1988 C3500 Dually - BBC to SBC Swap - Req'd Brackets, etc..?

[Frank Enstein]

ZyBar coating will drop the underhood temp a bunch more than wrapping the headers.

 

[Frank Enstein]

+1 on the 4L80E
I'm doing the BBC to SBC swap on Betty and a 4L80E is in the plans.

 

[KRS1]

I picked up the 2 piece aluminum bracket system off a TBI 350 from a U-pic yard..there must be a few of those place in Missouri?

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[KRS1]

I picked up the 2 piece aluminum bracket system off a TBI 350 from a U-pic yard..there must be a few of those places in Missouri, maybe even find a parts truck and tow it to your place ? the hydroboost is really only a extra "nipple" on the PS pump in relation to all the brackets etc..

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[mykytiuk]

Greetings Gentlemen:

Odd as it is.... I'm considering going the opposite direction, BBC to SBC.

BACKGROUND

I have a 1988 C3500 Dually, single cab restoration / mod project.
The stock 454 had a nice mild performance/towing rebuild, converted to Carb.
Turbo 400 transmission was also professionally performance rebuilt.
Rear gear ratio is stock 4:10. It's all pretty fresh, less than 10k miles on rebuild.

My intended purpose for the truck is to tow 24-27' boats short distances to boat ramp. I will likely never tow anything over 6-7k pounds and on occasion enjoy cruising the truck (non-towing) on the highway 250 miles, each way, back and forth to the lake. With the TH400 and 4:10 gears I'm at about 3400 rpm @ 65mph.

Spinning 454+ cubes at 3400 is simply a waste. The engine could be repurposed for a friends boat.
I'm very interested in purchasing a GM crate HT383 motor to use with the existing TH400 and 4:10 gear ratio. Seems the HT383 torque curve would be well suited for my needs. The truck is emissions exempt.

INPUT PLEASE

I believe mating the TH400 to a SBC will pose no problem.

My concern is frame mounts and drive pulley/mounting brackets. The truck has A/C and hydroboost power steering / brakes.

I'll love to get feedback regarding what bracket changes / mod's are required for the BB to SB swap.

Unfortunately, I will have little time to find a junkyard donor for components.
I'd entertain an "off the shelf" serpentine belt pulley/bracket kit, just haven't found one for a SBC with hydroboost.

Are components from 3/4ton (c/k 2500) trucks interchangeable? Do they use hydroboost?

I will genuinely appreciate any time you could devote towards guidance.

Thank you kindly.

Hello! I did this exact same thing with my ‘94 K3500. The exhaust at the manifold outlets and engine mounts all line up perfect. The manifold outlets are smaller but some new donuts sealed it fine. The only parts I couldn’t find at local junkyards were the lower bell housing cover for which I used the old BBC one and had to fabricate a spacer for where it would “seal” to the SBC block. Just a flat piece of aluminum cut out the right size for the smaller crank output area then siliconed it to the cover. Been there for four years now! And the top fan shroud. The fan is a little exposed due to the shorter SBC. As far as the hydroboost goes, I am still using the original PS pump....just a different bracket for SBC. I also luckily found a same year ECM for the TBI 350 with 4L80E. If I wouldn’t have come up with that I would have just used the BBC one and see what happened.

The only reason I did this swap is because I had a near new (less than 10K miles) 350 and it needed a home. My only regret is that I didn’t put a good HP cam in it while it was easy!

 

[88dually454]

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KRS1

Kind thanks for your response and efforts. Looks like I'm going "yarding" this spring

 

[KRS1]

KRS1

Kind thanks for your response and efforts. Looks like I'm going "yarding" this spring

Hi 88dually, there might be a off the shelf alternative if you are willing to pay. I recall youtuber "Eric the Car guy" had a March pulley setup on his GMT 400..

 

[RichLo]

Why not go "All-The-Way" to a 4.3!!!