I6 250 to v8 350 conversion questions

[Luke87gt]

Hello, my 1969 c10 (3OTT manual) currently has an i6 250 and I have a 350 small block sitting in my garage. I’ve read about the swap on this forums and have a pretty good idea of what’s involved but would like to ask for your help to eliminate some gaps

First, I understand that the 350 can utilize the i6 engine location, mounts, clutch, flywheel, starter.

a.) although I understand that the i6 trans and flywheel will work, I’ll replace these anyway. Given that, I plan to go with a v8 clutch/flywheel which is slightly larger in diameter if I recall. Wondering if anyone has any recommendation for a good value clutch/flywheel for a v8 that is strong, won’t kill my left leg, and reasonably priced? I actually don’t know the year of my 350, how can I be certain I’m buying the right clutch/flywheel?

b.) I’ve read that the block needs to be drilled and tapped for a clutch pivot ball? Can anyone steer me to a part number or link for this? It would help to know the drill/tap sizes

c.) does anyone have a picture of where the pivot ball needs to be located on the block? I’ve read that it’s self explanatory once the engine is in the car but I will be doing the drilling/tapping with the engine out of the car.

I think these are the last details I need. Thank you in advance!

[67 twins]

No you don't need to drill for the pivot ball. However you do need the correct bracket for the pivot ball and a different Z-bar for use with the SBC

[Getter-Done]

Here is some pictures and info in the Old Thread below.

Link: https://67-72chevytrucks.com/vboard/...+bar+stud+size

[CAMAROBOY68SS]

Originally Posted by 67 twins

No you don't need to drill for the pivot ball. However you do need the correct bracket for the pivot ball and a different Z-bar for use with the SBC

you actually dont need to change the bracket or Z bar if the motor is still set back in the I6 location. Im still running all my I6 stuff on my clutch setup.

With a small block there should already be a threaded hole kind of in the middle between the dipstick and oil filter and the ball screws into that.

[Luke87gt]

Motor will be set back in the i6 location for Porsche 911 F/R weight distribution (jk). But ya, will use the rear positioning which is set back.

My understanding is that you then do need to drill the block but can use all the bar hardware from the i6.

Maybe I can take a pic of what holes are there on my 350 later today.

[Luke87gt]

Originally Posted by CAMAROBOY68SS

you actually dont need to change the bracket or Z bar if the motor is still set back in the I6 location. Im still running all my I6 stuff on my clutch setup.

With a small block there should already be a threaded hole kind of in the middle between the dipstick and oil filter and the ball screws into that.

Interesting, so you never had to drill/tap?

I’ve read multiple posts here of i6 to v8 conversations saying that was necessary (in addition to needing to cut 1/2” from the bar)

[Getter-Done]

There is this bracket if you can find or fabricate one.



Here's a frame bracket.
https://www.ebay.com/itm/28584162943...3ABFBM5KXP5qVl


Here some pictures and possibly a place to buy?

https://4speedconversions-com.3dcart...k_linkage.html

[67 twins]

Originally Posted by Luke87gt

Interesting, so you never had to drill/tap?

I’ve read multiple posts here of i6 to v8 conversations saying that was necessary (in addition to needing to cut 1/2” from the bar)

All I know is the stock setup has a bracket. It does not thread into the block.

[Luke87gt]

So there are two holes there for the bracket which is good news.

What I need to figure out now is what do I need in order to connect my 6cyl Zbar to my 350 *if* the engine is to remain in the 6cyl position (set a few inches back from where Chevy put 350 in trucks from the factory)

[pjmoreland]

Since your engine won't be in the standard forward SBC position, a standard SBC bellcrank mount wouldn't be in the right position. I believe you would need one of these studs that screws directly into the forward hole in the engine block.

https://classicparts.com/1963-84-clu...ank-block-stud

[Luke87gt]

Originally Posted by pjmoreland

Since your engine won't be in the standard forward SBC position, a standard SBC bellcrank mount wouldn't be in the right position. I believe you would need one of these studs that screws directly into the forward hole in the engine block.

https://classicparts.com/1963-84-clu...ank-block-stud

Thank you, just ordered it

Although it is surprising to hear it’s the front hole and not the rear hole given that the engine is being set back? I guess it’ll be obvious once the engine is in.

[pjmoreland]

Originally Posted by Luke87gt

Thank you, just ordered it

Although it is surprising to hear it’s the front hole and not the rear hole given that the engine is being set back? I guess it’ll be obvious once the engine is in.

The bellcrank bracket on the frame is in the same position regardless of the engine position. If the engine is moved rearward relative to the stock position, then the engine mounted stud moves forward to compensate.

[Luke87gt]

Visualized that improperly.

You sir are correct, thank you

[pjmoreland]

Post a photo of the rear of the engine. That should help with sorting out whether your engine has a one-piece or two-piece rear main seal. This will help in determining which type of flywheel you will need.

[mr48chev]

Originally Posted by pjmoreland

Post a photo of the rear of the engine. That should help with sorting out whether your engine has a one-piece or two-piece rear main seal. This will help in determining which type of flywheel you will need.

He has an 010 block 4 inch bore two piece seal,

[mr48chev]

When John and I did the swap in his 70 we left the transmission where it was and as I said earlier left the transmission and bellhousing in the truck and unbolted the engine from the bellhousing. Moving the SM465 would have mean cutting a new hole in the floor for the shifter and building a new front half for the drive shaft. In truth I don't believe that the transmission moves be it six or V8 but you move the mounts on the frame back to the V8 spot.

Checking on the rock auto what options for clutches are listed a 250 could come with a 10 or 11 inch clutch and a 350 came with a 11 or 12 inch leg killer clutch. To my way of thinking unless you are going to actually hook onto heavy trailers and tow them or pull stumps you don't really need a 12 inch clutch. I think my 77 454 has one but that is in a 1 ton dual wheel flatbed with a 10 ft bed with a hoist and it might get asked to tow just about any bumper pull trailer that it can handle. If I drive it in traffic very far I have a hard time walking for a bit because my left knee is throwing a fit about the clutch.

[Luke87gt]

If I get an 11” clutch and flywheel, does that mean the position of the starter needs to change?

I also wonder why the part numbers for the 11” clutch kit differ between the i6 and v8

[mr48chev]

Originally Posted by Luke87gt

If I get an 11” clutch and flywheel, does that mean the position of the starter needs to change?

No, the truck should have a 168 tooth flywheel ring gear in it now.

Unless time to get a flywheel and clutch is short and critical and you can't wait for the brown truck to show up or the parts house to get them in I would wait until I pulled the 250 as it could come with a 11 inch clutch and if it has a granny 4 speed it most likely does. You might look on the spid on the glove box door and see if it shows anything for clutch and if you can't figure it out one of the guys here can put on his decoder ring and get the answer. I know where to find the answers for AD trucks but often have to ask for 67/72 on things like that.

[67 twins]

Originally Posted by mr48chev

When John and I did the swap in his 70 we left the transmission where it was and as I said earlier left the transmission and bellhousing in the truck and unbolted the engine from the bellhousing. Moving the SM465 would have mean cutting a new hole in the floor for the shifter and building a new front half for the drive shaft. In truth I don't believe that the transmission moves be it six or V8 but you move the mounts on the frame back to the V8 spot.

Checking on the rock auto what options for clutches are listed a 250 could come with a 10 or 11 inch clutch and a 350 came with a 11 or 12 inch leg killer clutch. To my way of thinking unless you are going to actually hook onto heavy trailers and tow them or pull stumps you don't really need a 12 inch clutch. I think my 77 454 has one but that is in a 1 ton dual wheel flatbed with a 10 ft bed with a hoist and it might get asked to tow just about any bumper pull trailer that it can handle. If I drive it in traffic very far I have a hard time walking for a bit because my left knee is throwing a fit about the clutch.

The bellhousing crossmember is definitely different & further back in the six cylinder truck

[CAMAROBOY68SS]

Originally Posted by Luke87gt

Interesting, so you never had to drill/tap?

I’ve read multiple posts here of i6 to v8 conversations saying that was necessary (in addition to needing to cut 1/2” from the bar)

This is how my whole setup works in my truck.

[MikeB]

Guys, how much room is there for the HEI cap with the engine mounted in the rearward position?