94 c1500 big block swap (not tbi)

[Dominooch89]

So I bought a 94 c1500 with my pops he’s a retired mechanic very accustomed to old school cars. We want to do an all out build we are scrapping the 350 vortec and going dart block. Originality I wanted a 383 boosted but he hates turbos and we want to make power. so we are settling on going with a big block platform. What physical changes do we need to make to bolt up? It’s going to be old school carb so wiring is not an issue. Any clearance issue I need to know about? Motor mounts? Ect. Thanks in advance

 

[b454rat]

pull small block, install big block.

 

[Supercharged111]

pull small block, install big block.

This. Worst case you need the motor mounts that bolt to the block itself, but the ones on the frame are all the same. I'm hesitant to think you'd need to though as my dad put a 454 in place of a small block in his 1983 Monte Carlo and even that was bolt in and go.

 

[Schurkey]

Use wing-nuts on the bellhousing studs, so you can easily remove the transmission every time you shatter it. If the gauge cluster is anything like my '88, you'll still need the speed sensor in the trans to operate the speedo, odometer, cruise, and anti-lock brakes.

You'll have to dig into the schematic to get the tach to run from the Tach terminal of an old-style HEI.

At some point GM switched from old-style gauges to stepper-motor gauges. Far as I know, all the stepper motor gauges are driven by the computer. Disconnect the computer, gauge cluster is dead.

I wouldn't trust the rear axle, either; although the 8.5 would probably be fine if you don't have a Gov-Bomb and you use narrow, crappy tires. I really despise the leading-trailing shoe rear brakes that come on the 1500s. When it was me, I found a light-duty 2500 that had a 9.5 semi-float and decent rear brakes. No idea how that's gonna work with five-lug front wheels.

How are you going to regulate fuel pressure?

What are you using for an exhaust? I assume you're scrapping the catalyst while you're vandalizing all the rest of the emissions system. I thought NY was tough on emissions. I guess I'm wrong, 'cause there's no way you'd pass an inspection.

Bigger radiator Probably do not need the engine oil cooler; but it wouldn't hurt.

 

[langkg]

I wouldn't go big block especially if you're going to spend the coin for a Dart block. You're going to want a 4L80E with the BBC which means wiring changes as the 60 and 80 are different. Additionally, the larger trans will require moving the cross member back (probably already holes in the frame) and a shorter propshaft. If you stay with the stock TBI you'll need to swap ECU's but if you're going full bore Dart BBC I'd imagine you're thinking aftermarket EFI or carb anyway.

I have a '94 K1500 and built a Vortec roller cam block with aftermarket heads, etc. Running Holley Sniper and Hyperspark ignition. Get rid of the stock TBI garbage and run the Sniper would be my advice. Best change I made. The stock ECU really only runs the 4L60E transmission at this point. My next step is a transmission build. Future plans are either building a 383 or doing the afore mention 400 Dart. If i go that route I will probably have the engine built rather than me doing it.

Somebody mentioned larger radiator. I had a C3500 donor truck that I used as a donor to convert my truck to Hydroboost (HIGHLY recommended) and I saved the radiator shrouds and mounts. The 3500 got a larger radiator. I would have kept the radiator too however the guy I sold the truck to after raiding the brake parts wanted it. Radiators are relatively cheap. I mainly wanted the shrouds as they'll bolt right in and I can run the big radiator in the future if needed.

 

[Dominooch89]

Use wing-nuts on the bellhousing studs, so you can easily remove the transmission every time you shatter it. If the gauge cluster is anything like my '88, you'll still need the speed sensor in the trans to operate the speedo, odometer, cruise, and anti-lock brakes.

You'll have to dig into the schematic to get the tach to run from the Tach terminal of an old-style HEI.

At some point GM switched from old-style gauges to stepper-motor gauges. Far as I know, all the stepper motor gauges are driven by the computer. Disconnect the computer, gauge cluster is dead.

I wouldn't trust the rear axle, either; although the 8.5 would probably be fine if you don't have a Gov-Bomb and you use narrow, crappy tires. I really despise the leading-trailing shoe rear brakes that come on the 1500s. When it was me, I found a light-duty 2500 that had a 9.5 semi-float and decent rear brakes. No idea how that's gonna work with five-lug front wheels.

How are you going to regulate fuel pressure?

What are you using for an exhaust? I assume you're scrapping the catalyst while you're vandalizing all the rest of the emissions system. I thought NY was tough on emissions. I guess I'm wrong, 'cause there's no way you'd pass an inspection.

Bigger radiator Probably do not need the engine oil cooler; but it wouldn't hurt.

Use wing-nuts on the bellhousing studs, so you can easily remove the transmission every time you shatter it. If the gauge cluster is anything like my '88, you'll still need the speed sensor in the trans to operate the speedo, odometer, cruise, and anti-lock brakes.

You'll have to dig into the schematic to get the tach to run from the Tach terminal of an old-style HEI.

At some point GM switched from old-style gauges to stepper-motor gauges. Far as I know, all the stepper motor gauges are driven by the computer. Disconnect the computer, gauge cluster is dead.

I wouldn't trust the rear axle, either; although the 8.5 would probably be fine if you don't have a Gov-Bomb and you use narrow, crappy tires. I really despise the leading-trailing shoe rear brakes that come on the 1500s. When it was me, I found a light-duty 2500 that had a 9.5 semi-float and decent rear brakes. No idea how that's gonna work with five-lug front wheels.

How are you going to regulate fuel pressure?

What are you using for an exhaust? I assume you're scrapping the catalyst while you're vandalizing all the rest of the emissions system. I thought NY was tough on emissions. I guess I'm wrong, 'cause there's no way you'd pass an inspection.

Bigger radiator Probably do not need the engine oil cooler; but it wouldn't hurt.

Thanks for all the knowledge appreciate it. Pre 96 is only safety in nys. The hardest thing out of everything you said is the wiring. My electrical skill is lacking and my dads worse. I will probably pay someone to do that. I don’t know what rear end will hold that power if you know enlighten me. Is there a junkyard rear end I can swap to and rebuild to work for me? Ive helped my dad rebuild them before if that’s the case. Im good at welding too if we need to do some fab

 

[Dominooch89]

I wouldn't go big block especially if you're going to spend the coin for a Dart block. You're going to want a 4L80E with the BBC which means wiring changes as the 60 and 80 are different. Additionally, the larger trans will require moving the cross member back (probably already holes in the frame) and a shorter propshaft. If you stay with the stock TBI you'll need to swap ECU's but if you're going full bore Dart BBC I'd imagine you're thinking aftermarket EFI or carb anyway.

I have a '94 K1500 and built a Vortec roller cam block with aftermarket heads, etc. Running Holley Sniper and Hyperspark ignition. Get rid of the stock TBI garbage and run the Sniper would be my advice. Best change I made. The stock ECU really only runs the 4L60E transmission at this point. My next step is a transmission build. Future plans are either building a 383 or doing the afore mention 400 Dart. If i go that route I will probably have the engine built rather than me doing it.

Somebody mentioned larger radiator. I had a C3500 donor truck that I used as a donor to convert my truck to Hydroboost (HIGHLY recommended) and I saved the radiator shrouds and mounts. The 3500 got a larger radiator. I would have kept the radiator too however the guy I sold the truck to after raiding the brake parts wanted it. Radiators are relatively cheap. I mainly wanted the shrouds as they'll bolt right in and I can run the big radiator in the future if needed.

Thanks man I appreciate it but it seems like we’re going for it. So my question is when putting the 4L80e into the 1500 You said the wiring is different. Any idea how to make it compatible. Remember this is a project truck not a daily as for the prop I don’t mind the work and I’m not sure if the original driveshaft was going to hold up anyway.

 

[Schurkey]

I don’t know what rear end will hold that power if you know enlighten me. Is there a junkyard rear end I can swap to and rebuild to work for me? Ive helped my dad rebuild them before if that’s the case. Im good at welding too if we need to do some fab

I really despise the leading-trailing shoe rear brakes that come on the 1500s. When it was me, I found a light-duty 2500 that had a 9.5 semi-float and decent rear brakes. No idea how that's gonna work with five-lug front wheels.

A 9.5 semi-float will hold up just fine. You wanna go crazy, you could stuff a 10.5 full-float under there. When GM built 454/7.4L GMT400s, they used the 10.5; but those vehicles were expected to work hard, and yours isn't. A 9.5 will be enough.

I'm waiting on parts to install a Truetrack posi in my 10.5; my 9.5 in the K1500 has a Gov-Lock.

 

[b454rat]

Get a Ford 9". Or if spending money build a Dana 60.

 

[Schurkey]

Get a Ford 9". Or if spending money build a Dana 60.

Yeah, you can spend real money getting a "new" custom axle, or a used, kludged-up mess that you hope has the leaf spring and shock mounts welded-on at the correct location and angle.

Or you can dig a stronger axle out of a 2500 or 3500 at a Treasure Yard for peanuts; and it bolts right in except for the U-joint.