Do I need a lead fuel additive for my engine? It's a '69 383 with what I believe are 906 heads.
From what I understand, later 70's heads had redesigned valve seats that didn't need lead as a lubricant, but the earlier heads do?
Thanks for the help!
The reason is that the valve seats won't be hardened. But I don't think you can add it legally. My understanding is we just run with the current gas.
906 - no hardening
346 - induction hardened
452 - hardened seats.
Course anything could have been changed over the last 40-50 years.
I ran lead additive all the time once everything got switched to unleaded, but not sure what's available in stores these days though. Not that I care, I'll be adding 100LL Aviation fuel to my tanks to keep the lead ratio old school for my driving needs, I have a 500 gallon tank of it in the yard. :yesnod:
If you can mix run some leaded race fuel or av gas once it while you should be ok, or just run it as is and if and when the heads wear out just replace them with some Stealth or Edelbrock heads which would have the hardened seats and be good performance upgrade over the prehistoric 906 heads.
After 50 yrs, they are probably wore out anyway. But i have found that unless you are running a big cam, you will be fine, dont worry about it.
Quote from: birdsandbees on March 19, 2017, 06:50:36 PM
Aviation fuel to keep the lead ratio old school for my driving needs, I have a 500 gallon tank of it in the yard. :yesnod:
Good idea.
There was an extensive work-up by someone about this, and we've been adding 1/2 gal leaded race fuel per tank for our '69 906s. And a warning against aviation fuel.
Gunk makes a lead additive that I have used for years in my 67. I post a bottle in every few tanks.
Advance & Auto Zone carry it.
Thanks for the replies, all :cheers:
I used a concentrated additive produced by CD2. I got it at the Farm & Fleet stores. The label said it was for off road vehicles.
I remember there being claims that avgas has changed, losing old benefits and gaining new problems for cars, and that most additives only use non-lead substitutes (at least non-Tetraethyllead). Also that unless it's a high-mileage or high-hp/blown engine, non-hardened valve seats are a non-issue. Still tryin to dig up the technical paper we relied upon months ago to use leaded race fuel (erring on side of caution but probably unnecessary).
This thread has surprised me. We can only get unleaded over here but I never even dreamt that it may be an issue when I get my 69 on the road. The reason was that we have had unleaded since the eighties here and it became mandatory in about 92...when cats became compulsory on new cars which of course will be damaged by lead. Now I thought you guys had unleaded fuel for many years before us so I assumed the valve seats on a bb would be designed for the job.....guess I never thought about actually how far back you guys had that fuel...or didn't! You can buy lead substitute additive here at least!
So even if you are running E-85 you still need hard seats because of the recession factor I would assume ?
We don't have those due E numbers over here....I've no idea about those. If it's the % like I've read before then that does not apply to fuel here....yet.
You can add all these additives OR......
Just replace the stock iron heads with rebuilt ones with hardened seats OR better flowing, better performing aftermarket aluminum heads.
I see it as a waste of money.... snake oil if yku will. Think about it, there are only a few scenarios here. 1: the heads have been rebuilt and have hardened seats. 2: the heads are 50 years old and have never been apart and the valves are sunk so far into the seats after 50 years of run time that no additive in the world will prevent. Guides are probably shot as well. 3: you have a low mile bone stock survivor engine and the valve springs are so weak that you will never hurt the heads anyway.