71 Big Block - Lead?
Team Owner
Joined: Jun 2000
Posts: 38,923
Likes: 1,482
From: Southbound
Cruise-In II Veteran
'74 and up heads can run on either fuel. Pre-74 heads are set up to run on leaded fuel and most do not have hardened valve seats. I agree with your mechanic. I run a can of lead substitute every other tank full in my '68. The alternative is to use '74-up heads or have hardened valve seats installed in your stock heads.
Team Owner
Joined: Feb 2005
Posts: 32,519
Likes: 1
From: central America
St. Jude Donor '08-'09
All information I've read says that 71 and up heads have the hardened valve seats for unleaded gas...GM was tooling up for when no leaded gas would be around
From personal experience, when I had my heads redone this spring, they took out the original hardened seats (72), so they should be hardened in a 71.
If you're really that worried about it, pull the heads off, and have hardened seats put in.
trw
From personal experience, when I had my heads redone this spring, they took out the original hardened seats (72), so they should be hardened in a 71.
If you're really that worried about it, pull the heads off, and have hardened seats put in.
trw
Safety Car
Joined: Aug 2000
Posts: 3,711
Likes: 43
From: San Antonio TX
Originally Posted by 72 stingray owner
All information I've read says that 71 and up heads have the hardened valve seats for unleaded gas...GM was tooling up for when no leaded gas would be around
From personal experience, when I had my heads redone this spring, they took out the original hardened seats (72), so they should be hardened in a 71.
If you're really that worried about it, pull the heads off, and have hardened seats put in.
trw
From personal experience, when I had my heads redone this spring, they took out the original hardened seats (72), so they should be hardened in a 71.
If you're really that worried about it, pull the heads off, and have hardened seats put in.
trw
For '70 and earlier engines, how the engine survives without hardned seats greatly depends on how the engine is used. The higher the exhaust gas temperatures, the higher the probability of the micro-welding that occurs and the valve sinking the seat.
To blanketly say that these non-hardened seats can or will benefit, or whether it's worthwhile to even bother, from a TEL additive ignores the primary consideration of how the engine is used. In a boat or work truck that sees peak torque for long periods of time, sure. For an occasional driver that doesn't usually see sustained operation at peak torque, probably not worth bothering about. At least not for many thousands of miles.
If the engine were going to the machine shop I'd probably have it done. But I wouldn't bother doing it just for this operation unless I was going to be hard on the engine.
