)
4. Fuel Pump
5. New Throttle Cable (?)

Am I missing anything else?

After posting pics of my engine bay, I was told that I have center-bolt heads. Then I was told that having those would eliminate me using any stock carb setup. What's the difference between my heads (center-bolt) and the stock ones?

I've already taken off my current upper and lower intakes, distributor, throttle body, and fuel rails. All that's left for me to remove is the wiring harnesses, computer, and the fuel pump (which is located under the hood).

Thanks for any info that may help me with this.

 

[80' 427]

1. Lower Intake Manifold Yes, performer eps
2. Carbuerator I recommend a holley truck avenger or Q-jet
3. Distributor (can I use mine ??) No you need a pre ecu controlled hei
(buy a new hei from a parts store.)

4. Fuel Pump An 89 has all the stuff but my not be drilled
for a pump most likely just need to use a return
regulator and the tpi pump

5. New Throttle Cable (?) Yes, just order the right one for your truck.

Other stuff
6. Different kick down cable for th 350 with a carb
7. Air cleaner
8. Throttle cable bracket
9. intake bolts?
10. Thermostat housing?
11. Heater fittings?

 

[Thunder]

89 truck blocks are drilled and set up for a mechanical fuel pump. The cam has a lobe to drive it. There is just a block off plate you have to remove. You Will need to install the push rod for the pump.

If you do use the TPI pump you must use a regulator with a return line as said above. You will burn up the pump without a return.

Center bolt heads are different from older heads in that the center 2 bolts on each side of the intake are at a different angle than the older bowtie heads. Valve covers are attached with bolts thru the center of the covers instead of the side. There are some internal differences but those dont affect bolting on parts.

The 89 center bolt heads wont bolt up to an older style carb manifold without machining out the 2 center bolt holes on each side in the intake manifold. you can elongate the holes your self with a drill bit. Then grind off the seats for the bolts so they sit flat. A machine shop will also do it cheap.
Edelbrock sells a performer carb manifold that bolts directly to center bolt heads.
(Dont get the Vortec carb manifold it wont bolt up)

 

[80' 427]

I have seen tbi 350s that were not drilled for the fuel pump pushrod. The intake story is correct. The other fact is they are some of the worst heads ever.

 

[Thunder]

IIRC only the roller cam TBI blocks dont have the pushrod hole.
I also dont agree about your statement about TBI heads being crap. They are far better head for a truck. Than pre 87 smog bowtie heads, Espically for building low rpm torque . 193 TBI heads made more horsepower/torque stock in trucks than older smog Bowtie heads ever did.

 

[eagle mark]

OK your nuts! If you get this running correctly you won't have to touch it for years. Why do you want to do all this work for less power, less fuel milage and more maintenece???

 

[CobraEatr]

80'427 & Thunder,

So if my block doesn't have the hole drilled (which is what the previous owner told me in a round-about way) then what are my options? He told me I would need an electric fuel pump if I switched to a carb. Can I get away with an inline pump or do I need to pull the tank and use an intank pump (I'd rather not pull the tank)?

Eagle Mark,

You're correct about less HP and less MPG, but IMO you're wrong about the maintenance. Yes, if properly tuned or programmed an EFI is the way to go. However, I like clean engine bays, less wires, and less parts in general on my truck. I live in Florida where it's always hot and there are no hills around where I live. So having carb issues while trail riding isn't a problem for me. I replaced every damn sensor on the EFI setup and was then told that I needed to send a list of my modifications and engine specs to a company so they could 'tune' my truck over in California without ever even seeing it. Then they'd mail my chip back and wha-la, my truck would run perfectly. I DON'T THINK SO. I like to know exactly what's going on under the hood and the less electrical components the better. If I have to rebuild a carb every 3-5 years then so be it.

 

[4X4HIGH]

First let me say that "chip tuning" can be done without having seen your truck BUT you must have the ability to datalog and send the file to the "chip burner guy" so he can see what your engine is doing when you're driving and what he needs to do to correct any issues. This may need to be done several times until it is correct. I've done this and am very happy with the results.

Now, you can just run an inline electric fuel pump but remember that an electric pump is designed to push fuel not suck fuel so the pump needs to be mounted as close to the fuel tank as possible and as near the bottom of the tank as possible. Installing an electric pump under the hood will burn the pump up fairly quick as you are expecting it to do a job that it was never intended to do.

 

[CobraEatr]

Anybody know where I can pick up a cheap inline? I've looked on Summitt but there are 5,000 different kinds and I'm not sure which one is best for my application. I'd like an inline pump for a carb, one that I can mount close to the fuel tank like 4x4high described. I'm also looking for one that's a good price. Thanks for all your input guys.

 

[82355]

I am sure there has to be a local performance shop around your area that would be able to dyno tune your TPI setup. That would be my recommendation.

Martin

 

[CobraEatr]

82355, it's too late now because I've already yanked most of the bolt-ons off. I'm really looking forward to a lot less wires in both the engine bay and in the glove box.

If anyone has a link to a cheap inline fuel pump it would be greatly appreciated.

 

[dyeager535]

Did you figure out if the block will run a stock pump? You are far better off just sticking with that if you can. Avoid the electric at all cost, if you can.

 

[79rustyk10]

IIRC only the roller cam TBI blocks dont have the pushrod hole.
I also dont agree about your statement about TBI heads being crap. They are far better head for a truck. Than pre 87 smog bowtie heads, Espically for building low rpm torque . 193 TBI heads made more horsepower/torque stock in trucks than older smog Bowtie heads ever did.

I have a roller cam block out of my old 89 k2500 LD that is drilled for the fuel pump pushrod.

 

[CobraEatr]

I don't even know where to check, however, the previous owner said point blank "if you switch to a carb then you will have to use an electric fuel pump because this block was designed for fuel injection and it is not drilled for a mechanical fuel pump". Now I haven't checked this to be sure (because I don't know where to look), but if I had a million dollars then I'd put my money on him being correct.

 

[4X4HIGH]

Just look at the passenger side front of the block to see if the block is drilled and tapped for a fuel pump and then if it is look inside the cavity to see if the hole is there for the fuel pump pushrod. My 89 blazer engine is drilled and tapped and the hole is there for the pushrod and the block was machined from the factory for roller cam.

 

[dyeager535]

I think we answered this before, but if the block is not drilled/tapped for mech. fuel, there will not be a blockoff plate on the fuel pump boss, correct? I know there would be no point if it wasn't drilled, but GM didn't always do things that made sense.

 

[bp71k5]

If anyone has a link to a cheap inline fuel pump it would be greatly appreciated.

Summit sells tons of electrics that will work for carbs. Look for something made by walbro, airtex, or carter. You'll likely need a regulator as well.

Also, if you have an in-tank electic pump on there now, you need to remove it, but your post says you have an underhood fuel pump? I assume it's electric?

 

[80' 427]

I think we answered this before, but if the block is not drilled/tapped for mech. fuel, there will not be a blockoff plate on the fuel pump boss, correct? I know there would be no point if it wasn't drilled, but GM didn't always do things that made sense.

Yes the mount is just open if its not drilled. I have drilled them (on dirt track cars) but it may not last a long time due to misalignment.

 

[CobraEatr]

Here are some pics....

Here are a couple pics of the passenger side of the block. It looks like there is a place for a pump to mount but there isn't a hole drilled anywhere. Is that the case?

 

[CobraEatr]

Fuel System???

Also, attached are a couple pics of my fuel setup, which is located under the hood on the driver side. It looks like there is a fuel pump, a fuel filter, a canister of some sort, and maybe an adjustable fuel pressure regulator??? Can someone explain what all this stuff is and if I can reuse any of it when I go to a carb. Thanks in advance!