Big Block in 4x4

[brinegar]

Need some input on putting a big block in a 72 4x4. I heard it was a pain, but would like to here from some of you who have done it. It would be an older 400.
Thanks
Bill B

[1969k10stepside]

Clearance issues are in the future if you do it.You can move all the crossmembers forward but new d shafts will be needed.You could add a body lift,or take your favorite hammer to the firewall and make room
I would modify the firewall if I was doing it as I hate body lifts and wouldnt want to move the motor and t case crossmembers forward and have longer d shafts made.

[Bishops Trucks]

I had a 396 in my '71 which was an original 350 truck. The people that put it in didn't change anything, all they did was dent the firewall were the distributor is. You wouldn't have to do that if you get a distributor that is made for tight places.

[Yukon Jack]

A guy over on www.ck5.com is dropping his motor 1 inch by using spacers to drop the engine crossmember - he states that is working for him. Be sure to check out my sig for more info on my bbc install pain.

[Joe Gribben]

check out my sons suburban build we put a 502 in we purchased a universal cross member from summit it works good moved motor forward a couple inches not much 68 suburban buil thread

[brinegar]

Thanks for all the input. That will help me out a bunch. I will post pics. of the project when I get around to it.
Bill

[454_72_4X4]

Originally Posted by Bishops Trucks

I had a 396 in my '71 which was an original 350 truck. The people that put it in didn't change anything, all they did was dent the firewall were the distributor is. You wouldn't have to do that if you get a distributor that is made for tight places.

My distributor fits tight, (big cap HEI) but I didn't have to do any firewall mods for clearance in that area.
Now the valve covers...that was a different story.

[Bishops Trucks]

Originally Posted by 454_72_4X4

My distributor fits tight, (big cap HEI) but I didn't have to do any firewall mods for clearance in that area.
Now the valve covers...that was a different story.

You have the tall valve covers? Mine had the stock low covers on it. I have since taken the bigblock out and put a 350H.O. in it.

[454_72_4X4]

Originally Posted by Bishops Trucks

You have the tall valve covers? Mine had the stock low covers on it. I have since taken the bigblock out and put a 350H.O. in it.

Not really tall covers but they are aftermarket aluminum and probably taller than the stock tin covers.

[Bishops Trucks]

That is tight!

[JAKES 68GMC]

Originally Posted by Bishops Trucks

I had a 396 in my '71 which was an original 350 truck. The people that put it in didn't change anything, all they did was dent the firewall were the distributor is. You wouldn't have to do that if you get a distributor that is made for tight places.

No crossmember or d-shaft mods at all?? It just bolted in the SBC mounts perfectly??? Makes me wanna put a 396 in my truck.

[DieselEater]

I used a motor mount/cross member from an 80'. Also, used rest of drive train from 80' (3/4 ton). Using stock holes in frame for motor mounts...(added some to utilize all bolts on new cross member. Whole set-up ended up forward about 2". Had to extend 4-speed shifter hole a bit. 80' rear shaft too long anyway, so had it shortened to needed length. Front shaft no mods (slip-yoke). This was my first time, and If I had to do it again I would find stock mount/member. I still have very little clearance on valve covers, but lots on distributer.

[Bishops Trucks]

Originally Posted by JAKES 68GMC

No crossmember or d-shaft mods at all?? It just bolted in the SBC mounts perfectly??? Makes me wanna put a 396 in my truck.

No crossmember or driveshaft changes. When I put the smallblock back in I changed the fan shroud and the alt. and powersteering brackets. Whoever put the 396 in it left the small block stands in it and that made the header on the driverside rub the stands. Real tight header clearance.

[tommy knotts]

i had a 427 tall deck in my 1969 k10. a little clearencing the fire wall in valve cover area with BFH.i even ran the truck oil pan,it barely cleared the axle.i ran that old engine for about 15 years,until the truck fell apart.saved engine,junked truck.it would pull all i could haul on my trailer.i had more than one scary moment with them drum brakes.

[454_72_4X4]

Originally Posted by JAKES 68GMC

No crossmember or d-shaft mods at all?? It just bolted in the SBC mounts perfectly??? Makes me wanna put a 396 in my truck.

What alot of people don't seem to understand is that Chevy smallblock and bigblock engines all have the same engine mount and bellhousing dimensions.

Barring external size itself a BB will bolt into anything a SB will. No drivetrain mods required at all.

The next time I have mine apart I'll be swapping to the 73-up crossmember.
4 reasons;
1. The 73-up style motor mounts are much better design than the older ones.
2. Now I have to unbolt the crossmember and slide it forward to remove the engine. (The newer one should eliminate this).
3. With the newer crossmember I can remove the oilpan without removing the crossmember. (Hope I don't have to do that though!)
4. Additional clearance for headers.

[Yukon Jack]

Originally Posted by 454_72_4X4

What alot of people don't seem to understand is that Chevy smallblock and bigblock engines all have the same engine mount and bellhousing dimensions.

Yep, the problem us 67-72 guys run into is the external dimensions of the big block:

Small block dimensions 26 width 28 length 27 height 575lbs
Big block dimensions 28 width 30½ length 29 height 685lbs

That extra height and width cause the firewall issues for the 67-72's.

[Burt4x4]

Kinda hard to see the dent I made in the firewall so the driver's side valve cover would clear. The head it self is about 1/4" away from the sheetmetal.

I started with a 73+ crossmember but then it cracked, I welded the crack but then decided my 454 needs more support under there so I changed to the ORD one:

[JAKES 68GMC]

Originally Posted by Bishops Trucks

No crossmember or driveshaft changes. When I put the smallblock back in I changed the fan shroud and the alt. and powersteering brackets. Whoever put the 396 in it left the small block stands in it and that made the header on the driverside rub the stands. Real tight header clearance.

So, theroetically, I could take a short-deck BBC, get some SBC engine stands and mounts, and bolt a BBC in my truck with a few clearence mods?? Is this a dream, or a dream come true????

[1969k10stepside]

Jake,your gonna kill yourself

[JAKES 68GMC]

Hehehe, I know where theres a running 402 resonably cheap.

[1969k10stepside]

Dibs on the v6 j/k..

[454_72_4X4]

Originally Posted by JAKES 68GMC

So, theroetically, I could take a short-deck BBC, get some SBC engine stands and mounts, and bolt a BBC in my truck with a few clearence mods?? Is this a dream, or a dream come true????

In a word, Yep!

Your dream come true! Better grab that 402!

[JAKES 68GMC]

Thats cool! Maybe a 402 BBC would even make my old GMC smoke some rice. According to the seller, the motor is from a 72 Nova and is in a 78 blazer plowtruck.

[454_72_4X4]

Originally Posted by JAKES 68GMC

Thats cool! Maybe a 402 BBC would even make my old GMC smoke some rice. According to the seller, the motor is from a 72 Nova and is in a 78 blazer plowtruck.

Now that I read your signature, I'm guessing you're thinking about you 68 GMC?
One problem....it's a 4 speed truck. That's a whole new bag of worms.
Clearance and mounts are gravy issues, but the clutch linkage is sorta complicated.
These trucks are designed to use the front pivot hole, (in the engine block) for the clutch Z bar. Since every BB manifold I've ever seen, (and headers too), cover up that pivot hole, you need to use the rear pivot hole in the block but yet retain the angle of the clutch pedal rod that goes through the firewall.
I know of a couple guys that have moved the engine forward for this reason alone.
Personally I'm not a "move it forward" kind of guy, so I fabbed up a linkage system that uses the rear pivot in the engine and retains the stock clutch rod angle going through the firewall.

Before long I'm going to be swapping in a NV4500 5 sp and switching to hydraulic clutch release bearing though...

[1969 GMC]

Originally Posted by 454_72_4X4

Before long I'm going to be swapping in a NV4500 5 sp and switching to hydraulic clutch release bearing though...

there is a thread right now in 67-72 about yukon jack's hydro clutch conversion in his '69 with a 454. a tad more in depth than just swapping engines, but pretty straightforward. that's the route i would take (and who knows, I may anyway?)

novak sells this kit:
http://www.novak-adapt.com/catalog/kit_hcr3.htm

its a bit cheaper than you usually have to fork out for factory hydro clutch parts (which probably need replaced after 20 or so years of use anyway), and kinda cool too.