C1 '62 - Octane recommendation

[Donald B.]

I have a '62 327 250HP that has never been restored. I want to add Kemco's Octane Supreme 130 to the fuel but don't know how much to add. I need to know what the original recommendation was for the gasoline octane rating.

Correct me if I'm wrong - once I know the recommended octane rating I can simply calculate the difference between the original octane recommendation and the current fuel rating of 91 octane and add Kemco to make up the diffence.

RIGHT ?

Thanks

[Dave S.]

Re: C1 '62 - Octane recommendation

Don,
I use tetraethyol lead in my original motor cars. From memory I think it is Supreme 130. I add 12 ounces per tank. Many knowledgeable people who contribute to this board seem to think it is not necessary but I happen to have some on hand and will use it until its gone. It does serve as a good octane booster and the cars seem to run well with it.

[Bob R.]

Re: C1 '62 - Octane recommendation

Just my opinion but I don't believe you should need any octane booster for a 250hp engine. You shouldn't need the lead additive either under normel driving conditions.
My 63 with 300hp runs fine on todays high test fuel. When the engine was rebuilt a couple of years ago I asked about lead additive and was told it would only be needed if the car was raced or driven very hard. I've got about 2000 miles on the engine with no problems.

[Mike McKown]

Re: C1 '62 - Octane recommendation

I'm not sure you should have to add any. My '63 300 hp and '65 250 run fine on 92. They seem to also run just as well on 89 octane. No ping, no knock. Timing set to factory specs. Essentially the same engine configurations as yours'.

[Duke W.]

Re: C1 '62 - Octane recommendation

I doubt if you need anything more than the best pump premium available: 91 might be marginal, 93 should be okay. Run a test! Check that your original timing is to spec. I think it is only 4 degrees, but can be increased if it doesn't detonate.

Duke

[Tom S.]

Re: C1 '62 - Octane recommendation

My 69 350/350 runs just fine on 93 octane, I have the timing set at 12 degrees and no ping at all.

Tom

[Chas Henderson #28127]

Re: C1 '62 - Octane recommendation

I have been running on 87 octane for over 20,000 miles sense I had my original 350 rebuilt in my 71.(1999) I have no run on or pinging. Starts well and seems to run well. Not crazy about 12-14 mpg, but it is set to factory spects and doesn't over heat. I know the 71s' were set up to run on unleaded fuel, but I don't know what octane rates were suggested. If I ran 89 or even 91 octane, how would I tell the differance?

Chasman

[Duke W.]

Re: C1 '62 - Octane recommendation

All 1971 GM engines were designed to operate on 91 RON unleaded gasoline, and today's 87 PON has essentially the same antiknock qualities. If your engine was rebuilt with the OE 8.5:1 speced CR it should run without problem on 87.

The 250 and 300 HP early 327s had a specified CR of 10.5:1, and the octane requirementfrom the ownwer's manual IIRC was 97-98 RON. SHP engines were 99-101 RON. As a rule of thumb RON = PON + 4 to 5.

Keep in mind that ACTUAL CRs as built are about a half point lower than specified because in production the decks were machined higher than the "blueprint" spec to achieve the advertised CR.

Duke

[Jon S.]

Re: C1 '62 - Octane recommendation

Don, my 62 250hp runs great on Sunoco 94 with stock settings. I've even used 93 octane when I wasn't around a Sunoco station without any problems. In early ownership, I mixed a little race gas in. Never really saw much of a difference other than the weight of my wallet. Best of luck! Jon

[Jim #42767]

Re: C1 '62 - Octane recommendation

I run Avgas, 100 octane, buy it from the local airport, its what small airplane run on. Car runs real smooth, cool and lots of power. $3.05 a gallon, timed to factory specs.