Hi Guys,

Was wondering what the opinions are about octane boost and lead additives? Are you guys using them on your BB C3's or even the SB C3's? Do they make the car run better? Considering how manipulated today’s gas is? Or are they a waist of time? Any thoughts would be appreciated. If so which brands are you guys using?

Thanks
MMH

 

lead will destroy your CAT. i personally only use the carb cleaner/fuel filter cleaner junk. put it in when i first bought it and thats it. idk about octane boost but i doubt its very helpful in the later c3s. if u have low compression i think that lower octane is better. not sure tho. ask one of the engine gurus

 

This used to be an interesting question the first 1000 times it got asked. I hear that search function doesn't work so, it's not your fault that you can't see this poor beaten to death topic.

Summary:

You don't need, and will not benefit from any additives for your gasoline.

This presumes that you are not suffering from pre-ignition and are using the recommended octane level of gas.

Bubba and his friends will soon jump in to tell you that the additives will make your car do wonderful things and maybe even it will improve your own performance under the sheets.

It's up to you whether you want to believe in fact or myth.

 

Lead additive not needed even in an old engine originally designed for it. And octane boost is a waste of $$.

 

ok an note on octane here

if your running 6:1 to about 9.5:1 87 octane will work just fine
you can push 10.5:1 with it but only if u have Knock sensors but i would not do it unless u hate your car engine

9.6:1 to about 11.1:1 92 Octane will work just fine

11.2:1 to 12:1+ i would use 100+ octane gas

Ryan

 

And what has this got to do with C3 Corvettes?

 

Mike W i was referring to Octane in general on that comment not realy aimed to C3s but just for the average Joe who reads this and is a little confused about octane. I should have added what octane is though to. octane rating is just an rating given to show gases ability to detonate under pressure and heat the higher the better ie more compression and or boost you can run.

on gas additives many of them are made to make money ie meaning you really don't need them

about the only good ones are Injector/Carb cleaners some filter cleaners.

Ryan

 

Octane Booster is a waste of money.
Lead Additive however, is required in my 69 small block, or has been(I'm about to rebuild it).
The valve seats in the "older" cars are soft, and were lubricated by the lead in older gasoline. I add a bottle with every fill-up, and have been told to do so even by old school mechanics also.
Since I'll be putting in hardened seats, I'll no longer need the additive.

 

Ryan, How do aluminum heads effect the octane needed?

 

not shure its more on the combustion chamber type ie how it swirls in there. and what compression it runs. just giving the nature of Aluminum heads from what i have seen i would guess 92 octane would be safer

if they are in the 8.0-9.5 range i would image 87 would be ok

Ryan

 

Aluminum heads dissipates heat better, which bring the combustion chamber temp down a bit and as a result you can get away with a bit more CR probably about .5 over iron heads. The only possible way that octane boost can help is if you tune your ignition for higher octane, If you do this you will need to run higher octane all the time. higher octane on newer car can increase power but only if the computer will advance the timing enough. On your C3 probably a waste of money and time

 

 

Thanks Guys!

 

Thank you

 

Sorry, that is false and is one of the oldest myths surrounding these cars. You've been wasting your money on additives that 1) you didn't need in the first place 2) didn't have enough lead to do anything anyway.

This legend started when manufacturers starting adapting engines to meet upcoming pollution requirements of the early 70s. It was noted that engines run flat out under max load would suffer from 'microwelding' of the exhaust valve face and seats. This lead to the development of hardened valve seats that became the production standard across all car lines a few years later.

No Corvette runs hard enough or long enough to develop the extreme valve seat temps that would lead to microwelding. A full loaded dump truck climbing a mountain probably, a motor home pulling a trailer at highway speed maybe, but never a Corvette. 40 years later we're all a bit smarter and realize now that the sky is not falling. Don't believe me? Go to any engine shop and demand to see burned valve seats from a car engine. There aren't any- so don't hold your breath.

Most responsible engine builders will refuse to install hardened seat on a set of vintage heads due to the possibility of machining right through the walls into a passage and rendering them scrap on the spot.

It never fails to amaze me how many people put unquestioning faith in what 'old school mechanics ' say, then repeat what they've headr without question as being 'the gospel'

 

good point

 

Don't be so sure about all this being a myth. I HAVE seen the effects of valve recession at the machine shop in the local NAPA where I worked for a while after retirement. According to the machinist, who also built and ran several cars at the strip for many years, valve recession might not show effects for many thousand miles and then progress rapidly in a short time. The problems I saw were from customers' cars and not the ones he raced.
I know from some of your past responses on the forum that you will answer to defend your belief but I will not continue an argument or get into a pi**ing contest. This topic as well as oil, religion, and politics are ones that most of us have firm opinions.
Terry

 

You're right- but what you saw was normal engine degradation normally seen after many thousands of miles on engines run with or without lead and with or without hardened seats. Big difference between that and the valve recession caused by microwelding.

I used to do tons of valve jobs in the late 60s and early/mid 70s on all makes of V8s from 260 Fords up to 455 Rockets, not to mention straight 6s.

No difference in service life between the two types of seats.

 

no octane booster, nor lead additives here...using Sunoco highest blend, 260, and compression is around 10.5

 

Mr Ward is correct. TetraEthyLead was developed as an octane booster, PERIOD. The story of lead as a lubricant was started by oil companies who did not wish to spend the $$ to switch boosters.