6 cly to 350 swap

[NEWBIEC10]

I'm going to swap my 250 inline 6 to a 350. Was wondering if I use my existing 3 speed manual transmission ( on the column ) if I would have any problems with the drive line being to long or short? Also linkage issues? And would I use the same motor mount holes in the frame. Or use the forward holes?

Thanks for your help.

[Tx Firefighter]

Easiest way is to drop the 350 down onto the same mounts as the six cylinder (as long as it's a 250 and not a 292 inline six cylinder).

This way you can reuse everything from there back with no mods. When I do that swap, I don't even remove the transmission or driveshaft during the swap. It all stays put right where it is now.

[NEWBIEC10]

Originally Posted by Tx Firefighter

Easiest way is to drop the 350 down onto the same mounts as the six cylinder (as long as it's a 250 and not a 292 inline six cylinder).

This way you can reuse everything from there back with no mods. When I do that swap, I don't even remove the transmission or driveshaft during the swap. It all stays put right where it is now.

Thanks for the knowledge. It is a 250. I'm trying to do it as easy as possible. Do you know if the flywheel will work?

Also Happy Easter.

[Tx Firefighter]

My answer is true for a 350 with 2 piece rear main seal. That is, 70's to mid 80's vintage.

Yes, starter, flywheel, clutch, everything works.

[68gmsee]

Originally Posted by Tx Firefighter

My answer is true for a 350 with 2 piece rear main seal. That is, 70's to mid 80's vintage.

Yes, starter, flywheel, clutch, everything works.

Agree. I have a six cylinder flywheel in one of my 350's.

Not sure about this, but seems like I read in here that the clutch bellcrank (z-bar) may be need to be changed. At least maybe the ball socket??

[Maladd]

Not sure what it's called, but the ball that is threaded in to the engine had to be swapped for one from a v8. Got one free from a friend, but think they were less then $20 from LMC.

[Tx Firefighter]

Agree with Maladd, you need the screw in pivot ball.



http://www.classicparts.com/1963-84-.../#.U1RrmPldWSo

On the bellcrank, you can modify the six cylinder one to work easily. The V8 is wider so you have to take a hacksaw and cut the end off the bellcrank tube by about half an inch. You cut the end that the ball slips into. The cavity in the bellcrank is deep enough to allow your shortening it and the pivot ball (above) fits into it deep enough still.

[Captainfab]

What year of truck are we talking about here?

[Maladd]

Before relocating to the forward position, I had my v8 in the I6 position and no problems other than that ball for the manual trans linkage, and distributor was VERY close to the firewall.

If you plan on running HEI I'd get one of the small HEI's. Also remember to replace the resistor wire to the HEI...if i remember right the original runs ~9 volt, and the HEI needs a full 12 volt.

IIRC I even used the flywheel off of the I6.

Pretty easy swap, even I managed to do it.

[NEWBIEC10]

Originally Posted by Captainfab

What year of truck are we talking about here?

Its a 68. 250 inline six. 3 on the tree

[NEWBIEC10]

Originally Posted by Maladd

Before relocating to the forward position, I had my v8 in the I6 position and no problems other than that ball for the manual trans linkage, and distributor was VERY close to the firewall.

If you plan on running HEI I'd get one of the small HEI's. Also remember to replace the resistor wire to the HEI...if i remember right the original runs ~9 volt, and the HEI needs a full 12 volt.

IIRC I even used the flywheel off of the I6.

Pretty easy swap, even I managed to do it.

Not sure on what distributor is on the motor. A buddy at work has one and he wants to do a trade motor for motor. He's a inline six guy. I love the sound of V8's that's why I'm wanting to do the swap

[NEWBIEC10]

Originally Posted by Tx Firefighter

Agree with Maladd, you need the screw in pivot ball.



http://www.classicparts.com/1963-84-.../#.U1RrmPldWSo

On the bellcrank, you can modify the six cylinder one to work easily. The V8 is wider so you have to take a hacksaw and cut the end off the bellcrank tube by about half an inch. You cut the end that the ball slips into. The cavity in the bellcrank is deep enough to allow your shortening it and the pivot ball (above) fits into it deep enough still.

Thanks for the photo of the part. That helps a bunch. I will check LMC and other parts catalogs for that.

[Tx Firefighter]

Originally Posted by NEWBIEC10

Thanks for the photo of the part. That helps a bunch. I will check LMC and other parts catalogs for that.

I gave you the link for them. Just click on it.

Originally Posted by Maladd

Before relocating to the forward position, I had my v8 in the I6 position and no problems other than that ball for the manual trans linkage, and distributor was VERY close to the firewall.

If you plan on running HEI I'd get one of the small HEI's. Also remember to replace the resistor wire to the HEI...if i remember right the original runs ~9 volt, and the HEI needs a full 12 volt.

IIRC I even used the flywheel off of the I6.

Pretty easy swap, even I managed to do it.

There is no need to run a small cap HEI. There's enough room.

[NEWBIEC10]

Originally Posted by Tx Firefighter

I gave you the link for them. Just click on it.



There is no need to run a small cap HEI. There's enough room.

Awesome, thanks for the link and the info on the HEI. So from what I'm assuming is all I need is that $13 part and everything else should work?

Do you recommend a V8 fan shroud? Or can I run my inline six shroud and radiator?

[Tx Firefighter]

Just screw that pivot ball into your 350 block when you install the engine. Then, when you go to put the Z bar in place, you'll find it is now too wide to fit into the gap. Cut the end with a saw to make it the right length so it fits.

I'm assuming your truck has the original cooling system, which is no shroud. The six cylinder trucks usually had a narrow steel upper guard right in the center rather than a full shroud like most people would think. In my experience, here in a Texas heat, I've always been fine with using the original six cylinder cooling system. If you have a real hot rod engine or add air conditioning or something, you'd likely run into troubles. In my opinion, try it and see if it runs cool enough. You already own the parts and it will probably save you some money by not buying new V8 cooling system components without them being totally necessary.

[NEWBIEC10]

Originally Posted by Tx Firefighter

Just screw that pivot ball into your 350 block when you install the engine. Then, when you go to put the Z bar in place, you'll find it is now too wide to fit into the gap. Cut the end with a saw to make it the right length so it fits.

I'm assuming your truck has the original cooling system, which is no shroud. The six cylinder trucks usually had a narrow steel upper guard right in the center rather than a full shroud like most people would think. In my experience, here in a Texas heat, I've always been fine with using the original six cylinder cooling system. If you have a real hot rod engine or add air conditioning or something, you'd likely run into troubles. In my opinion, try it and see if it runs cool enough. You already own the parts and it will probably save you some money by not buying new V8 cooling system components without them being totally necessary.

You are dead on with what cooling system I have. Here in western Washington we are lucky to hit 80° once a summer. So I will just run tge 6 cyl cooling system.

Thanks again for the info.

[NEWBIEC10]

Anyone else have any tips or tricks for making this swap as easy as possible?

[68gmsee]

Originally Posted by NEWBIEC10

Anyone else have any tips or tricks for making this swap as easy as possible?

If you wait until later in the summer, I'm thinking of doing the exact same to my 68. At least temporarily. I'm swapping a 350 in for the 250 with three on the column and leaving the existing Saginaw in it. Later I will rebuild the 250.

[NEWBIEC10]

Originally Posted by 68gmsee

If you wait until later in the summer, I'm thinking of doing the exact same to my 68. At least temporarily. I'm swapping a 350 in for the 250 with three on the column and leaving the existing Saginaw in it. Later I will rebuild the 250.

Yeah I'm not getting around to it until probably September. Waiting for my buddy with the motor and shop. To recover from bicep surgery. Was just wanting to get everything in order so it's simple and I have everything to do it.

Definitely keep me posted on your swap. Also does your 3 speed have overdrive? Mine does and I'm wondering if the 350 will eat it up?

[68gmsee]

Originally Posted by NEWBIEC10

.....Definitely keep me posted on your swap. Also does your 3 speed have overdrive? Mine does and I'm wondering if the 350 will eat it up?

Unfortunately, I don't have an overdrive. Rear end ratio is 3.54 but I have access to a 3.08 if I need it.

I don't see an issue with your overdrive as long as used properly but how does your O.D. work with the column shift? Does it have a solenoid for disconnecting?

[NEWBIEC10]

Originally Posted by 68gmsee

Unfortunately, I don't have an overdrive. Rear end ratio is 3.54 but I have access to a 3.08 if I need it.

I don't see an issue with your overdrive as long as used properly but how does your O.D. work with the column shift? Does it have a solenoid for disconnecting?

It has a push/pull lever under the ignition and on the tail piece of the tranny there are 2 solenoids that operate it,and on the carb there is a kick down lockout switch.

I'm going to half to figure out how to mount tge kick down lockout switch to the 4 barrel on the 350.

[crazy longhorn]

Originally Posted by Tx Firefighter

Just screw that pivot ball into your 350 block when you install the engine. Then, when you go to put the Z bar in place, you'll find it is now too wide to fit into the gap. Cut the end with a saw to make it the right length so it fits.

I'm assuming your truck has the original cooling system, which is no shroud. The six cylinder trucks usually had a narrow steel upper guard right in the center rather than a full shroud like most people would think. In my experience, here in a Texas heat, I've always been fine with using the original six cylinder cooling system. If you have a real hot rod engine or add air conditioning or something, you'd likely run into troubles. In my opinion, try it and see if it runs cool enough. You already own the parts and it will probably save you some money by not buying new V8 cooling system components without them being totally necessary.

Pretty much "right on", as usual Tex Just to add a bit...I like to run the later (73 up water pump & all accessories), on that swap. You can then use the stock 2wd ,V8 sb rad shroud for your 67-72. The HEI does fit, but very tight to the firewall....that is a matter of preference? longhorn

[storm9c1]

Originally Posted by crazy longhorn

Pretty much "right on", as usual Tex Just to add a bit...I like to run the later (73 up water pump & all accessories), on that swap. You can then use the stock 2wd ,V8 sb rad shroud for your 67-72. The HEI does fit, but very tight to the firewall....that is a matter of preference? longhorn

One thing that helps with firewall clearance is to loosen up the frame mounts at the frame BEFORE you bolt in the new engine. Then bolt them to the engine, then push the whole drivetrain forward as far as it will go (there is usually some wiggle room in the frame mounts). You may be able to gain up to 1/2" this way, which every little bit counts. Unfortunately things like the shifter linkage will need to readjusted.

My personal preference is to mount the V8 in the proper position, but that requires drive shaft work, etc.

[Zeroman]

Originally Posted by storm9c1

One thing that helps with firewall clearance is to loosen up the frame mounts at the frame BEFORE you bolt in the new engine. Then bolt them to the engine, then push the whole drivetrain forward as far as it will go (there is usually some wiggle room in the frame mounts). You may be able to gain up to 1/2" this way, which every little bit counts. Unfortunately things like the shifter linkage will need to readjusted.

My personal preference is to mount the V8 in the proper position, but that requires drive shaft work, etc.

When I bought my truck someone had done the 6 cyl to V8 swap. They left the V8 motor mounts at the 6 cyl motor mount location using the 6 cyl motor mount towers. I replaced the motor and moved the V8 to the correct position and used a 9" tail shaft on the 350TH instead of the 6" and mine fit up fine without having to replace the drive shaft. Although you will need the proper V8 engine mount towers if you move it to the correct position.

[Luke87gt]

Originally Posted by Tx Firefighter

Agree with Maladd, you need the screw in pivot ball.



http://www.classicparts.com/1963-84-.../#.U1RrmPldWSo

On the bellcrank, you can modify the six cylinder one to work easily. The V8 is wider so you have to take a hacksaw and cut the end off the bellcrank tube by about half an inch. You cut the end that the ball slips into. The cavity in the bellcrank is deep enough to allow your shortening it and the pivot ball (above) fits into it deep enough still.

That threads directly into the rear hole in the block? There is no need for the stock v8 bracket that bolts into those two holes?

For reference, I am keeping my 350 in the rearward i6 location