# 68 GTO stock engine



## rob40999 (May 18, 2018)

Hello All: It's Bob again:

Got a question:

1. Does anyone out there put Lead in there Gas for a 68GTO 400cu engine stock.

2. My gas station has 93 octane.

3. I've heard so many different stories.

4. Also does anyone put Miricale oil in there gas or engine?

Thank you, Bob


----------



## BearGFR (Aug 25, 2008)

You'll get different opinions on the leaded vs. unleaded gas question with regard to running it in 'older' engines that don't have hardened exhaust valve seats.

My personal opinion is that unless you're consistently putting heavy loads on the engine, such as pulling a trailer, climbing steep hills, racing a LOT... you're not likely to experience any valve seat recession problems running unleaded 93 in these engines.

The bigger and more frequent issue is that of detonation.

Bear


----------



## PontiacJim (Dec 29, 2012)

I asked the question of unleaded gas and valve seats to Nightmare Performance who is a known Pontiac engine builder. I am too of the mindset that you are OK without the hardened exhaust seats as long as you do not build a lot of heat in the cylinders from things like towing a heavy load for long periods which causes engine/exhaust temps to climb or probably long periods of a lean mixture condition or even heavy nitrous use. Nightmare performance stated that even with stainless steel valves and wide margins on the valves, he said an additive is still needed to make the stock (non-hardened) valve seats last. Now I don't know what the definition of "last" means and I would also suspect that from my research/reading that high valve spring pressures pulling on the valve is a contributing factor on valve seat life.

Nightmare Performance emailed me back with this response, ".......Drivens Defender/Booster is the best additive and it does 3 things; saves the carb during storage, gives very small octane increase and makes the exhaust seats live. ½ bottle per tank full for normal driving and a full bottle per tank full when racing."

I have not tried the product, but will once my car hits the road. I use Stabil 360 right now in my other older vehicles, as does my brother, and in my opinion, it seems to work by preserving the ethanol gas longer and my cars run better. It does not have any octane improving properties like Defender/Booster does.

https://www.drivenracingoilsales.com/defender-booster-10oz-bottle/


----------



## rob40999 (May 18, 2018)

WOW !!!!!!! Bear what a great reply to my valve tapping problem... I surely will take the valve cover off and torque down that nut to 20 feet lbs.

WOW !!!!! Good reply Jim on the gas... 

I'll get back to you two on the Tapping noise...

Thank you, Bob


----------



## BearGFR (Aug 25, 2008)

rob40999 said:


> WOW !!!!!!! Bear what a great reply to my valve tapping problem... I surely will take the valve cover off and torque down that nut to 20 feet lbs.


... Please, ONLY if you're POSITIVE that what you have is the stock setup. If that's what you have, then don't just do one - do all 16.

Bear


----------

