Big block into 71? Crossmember built
 

Going to put the 454/ TH400/ Doubler into the 71. It is currently in an 83 frame. What do I need to know about motor mounts? Will the ones from the 83 fit? Crossmember clearance? It has HEI and tall valve cover to cleare roller rockers. I am putting a 1" body lift on the rig. Will I need to do some creative BFH mods to firewall to fit it? It also has hedman headers, will they fit? Looking in a jegs mag it looks like the application could be the same. Any other tips regarding the swap?Thanks

Re: Big block into 71?
 

as long as the 83 frame has v8 mounts you are all good to go. bbc is a direct swap in the 73+.

Re: Big block into 71?
 

Talk to a couple of guys on the 4x4 forum. I have heard many different ways depending.......
A good start would be to use al the brackets, crossmembers etc off the 83, install the lift and get out the measuring tape.
I am in the process of putting a 83 6.2 diesel in a 68 burb frame with a 72 body, it started out being a BB swap. the BB and the diesel use the same mounts. I had it mocked up using the 83 stuff, crossmember etc and measured it, it was close but looked like it would work.

Re: Big block into 71?
 

I put a 369 in my 71 after the sbc with south. I took it out after realizing that it would require me to either move it forward or put a body lift. From my experience I would say that at least a 2 inch body lift would be necessary. I don't think 1 inch would be adequate. Mine had the MSD pro billet distributor and stock valve covers ( I originally had tall aluminum ones but sent them back as they wouldn't clear ). Also I noticed your putting an automatic in it instead of the 4 speed, that's good because the clutch linkage posed another problem for me with headers and clearance in general.

Re: Big block into 71?
 

Have you tried the search function? :gi:
There's been several (lots) of big block threads over the last year or so, I'm sure there's great post's with tons of info that have been all but forgotten about.

I can think of three right off...
*Yukon Jack
*Burt4x4
*Orangeuoval
All these had threads going not to long ago about their installs.

Re: Big block into 71?
 

i read through alot of old posts but haven't really figured out what way to go it really the "best". I think I am going to go with the 83 crossmember so hopefully my headers fit. I think that is my biggest thing is header fitment and how far forward to move crossmember. Maybe I should drill it for 1" more forward and another set for 2" forward then if 1" isn't enough I can just slide it ahead

Re: Big block into 71?
 

I have a 72 blazer with a 454 HEI, th400, np205, 6" spring lift, 44/14ff. The PO pounded the heck out of the fire wall to fit the distributor. Since I got it, the engine has been moved forwad 2".

Without moving the engine, the top frame rail needed to be trimed 1/4"x2" to fit the headers, and the old headers were dented by the frame. With the engine moved, they fit well (trimming still there)

I did not have tall valve covers when I removed the motor, but have bought them to put on my rebuilt 496 when I get it back next week. :metal:

The body lift will not be necessary if you move the motor forward.

Re: Big block into 71?
 

sweet, that is alot of the info I was after. looks like you are using the stock crossmember? Is that the stock motor mount or the newer style? Also what application of header are you using? thank you kindly

Re: Big block into 71?
 

I did the 454 swap into my '72 3/4ton 4x4. I did a 3" body lift and had no clearance issues. Itwas a 4-speed and my only issue was the headers. I went through 3 sets all of which had problems with clutch pivot, Finally bought a set of Hookers-problem solved, they fit great.


Shane

Re: Big block into 71?
 

I bought headman elite, but they are not on the truck now. Still waiting for the 454, .20 over 450 HP, 550 torque:metal:

Sould be soon.

The motor mounts needed to be changed when I bought it, and the cross member is custom.

Alot of good stuff was done to the truck before I bought it, but the #1 upgrade I did was the rear disc brakes. Now it stops on a dime, with no skidding.

Re: Big block into 71?
 

rear disks rock. The 14FF i am putting in rear has disks, 4.56 gears, detroit locker, and a diff cover I built out of 3/8" plate, and tringulated shocks.

Re: Big block into 71?
 

well got then 350/465/205 out this weekend and got my 454/th400 out of the other rig and ready to strat the swap. I want to move the engine forward an inch or so forward for firewall clearance and driveline lengths. Here are the 80s style engine mount towers bolted in the frame with the center of mounts roughly 1 inch forward. I messed around with the 80s style crossmember but it looks like a hack job to use it so gonna build something like this out of 1.5x3/16" sq tube. Opinions?

I already have the scale blueprints drawn out. Should have 1" clearance from oil pan. This drawing was just for visiual aid.

Re: Big block into 71?
 

went ahead and built a crossmember out of1.5" 3/16 sq tube. Just need to make mounting holes and tabs.

Re: Big block into 71?
 

get the big block in tonight. More better pics on my digital camera i left at work. Had to do some creative beating on the firewall to clear valve covers and i pulled the master cylinder to drop it in. Tranny isn't in yet so it is laying back right now.

Re: Big block into 71?
 

How soon do you think it will be before you get to take it for a test drive?

Re: Big block into 71?
 

i'll get the tranny in tomarrow. Procrastinating today... then see how well the doubler fits in the floorboard and go from there. Gott put the 60 in the front and the power steering/crossover box in too.. then shafts....

Re: Big block into 71?
 

Cool! Big Blocks are fun :metal:

Re: Big block into 71?
 

sick:metal:

Re: Big block into 71?
 

got the th400 bolted up and the headers and such installed. Got the external regulator removed and re-wired for internal reg alt. Still gotta rewire for HEI and find a place to mount my fuel pump. Still waiting on getting body mounts to put doubler in and finish it up.

Re: Big block into 71?
 

I wish I had a 150 dollar blazer to modify the heck out of, lucky guy.