383 TBI vs 454 TBI, need opinions

[Daveo91Burb]

I'm trying to decide between building a 383 with vortec heads vs swapping in a stock (relatively) 454 TBI from a donor truck.

I've been planning the 383 for a while now and have accumulated some parts: a 4-bolt main, '90 350 for the block, rebuilt vortec heads, GM 4-barrel vortec intake and adapter for TBI, and complete roller valve train from a vortec 350 (cam, lifters, pushrods, spider plate and guides, etc.). The thing that has always concerned me tho is the complication of trying to get the TBI to work well with this build. I have a guy (Old School EFI here in Vancouver, WA) that says he can do it, but I'm still leery of spending a bunch of time and $$ to get it to work. Now I'm wondering if a pretty much stock 454 TBI from a '91 or later donor would be a better way to go. I'd go with a donor that had a 4L80e (like my '91) and use that computer.

Was browsing CL and came across this one: http://portland.craigslist.org/mlt/cto/5867026434.html

Any opinions? Would mileage be much different between the two options? Would the '95 computer be plug and play or would I have lots of conversion work to do to get it to work in my '91 burb?

 

[yevgenievich]

I have been thinking big block for a while, but 97+ is the better one to get. Engine/trans harness is relatively seperate and not too much work to swap over from a donor. On other side, 383 tbi has been done before and can be done for sure. No changes for unless stock motor takes a dump

 

[Daveo91Burb]

Yeah, I gotta do something. I was pulling a lightly loaded small utility trailer over a (not too steep) mountain pass this weekend and tranny was dropping down to 2nd off and on just to maintain 55 mph. I even have 4.10s.

Would love to go for a '97+ vortec BBC, but not sure what I'd do for F.I. and computer. Or are you saying to keep the whole vortec set-up? My thought was if I bought a whole donor truck with 454 TBI I'd be able to just swap everything over to my burb, including radiator, TB, computer (or chip), etc. And everything existing (like gauges) would plug and play.

But, I'm probably just going to go with the 383 since I have a lot of the parts already.

Thanks.

 

[glockholiday]

Build what you got. A 1998 454 Vortec has 290hp and 410 torque. Those numbers are easily achieved/surpassed with a 383.

 

[yevgenievich]

I had good experience with vortec big blocks. The 97 one ton with vortec big block was the most fuel efficient truck on the highway I have ever owned. And it pulled a car hauler on texas highways at 75+ mph with no problems in 5th gear. 383 tuned properly should be able to archieve your goals. As a side note, slightly improved 8.1 versions did have over 300 torque at idle, i believe similar on 454.

 

[Derick C.]

I just put a stock 454 tbi motor in my burb and it tows amazing now.

I had thought about building a 383 but the 454 swap was way cheaper.

 

[Daveo91Burb]

I just put a stock 454 tbi motor in my burb and it tows amazing now.



I had thought about building a 383 but the 454 swap was way cheaper.

I'm still thinking about the 454 swap. The 95 burb in my OP is still for sale - texted the guy last night.

Did you have to change out front springs for the increased weight? My burb is a 3/4 ton - I'm thinking I'll be ok? It doesn't even notice me when I stand on the front bumper.

Also will I have any problems with motor mounts on a 4x4? I've heard there may be a slight conflict, maybe with the upper shock mounts?

I've always wondered why GM didn't have a 454 option for the 4x4 squares - hopefully I won't find out the hard way


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[Derick C.]

I'm still thinking about the 454 swap. The 95 burb in my OP is still for sale - texted the guy last night.

Did you have to change out front springs for the increased weight? My burb is a 3/4 ton - I'm thinking I'll be ok? It doesn't even notice me when I stand on the front bumper.

Also will I have any problems with motor mounts on a 4x4? I've heard there may be a slight conflict, maybe with the upper shock mounts?

I've always wondered why GM didn't have a 454 option for the 4x4 squares - hopefully I won't find out the hard way


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I didn't have any problems at all, hell it was the first time I set a motor in place and was able to slide the motor mount bolts right in.

My burb is a half ton but the lift kit is for a 3/4 ton so it actually rides better with more weight on those stiff ass springs.

I did have to change out 2 pig tails on the engine harness, 1 for the IAC and the other for the TPS.

I do have pics in my pic thread

 

[yevgenievich]

Gm likely did not offer a big block in 4x4 form because of the weight. More front weight is also more likely to sink the front end in offroad situation. And also reduces load capacity

 

[Derick C.]

They did have 454's in 1 ton crew cab 4x4's

 

[Rusty Nail]

My opinion votes big block.

 

[Daveo91Burb]

They did have 454's in 1 ton crew cab 4x4's

That's right, they did. I think they had 205 t-cases, though. But I'm thinking the NP 241 will do ok behind a 454. That's what they used in 4x4 big block burbs and pickups in the GMT 400 trucks, correct?

Did you swap to a big block radiator? Did MPG change significantly after the swap?

 

[Derick C.]

That's right, they did. I think they had 205 t-cases, though. But I'm thinking the NP 241 will do ok behind a 454. That's what they used in 4x4 big block burbs and pickups in the GMT 400 trucks, correct?

Did you swap to a big block radiator? Did MPG change significantly after the swap?

I bought an all aluminum 3 row radiator, had to trim a couple inches off the fan shroud, still using the small block fan/clutch assy.

I daily drive it and it does use a little more gas than it did but towing my trailer it does better on gas.

 

[Daveo91Burb]

I was too late on the draw and missed the 454 Burb. Back to building what I got: vortec 383, roller cam


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[MikeB]

That 98 454 was designed to tow heavy loads, and made peak torque at 3200 RPM. And those 290hp/410lb/ft specs are NET, not the GROSS number you see on dyno tests. I'd say that 290/410 net is closer to 360/510 "gross".

On the other hand, if you see a 383 crate engine rated at 425hp/450lb/ft, those numbers are already "gross", and peak torque is probably at 4000-4500 RPM. That's not to say a 383 can't be built to make peak torque at a lower RPM, but it will never make as much at towing-friendly RPMs as a 454.

Good article on net vs. gross measurement methods here: http://ateupwithmotor.com/terms-technology-definitions/gross-versus-net-horsepower/