Crate engine swap in my 1981 C3
Thread Starter
6th Gear
Joined: Mar 2015
Posts: 6
Likes: 0
Crate engine swap in my 1981 C3
I have a '81 with 3000 miles (original barn find earlier this year). It has the doggie 350 stock motor un-molested.
I want my Vette to run like everyone assumes it does (Including me). I want drivability and a solid street runner, keeping the stock TH350 Automatic (may upgrade in the future), keeping the budget at $5000 I am thinking GM Performance 350/330HP.
What are everyone's thoughts?
Thanks
Doug
I want my Vette to run like everyone assumes it does (Including me). I want drivability and a solid street runner, keeping the stock TH350 Automatic (may upgrade in the future), keeping the budget at $5000 I am thinking GM Performance 350/330HP.
What are everyone's thoughts?
Thanks
Doug
Melting Slicks
Joined: Apr 2009
Posts: 2,632
Likes: 112
From: Great Plains Iowa
If you want tire burning performance and retain good gas mileage you should consider a TH700R4 and a set of 3.73's. Then down the road you can boost your engine's performance with aftermarket goodies.
Race Director
Joined: Jan 2000
Posts: 13,018
Likes: 2,262
From: Corsicana, Tx
2020 C2 of the Year - Modified Winner
2020 Corvette of the Year (performance mods)
C2 of Year Winner (performance mods) 2019
2017 C2 of Year Finalist
For that sort of $$$ I'd be looking for at least 383 cubes. You can easily get more power with stronger parts for the same money.
Or I'd start with the basic GM $1800 350 and add some good heads and cam.
JIM
Or I'd start with the basic GM $1800 350 and add some good heads and cam.
JIM
Team Owner
Joined: Oct 2004
Posts: 81,241
Likes: 3,063
From: altered state
St. Jude Donor '05
saw that in the gmpp catalog last night. Fully dressed carb to pan w/everything for 5k isnt bad. All that little stuff adds up doing it on your own. No dicking with the carb, recurving etc etc its all done for you and new
Last edited by cv67; Nov 23, 2015 at 09:15 PM.
Melting Slicks
Joined: Apr 2006
Posts: 2,331
Likes: 61
From: Sunnyvale CA
If you buy a new GM engine and then change out the heads and cam, aren't you voiding the warranty, which many tout as a significant reason to buy a new GM engine in the first place?
Race Director
Joined: Jan 2000
Posts: 13,018
Likes: 2,262
From: Corsicana, Tx
2020 C2 of the Year - Modified Winner
2020 Corvette of the Year (performance mods)
C2 of Year Winner (performance mods) 2019
2017 C2 of Year Finalist
Sure...but so what? Sell off what you remove...you've still got a great shortblock for low $$$.
How many folks run this stuff enough to use the warranty? I've got a buddy that was so happy he bought a ZZ502 complete carb to oil pan and plugs...then it sat on a stand for two years...then another in the car before it moved. I bet it's got less than 100 miles on it in the last 15 years!
Most other stuff you buy has very limited warranty..and even GM's doesn't cover everything. People worry too much these days.
As a side note, I was recently speaking with some GM exec's and asking how the market is for "old school" small blocks. I mean everyone talks LS these days. They told me it was good enough that they just invested in all new tooling to make small blocks because the old stuff was pretty worn. So the odds are you're going to get a better engine than you've seen in 20 years going forward!
JIM
How many folks run this stuff enough to use the warranty? I've got a buddy that was so happy he bought a ZZ502 complete carb to oil pan and plugs...then it sat on a stand for two years...then another in the car before it moved. I bet it's got less than 100 miles on it in the last 15 years!
Most other stuff you buy has very limited warranty..and even GM's doesn't cover everything. People worry too much these days.
As a side note, I was recently speaking with some GM exec's and asking how the market is for "old school" small blocks. I mean everyone talks LS these days. They told me it was good enough that they just invested in all new tooling to make small blocks because the old stuff was pretty worn. So the odds are you're going to get a better engine than you've seen in 20 years going forward!
JIM
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer
Brett Foote
10 Things Every Corvette Owner Needs (2026 Edition)
Michael S. Palmer
8 Most "Only Corvette Owners Understand" Quirks and Problems
Pouria Savadkouei
10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years
Joe Kucinski
How Much Horsepower Every Corvette Engine "LOST" in 1972
Joe Kucinski
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!
Michael S. Palmer
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Drifting
Joined: Jun 2012
Posts: 1,990
Likes: 183
From: Port St. Lucie Fl
I have a '81 with 3000 miles (original barn find earlier this year). It has the doggie 350 stock motor un-molested.
I want my Vette to run like everyone assumes it does (Including me). I want drivability and a solid street runner, keeping the stock TH350 Automatic (may upgrade in the future), keeping the budget at $5000 I am thinking GM Performance 350/330HP.
What are everyone's thoughts?
Thanks
Doug
I want my Vette to run like everyone assumes it does (Including me). I want drivability and a solid street runner, keeping the stock TH350 Automatic (may upgrade in the future), keeping the budget at $5000 I am thinking GM Performance 350/330HP.
What are everyone's thoughts?
Thanks
Doug
True 2.5 duals w/xpipe 500-2k depending on what you choose
headers 100-1k depending on choice
355:1 gears 200+ for gears, 100+ install kit, ?$ paying someone to set it up. Anyone know if a stock th350 from these cars hold up to 350hp?
Then I would buy a running roller cam 350 from a 96+ truck, rebuild it as a 383 aftermarket heads if you have enough or reuse vortecs if low on budget. New vortec intake drive it till you have enough saved for aftermarkt heads, bigger cam.
reference for what is possible
http://www.hotrod.com/how-to/engine/...l-block-chevy/
Burning Brakes
Joined: Jun 2013
Posts: 798
Likes: 26
From: salinas CA
Le Mans Master
Joined: Oct 2007
Posts: 7,455
Likes: 977
From: RI, Now Franklin/Nashville TN
With some basic mods that engine will run pretty strong with some minor effort and small $'s. Not sure I would pick a 3,000 mile 81 to hot rod either...
Another option would be to just pull the OEM motor (document the mileage) and drop a crate engine in like blueprint (remember that crate engines are rated at Gross HP versus the 190 NET HP of the OEM motor, not apples to apples comparison).
Option #3: Buy a used 350 block and build it into what you want...I took my stock 78 L-82, built it into a 355 using pretty much the best components you can buy (forged JE racing pistons, AFR aluminum heads, Howards Roller cam (.525 lift), compression 10.2:1 with a Holley 4175 vacuum 650 CFM carb and L-82 aluminum intake, and the engine is a monster that is more than a match for a typical 383 crate engine...My L-82 355 looks like a stock L-82 unless you look closely at the aluminum heads...
Last edited by jb78L-82; Nov 25, 2015 at 05:50 AM.
Drifting
Joined: Dec 2011
Posts: 1,743
Likes: 289
From: Chardon Ohio
start small with things that will need to be done for later when an performance engine is installed.
True 2.5 duals w/xpipe 500-2k depending on what you choose
headers 100-1k depending on choice
355:1 gears 200+ for gears, 100+ install kit, ?$ paying someone to set it up. Anyone know if a stock th350 from these cars hold up to 350hp?
Then I would buy a running roller cam 350 from a 96+ truck, rebuild it as a 383 aftermarket heads if you have enough or reuse vortecs if low on budget. New vortec intake drive it till you have enough saved for aftermarkt heads, bigger cam.
reference for what is possible
http://www.hotrod.com/how-to/engine/...l-block-chevy/
True 2.5 duals w/xpipe 500-2k depending on what you choose
headers 100-1k depending on choice
355:1 gears 200+ for gears, 100+ install kit, ?$ paying someone to set it up. Anyone know if a stock th350 from these cars hold up to 350hp?
Then I would buy a running roller cam 350 from a 96+ truck, rebuild it as a 383 aftermarket heads if you have enough or reuse vortecs if low on budget. New vortec intake drive it till you have enough saved for aftermarkt heads, bigger cam.
reference for what is possible
http://www.hotrod.com/how-to/engine/...l-block-chevy/
Burning Brakes
Joined: Jul 2015
Posts: 823
Likes: 57
From: Austin TX
That's exactly where I'm headed with my '82. Having the 700R4 factory-installed is the primary reason I selected this year. The car itself was cheap, so I have enough budget to swap out the rear and refresh steering and suspension. Can't wait to drive a "new" C3 again!
Thread Starter
6th Gear
Joined: Mar 2015
Posts: 6
Likes: 0
I appreciate the comments, one note I didn't mention, was although in the past I would have gladly built a motor, now days I don't have the time. Pulling the stock motor and dropping in a crate motor is about all the time I have. I would rather drive it than wrench it.
I will look at the 383 crate motors for this coming springs engine swap.
I will look at the 383 crate motors for this coming springs engine swap.
Thread Starter
6th Gear
Joined: Mar 2015
Posts: 6
Likes: 0
I thought about this, but this car will never be a uber collectible car and I don't intend on selling it. My Vette loving buddy had a litter of kittens when I told him I wanted to pull the stock motor out. He was hung up on the 35 year old car with 3000 miles thing. I see a car that needs more power and I've watched too many hot rod shows while traveling.
Last edited by drparkwood; Nov 25, 2015 at 09:00 PM.
Thread Starter
6th Gear
Joined: Mar 2015
Posts: 6
Likes: 0
Burning Brakes
Joined: Sep 2011
Posts: 896
Likes: 7
Le Mans Master
Joined: Oct 2007
Posts: 7,455
Likes: 977
From: RI, Now Franklin/Nashville TN
A totally OEM stock 78 L-82 was NET rated a 220 Net HP. My L-82 with the changes above with a weak compression #6 cylinder did 233 RWHP on the dyno before the rebuild. Using a 15% conversion factor from RWHP to Net HP for a rough comparison, the L-82 with exhaust mods/other changes made approximately 275 Net HP versus the stock Net 220 HP, 55 HP difference and you could definitely feel the difference mid to high rpm. Figure exhaust only changes for about 40-45 HP.....easy HP gain and cheap....
Last edited by jb78L-82; Nov 26, 2015 at 06:03 AM.
Team Owner
Joined: Oct 2004
Posts: 81,241
Likes: 3,063
From: altered state
St. Jude Donor '05
Heavy car needs torque to get it going, stroke that puppy with some decent heads/roller cam you WILL feel the difference
Like the gear/overdrive, also. Have your cake and eat it too.
Couldnt believe the diff between the 350 and 383 esp up top, wish I did a 421 now
Like the gear/overdrive, also. Have your cake and eat it too.
Couldnt believe the diff between the 350 and 383 esp up top, wish I did a 421 now
Le Mans Master
Joined: Oct 2007
Posts: 7,455
Likes: 977
From: RI, Now Franklin/Nashville TN
Well if you are just installing a crate motor than a 383 would be the way to go for the most easy power but if you build or have someone build for you a 355 with the right components, the 355 will easily match the crate 383...here is a mild 355 build similar to my 355 L-82 making some impressive numbers (less compression than my 355 BTW). Note the torque numbers and where in the RPM they occur...I have the same exact real world experience with my 355 L-82 versus crate 383 cars I have driven or been in....
http://www.superchevy.com/how-to/148...-engine-build/
slightly More aggressive roller cam and more compression in the build above would net a 355 making 450/460 Gross HP/475/480 ftlbs Gross torque in the useable RPM range.
http://www.superchevy.com/how-to/148...-engine-build/
slightly More aggressive roller cam and more compression in the build above would net a 355 making 450/460 Gross HP/475/480 ftlbs Gross torque in the useable RPM range.
Last edited by jb78L-82; Nov 26, 2015 at 07:04 AM.