I have a 427 in my 69 and it doesn't
have hardend seats.
Does anyone have any suggestions for
me on a gas additive? Is a lead substitute
OK to use? or is there something better?
Has anyone heard of using ATF? I was told
that about 3 oz. for about 10 gallons of gas
would take care of it. Is this true??

Don't know about ATF. I've head of using it to clean fuel injectors. My neighbor swears by it. My neighbor is also one wave short of a shipwreck.

I use Gunk lead additive. Haven't had any trouble so far.

If you're going to keep those heads you might want to invest in hardened seats. It's bad enough with gas prices how they are. Worse when you add in an extra $3 or $4 per fill up for the additive. The new seats would pay off relatively fast.

Chad

I use the lead substitute made by CD-2. Last time I bought it was from WalMart. One bottle treats 240 gallons.

Unless you're towing a trailer at 100mph all day or otherwise keeping the engine under heavy load all the time, valve seat recession isn't an issue; when the time comes for a rebuild, hardened exhaust seats are probably a good idea, but in the meantime I wouldn't worry about it. Most of the store-shelf additives are LOADED with alcohol, and they'll do more damage to the gaskets and seals in your fuel system (and eat the plating off the inside of your float bowls) than they're worth. graemlins/thumbsup.gif

I would agree with John. I used 2 tanks full of leaded race fuel mixed with pump gas on a fresh engine with no hardened seats and figure that should be enough. I doubt that you will ever need any repairs for many miles and the danger of trashing a head during the seat instalation process makes it questionable unless they have already receeded. If you must install the hardened seats, put them on the exhaust side only. The intakes should be fine. Just my opinion.

-Mark.

I'll throw in one more "just keep driving it" for grins. Big Blocks just dont seem to have the problems that small blocks do with valve recession. You probably wont drive it enough in ten yers to have a problem.
Enjoy,

When I had my heads reworked, the machine shop installed hardened exhaust seats for 5 bucks each. Money well spent, even if I don't drive it much.