72 350 rebuild
Thread Starter
Instructor
Joined: Jul 2007
Posts: 193
Likes: 0
72 350 rebuild
I plan to rebuild my numbers matching 350 base motor. Of course I want more hp's and don't want to kill the value by changing heads to the higher compresion heads. Does anyone know if I can get the same result by going to a high compresion piston instead? I may pocket port the heads but thought I should keep al the original castings.
Thanks
Thanks
Team Owner
Joined: Aug 2006
Posts: 24,125
Likes: 15
From: Columbia Missouri
Sure, you can always bump the compression with pistons and maybe head work. I'm guessing you have an L48? You can probably find some flat top pistons pretty easily to bump the compression, and maybe mill the heads a bit. Stab in a more aggressive cam and you're good.
The stock manifolds will hold you back a little bit but are you against the idea of larger diameter exhaust and some better flowing mufflers?
The stock manifolds will hold you back a little bit but are you against the idea of larger diameter exhaust and some better flowing mufflers?
Burning Brakes
Joined: May 2007
Posts: 945
Likes: 0
From: Ventura California
You can change out the pistons and get higher compression. Just my opinion here so hang in there with me. I understand your concern about affecting the value of your Corvette by changing heads but changing pistons is no different. The engine will still not be original factory specs after doing that change. So, that being the case, to return the engine to original specs, which would be easier? Changing a set of heads or pulling the engine to change out pistons? Personally, I would look to different heads and hang onto the originals. In changing out the pistons, you will also need to hone the cylinders to get correct ring seat.
Intermediate
Joined: Dec 2005
Posts: 40
Likes: 0
From: Las Vegas Nv.
I had a local shop do my 882 castings. 2.02/1.65 and took the chambers down to 67cc. I would do it again. What a difference!!!
The 882s are not a great flowing head and are a prone to cracking. They recomended against any porting.
With the head work and a nice crane cam my L48 put out around 320hp.
Wouldn't roast the tires but it did run well.
I have since stored that engine and am running a 383.
The 882s are not a great flowing head and are a prone to cracking. They recomended against any porting.
With the head work and a nice crane cam my L48 put out around 320hp.
Wouldn't roast the tires but it did run well.
I have since stored that engine and am running a 383.
Le Mans Master
Joined: Apr 2005
Posts: 6,349
Likes: 419
From: Seattle Area WA
I take it you have the '882 heads with 76CC chambers? You should have a stock dished piston resulting in a mid 8.5:1 compression. Yes you can certainly change to a dome piston like a Speed Pro H618CP, and as listed in the catalog with 76CC heads combined with a std. .039head gasket results in a SCR of 9.5:1. A thinner gasket will bump you up a bit more. You didn't mention if your plan included a more radical cam or not. I would tend to disagree with not porting them. These do tend to be thinner castings and milling is much more risky than simple pocket porting and cleaning up the flash. A competition port job would be out of the question where one can really hog out castings.
The other option is to build a 383 with your existing block, heads and intake. This would make for a very nice, easy driving combo. A 383 with a L-82 cam will idle like stock, have extremely nice manners, and will pin you against the seat when you nail it.
The other option is to build a 383 with your existing block, heads and intake. This would make for a very nice, easy driving combo. A 383 with a L-82 cam will idle like stock, have extremely nice manners, and will pin you against the seat when you nail it.
Last edited by Scott Marzahl; Oct 12, 2007 at 06:43 PM.
One gear at a time
Joined: Aug 2003
Posts: 5,195
Likes: 24
CI 8-9-10 Veteran
St. Jude Donor '07-'08-'09
If your heads are still the 1972 casting, they are not the light weight castings. I would build a 383 out of the stock short block, with an internally balanced rotating assembly, and flat top pistons.
At a minimum, have your heads cut for 2.02/1.6" valves, and have the heads cut with a bowl hog, and pocket ported. I wouldn't hesitate to have the heads more fully ported. Port the stock intake (for ideas of how to port your intake, go to www.castheads.com and look at how they modify the OE intakes). Add a high lift short duration cam, and you will have a torque monster.
BTW, if you want your heads done right, send them to Mike Stark at www.cfmperformance.com . With his stage 4 or stage 5 port job, you will outflow most out of the box 200 CC and smaller aftermarket heads.
At a minimum, have your heads cut for 2.02/1.6" valves, and have the heads cut with a bowl hog, and pocket ported. I wouldn't hesitate to have the heads more fully ported. Port the stock intake (for ideas of how to port your intake, go to www.castheads.com and look at how they modify the OE intakes). Add a high lift short duration cam, and you will have a torque monster.
BTW, if you want your heads done right, send them to Mike Stark at www.cfmperformance.com . With his stage 4 or stage 5 port job, you will outflow most out of the box 200 CC and smaller aftermarket heads.
Last edited by Uesu; Oct 12, 2007 at 07:21 PM.
Le Mans Master
Joined: Apr 2005
Posts: 6,349
Likes: 419
From: Seattle Area WA
Wes likes strokers too 
Thanks for the clarification on the heads too Wes. Didn't the thin ones come in around '76 or so?? The L-82 cam is 224/224...114/114/114 with .450" and .460 lift. It's relatively mild with a later closing inlet (42 ABC) so it tends to like higher compression. With the 114 LSA it is designed for stock exhaust manifolds and has a nice idle.
Thanks for the clarification on the heads too Wes. Didn't the thin ones come in around '76 or so?? The L-82 cam is 224/224...114/114/114 with .450" and .460 lift. It's relatively mild with a later closing inlet (42 ABC) so it tends to like higher compression. With the 114 LSA it is designed for stock exhaust manifolds and has a nice idle.
Last edited by Scott Marzahl; Oct 12, 2007 at 07:07 PM.
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
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
Top 10 Corvette Engines RANKED by Peak Torque (70+ Years of Muscle!)
Joe Kucinski
Corvette ZR1X Will Be Pacing the Indy 500, And Could Probably Race, Too!
Verdad Gallardo
Top 10 Corvettes Coming to Mecum Indy 2026!
Brett Foote
Top 10 C9 Corvette MUST-HAVES to Fix These C8 Generation Flaws!
Michael S. Palmer
10 Revolutionary 'Corvette Firsts' Most People Don't Know
Joe Kucinski
5 Reasons to Upgrade to an LS6-Powered Corvette; 5 Reasons to Stay LT2
Michael S. Palmer
One gear at a time
Joined: Aug 2003
Posts: 5,195
Likes: 24
CI 8-9-10 Veteran
St. Jude Donor '07-'08-'09
Scott, not sure if the thin castings came out in 1975 or 1976. I would have to look at the outside edge of the head to tell.
I really like the Voodoo line of cams. For the OP's engine, I would run a 262 Voodoo, or a 268 Voodoo, but have lunati grind it with a 112* or 114* Lobe Separation. The 383 from my truck, that we briefly ran in the 62 Vette had a 268 Voodoo on a 112* LS.
With a stock TH350 and stock converter, the car would blow the tires away at LACR halfway to the 1/8 mile mark (massive spin, not a little chirp). That was done through a 1965 GM intake, that was less than ideal.
I really like the Voodoo line of cams. For the OP's engine, I would run a 262 Voodoo, or a 268 Voodoo, but have lunati grind it with a 112* or 114* Lobe Separation. The 383 from my truck, that we briefly ran in the 62 Vette had a 268 Voodoo on a 112* LS.
With a stock TH350 and stock converter, the car would blow the tires away at LACR halfway to the 1/8 mile mark (massive spin, not a little chirp). That was done through a 1965 GM intake, that was less than ideal.
Safety Car
Joined: Aug 2001
Posts: 4,883
Likes: 11
From: North Easton Mass
I plan to rebuild my numbers matching 350 base motor. Of course I want more hp's and don't want to kill the value by changing heads to the higher compresion heads. Does anyone know if I can get the same result by going to a high compresion piston instead? I may pocket port the heads but thought I should keep al the original castings.
Thanks
Thanks
Rick B.
Racer
Joined: Mar 2005
Posts: 393
Likes: 3
From: Dallas, TX
Any modification that you do to the original engine components is going to affect the 'collector' value. If you do some research you will probably find that for what it would cost you to rebuilt the original engine you could buy a higher HP crate engine. I would (and did) store the original engine and drop in any engine that you want, and go have some fun!
Rick B.
Rick B.
yank that old motor out and buy a nice powerful crate motor, if some day you want to or have to sell the car you can always put the original motor in to get top dollar. good luck with whatever you decide.-alex
Thread Starter
Instructor
Joined: Jul 2007
Posts: 193
Likes: 0
casting # on the heads are 3998993 and matches the black book. All the help Is appreciated although I am more undecieded whatr to do as my budget is around $2000. I plan to do the assembly myself but out source all the block and head work
Thanks
Thanks
Le Mans Master
Joined: Dec 2003
Posts: 5,727
Likes: 38
From: Fremont CA
Buy a set of Brodix IK180s, Edelbrocks, RHS 180cc heads or Vortec heads and "save" those valuable open chamber smog heads for the NCRS restoration that you must be planning in the future. The hardened exhaust seat is done by induction hardening that can be thin enough that it gets cut through on the first valve job. I wouldn't spend a dime on a 487 or 993 head for a performance engine.
