BBC Conversion Troubles

[loyalist_towing]

I have been going over quite a few previous posts regarding a SBC to BBC conversion in a mid 80's 1/2 ton.

One poster recommended transplanting the entire drivetrain including rear diff from a 90 SS454 truck.

I am in the process of doing exactly that....but it doesn't exactly work.

Here why.

The LH exhaust manifold dumps right on the shifter linkage and the LH frame rail.
The RH exhaust manifold may work providing you remove the stove assembly for the intake off it.
I have a Pypes exhaust that will be mated to the stock manifolds which I prefer to retain or find an acceptable stock manifold alternative.

For laughs, I tried putting the fan assembly (orig one off the SS truck retaining the serpentine pulley system).

Now here is the problem...

The lower crank pulley is into the shroud and the fan is obviously too low in shroud as well.

I have retained all the original motor mounts from the 305 that once occupied the hole and had the 700R4 done with a Corvette Servo thicker SunShell and few other goodies.

I haven't even tried the 14 Bolt diff yet.

What am I missing here?

Just about everyone says "this is a direct bolt in".

Any knowledgable input would kindly be welcomed.... Thanks in advance.

[choptop]

I believe you will need to use the bigblock manifolds off of a truck from the 80's bidy style truck. This would be a good time to ungrade to headers anyway.
 The fan problem may be related to the engine mounts. Im not sure the 305 mounts on the engine are the same as the bigblock. Someone will chime in and answer that, but Im sure you'd need the mounts for the 80s style trucks. This may solve your fan clearance issues as well.
 As far as a direct bolt in, it should be pretty much direct, but you'll have to use the mounts and manifold for 80's trucks Im sure. Gonna be a nice install when done.
 On the rear axle, you'll probably have to move the spring perches. From what I understand, there is really nothing special about the 454SS drive train other than the "cool factor" of a bigblock in a halfton. The trucks were pretty much lethargic considering what they should have been. Gonna be cool for sure regaudless.

[loyalist_towing]

Thanks.

It definately appears to be a motor mount issue, either the rail to the X-member or the motor mount itself.

This will hopefully correct the drivetrain geometry.

BTW: We did a camshaft upgrade to wake up the lethargic SS454 motor and have converted to carb from TBI.

It would be nice to know EXACTLY what I need to change, instead of trial and error.

Anyone that has the parts to correct this problem, I would be interested in buying them.

 

[VileZambonie]

Whoever's advice you followed to swap in a 454ss drivetrain as a direct bolt in was poor advice taken. The 454SS was an embarassing piece of crap. If you have the drivetrain you can obviously make it work as these trucks came with bbc. The 700R4 will bolt up and I wouldn't bother going to the 14 bolt rear end unless you have a problem with your existing rear. Is your truck a 5 lug?

Now keep in mind manifolds on these engines were garbage no matter what you've read on the internet. Get some headers and make your pypes fit. Build the 454 which you can easily and inexpensively make 500hp instead of the slug it is now. As far as the fan is concerned just use a 73 up bbc fan set up

[Captkaos]

You need to use the mounts bolted to the 305 on the 454, there is no difference.  The engine should drop in place with it.
BBC engines used a completely different fan shroud setup than any other engine, but a late 80's should work if it is a HD radiator, if it isn't, you need one.
With just a set of heads and a Cam the 454 will wake up big time.
With manifolds, you MUST use ones from a 73-79 pickup if you want manifolds.  Otherwise you need headers.
For the 14bolt, I don't think you have to move the perches at all, the leaf width should be the same, you can compare perch to perch measurements to find out.
The 14bolt is a semifloater and it is MUCH stronger than a normal 1/2T rearend, and it has 5x5 bolt pattern.
If you want your Pypes system to work, get some long tubes for the motor.  If you are severly lowered you will have problems.

[loyalist_towing]

Hey Guys, thanks for the input.

I am not trying to build a huge HP axle twister.

I ended up with a wrecked SS truck (tow yard) and thought it would be a "cool" swap to change a tired and dismal 305 in an 86 SWB we bought in Georgia a few months ago.

My intent was to make in look as factory as possible without little or any aftermarket stuff.

So, to be clear manifolds need to come from a 73-79 vintage truck and the fan shroud and HD rad need to come from a 81-87 truck?

Are there any passenger car manifolds that might work as well, like a BB Camaro or Impala?

Thanks Again.

[Captkaos]

1/2T trucks only got the 454 from 1973-1979, so you know they fit.  Chevelle ones should fit also.  You said the ones on it now dump over the framerail and into the shift linkage.  I don't remember what 454SS manifolds look like, but I don't remember them being that long.