Poor Gasoline Quality

[gchandler]

I live in Los Angeles, and over the last few months both my Mustang (1990 bone stock) and Chevelle (zz383) have been detonating like mad under full load.

I have made no changes to the cars recently. Last time I had the Mustang at the track I put in a few gallons of 100 octane, the car became quite happy.

Note that the Mustang is designed by Ford to run on 87 octane, I always use 91, but lately it seems that this is still not enough.

Has some major change been made to our gas out here recently?

Do I need to start mixing in race gas with each tank just to get up to a reasonable fuel quality?

[shmoov69]

I was wondering the same thing. On low boost my 69 is still rattling also. I have heard that the "winter grade" of gas is not as good as "summer grade", but dunno? Also, you would think that SoCal would not have 2 grades.

[gchandler]

I'm not crazy.

It seems that if you have a car that does not have knock sensors these days you are plain out of luck, while everyone else just gets to enjoy sweet, sweet, low performance and poor mileage.

[1969CamaroRS]

I dunno maybe it is the brand of gas, I just broke in my new 489 (9.8:1 compression) on Chevron super(91) and didn't have any problems.

[MonzaRacer]

The one thing you may need to do is add on water/ethanol injection. it will help in 2 ways by one increasing the engines "seen" octane ingestion, it will also help clean out the carbon in the conbustion chamber and it allows much harder running.
Now in the real world terms you should take your cars into someone who can custom taylor the tune for fuel in your area.
Now if you want to do it your self try www.megasquirt.com as you can do as much or as little as you want with that and with one of the guys on there EEC adaptor you can ajust plug the stock computer back in too.
But the big thing is it woul allow you to add in knock sensors to the heads and then taylor a retard strategy so you dont get a lot of knock.
I actually have several 5.0 Mustangs running around and we simply swapped in GM TPI computers and on one went to www.moates.net and get several multi step chips and tuned several differernt stratagies and we had a simple 5 place settings and we had one for "stock" and went up to the last place as it tuned for a 200 shot of NOS.
Seimans makes several knock sensors that simply sit under a bolt.
Now in Sunny Cali I would give Evans Cooling a call (1-888-990-2665) and I would order up some flush and 2 or 3 gallons of NPG-R.
In several extreme tuned engine that we had spec fuel to use and with a few of them we had knock issues, both heard and unheard(ie we had aluminum specs on plugs) the NPG-R is a done deal and it added qite abit of torque and hp as we had the ability to tune the engines even harder and the spec engines we set up started setting records. What pissed one guy off was that we had the engine all within 5 hp and 3 lbft of torque hahaha so buying 3 engines got him nothing but broke.
$13,000 engines(air cleaner to oil pan with 5 galons of coolant in crate) and he got sponsors to buy 3 and one showed up on ebay(not supposed to be sold actually) and went for $4380 OUCH.
But tuning and a water injection kit should fix your issues and Evans NPG-R as a close third.