Upgrade to 383
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Joined: May 2021
Posts: 64
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From: Austin, TX
Upgrade to 383
Hi folks. Im considering swapping out my crate 350/330hp engine with a 383/450hp new chevy crate engine. I'm looking for more zip off the line and passing power. I have a 1972 C3 with a 3sp AT. Its a weekend around town driver. Has anyone done this? Were you happy after the $10K investment? Would you have done anything different? Many thanks in advance for your responses.
Team Owner
Joined: Apr 1999
Posts: 21,953
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From: Reno Nevada
2024 C3 of the Year Finalist- Modified
450 is kinda low for fun these days when you have new cars over 650 hp. I notice a vast improvement going from a 350 to an over 500 hp 383, but within a year or two I was already hopping it up. I won't build a 383 anymore when 396 with a slightly longer 3.875 stroker crank makes much more TQ. I have two vette motors a 396 in the mid 500 and a 434 in the mid 600. Both are really fun. I also went to a 5 speed to even make them more safe and fun.
You lost the novelty of the 330 HP. The more ci the more TQ. I was very impressed with my first 427 small block
You lost the novelty of the 330 HP. The more ci the more TQ. I was very impressed with my first 427 small block
Race Director
Joined: Mar 2016
Posts: 14,351
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From: Napa Valley California
Have you checked what rear end gears you have?
A 383/450 hp engine could still be slow off the line if you have 3.08 rear gears.
Swapping from a 3.36 to a 3.73 would make it quicker off the line but may not help with any passing power you are looking for on the highway.
What are the spec's for the 350 you have now and for the 383?
You might find a simple camshaft swap is all you need to wake up that 350/330 hp.
The engine spec's and rear end gearing all need to work together so you get the best bang for your buck.
A 383/450 hp engine could still be slow off the line if you have 3.08 rear gears.
Swapping from a 3.36 to a 3.73 would make it quicker off the line but may not help with any passing power you are looking for on the highway.
What are the spec's for the 350 you have now and for the 383?
You might find a simple camshaft swap is all you need to wake up that 350/330 hp.
The engine spec's and rear end gearing all need to work together so you get the best bang for your buck.
Last edited by OldCarBum; Aug 18, 2021 at 01:04 PM.
Team Owner
Joined: Jan 2006
Posts: 37,637
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From: Crossville TN
Have you tuned the distributor for 'performance' timing and made certain the the carb is opening fully at WOT (floor pedal, not hand-on-linkage) so that you have maximized the available power in your stock engine? If you don't "race" the car, I can't imagine a well-prepared L-48 engine not having enough power for passing and 'spirited' acceleration. Do your homework and make certain your present engine is getting the most out of it before pitching it and spending several K-notes for a new engine. Then, if it's not enough, drop some ca$h.
Team Owner
Joined: Oct 2004
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From: altered state
St. Jude Donor '05
Youll love it, best thing I did was put "a bigger arm" in that 350 I kept throwing different cams gears heads at to make it move.
That stroke (torque) is what youre after. Get some decent heads
Id never build the same CI engine again what a letdown. Why 10k do you have a link?Is it a carb to pan deal with accessories
Not to screw you up but a vortecpro 468 or 496 can be had for that. Hmm..
That stroke (torque) is what youre after. Get some decent heads
Id never build the same CI engine again what a letdown. Why 10k do you have a link?Is it a carb to pan deal with accessories
Not to screw you up but a vortecpro 468 or 496 can be had for that. Hmm..
Melting Slicks
Joined: Apr 2001
Posts: 2,030
Likes: 363
From: Lubbock Texas
Hi folks. Im considering swapping out my crate 350/330hp engine with a 383/450hp new chevy crate engine. I'm looking for more zip off the line and passing power. I have a 1972 C3 with a 3sp AT. Its a weekend around town driver. Has anyone done this? Were you happy after the $10K investment? Would you have done anything different? Many thanks in advance for your responses.
I did this just last year. Had about the same engine as you to start. Put in a 383 fuel injected crate engine from Smeding Performance (somewhat close to you in Boerne Texas). Engine dynoed at 423 HP / 457 Ft-lbs. I gained nearly 100 HP and probably more torque, better fuel economy and much more fun to drive. I also swapped in a 4L60E transmission to replace the TH400. Much better first gear ratio for better launches and OD for the highway. I kept my 3.08 rear gears. I wanted to bump it up to 3.23s but those gear sets are no longer available for our cars. I went back and forth about swapping to 3.36s but my 3.08s were in such good condition, I just let Gary rebuild my diff the way it was. I'm very happy with the overall package.
DC
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Le Mans Master
Joined: May 2002
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From: Lebanon Township New Jersey
Most of us reading this thread understand that your car does not have an L48 engine in it now. It was already replaced with a 350/330 HP crate motor. You want more "zip" off the line and aren't too concerned with highway driving. Your rear axle ratio is probably 3.08. Change that to 3.73. Put in a good 3K stall speed converter. Upgrade your cam to something a little hotter, preferably a hyd. roller. Add full length headers. This will add a lot of off the line zip for less than $10K.
Navigator
Joined: Jul 2021
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From: Upstate NY
Pro
Joined: Jan 2001
Posts: 642
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From: San Jose CA
The 383 combo is potent, and without a doubt adding 120 horsepower to your car will be felt. BUT - very few cars can actually our down 450 horsepower on street tires. Those than can, tend to break stuff. C3's destroy half-shafts and the spines in spindles if not prepped.
A few questions before you go through an engine swap with what I assume is already a healthy engine.
A few questions before you go through an engine swap with what I assume is already a healthy engine.
- What are you running for a torque converter and rear gear set? Nothing adds more torque than deeper rear gears. Gears multiply torque. Consider: In top gear with 300 ft/lbs of torque through a 3.08 rear gear, you're putting 924 ft/lbs to the ground. Bring that up to a 3.73 gear and it goes to 1119 ft/lbs
- Has the car ever been dyno-tuned? You'll be absolutely shocked by how much throttle response can be had with simple changes to the timing and fuel curves. Most people make educated guesses at tunes and leave it at that. It's a huge mistake. A dyno is really to only way to do it "right"
- What are you running for Wheels/Tires? Believe it or not, a lighter set of wheels/tires is one of the best ways to improve the seat of the pants throttle response. This is unsprung reciprocating weight, reducing it improves acceleration, braking, and suspension response. Not to mention there is no real performance tire available in 15" size anymore. Factory rally wheels are ~ 27lbs each. The ubiquitous American Racing Torque Thrust II in 18x8 is only 19lbs
Last edited by Lowend; Aug 19, 2021 at 12:44 AM.
Thread Starter
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Joined: May 2021
Posts: 64
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From: Austin, TX
I’m not sure what I have for a torque converter. Probably the original stock one. But my mechanic said he will want to put in a new one with the engine swap. I have the TH400 3spd AT. So whatever gear ratios that has is what I have. I’m running a set of 15 inch BFGs.
Thread Starter
Advanced
Joined: May 2021
Posts: 64
Likes: 17
From: Austin, TX
Some of you have mentioned the camshaft swap. I mentioned this to my mechanic before he suggested the 383. I originally went in thinking that a new cam and headers would be what I needed. He said that a new cam will not really benefit me because I am limited by the TH400 3spd automatic that I have.
Dr. Detroit
Joined: Mar 2012
Posts: 10,097
Likes: 4,027
From: New Braunfels Texas
Some of you have mentioned the camshaft swap. I mentioned this to my mechanic before he suggested the 383. I originally went in thinking that a new cam and headers would be what I needed. He said that a new cam will not really benefit me because I am limited by the TH400 3spd automatic that I have.
10k to put a 383 in a car installed when it already has a 350/330 in it is ridiculous......if you are spending that kind of money, build or buy a 406. I never build 383's anymore because it simply isn't a great upgrade for the money when a 406 is just a few hundred dollars away......
If this were my car.....I would put a better cam in it and a 2004r or 700r4 trans......you want a boost? The first gear of either OD trans is much lower and you end up with a cruise gear for interstate driving......and long tube headers with the cam will boost torque throughout the range and flow better on the top end. You would end up with a 380-390 horse car that is much more well rounded for half of what you plan on spending.
The 50 horse shot in the arm and the OD trans will feel like a hit of nitrous when you hit it the first time........
Jebby
Heel & Toe
Joined: Dec 2020
Posts: 18
Likes: 11
From: New York
Hi folks. Im considering swapping out my crate 350/330hp engine with a 383/450hp new chevy crate engine. I'm looking for more zip off the line and passing power. I have a 1972 C3 with a 3sp AT. Its a weekend around town driver. Has anyone done this? Were you happy after the $10K investment? Would you have done anything different? Many thanks in advance for your responses.
Dr. Detroit
Joined: Mar 2012
Posts: 10,097
Likes: 4,027
From: New Braunfels Texas
If you just go putting a bad *** engine in it right now with no other changes......it will feel like the exact same car but much more powerful......and you did nothing to improve it flexibility as a driver.....
Cam, headers and OD trans will make a solid low 13 second car out of it......and if tuned properly....pull down terrific fuel economy on the road.....you could see close to 20MPG on I-35 or better.....no lie.....and it will just cruise along....not running with its tongue hangin' out all the time......
Just do not over cam it......GM cams have a tendency to be small due to the lawyers.....the right cam will inject a lot of power into this setup, although with the Vortec heads on your 330 crate...the heads will have to be modified for higher lift......I think, someone correct me if I am wrong....never had a 330 crate apart.
Jebby
Last edited by Jebbysan; Aug 19, 2021 at 09:13 AM.