6 cyl to 8 swap flywheel ?

[Downtown]

my brother-in-law has a 67 GMC 3 speed inline six. He wants to put in a 350 and keep the 3 speed trans. Will the flywheel off the 6 cyl bolt up to the 350? Anything else you want to add to the swap. He knows he needs to move the motor mounts forward.

[Tx Firefighter]

As long as it is the pre 87 small block with the two piece rear main seal. The flywheel, clutch, starter all will work.

Leave the engine mounts alone. Just drop the 350 right in where the 6 was. You don't have to move anything.

Last 6 to 8 swap I did this exact same thing. Reused all the 6 flywheel and clutch stuff. Same engine mounts too. The mounts unbolt from the 6 cyl brackets and bolt straight to the V8 block. I even reused the 6 cyl radiator with no problems. The whole swap to about 3 1/2 hours. The engine was still warm when I set it on the floor.

Make sure you have the clutch pivot ball that screws into the threaded hole above the oil filter on the side of the block. GM dealer if you need it. Re use the clutch linkage and z-bar.

Kevin

[1972ChevyGuy]

I beleive you can mount the sb in the I6 position and bolt it right up to the flywheel. Hard time to get to the distributor but it saved me some $$ on new mounts. Also, I have a 10.5" clutch instead of the v8 11" or 11.5? It has held up though.

[Tx Firefighter]

I forgot, you will need to build a longer rod for the accelerator hook up to the carb.

I used Hooker Comp headers and they cleared everything including the clutch z-bar, even though the engine was back in the 6 cylinder position.

[crazy longhorn]

I 3rd that swap on the 250 stands......no driveline or bell crossmember issue to deal with(the bell crossmember is different from I6 to V8). My longhorn is set up that way, & has #2452 Hooker comps(60690 headmans will also work). The HEI dist does fit a little tight. good luck,crazyL

[Downtown]

Thanks Kevin, 72chevyguy, and longhorn. I will pass this information on to him.

Mark

PS: Kevin I sent you a PM about some parts.

[72shorty]

Did I hear you guys correctly...you can drop the SBC right in where the L6 was using same motor mounts? Giddy up! That will save some money when I get to that point. Thanks guys!

[CPNE]

Originally posted by 72shorty
Did I hear you guys correctly...you can drop the SBC right in where the L6 was using same motor mounts? Giddy up! That will save some money when I get to that point. Thanks guys!

Except you'll run into fan shroud issues and clutch/or tranny linkage issues. You'll have to fabricate and/or improvise/compromise on these items. Plus when it comes to parts chasing you'll never know whether the part you need is for a I6 or the V8 application because of the configuration. If you're good at fabricating and like these headaches then by all means the 8 in the 6 position will work. I believe the people who favored this method are extremely talented and creative with fabricating and engineering skills, so the veiwpoint I propose doesn't enter their minds as an issue.

But for the rest of us with limited skills, equipment and time resources...

If you're like me and prefer to have all the parts work and fit out of the box, then I suggest you take the time and effort up front and mount the motor and tranny in the location as intended by the engineers. You'll have to locate a few extra parts up front and lengthen your driveshaft, but this approach virtually guarantees any aftermarket or stock part you'll need/want in the future will fit as designed.

A lot people disagree with me on this, but I'm driving while they're cussing, fabricating, and scratching their heads.

Like the old Fram filter commercial "You can pay me now...or you can pay me later..."

[Classic Heartbeat]

I agree with Jeff on this one, and I would also like to add that the V-8 in the 6 cylinder possition is a dead give a way to this modification. This is another reason why I wont do things that way. I like for someone to open the hood of my truck and not tell that it ever has been modified. I purchased a 68 that had been converted that way, and had nothing but trouble with the re-ingineered clutch linkage.. I could never figure out why someone who is spending big bucks restoring, and modifying their truck wouldn't take the extra time and effort to move the engine forward. The largest expence would be the driveline, but in the big picture this isn't a huge expence. If someone was in a pinch I could understand, but I guess to each his own. That is what makes these truck so fun. They are easy to work on and modify. WES www.ClassicHeartbeat.com

[CPNE]

I agree with Jeff on this one

Wes, you're going to lose your good name and reputation with statements like this.

All I have to say to the I6 position guys is :p

[tom hand]

Originally posted by CPNE


Except you'll run into fan shroud issues and clutch/or tranny linkage issues.

This was the first engine swap I ever did...I was 17 years old and had no experence...it was a piece of cake. Putting the V-8 in the I-6 position saves you a bunch of money. I have never had any clutch/tranny issues. And having the motor set back allows you to run long waterpump brackets which are much more plentiful at the junkyard and a better design to boot. The long waterpump puts the fan in the perfect place for the stock shroud.

[CPNE]

the motor set back allows you to run long waterpump brackets

True but that's just another one of the "issues" I was referring too. Now you have to change brackets, pulleys, belts, PS gearbox, and on and on.

Again, small issues if you're aware of them and mechanically inclined, but big issues if you inherit or embark on such a swap uninformed. Imaging going to NAPA and asking for an alternator belt for a 72 350 which you assume is stock, not knowing better. You get the wrong belt and a lot of frustration to boot.

Again, my point was that giving advise based on personal experience no matter how well intended and how good it is, needs to be tempered with the caveat that you're assuming the recipient of said advise has same level of knowledge and expertise.

That being said, for some of us just trying to refurbish an old truck with limited resources, it's better to travel as close to conventional as possible. Nowhere did I say anyone's ideas were wrong or incorrect, I was just trying to impress on these guys that its not necessarilly the "slam dunk" it sounds like and they need to consider their own personal circumstances before saying "cool, I can do that".

[Classic Heartbeat]

Well said Jeff... Somewhere down the line the truck will be sold and resold. The issue isn't generaly for the person doing the swap, however it becomes an issue for anyone who buys the truck down the line. WES www.ClassicHeartbeat.com

[1972ChevyGuy]

Thats a good point WES. Didnt think about that... (I was young, and had no $$ ) One problem though with the I6 position... its HARD to run headers, the clutch linkage is just in the way, but if you like manifolds go for it. There are a few brands of headers that will fit but I cant think of them off the top of my head - Jeremy

[shadetree]

It takes all types to make this world go around. Me, I like to fab and scratch my head (lice?). I can understand, though, those who strive to keep a vehicle "correct". To keep my head scratching at a minimum, I use a small "parts book". This book tells me that the water pump (example) is a 1975, for belt, pump itself, ect. I often have trouble with pep boys types, who SEE my 72 truck, and HEAR me say "1975". hehe, I love it.

[tom hand]

Well what I was trying to say is unless the person has a v-8 truck sitting there to rob all the parts off of, it would be much easier for a person that was less "mechanically inclined" to put the V-8 in the I-6 position, than to round up all the parts and modifications it takes to do it correctly. Again unless you have a parts truck, you have to round up brackets, pulleys, belts, PS gearbox, anyway...why not try to look for some that are easy to find. And I don't know what NAPA you're going to, but around here you better have the mesurement, number, or old belt with you or you will get the wrong one anyway...lol

[crazy longhorn]

Clutch linkage & headers is not an issue in I 6 position......I have run both Headman(69090), & Hooker(2452). The mods to the linkage are very simple, & the clutch works fine As far as brackets /pulleys on the front......if you are swapping, you are looking for parts.......what will you find more of in the boneyards? My bet will be 73 up pcs! For the guys doing a "resto", disreguard this post......for the rest that want cheap, & AVAILABLE parts, the 73 up pcs can be very easily adapted A 75 C10 gave up a bunch of parts to my old longhorn......now I dont need to worry about finding some of those obsolete parts. CrazyL

[CPNE]

To keep my head scratching at a minimum, I use a small "parts book".

Shadetree to new owner he just sold his vehicle too:

"Owner's manual? No, don't have it. I did have one but I replaced it with the Hollanders Interchange manual you'll find under the seat. Comes in handy when you want to change the plugs." (J/K).

Again unless you have a parts truck

You mean having a parts truck is optional?

As usual there's good arguments either way, and no wrong way to do it (but my way is more correct :p )

[CPNE]

Originally posted by crazy longhorn
Clutch linkage & headers is not an issue in I 6 position......I have run both Headman(69090), & Hooker(2452). The mods to the linkage are very simple, & the clutch works fine As far as brackets /pulleys on the front......if you are swapping, you are looking for parts.......what will you find more of in the boneyards? My bet will be 73 up pcs! For the guys doing a "resto", disreguard this post......for the rest that want cheap, & AVAILABLE parts, the 73 up pcs can be very easily adapted A 75 C10 gave up a bunch of parts to my old longhorn......now I dont need to worry about finding some of those obsolete parts. CrazyL

For those not so mechanically gifted please note the careful use of the words "mods" and "adapted". Always read the fine print kiddos. And 've never had a problem finding pre-73 pulleys, brackets, linkage, etc for small blocks.

[Tx Firefighter]

I did the V8 into stock 6 cyl place using Hooker Comp headers. The V8 used a screw in pivot ball which screws into the block right above the oil filter. The clutch linkage lined up perfect with zero mods at all. Simple R&R. Repeat no mods at all to the clutch linkage, other than readjusting the clutch afterwards

[CPNE]

Originally posted by Tx Firefighter
I did the V8 into stock 6 cyl place using Hooker Comp headers. The V8 used a screw in pivot ball which screws into the block right above the oil filter. The clutch linkage lined up perfect with zero mods at all. Simple R&R. Repeat no mods at all to the clutch linkage, other than readjusting the clutch afterwards

That is exactly what the v8 4x4 set up is as well so no argument there, except to point out you had the benefit of knowing about the 4x4 ball stud and that the I6 bracket would not work (which I think qualifies as a modification to the existing linkage, albiet trivial). To your credit you did mention this fact in your original post.

Again, everybody is missing my point so it warrants repeating (my turn to roll eyes ):

Again, my point was that giving advise based on personal experience no matter how well intended and how good it is, needs to be tempered with the caveat that you're assuming the recipient of said advise has same level of knowledge and expertise.

That being said, for some of us just trying to refurbish an old truck with limited resources, it's better to travel as close to conventional as possible. Nowhere did I say anyone's ideas were wrong or incorrect, I was just trying to impress on these guys that its not necessarilly the "slam dunk" it sounds like and they need to consider their own personal circumstances before saying "cool, I can do that".

[tom hand]

Originally posted by CPNE


And 've never had a problem finding pre-73 pulleys, brackets, linkage, etc for small blocks.

Cause when the salt gets through with 'em, that all that's left

[CPNE]

Originally posted by tom hand



Cause when the salt gets through with 'em, that all that's left

LOL. There is a lot of truth to what you said. The life expectancy of a vehicle is far less here because the bodies tend to rot off the frame far sooner than the engines wear out. So when you find one for parts, it usually has all it's original equipment, making the type of swap we're talking about in the manner I suggest a "slam dunk" as noones ever boogered them up.