Big Block Swap How-To

[69-350]

I've got a little request here... I guess I've got a 454 lined up that I am going to buy and shove into my 69. So I wanted to come along here and hopefully get a fairly clean, easy-to-read thread stuffed with good ideas, tips, etc to create a good little How-To thread for future reference by anybody hoping to swap a big block.

First off, I would like some information and maybe some tips on everything I need.
My '69 was an Inline-6 truck, somebody shoved a 350 in there, and now I want to convert that to a 454 (that thing's powertrain is moving up in the world, ain't it? ) which is from a 79 4WD Chevy.

-Starting with the engine, should I have to move the transmission forward any to be able to hook it up to the new big block? Will I have to modify the cab to fit the big block in there?
-Also, will my original 1969 4-Spd Tranny hook directly up to that 1979 454?
-What motor mounts should I go with?
-Anything else with bolting the engine in that I should know?

Next, comes non-engine parts, such as suspension/steering, etc.
-What do I need for steering parts?
-This 1979's 454 comes with Pwr Steering, how can I go about to converting this so it can work on my 69? (or removing it all together, is an option)
-Should I replace any stock Inline-6 suspension parts? Will the suspension sag too much?

After the basic installation, parts swapping, I guess comes wrapping up with the installation of a nice big block, including Wiring, Misc. things, and little odd jobs.
-What do I need to do for wiring? What do I need to modify for wiring?
-Anything else I need to do past the drop in, bolt in, wire in?
-What outside of the engine bay area needs to be modified? (including inside of the cab, etc)
-Anything else I missed or need to know about swapping in this Big Block pushing 454 cubic inches of Chevy fire-power?

All creative, productive, and helpful posts are more than welcome, and anyone who can give me and anyone else who reads this thread some help to install this 454 at least semi-professional (or semi-rednecked) is more than welcome to post their input. Thanks in advance!

[ChevyDude]

I am by no means the big block expert, But I can tell you the first thing you need to do is locate some Big block engine towers, without those your 454 cannot sit in the engine compartment. Oh and by the way, hang on to your wallet when looking for the towers,,,,they can be spendy! And speaking of spendy, you'll need a good chunk of change to do this right! Good Luck.

[69-350]

Yup, yup! Towers and mounts for sure. Keep on with the advice here (I really think somebody should compile all the info they can and make a good guide on swapping in a big block for the boards) Oh yeah, and I'm pretty sure I'm going to have to move my tranny forward, won't I? I've got a two-piece V8-position driveshaft already, I'm hoping that'll do... Anyways, more advice, help, tips and info would be much appreciated, I want to collect every bit of info I can about the correct way to do a swap.

[AKChevyman]

The tranny doesn't have to go any where and it will bolt right up to the back of the 454. As for modifing the cab no need these trucks came factory with the bigblocks. The wiring is the same from small block to big and you can even reuse your distributor. If you truck doesn't have PS now then you will need a new gear box. The front suspension may need new springs but I am not 100% on this. Now I am not sure about Manual trannies but you may have to upgrade the clutch to handle the extra power but someone with more experiance in that area can help. If I am way off base here other people will correct me and that is fine.

[ChevyDude]

You are correct, Tranny bolts right to big block, BB sits in the forward mounts on the frame. Front springs should be changed to handle the additional weight. Power steering would be a "must" for me. Someone who has done this swap will chime in.

[69-350]

I know the BB will bolt right to my 4 Speed, I know springs need to be changed (eventually...) One more thing, I think the towers right now are in the I6 spot (I don't even know if they're correct SBC mounts and towers, I'd have to check, it's been a while since I've looked that hard under my hood) so when I dump the SBC and put the BBC in there, I'll probably have issues with it sitting so far back, right?

As for steering, if I want to stay with manual steering for right now, can I reuse anything with my old steering (box, etc)?
Anything else you guys know?

[Torque]

I too am interested in the 454 swap 69-350 has asked about in this thread. I can handle all the adaptation between a sbc and a bbc but just need to know what PARTS are required to do the swap....

[72gmcshorty]

You will have small clearance issue with aftermarket headers. I had to grind a half inch moon shape on the passenger side frame for header pipe.

[corn]

Ive seen them bolted to small block towers with no problems except exhaust manifolds. Headers will cure that problem. Theres a guy down the street from me that has a 454 in his on small block mounts & has chevelle headers in it. I think it may sit a little lower in the frame with small mounts so thats probably the exhaust issue. He has a tunnel ram on it with dual carbs & they sit under the hood without the aircleaners. I have a tall intake with a single carb & had to take my 1" carb spacer off so the air cleaner would clear the hood on mine with a factory big block...

[farmtruckIII]

I have a list of do's and don't do's if ya need them.

[Torque]

Originally Posted by cornfed63

Ive seen them bolted to small block towers with no problems except exhaust manifolds. Headers will cure that problem. Theres a guy down the street from me that has a 454 in his on small block mounts & has chevelle headers in it. I think it may sit a little lower in the frame with small mounts so thats probably the exhaust issue. He has a tunnel ram on it with dual carbs & they sit under the hood without the aircleaners. I have a tall intake with a single carb & had to take my 1" carb spacer off so the air cleaner would clear the hood on mine with a factory big block...

I would have never came to that conclusion. I am planning for 454 with a dual-quad tunnel ram intake and a large nitrous system. As for the potential exhaust issues, I am a journeyman welder and can fab-up some headers if need be, so that's not a problem. Will the small block towers and mounts be okay with the extra weight and torsion? The big block will be pretty wild so I don't want to overlook any details that might cause me problems when I get my foot into it.

[Torque]

Originally Posted by farmtruckIII

I have a list of do's and don't do's if ya need them.

farmtruckIII, I would be ever so appreciative if you could either post that list or a link to where I can view it. By the looks of it you have a BB, 454 truck, so I think I am talking to the right person.

[FormerMember]

You can take the powersteering box from the engine donor truck, it's a bolt up.
Allows you to use the 79 lines and powersteering box as well.

[69-350]

alright, thanks grendel. I too was concerned about just hooking them into the stock SBC mounts, as I'm not sure how much this motor's going to pony up, or torque off, so I don't want to be jamming on the throttle and have a mount snap.

[FormerMember]

Originally Posted by 69-350

alright, thanks grendel. I too was concerned about just hooking them into the stock SBC mounts, as I'm not sure how much this motor's going to pony up, or torque off, so I don't want to be jamming on the throttle and have a mount snap.

Well, I went with the 1972 BBC Towers in mine, with poly later style mounts. Seemed to be stronger than the earlier set up.

Like others have said, they're not cheap...

[Green Machine]

If it had a I6 before, is the current 350 installed in the I6 position or in the more forward V8 position ? I believe any answer to what fits and doesn't depends first on where the tranny sits now.
For instance, if the 4spd tranny is sitting in the stock I6 position, you will have more problems with clearance in back, and I don't know if big block towers will fit.
If you want to move the tranny forward to the V8 position, the I6 crossmember will have to be removed, and graft in a V8 manual crossmember, change driveshaft and tranny hump cover. So where it sits or will sit determines what header and everything else will fit/clear.

[FormerMember]

Originally Posted by Green Machine

If it had a I6 before, is the current 350 installed in the I6 position or in the more forward V8 position ? I believe any answer to what fits and doesn't depends first on where the tranny sits now.
For instance, if the 4spd tranny is sitting in the stock I6 position, you will have more problems with clearance in back, and I don't know if big block towers will fit.
If you want to move the tranny forward to the V8 position, the I6 crossmember will have to be removed, and graft in a V8 manual crossmember, change driveshaft and tranny hump cover. So where it sits or will sit determines what header and everything else will fit/clear.

A different crossmember for the transmission? I thought it was knock out the rivets and slide it forward? That's what I did on mine...
(I may have learned something new today, different crossmembers per motor for the transmission???) I mean, I know of two types, Auto and manual. Heck, even the holes were drilled in the frame for the different transmission lengths.

Also, he should already have a high hump tranny cover, if he has the four speed...

[Green Machine]

Grendel, then the manual cross members are the same, I didn't know. Yes, the high hump cover is in there, but it could be changed out, the hole will be in the wrong spot, depending if you want to modify the old hump or swap it out, that's what I meant.

[70rs/ss]

You can do the sbc mounts frame and motor onto the BBC, but the SBC truck mount is one bolt from the back of the frame mount into the motor mount, so you are letting a lot ride on one bolt. That being said, you can get a set of 73 and up frame and motor mounts (sbc and bbc mounted into the 73 and up trucks to the same mount, just make sure you pull frame mounts and engine mounts that match from the same truck if possible) and make em fit (they look very similar to the 72 BBC mount and then you will not have header/manifold clearance issues. You can pick up the set up from a wrecking yard and then buy the urethane inseft for the clamshell mount and it will stand up under any bbc. The motor should be mounted in the fron holes to allow clearance for the distributor, especially an hei. Everything else is straight foward.

Good Luck!

[69-350]

Originally Posted by Green Machine

If it had a I6 before, is the current 350 installed in the I6 position or in the more forward V8 position ? I believe any answer to what fits and doesn't depends first on where the tranny sits now.
For instance, if the 4spd tranny is sitting in the stock I6 position, you will have more problems with clearance in back, and I don't know if big block towers will fit.
If you want to move the tranny forward to the V8 position, the I6 crossmember will have to be removed, and graft in a V8 manual crossmember, change driveshaft and tranny hump cover. So where it sits or will sit determines what header and everything else will fit/clear.

I think the 350 in there now is in the I6 position. I have the correct V8-type tranny hump, and a two-piece driveshaft for a V8, so I'm not too concerend with moving the tranny forward.

That being said, what seems to be the last major obstacle in my path (other than me not being made of money) seems to be BBC mounts and towers. Let's say this engine is going to put down a lot of torque or ponies... I don't want to skimp out on the towers/mounts... what should I go with? Remember, I'm on a T.I.T -tight budget here... I don't want to spend any more money on mounts than I have to... say, 100 bucks area....

[wibilly]

remember that 454s are externaly balanced, so you will need the flywheel from a 454

[69-350]

Originally Posted by wibilly

remember that 454s are externaly balanced, so you will need the flywheel from a 454

how's that going to work with a clutch?

[kansas city cheyenne]

Originally Posted by grendel

Well, I went with the 1972 BBC Towers in mine, with poly later style mounts. Seemed to be stronger than the earlier set up.

Like others have said, they're not cheap...

So nobody makes these towers anymore? You can't buy aftermarket ones or anything? I really didn't know that they were so hard to get ahold of. What kind of cash does it take to buy a set?

[70rs/ss]

They'll set you back $200-500 depending if the seller knows what they have. The 67-68 can be had for $50-150, but the motor part of that mount is discontinued, but Obsolete Chevy has them for like $150 a side!! That is why I suggested adapting the 73 and up mount. You use the frame mount and motor mount from a 73 up and it will work.

[1970 CST Short Wide]

I think ECE has after market BB mounts