Go Back   Corvette Forum > C3 Corvettes, 1968 - 1982 > C3 Tech/Performance
Sign in using an external account
Register Forgot Password?
Register Search Today's Posts Mark Forums Read FAQ Vendor Directory
Search
C3 Tech/Performance
V8 Technical Info, Internal Engine, External Engine, Basic Tech and Maintenance for the C3 Corvette Sponsored by
VBP

Welcome to Corvetteforum.com!
Welcome to Corvetteforum.com.

You are currently viewing our forum as a guest, which gives you limited access to view most discussions and access our other features. By joining our community, at no cost, you will have access to post topics, communicate privately with other members (PM), respond to polls, upload content and access many other special features. Registration is free, fast and simple, join Corvetteforum.com today!


Corvette Store
 
 
C7 Parts & Accessories
C6 Parts & Accessories
C5 Parts & Accessories
C4 Parts & Accessories
C3 Parts & Accessories
C2 Parts & Accessories
C1 Parts & Accessories
Wheels & Tires
Sponsored Ads
 
 
Vendor Directory
  
Reply
 
 
 
 
Thread Tools Search this Thread
Old 04-23-2013, 01:16 PM   #1
jrheyerly
CF Member
 
Member Since: Feb 2011
Location: Molalla Oregon
Default 1972 LT1 heads and performance vs 1970 LT1

What are the specifications for the factory heads on a 1972 350 LT1?

Intake and exhaust diameter?

- Combustion chamber size and design vs 70 350 LT1 and 72 base 350.

How do these engines perform in stock form compared against the 70 LT1(370 HP) or say even a 70 base engine 350? I had the base 300 hp 350 engine in a Chevelle with a Muncie M20 and it was impressive. That was 30 years ago, but I still remember the mid range of that motor. It would rev to about 6200 and stop. I think the hydraulic lifter cam would start to float about that RPM range.

Currently dealing on a 72 LT1 in the $20-22 range. I have just started the inspection and numbers process on the car. Will post pictures soon, as your opinions here are interesting and valuable.
jrheyerly is offline   Reply With Quote
Old 04-23-2013, 01:24 PM   #2
keithinspace
CF Senior Member
 
keithinspace's Avatar
 
Member Since: Jan 2012
Location: Fredericksburg Virginia
Default

I could be totally off base, but I think the heads are nearly identical.

The big difference is the decrease in compression ratio which was achieved by a change in the piston.

And, of course, the addition of the air pump crap.

All in all, though, I think the fundamentals of the engine are identical from 1970 to 1972.
keithinspace is offline   Reply With Quote
Old 04-23-2013, 02:31 PM   #3
Ben Lurkin
CF Senior Member
St. Jude Donor '09
 
Ben Lurkin's Avatar
 
Member Since: Dec 2006
Location: Oquirrh Mountains
Default

Quote:
Originally Posted by jrheyerly View Post
What are the specifications for the factory heads on a 1972 350 LT1?

Intake and exhaust diameter?

- Combustion chamber size and design vs 70 350 LT1 and 72 base 350.

How do these engines perform in stock form compared against the 70 LT1(370 HP) or say even a 70 base engine 350? I had the base 300 hp 350 engine in a Chevelle with a Muncie M20 and it was impressive. That was 30 years ago, but I still remember the mid range of that motor. It would rev to about 6200 and stop. I think the hydraulic lifter cam would start to float about that RPM range.

Currently dealing on a 72 LT1 in the $20-22 range. I have just started the inspection and numbers process on the car. Will post pictures soon, as your opinions here are interesting and valuable.
The primary value of those heads is for restoration purposes. Beyond that, "performance" and 1960-1970's cylinder heads should not be used in the same sentance. They were good heads - fourty years ago.

It's been way too long since I played with these to remember exact specs. but there's not much difference between them other than '70 has a 64 cc combustion chamber and '71-72 had 76 cc chambers. Valves in both should be 2.02"/1.60".
Ben Lurkin is offline   Reply With Quote
Old 04-23-2013, 03:51 PM   #4
farmall
Junior Member
 
Member Since: Dec 2008
Location: Central Oregon
Default

I remember something about hardened valve seats on the 71-72.
Lower compression is easier on the wallet at fill up.
I cant speak for 70 power but the 71 LT1 is plenty fun.
farmall is offline   Reply With Quote
Old 04-23-2013, 04:05 PM   #5
Mike Ward
CF Senior Member
 
Mike Ward's Avatar
 
Member Since: Jul 2001
Location: about an hour away from Paul74 in Ontariariario
Default

Quote:
Originally Posted by keithinspace View Post

And, of course, the addition of the air pump crap.

All LT-! engines 70 through 72 had AIR crap. It cost a whopping 1 HP.
Mike Ward is offline   Reply With Quote
Old 04-23-2013, 06:42 PM   #6
Ironcross
CF Senior Member
 
Ironcross's Avatar
 
Member Since: Nov 2002
Location: Taylor Michigan
Default

1970 engines had pink rods and much better that the following LT-1`s, Several years ago a set of 8 were $800.00 bucks...the heads have guide plates and screw in studs...the 71-72 engines also had a cam change and quite possibly be hydraulic .....and the reason Air could be ordered in 72....the solid lifter 370HP was not available if Air was ordered......The heads as far as I was concerned was the best available for SB engines...Being a simple engine swap I ordered one for my 62 and the cost complete, was $612.00 over the counter and delivered....all the engine lacked was the carb and coil through 'Art Moran Pontiac in 1970
Ironcross is offline   Reply With Quote
Old 04-23-2013, 09:55 PM   #7
LT-1 kid
CF Senior Member
 
Member Since: Sep 2007
Location: cary Il
Default

the only diff was 70 had 11:1 compresion and small chamber heads, all year LT-1s had upgraded hardware, {rods, crank, pistons} soild lifters same cam, scwew ins guide plates big holly . and 72s had no ti, thats it.
LT-1 kid is offline   Reply With Quote
Old 05-10-2013, 02:37 AM   #8
edmguru
Junior Member
 
Member Since: May 2013
Default

Quote:
Originally Posted by Mike Ward View Post
All LT-! engines 70 through 72 had AIR crap. It cost a whopping 1 HP.
Wrong wrong wrong---domestic U.S.A only corvettes had AIR installed. Export versions I.E Canadian versions had AIR delete options.How do I know, you ask. I own one with an original build sheet listing the AIR delete export option, listed
edmguru is offline   Reply With Quote
Old 05-10-2013, 08:06 AM   #9
Easy Mike
CF Senior Member
Cruise-In II Veteran
Support Corvetteforum!
 
Easy Mike's Avatar
 
Member Since: Jun 2000
Default

Quote:
Originally Posted by edmguru View Post
...I own one with an original build sheet listing the AIR delete export option, listed...
Can you post a pic of your build sheet? I am sure many of us would love to see it.

Easy Mike is offline   Reply With Quote
Old 05-10-2013, 08:10 AM   #10
7t9l82
CF Senior Member
Support Corvetteforum!
 
7t9l82's Avatar
 
Member Since: Oct 2010
Location: melbourne florida
Default

LT-1 kid is 100 percent correct, and no the LT-1 never had a hydraulic cam, that was the L-82.

Last edited by 7t9l82; 05-10-2013 at 08:15 AM. Reason: delete quote
7t9l82 is offline   Reply With Quote
Old 05-10-2013, 08:29 AM   #11
Solid LT1
CF Senior Member
 
Solid LT1's Avatar
 
Member Since: Dec 2003
Location: Fremont CA
Default

We have both a 70 and 72 LT-1 in our garage so maybe I can give some insight. The 186/492 casting 1970 LT-1 head is THE BEST head ever installed on a production line small block motor needing end bolt bosses for accessories. Even the base 350 motor was equipped with a variation of this head but lacked the screw in rocker studs guide plates big valves and combustion chamber rework for those big valves. Bolting on a set of 70 LT-1 heads was common practice for 71-72 owners back in the early 70's you would pick up 20-30HP and much more bottom end torque ( also raised your compression ratio almost a point.) The early heads actually will lose to the 71-72 heads on a flow bench comparison but there is more than flow happening in the cylinder. The closed chamber design is more efficient at combustion and helps create more power hence more NOX emissions so GM and all automakers had to modify their motors for changing emissions standards.

The late great John Ligenfelter onced tried to lobby the NHRA to allow Chevy Super Stock cars of the early 70's to use the early heads but failed. John made his reputation racing a 73 Vette sponsored by Graf Enterprises and once while competing at the US Nationals had a helicopter fly to his Decauter shop to source a replacement engine to continue competing (didn't have a Hollywood ending but the tale of his extreme effort lives on.) Johns advantage in using the Vette in Super Stock was the weight distribution, traction advantage of IRS and the giant oil pan the Corvette chassis allowed him to run.
Solid LT1 is offline   Reply With Quote
Old 05-10-2013, 08:43 AM   #12
7t9l82
CF Senior Member
Support Corvetteforum!
 
7t9l82's Avatar
 
Member Since: Oct 2010
Location: melbourne florida
Default

glad you pointed out they unshrouded the valves, lots of people install bigger valves in their heads and lose power because of the curtain.

Last edited by 7t9l82; 05-10-2013 at 12:13 PM.
7t9l82 is offline   Reply With Quote
Old 05-10-2013, 10:16 AM   #13
Mike Ward
CF Senior Member
 
Mike Ward's Avatar
 
Member Since: Jul 2001
Location: about an hour away from Paul74 in Ontariariario
Default

Quote:
Originally Posted by edmguru View Post
Wrong wrong wrong---domestic U.S.A only corvettes had AIR installed. Export versions I.E Canadian versions had AIR delete options.How do I know, you ask. I own one with an original build sheet listing the AIR delete export option, listed
Quote:
Originally Posted by Easy Mike View Post
Can you post a pic of your build sheet? I am sure many of us would love to see it.

Many of us would just love to see that. Cars other than Corvettes exported to Canada and before 1969 are known to have 'smog delete' RPO KD1.

Never seen a Corvette with that option, in fact every original Canadian LT-! I've ever seen most definitely had AIR.
Mike Ward is offline   Reply With Quote
Old 05-10-2013, 10:16 AM
 
Go Back   Corvette Forum > C3 Corvettes, 1968 - 1982 > C3 Tech/Performance
Reload this Page 1972 LT1 heads and performance vs 1970 LT1
 
 
 
Reply


Thread Tools Search this Thread
Search this Thread:

Click for Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Which build should I plan for? 69L71 C3 Tech/Performance 8 08-06-2014 12:57 PM
1972 LT-1 engine question thomaswat C3 Tech/Performance 12 04-20-2014 12:49 PM
L46 350cid engine 1968-72 Corvette PR C3 Tech/Performance 6 12-29-2012 10:05 AM
'72 horsepower question TSAGG C3 Tech/Performance 20 12-21-2005 10:46 AM
350 vs 406 69L71 C3 Tech/Performance 9 06-20-2002 06:19 PM


All times are GMT -4. The time now is 04:26 AM.


Emails & Password Backup