'79 K5: SBC to BBC Swap, what do I need?

[guido666]

I have a '79 K5 Blazer with a I6-250 and a 4-speed manual. I threw a rod and broke the block. I have a 454 I was building up but wasn't expecting to have to put it in this soon. What am I going to need to change to put it in?

Bell housing? Mounts?

I have a new radiator for it by the way, six core I think. I also have a new ceneter force clutch and flywheel (are there different flywheels for the different BBCs?).

I plan to do the work this weekend, and I'm wondering what all I need to get/modify/do to make the changeover smooth.

 

[K5er4Life]

dont qoute me on this but I do think the flywheels are different, the bellhousing should be the same, and I am pretty darn sure the engine mounts are different. But it seems to me that when switching from a sbc to bbc that it was just a matter of bolting on the mounts to a different hole than what is used for the sbc. like I said, dont qoute me on this and I am sure someone can explain the different mount position than I. Oh and if the radiator if for a stock bbc than it is a 4 core and you might have to run fuel lines in a different location. Thats all I can think of right now but as seeing I have never done a bbc swap I can only guess for the most part. godd luck with it and enjoy big block chevy power.

 

[supersize75k5]

motor mounts..same
tranny bolt up...same

flywheel...different, a 454 is an externally balanced motor

fuel lines are the same ect.

exhaust...different!

you should have no issue plopping her in there, that the beauty of dealing with chevy's, I would recommend putting a 4 core in there, in the members parts # section, someone mentioned one from a vendor for less than 150.00 shipped if I remember correctly. I however was able to get by on a 3 core for a long time, at one point I drove on a 2 core for a couple weeks!


while your in there and the motor is out make sure to check for cracks in the crossmember, and on the frame, they are alot easier to fix when you have the motor out..


any questions just ask, sad to say I have gone from small block to big block and back way toomany times for my young age


enjoy the throttle!!!

 

[supersize75k5]

dont qoute me on this but I do think the flywheels are different, the bellhousing should be the same, and I am pretty darn sure the engine mounts are different. But it seems to me that when switching from a sbc to bbc that it was just a matter of bolting on the mounts to a different hole than what is used for the sbc. like I said, dont qoute me on this and I am sure someone can explain the different mount position than I. Oh and if the radiator if for a stock bbc than it is a 4 core and you might have to run fuel lines in a different location. Thats all I can think of right now but as seeing I have never done a bbc swap I can only guess for the most part. godd luck with it and enjoy big block chevy power.[/QUOTE

the motor mount issues arise on the 67-72 c-series trucks, they used different motor mount towers.

also look out for that brake booster and fire wall clearance when installing it, keep you dist. cap off just in case!

-shawn

 

[bigbadchev84]

the bbc flywheel for a 454 has a counter wieght on it, and i know that a 396 can use a 350 flywheel, but the 454 needs a specific one

 

[supersize75k5]

the bbc flywheel for a 454 has a counter wieght on it, and i know that a 396 can use a 350 flywheel, but the 454 needs a specific one

thats right, also I just remembered, its the 454 and the 400 that have specific flywheels...memory is just kickin in

 

[guido666]

I have a flywheel I was told was for the 454. I bought it a long time ago. Is there any way I can identify it? It has a part number N6668866 cast into it. Can anyone tell me if it is correct?

 

[diesel4me]

Hollander interchange manual

A junkyard 's Hollander Interchange book will likely have the casting # listed,but you'll have too look at all the listings for 454's to find it...maybe someone here knows of a website with casting # listings for flywheels...

You will have to move the motor mount pads to the other set of holes in the crossmember when going from a 6 to a V8,the bolts suck to get at(ask me how I know! )--pretty much everything from the 6 will work except the flywheel,radiator,hoses,exhaust,some wires might not reach and need some modifications -the throttle cable may not work in some cases,but basically its a bolt in swap--since your truck was a 6 cylinder,it likley has fairly low rear end gears--you will love the acceleration!--putting a 305 in my 79 C10 that came with a 250 made a world of difference--I have to be careful not to "light em up" when I take off from a stop now!..

 

[supersize75k5]

ahhhh crap


I just read you have an I-6

sorry!

 

[guido666]

Just from looking, I don't really see another set of holes where the mounts will bolt to the frame crossmember. The engine is still in there mind you. Do I move the whole crossmember, or just the mount around on the crossmember?

What's wrong with the I6? It was a good engine. The person I bought it from did some nice work on it, and put Roades lifters in it that added some punch. It was a little underpowered for a 5000lb vehicle, but it ran very well. Had I not thrown a rod, it would have lasted a long time I imagine.

 

[jtl_77]

Use a short bowl style fuel pump. The tall bowl style will hit your cross member. Atleast it did on the first 2 I've done. The last 2 went right with the short style.

 

[guido666]

Do you know a year/model that the style fuel pump came off of so that I can ask for it at the auto parts store?

 

[jtl_77]

I don't remember off hand . Just picked up one 2 nights ago at advanced auto for a friend , parts guy kept changing years, vehicles and all where the long style. after about 10 different tries he walked back and opened boxes till he found one . For mine I ordered it from jegs.

 

[guido666]

Ok, upon further inspection (after looking through some parts interchange manual and noticing that all the flywheel casting numbers start in "3") I realized I was reading the numbers upside down. The number is 3988999N. Can anyone give me any info on this one?