Swapping Straight 6 (I6) to newer style 350 or 454

[grancuda]

My daily driver I6 is just about done, I put 35,000 miles on it in the past year and a half and it is very sick so I need to start gathering parts for swapping to a V8. I am searching craigslist and salvages for low mileage, good running long blocks and I am either going with a TBI based 350(running a carb), a Vortec 350(running a carb) or a '96 454 Vortec(running a carb).

The thing I am most uncertain about swapping is the motor mount arrangement, do I keep the current frame mount but move it forward and what style motor mount is best with headers.

Do each of the motors above have provisions for the clutch Z-bar(bell crank) in the side of the block and do each have provisions for a Pilot bushing and if so is it just the stock pilot bushing or a special one for running an old Saginaw 3 speed behind a newer motor

Is there a way I can mount my alternator on the drivers side down low since that is where the factory wiring is now, I have no power steering or air so hopefully there is something I can do there.

[lyrikz]

Originally Posted by grancuda

My daily driver I6 is just about done, I put 35,000 miles on it in the past year and a half and it is very sick so I need to start gathering parts for swapping to a V8. I am searching craigslist and salvages for low mileage, good running long blocks and I am either going with a TBI based 350(running a carb), a Vortec 350(running a carb) or a '96 454 Vortec(running a carb).

The thing I am most uncertain about swapping is the motor mount arrangement, do I keep the current frame mount but move it forward and what style motor mount is best with headers.

Do each of the motors above have provisions for the clutch Z-bar(bell crank) in the side of the block and do each have provisions for a Pilot bushing and if so is it just the stock pilot bushing or a special one for running an old Saginaw 3 speed behind a newer motor

Is there a way I can mount my alternator on the drivers side down low since that is where the factory wiring is now, I have no power steering or air so hopefully there is something I can do there.

I kinda JUST went through this. I put in a 454. I just purchased after market mount kit for 100 bucks and mounted them on the forward bolt holes. Everything clears beautifully. As for the transmission, id just pick up a th350 or 400.. I have heard you can run the saginaw (which i had) but i couldnt find info on how to...

As for the alternator, im sure you can find someway to run it where you want to run it.. I know on the driver side of my motor the PS pump is there... But im sure you can figure some way to move the alt over there.. Or just spend a few mins and extend the wires... If you go to my build thread you will see the mounts i used and where i put them...

[grancuda]

I guess my main concern is the tranny then because I want to keep the 3 on the tree because the inteior of the truck is 100% stock and it was a garage kept low mileage truck. I just want a v8 for more towing power(have a 2800lb boat) and a better sound. I am planning on keeping it a stock look under the hood with exception of headers and a aluminium intake which will probably end up orange.

[lyrikz]

Originally Posted by grancuda

I guess my main concern is the tranny then because I want to keep the 3 on the tree because the inteior of the truck is 100% stock and it was a garage kept low mileage truck. I just want a v8 for more towing power(have a 2800lb boat) and a better sound. I am planning on keeping it a stock look under the hood with exception of headers and a aluminium intake which will probably end up orange.

From what i have read it bolts up to a 350.... If you cant find the info your just gonna have to investigate it yourself and try it.... it should work.

[grancuda]

From what I have read, I need to find some motor mount brackets for the engine side, and leave the frame motor brackets in the back holes, screw a ball mount to the front hole on the side of the small block and leave the tranny where it is and get a 4x4 sbc fan shorud.

I still don't know if the vortec or thorttle body motors have the threaded hole for the ball mount for the Z-bar.

[Tx Firefighter]

Originally Posted by grancuda

From what I have read, I need to find some motor mount brackets for the engine side, and leave the frame motor brackets in the back holes, screw a ball mount to the front hole on the side of the small block and leave the tranny where it is and get a 4x4 sbc fan shorud.

I still don't know if the vortec or thorttle body motors have the threaded hole for the ball mount for the Z-bar.

You are on exactly the right path.

See, factory V8 engines were in the front engine mount holes on the frame. They sat forward of the inline 6 position. To do it "proper", you'd need to get the V8 frame stands and move it forward.

The problem is, you want to keep your truck as original as you can. The factory crossmember under the 3 speed bellhousing is riveted in place. You'd have to cut it out and replace it with a factory V8 under bellhousing crossmember, which is located forward of your present crossmember. This would in turn, require you to lengthen the driveshaft.

The best way, in my opinion, is to install the V8 in the rear holes where the six is now. That way you don't have to monkey with the crossmember or driveshaft. I have personally done it this way a few times and the job is very straightforward.

If the block isn't drilled for the pivot ball to screw into, there will be a flat, blank spot there, where it should be. Simply drill the block and tap the hole. It is very easy to do. Cast iron drill and taps like butter.

As far as the engine mounts, look at what you have now. Notice there is a frame stand, then a rubber mount, then an engine bracket mounted to the block. All you have to do is unbolt the rubber mount from the 6 cylinder engine bracket and bolt it to the V8. Same mount fits both. So, you wind up with the factory frame stands, factory 6 cylinder rubber mount bolted to the V8. No mods required whatsoever.

The present bellhousing will bolt right to the V8 using the same bolts. If you get an earlier small block engine (pre 87) which uses the older type 2 piece rear main seal, your present flywheel and clutch assembly will also bolt to the new V8. Again, no mods required whatsoever. It even uses the same bolts. The starter is bolted to the bellhousing rather than the block on the present inline 6. Simply bolt it right back to the bellhousing when you swap the V8 in place.

So, to sum up, if you get an earlier V8 engine, all of your present clutch, flywheel, starter, bellhousing, everything will 100 percent swap over. This alone is reason enough, for me at least, to use the earlier engine. Finding a manual trans flywheel and clutch assembly for the later model engine is often times quite costly.

Another compelling reason to use an earlier V8 is that the block will accept a mechanical fuel pump. Later model engines are blanked off where the mechanical pump would go, forcing you to run an electric pump instead. Myself, I hate electric pumps. Manual pumps cost less than 20 dollars and last hundreds of thousands of miles.

A generic parts store pilot bushing will tap into place in the V8 crankshaft. Nothing fancy needed there either. The inline 6 and V8 actually use the same part number pilot bushing if you feel the desire to reuse your old one.

Like I said above, I have done this swap myself before, so if you have any more questions, don't hesitate to ask.

[lyrikz]

Originally Posted by Tx Firefighter

You are on exactly the right path.

See, factory V8 engines were in the front engine mount holes on the frame. They sat forward of the inline 6 position. To do it "proper", you'd need to get the V8 frame stands and move it forward.

The problem is, you want to keep your truck as original as you can. The factory crossmember under the 3 speed bellhousing is riveted in place. You'd have to cut it out and replace it with a factory V8 under bellhousing crossmember, which is located forward of your present crossmember. This would in turn, require you to lengthen the driveshaft.

The best way, in my opinion, is to install the V8 in the rear holes where the six is now. That way you don't have to monkey with the crossmember or driveshaft. I have personally done it this way a few times and the job is very straightforward.

If the block isn't drilled for the pivot ball to screw into, there will be a flat, blank spot there, where it should be. Simply drill the block and tap the hole. It is very easy to do. Cast iron drill and taps like butter.

As far as the engine mounts, look at what you have now. Notice there is a frame stand, then a rubber mount, then an engine bracket mounted to the block. All you have to do is unbolt the rubber mount from the 6 cylinder engine bracket and bolt it to the V8. Same mount fits both. So, you wind up with the factory frame stands, factory 6 cylinder rubber mount bolted to the V8. No mods required whatsoever.

The present bellhousing will bolt right to the V8 using the same bolts. If you get an earlier small block engine (pre 87) which uses the older type 2 piece rear main seal, your present flywheel and clutch assembly will also bolt to the new V8. Again, no mods required whatsoever. It even uses the same bolts. The starter is bolted to the bellhousing rather than the block on the present inline 6. Simply bolt it right back to the bellhousing when you swap the V8 in place.

So, to sum up, if you get an earlier V8 engine, all of your present clutch, flywheel, starter, bellhousing, everything will 100 percent swap over. This alone is reason enough, for me at least, to use the earlier engine. Finding a manual trans flywheel and clutch assembly for the later model engine is often times quite costly.

Another compelling reason to use an earlier V8 is that the block will accept a mechanical fuel pump. Later model engines are blanked off where the mechanical pump would go, forcing you to run an electric pump instead. Myself, I hate electric pumps. Manual pumps cost less than 20 dollars and last hundreds of thousands of miles.

A generic parts store pilot bushing will tap into place in the V8 crankshaft. Nothing fancy needed there either. The inline 6 and V8 actually use the same part number pilot bushing if you feel the desire to reuse your old one.

Like I said above, I have done this swap myself before, so if you have any more questions, don't hesitate to ask.

Wholey ****, pardon my french, AWESOME FRIGGIN POST. Rep points coming your way...

[Tx Firefighter]

I appreciate the comment.

This is one subject that I have learned the hard way, out in my shop, scratching my head and figuring. I want to make sure this fellow is steered in the right direction and doesn't waste any money on bum steers.

[grancuda]

I have read somewhere the flywheel will work with the late model stuff up to the LS series stuff. What flywheel is required for this? I would like to get the roller cam and 1 piece seal for longevity.

[Tx Firefighter]

Originally Posted by grancuda

I have read somewhere the flywheel will work with the late model stuff up to the LS series stuff. What flywheel is required for this? I would like to get the roller cam and 1 piece seal for longevity.

That's bad information. GM changed the flywheel in 87 when they went to 1 piece rear seals. No doubt about that.

[grancuda]

Are the late model 454 motors the same as the late model 350s ?

[grancuda]

Originally Posted by Tx Firefighter

You are on exactly the right path.

See, factory V8 engines were in the front engine mount holes on the frame. They sat forward of the inline 6 position. To do it "proper", you'd need to get the V8 frame stands and move it forward.

The problem is, you want to keep your truck as original as you can. The factory crossmember under the 3 speed bellhousing is riveted in place. You'd have to cut it out and replace it with a factory V8 under bellhousing crossmember, which is located forward of your present crossmember. This would in turn, require you to lengthen the driveshaft.

The best way, in my opinion, is to install the V8 in the rear holes where the six is now. That way you don't have to monkey with the crossmember or driveshaft. I have personally done it this way a few times and the job is very straightforward.

If the block isn't drilled for the pivot ball to screw into, there will be a flat, blank spot there, where it should be. Simply drill the block and tap the hole. It is very easy to do. Cast iron drill and taps like butter.

As far as the engine mounts, look at what you have now. Notice there is a frame stand, then a rubber mount, then an engine bracket mounted to the block. All you have to do is unbolt the rubber mount from the 6 cylinder engine bracket and bolt it to the V8. Same mount fits both. So, you wind up with the factory frame stands, factory 6 cylinder rubber mount bolted to the V8. No mods required whatsoever.

The present bellhousing will bolt right to the V8 using the same bolts. If you get an earlier small block engine (pre 87) which uses the older type 2 piece rear main seal, your present flywheel and clutch assembly will also bolt to the new V8. Again, no mods required whatsoever. It even uses the same bolts. The starter is bolted to the bellhousing rather than the block on the present inline 6. Simply bolt it right back to the bellhousing when you swap the V8 in place.

So, to sum up, if you get an earlier V8 engine, all of your present clutch, flywheel, starter, bellhousing, everything will 100 percent swap over. This alone is reason enough, for me at least, to use the earlier engine. Finding a manual trans flywheel and clutch assembly for the later model engine is often times quite costly.

Another compelling reason to use an earlier V8 is that the block will accept a mechanical fuel pump. Later model engines are blanked off where the mechanical pump would go, forcing you to run an electric pump instead. Myself, I hate electric pumps. Manual pumps cost less than 20 dollars and last hundreds of thousands of miles.

A generic parts store pilot bushing will tap into place in the V8 crankshaft. Nothing fancy needed there either. The inline 6 and V8 actually use the same part number pilot bushing if you feel the desire to reuse your old one.

Like I said above, I have done this swap myself before, so if you have any more questions, don't hesitate to ask.

So do I need a new zbar pivot ball or do I just flip around the bracket that is holding the one on the exisitng v8(it is the factory setup that came out of a '71 w/3speed, that is where I ended up getting a motor). I am going to be putting this back in this weekend and I don't want to stab it in too many times.

[Tx Firefighter]

You need one of these to screw into the front threaded hole. It will run you about 12 bucks from any GM muscle car supply place.

[TDs6t9]

When I did mine, I used the z bar bracket you have the picture of, mounted just as you have it. I have a '69. The engine I used is a 350 from a 1975 Corvette. I am not sure if headers will clear so I am using rams horn with center dump. Everything bolted right up. I was pleasently surprised at the ease of it all. Did not have to lengthen drive shaft.Used the same flywheel off the original 6. It was very straight forward. The only thing I really need to add is a fan shroud as I still have the single core radiator. It will stay around 200 degrees even in the summer in heavy traffic.

[Slik69]

These have been my favorite swaps. 6's for 8's. Have done it many times on several make cars. I like your truck. Can you send me a pics of the rest of it so I can see how it look. Nice looking inside.

Good luck with it.

[grancuda]

I got the motor in and bolted up and the z-bar linned up perfectly and so did the motor mounts. The only problem so far is the drivers manifold, it is the stock v8 ram horn manifold and it angles back, I am guessing it needs to be a straight down outlet? Anyone know what the application is of the straight down manifold, would it be for a 4x4? I am hoping to find it tomorrow at the local parts houses. Any info & part numbers would be greatly appreciated, trying to get it back on the road this Friday.

[zermoa4]

Is all of this info still comparable on a 73-87? Or did they change the motor mounts or anything like that?

[grancuda]

Well, here are a couple of pics after the swap

[Mark B]

This is great stuff. Very helpful. I hope to do this swap someday, so please keep the information rolling!

thanks
Mark

[made2drag]

sorry to bring this thread back to life but grancuda did you use the stock straight 6 factory frame stands and not move them? im researching putting a 93 tbi 350 in mine and wondered if it would bolt in on the existing straight 6 mounts and I was also wondering if the th400 would just need a new crossmember to hold it or would there be a way to mount to the 3 speed manual mount? Thanks

[Luke87gt]

Sorry to raise an old thread but it covers a lot of what I’m curious about

I understand that a 350 can bolt into the same location as the i6 so the trans/driveshaft can stay in its same location.

What about 396 or 454?

[Snarf]

Originally Posted by Luke87gt

Sorry to raise an old thread but it covers a lot of what I’m curious about

I understand that a 350 can bolt into the same location as the i6 so the trans/driveshaft can stay in its same location.

What about 396 or 454?

I have these questions also with a BB...