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Lead gas additive

Red73BB

Well-known member
Joined
Jun 15, 2001
Messages
241
Location
Defiance, MO
Corvette
1969 dark red convert
I resently bought a '73 with a 454 was rebuild 3 yeas ago for 425HP (or so the previous owner said). I've been using 93 octane and he suggested adding a lead additive to raise the octane level to 103 for better performance. It runs petty well w/o the lead additve but very well with. Would this damage the engine over long term?
Gary
 
R

robert kirk

Guest
i think 71 was the year they switched to hardened seats for unleaded gas. running 93 should not be a problem. to make a jump of 10 points in octane is hard to do with over the counter products. if you are not having any knocking problems with 93 now i don't think it will hurt the motor. detonation will destroy a motor just some thing to watch for. i have noticed detonation usually shows up under load, going up hill in say 3rd instead of 2nd. might want to check to make sure. hope this helps. robert
 
B

BradC

Guest
It was suggested to me.. to use the lead additive.. cause all the gas around here is unleaded...

So that is what I am going to do.. my uncles can get me a good discount on a case of that lead additive stuff :)
 
B

BBB454

Guest
I'm in the same boat (well, car)...

I have a rebuilt, bored .030 over 454, which the prior owner claimed dyno'd at 425 hp. Both the prior owner and the car's mechanic told me to use lead additive to prevent engine damage, so I have plus I always use the highest octane gas at the pump. I did notice a few weeks ago when I put in lead additive AND octane booster, the car ran the best it ever has.

On a separate note, I'm curious to know what you get for gas mileage, Red73BB? I was averaging 10 city/12 hwy before I put on the K&N air filter. It was then about 11 city (didn't test hwy only). Now I've just had Flowmasters installed and have only been able to test it on the highway (going to Bloomington & back) and got almost 14 mpg. I'm really curious to see what my city mpg will be now! Not that gas mileage really matters that much, because I'll drive it anyway... :) Just fun to compare...

Barb :w
 

Red73BB

Well-known member
Joined
Jun 15, 2001
Messages
241
Location
Defiance, MO
Corvette
1969 dark red convert
I too have a K&N air filter but with stock exhaust system. My mileage is alway about 10 MPG. I don't do alot of highway driving, but even when I take it to work (64 miles round trip) it still is about 10. Mine is a automatic which probably make a difference. I was at Bloomington on Saturday, I bought a heat shield for under the carpet, tired of hot feet. I really enjoyed the day.
 
B

BBB454

Guest
Flowmasters...

I have also purchased the heat shield for under the carpet but haven't installed it yet. Please let me know if it helps...

I might be crazy :crazy, but I would swear that since installing the Flowmasters (kept the stock exhaust manifold & pipes), I don't feel as much heat through the floor and/or vents!

Barb :w
 

Red73BB

Well-known member
Joined
Jun 15, 2001
Messages
241
Location
Defiance, MO
Corvette
1969 dark red convert
I won't install the heat shields until I replace the carpet which is original. Thats my next project. My car is getting a new front bumper installed and repainted this week. The old bumper was original, I repaired it once with flexable glue but the results wern't very nice. So I bought a "trueflex" fiberglass bumper. The body man said it was the easiet bumper installation hes done on a Corvette.
Gary
 

charlie v

New member
Joined
Jun 12, 2011
Messages
1
Location
lebanon tn
Corvette
1969 coupe
lead additive

I resently bought a '73 with a 454 was rebuild 3 yeas ago for 425HP (or so the previous owner said). I've been using 93 octane and he suggested adding a lead additive to raise the octane level to 103 for better performance. It runs petty well w/o the lead additve but very well with. Would this damage the engine over long term?
Gary
i used the additive and it stopped up my fuel filter and settleed in the tank
 

Mac

Well-known member
Administrator
Joined
Feb 13, 2003
Messages
5,476
Location
Ottawa, Canuckistan
Corvette
1973 coupe L82 (gone as casualty of divorce)
i used the additive and it stopped up my fuel filter and settleed in the tank
Welcome aboard, Charlie!

In case you might not have realized such, this thread was last active in 2001. We keep our old threads around so if folks want to dig up information which was posted in the past.

-Mac
 

Bolisk

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Joined
Nov 2, 2007
Messages
441
Location
Crystal Lake IL
Corvette
1972 LS5 Convertible PS, PB, A/C
So a few things to note here. Most products that are marketed as a lead additive, do not actually have lead in it ( hence no octane boost ). Those products are specifically formulated to help protect non hardened valve seats, and that's it. I can also tell you that these products do not really work. I have a 1970 lt-1 with non hardened valve seats and i just got done rebuilding my heads because i burnt up my exhaust valves.The lead that was in fuel of the 60's and early 70's is called, Tetraethyllead. It was and additive that prevented knocking, or detination in hight compression engines because of the huge octane boots you got with the additive.There is only a few products on the market that has Tetraethyllead in it, and they cost a ton of money. Same type of thing for most of the octane boot products out there. They are various forms of alcohol and don't really give u much of a boost in octane rating. If you want highter octane fule, the right thing to do is buy racing fuel, higher than 93 octane fuel if you can find it, or find a additive with Tetraethyllead in it.However if your car has hardened valve seats and does not knock or detinate, then there is no need to run a octane boost of any kind. If your car does not have hrdened valve seats, get a Tetraethyllead additive, or get your heads machined for hardened valve seat.
 

Vettehead Mikey

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Joined
Aug 26, 2003
Messages
3,487
Location
Not that far from Ottawa
Corvette
1973 Coupe
As Mac said- this thread has been dead for ten years and the OP is apparently long gone.

Bolisk- I've never heard of a Corvette that experienced 'burnt valves' due to lack of lead.
 

Bolisk

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Joined
Nov 2, 2007
Messages
441
Location
Crystal Lake IL
Corvette
1972 LS5 Convertible PS, PB, A/C
Just because a thread is old, does not not mean that isn't valid for people who are looking/searching to solve a similar problem. Since the origional question/concern was never answered (in my opinion) and because people are clearly searching on the subject contained in this thread; why not try to add more detail to the discussion. That way, when people come accros this thread in a search. . .maybe it will have the answers they are looking for. . .therefore preventing it from being bumped again. Clearly, because it was bumped, this thread did not have the answers people were looking for. If people really have a problem with old threads being bumped, then the admins should consider deleting all threads older than a certain date.

With regards to burnt valves, I belive (and I may be wrong) that it is common knowledge that if you do not have hardened valve seats and you do not run leaded fuel, you run the risk of burning up your exhaust valves, or melting your non-hardened valve seats.
 

Vettehead Mikey

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Joined
Aug 26, 2003
Messages
3,487
Location
Not that far from Ottawa
Corvette
1973 Coupe
With regards to burnt valves, I belive (and I may be wrong) that it is common knowledge that if you do not have hardened valve seats and you do not run leaded fuel, you run the risk of burning up your exhaust valves, or melting your non-hardened valve seats.

As I said, I've never heard of a burnt valve in a Corvette from lack of lead. The 'need for lead or the sky will fall' is more of a common myth than common knowledge. GM had concerns that valve seats (not valves) would deteriorate through microwelding of the contact faces but this proved to be a phenomena pretty much restricted to heavy commercial vehicles or full size cars pulling trailers up the side of a mountain etc. It takes two factors to induce valve seat deterioration- heat and time. Corvette engines never run hot enough for long enough on the street to experience any issues. The large number of unmodified engines from the pre-hardened seat days that are still around is testament to this. Note that the valves them selves did not change in composition, only the valve seats themselves were considered at risk. They were hardened via an induction process, rather than the much more costly method of inserting a seperate machined seat. This latter process offers some collateral risks as well with the possibility of the seats dropping into the combustion chamber or the cooling passages accidentally becoming exposed during machining.

As for octane boosters, you are correct that very few of them actually contain tetraethyl lead due to environmental laws. Non-TEL octane boosters may contain other chemical compounds that can give a moderate boost in octane rating but none of them are economical enough to make it worthwhile or effective.

Having said all that, street driven cars that actually NEED or will benefit from anything higher than pump gas are few and far between. The OP mentioned a '73 that was modified to supposedly 425 horse- the equivalent of the '65-'68 BBCs in Corvettes that ran just fine on 93 pump octane. He also makes no mention of detonation while on pump gas, so running higher octane will be of no benefit as mentioned earlier. :beer
 

navy2kcoupe

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Dec 16, 2006
Messages
799
Location
West Central FL and SE Mass.
Corvette
2000 Navy Blue Coupe A4 Z51
Tetraethyl lead (lhttp://en.wikipedia.org/wiki/Tetraethyllead) will also destroy catalytic converters, and that's another reason they did away with it. I used Amoco "white gas" (unleaded) back in the day in my 1964 Dodge Polara 500 with no harmful effects whatsoever. Regular oil changes and maintenance let this engine run for 195,000 miles before the car was driven to the junkyard.
Andy :w
 

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