Engine swap 402 to 350 - The 1947 - Present Chevrolet & GMC Truck Message Board Network

terry b · 10-28-2021, 07:50 PM

What will I have to buy to mount a 2001 Chevy vortex 350 in place of my 1972 402 Big Block in my Cheyenne? Do I need to replace the tower's? I am going to use the 4l80 transmission also.

Accelo · 10-28-2021, 10:29 PM

I am assuming you are referring to the modern SBC with a roller cam, one piece rear main seal and the center bolt valve covers.
It will bolt in using the BBC towers using the motor mounts off of the BBC. However, using the BBC towers can complicate things like the fitment of headers. I would recommend using the SBC towers and mounts to avoid issues. But you will be able to bolt it in. It's easier to pull the wiring plug at the firewall, then transfer the wiring when the motor is out of the truck. Will speed things up. If you are using a carburetor.

**pjmoreland** · 10-28-2021, 10:56 PM

Is your 2001 Vortec machined for a mechanical fuel pump? If not, then you will need to switch to an electric pump. If you're going with fuel injection, then you probably already factored that in. How will you be controlling that electronic transmission?

**truckster** · 10-28-2021, 11:22 PM

Quote:

Originally Posted by pjmoreland

Is your 2001 Vortec machined for a mechanical fuel pump? If not, then you will need to switch to an electric pump. If you're going with fuel injection, then you probably already factored that in. How will you be controlling that electronic transmission?

He's planning to keep the fuel injection. He has a similar thread on the Engine and Drivetrain forum.

**kwmech** · 10-29-2021, 12:42 AM

Quote:

Originally Posted by Accelo

I am assuming you are referring to the modern SBC with a roller cam, one piece rear main seal and the center bolt valve covers.
It will bolt in using the BBC towers using the motor mounts off of the BBC. However, using the BBC towers can complicate things like the fitment of headers. I would recommend using the SBC towers and mounts to avoid issues. But you will be able to bolt it in. It's easier to pull the wiring plug at the firewall, then transfer the wiring when the motor is out of the truck. Will speed things up. If you are using a carburetor.

If he uses the big block frame stands he can use the factory log style manifolds if he does not want the run headers

terry b · 10-29-2021, 08:12 AM

I was hoping to run the factory computer to run the system with some kind of aftermarket wiring harness. I understand there is a adapter for the speedometer for around seven hundred dollars. Going to adapt the factory single exhaust with the factory catalytic converter so using the big block tower's and mounts is good news. Is there anyone on the forum making wiring harness? Hoping to adapt to vans fuel tank. Would really like to set my body on the van frame but am just now selling body and interior parts on ebay. Plans are to cut the van body up with saw and torch in December. when I get the van body off will have a better idea of the fit. Not holding my breath. I really appreciate your information it's a great way to move forward! Thank you!

MARKDTN · 10-29-2021, 10:27 AM

Can't speak to Vortec harness, but the van TBI harness was very nice. It was longer than a truck/suburban harness and put the ECM under the driver seat. Looks like a Voretc van PCM is mounted to the doghouse maybe? Why do you think you need a new harness? If you do, Vortec harnesses are available from places like Howellefi.com I have used several of their harnesses and they are well made. Not sure you can use rear-dump Vortec exhaust manifolds on a 67-72, but I don't know for a fact.

What are you doing for a fuel tank? Can you use the van tank behind the axle? This will be OBD2 so unless you plan on using every sensor and the cat from the van you will need your PCM modified to remove VATS, fuel tank, and rear O2s at a minimum.

Accelo · 10-29-2021, 01:34 PM

This may work for your application.
AutoMeter 5293 Speed Sensor, Mech to Elec, Gm & Chrysler, 7/8"-18 Thread, Vr, 8 Pulse

They are available on Amazon for $63.03.

It depends on which tail housing you have. You will require both outputs, mechanical and digital.
One for the computer to read the speed and another for the mechanical speedometer.

MARKDTN · 10-29-2021, 03:18 PM

Quote:

Originally Posted by Accelo

This may work for your application.
AutoMeter 5293 Speed Sensor, Mech to Elec, Gm & Chrysler, 7/8"-18 Thread, Vr, 8 Pulse

They are available on Amazon for $63.03.

It depends on which tail housing you have. You will require both outputs, mechanical and digital.
One for the computer to read the speed and another for the mechanical speedometer.

I think he needs to go the other way-electric to mechanical. May be better off just having your speedometer converted in stead of trying to generate a mechanical signal. Jegs has a converter for $350.

https://www.jegs.com/i/JEGS/555/4180...waAsdSEALw_wcB

But I would rather stay with an electric signal rather than converting twice.

Accelo · 10-29-2021, 09:17 PM

Here is a picture of the conversion I completed on a late model 4L60E with the 6 bolt tail housing. I kept the electronic output for the computer and added the manual output to the tail shaft. These are also sold commercially. I did mine with about 8 hours work and $30. You can see the hole for the stock electronic output in the center picture. As shown, in the center picture, the sleeve isn't centered yet. It was a tight fit and I took the picture before the final fit and epoxy.

10-28-2021, 07:50 PM	#1
terry b Registered User Join Date: Oct 2011 Location: jackson michigan Posts: 755	Engine swap 402 to 350 What will I have to buy to mount a 2001 Chevy vortex 350 in place of my 1972 402 Big Block in my Cheyenne? Do I need to replace the tower's? I am going to use the 4l80 transmission also.

10-28-2021, 10:29 PM	#2
Accelo Registered User Join Date: Mar 2015 Location: washington Posts: 2,161	Re: Engine swap 402 to 350 I am assuming you are referring to the modern SBC with a roller cam, one piece rear main seal and the center bolt valve covers. It will bolt in using the BBC towers using the motor mounts off of the BBC. However, using the BBC towers can complicate things like the fitment of headers. I would recommend using the SBC towers and mounts to avoid issues. But you will be able to bolt it in. It's easier to pull the wiring plug at the firewall, then transfer the wiring when the motor is out of the truck. Will speed things up. If you are using a carburetor.

10-28-2021, 10:56 PM	#3
pjmoreland Senior Member Join Date: Jan 2005 Location: CA Posts: 5,329	Re: Engine swap 402 to 350 Is your 2001 Vortec machined for a mechanical fuel pump? If not, then you will need to switch to an electric pump. If you're going with fuel injection, then you probably already factored that in. How will you be controlling that electronic transmission?

10-29-2021, 08:12 AM	#6
terry b Registered User Join Date: Oct 2011 Location: jackson michigan Posts: 755	Re: Engine swap 402 to 350 I was hoping to run the factory computer to run the system with some kind of aftermarket wiring harness. I understand there is a adapter for the speedometer for around seven hundred dollars. Going to adapt the factory single exhaust with the factory catalytic converter so using the big block tower's and mounts is good news. Is there anyone on the forum making wiring harness? Hoping to adapt to vans fuel tank. Would really like to set my body on the van frame but am just now selling body and interior parts on ebay. Plans are to cut the van body up with saw and torch in December. when I get the van body off will have a better idea of the fit. Not holding my breath. I really appreciate your information it's a great way to move forward! Thank you!

10-29-2021, 10:27 AM	#7
MARKDTN Registered User Join Date: Jan 2011 Location: Chattanooga, TN Posts: 2,131	Re: Engine swap 402 to 350 Can't speak to Vortec harness, but the van TBI harness was very nice. It was longer than a truck/suburban harness and put the ECM under the driver seat. Looks like a Voretc van PCM is mounted to the doghouse maybe? Why do you think you need a new harness? If you do, Vortec harnesses are available from places like Howellefi.com I have used several of their harnesses and they are well made. Not sure you can use rear-dump Vortec exhaust manifolds on a 67-72, but I don't know for a fact. What are you doing for a fuel tank? Can you use the van tank behind the axle? This will be OBD2 so unless you plan on using every sensor and the cat from the van you will need your PCM modified to remove VATS, fuel tank, and rear O2s at a minimum. __________________ '83 K20-TPI '73 C10 '79 C10-ex-diesel(SOLD) '07 Tahoe(Son driving) '14 Suburban-DD '71 C10-current project Last edited by MARKDTN; 10-29-2021 at 10:41 AM.

10-29-2021, 01:34 PM	#8
Accelo Registered User Join Date: Mar 2015 Location: washington Posts: 2,161	Re: Engine swap 402 to 350 This may work for your application. AutoMeter 5293 Speed Sensor, Mech to Elec, Gm & Chrysler, 7/8"-18 Thread, Vr, 8 Pulse They are available on Amazon for $63.03. It depends on which tail housing you have. You will require both outputs, mechanical and digital. One for the computer to read the speed and another for the mechanical speedometer. Attached Images Last edited by Accelo; 10-29-2021 at 02:05 PM.

10-29-2021, 09:17 PM	#10
Accelo Registered User Join Date: Mar 2015 Location: washington Posts: 2,161	Re: Engine swap 402 to 350 Here is a picture of the conversion I completed on a late model 4L60E with the 6 bolt tail housing. I kept the electronic output for the computer and added the manual output to the tail shaft. These are also sold commercially. I did mine with about 8 hours work and $30. You can see the hole for the stock electronic output in the center picture. As shown, in the center picture, the sleeve isn't centered yet. It was a tight fit and I took the picture before the final fit and epoxy. Attached Images



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