[Murf'sDad]

Originally Posted by 72pontiac

if 1960's 101 is the same as todays 93 then we could still have 10.5 to 1 compression then why did i bump mine down to 9.5

It isn't. The high octane, TEL containing gas of the '60's and early '70's would be about 95 - 96 octane by today's ratings. With that you could run your 10.5:1 compression iron heads.

, Stewart

[PONTIAC DUDE]

Originally Posted by Murf'sDad

It isn't. The high octane, TEL containing gas of the '60's and early '70's would be about 95 - 96 octane by today's ratings. With that you could run your 10.5:1 compression iron heads.

, Stewart

You could also run 12-1 as GM, Mopar and Ford had a few of those out there running on Pump gas. Octane was 100 and 101 back then. Plus LEAD. Lead makes a big difference. The octane today of 93 is 89 and bumped to 93 with the crap ethanol. Not the same as gas.............. back in the day.

[ITSBACK]

That was my reason for starting this thread. Whats the deal? Do I really have to use dished pistons with my 670 heads. I was at a car show Friday and talked to a couple of guys with 670 heads on their 67 GTO's like mine and they said they run great. I was reading Jim Hands book last night and he said the advertised 10-3/4:1 was an advertisement and that they where more like 10:1 maybe a touch higher. Did they not run great back then and my 428 put out 376hp. Why then with a bigger cam and my un ported 670's, headers, x-pipe,aluminum intake and 750 double pumper and bored .030 wont my motor run and put out 400-450hp? Some say 10.1:1 is optimum and others say 9:1.

[Murf'sDad]

Originally Posted by ITSBACK

That was my reason for starting this thread. Whats the deal? Do I really have to use dished pistons with my 670 heads. I was at a car show Friday and talked to a couple of guys with 670 heads on their 67 GTO's like mine and they said they run great. I was reading Jim Hands book last night and he said the advertised 10-3/4:1 was an advertisement and that they where more like 10:1 maybe a touch higher. Did they not run great back then and my 428 put out 376hp. Why then with a bigger cam and my un ported 670's, headers, x-pipe,aluminum intake and 750 double pumper and bored .030 wont my motor run and put out 400-450hp? Some say 10.1:1 is optimum and others say 9:1.

I have a set of ported #13's on my engine. They cc out between 79 - 81. The block has been "zero decked". I measure it as about .002" "out of the hole". AS best as I can calculate is will come out at 9.8:1. With the UD cam I don't foresee having any problems with detonation on the 91 I can get around here, and get about 450 hp. If I could get 93 octane Sunoco I'd be truly golden.

Every engine is different. If you do a search you will find references to 11:1 aluminum head motors running happily on 87 and 9:1 iron headed engines that won't live on 91 with octane booster.

For the difference of 1 compression point you aren't going to lose any noticeable hp. From what I understand you pretty much can't run a 670 headed 428 on pump gas. If you want to keep the 670's, pull them off and open up the chambers a bit and drop from 10.5:1 to about 9.5:1. You'll be happier and you won't have to dish your pistons.

And while todays gas is cleaner it doesn't run nearly as good as the old stuff and it doesn't have quite the octane rating.

JMO, Stewart

[Old Man Taylor]

The highest Octane that I remember after they starting using the new ratings was 95.5. I was able to run 11.0:1 with that. As they got lower I had to reduce the CR to 10.5. I think that was at about 94 Octane. With 91 Octane (the highest we have in CA) I like to keep it at or below 9.5:1.

[ITSBACK]

I think I am going to take all my stuff to my motor guy and let him figure it out.

[ITSBACK]

What do you mean open up the chambers? Do you mean the combustion chamber to raise the CC's. What if I dish the pistons and when I am ready to get rid of the 670's, bolt on a set of 72cc e-heads?

[Murf'sDad]

Originally Posted by ITSBACK

What do you mean open up the chambers? Do you mean the combustion chamber to raise the CC's. What if I dish the pistons and when I am ready to get rid of the 670's, bolt on a set of 72cc e-heads?

You can do that if you want. Dishing pistons is more expensive that pulling the heads and opening up the cambers to increase their volume thereby lowering the compression ratio. If you dish the pistons, the e-heads will probably have to be cut to raise the compression back up where you want it. Aluminum heads will take about another 1 to 1.5 points more compression ratio to equal iron heads because of the better heat dissipation.

Your choice, Stewart

[My442]

The gas back then smelled much different than today, and better in my opinion.

The Sunoco 260 I used to get was over 100 octane.

[goatman65]

Originally Posted by My442

The gas back then smelled much different than today, and better in my opinion.

The Sunoco 260 I used to get was over 100 octane.

I remember going to the Exxon station with my dad and filling up the his 66 GTO....i loved the smell.My dad had a 'tab' or 'bill' at that station that he would pay every month.The station also had 'free' air,not one of those air machines on a pole like now.It also had a service bay,the hose that rang the bell whrn you ran over it and 2 25 cent wash bays.

[scoob]

for those in the clearwater , fl area there is a spur gas station on hercules near the airport that should be selling 100 octane from the pump in the next few months.

[kate`s67gto]

A Spur gas station sheesh i thought they were extinct. Must have been in the early 70's since i last saw on of those. There was one just south of my home town then.

[ITSBACK]

Now you get gas and pay through the ... and some foreigner looks at you like your ruining his country.

[ITSBACK]

I can also get a ported set of 6x-4's for less than the e-heads. The aluminum just look so good and the technology is there to do as you please.

[Tom Vaught]

I remember the 60s Sunoco 260 fuel being 102 or 104 octane and the 280 Sunoco fuel being around 108-110 octane. Course this was leaded fuel too. And that was a RESEARCH Octane Number

Info:

"A numerical representation of the ability of a fuel to resist knocking when ignited in the cylinder of an internal-combustion engine. The octane number of a given fuel is determined by comparing the amount of knocking that fuel causes when combusted with the amount of knocking caused by two standard reference fuels, isooctane (which resists knocking and has an octane number of 100) and heptane (which causes knocking and has an octane number of 0). The octane number is then assigned as the percentage of isooctane required in a blend with normal heptane to match the knocking behavior of the fuel being tested."

Tom Vaught

[Forrest]

Originally Posted by Tom Vaught

I remember the 60s Sunoco 260 fuel being 102 or 104 octane and the 280 Sunoco fuel being around 108-110 octane. Course this was leaded fuel too. And that was a RESEARCH Octane Number

Info:

"A numerical representation of the ability of a fuel to resist knocking when ignited in the cylinder of an internal-combustion engine. The octane number of a given fuel is determined by comparing the amount of knocking that fuel causes when combusted with the amount of knocking caused by two standard reference fuels, isooctane (which resists knocking and has an octane number of 100) and heptane (which causes knocking and has an octane number of 0). The octane number is then assigned as the percentage of isooctane required in a blend with normal heptane to match the knocking behavior of the fuel being tested."

Tom Vaught

Yep, I worked at a sunoco station in Miami Fla. back in '74-75, Had the sunoco "280" the pumps had the dial that you could choose 280 down to 210 or something... I remember we used to go out and find the Cadillacs or big Lincolns and siphon/steal (late at night) the gas out of them ( we would smell the inlet to make sure it was the "purple stuff"!) for my 1970 gto with 12 1/2 to 1 compression "pop up pistons"! We knew that the "rich" people used the 280 in their big cars then! I was only 18 and didn't know better.. yea I did some wrong things when I was young.. I remember my '70 goat got a dead battery one night and the girls i was with went out and "borrowed" a battery from someone down the street so we could go out and DISCO! Ha!

[MYGOAT]

Don't know if they do this in the States but the refineries Down Under have different brews depending on the season.
Winter (cold weather) lower octane blend.
Summer (hot weather) higher octane blend
This is coming from the same pump.

[Lloyd-TX]

The old leaded "high-test", "Super", "Supreme", "No-Nox" etc from back in the good ol' days was mostly advertised around here as 100 octane.

Using the current R+M/2 formula, that old high-test would equal approximately 94 or 95 octane.

I recall the Sinclair stations around here had a dial on each pump, one could dial in 100 octane all the way down to ??? (can't recall the regular octane rating back then) in about 10 steps.

[Lloyd-TX]

There was a gas price war (remember those?) here in Houston back in the summer of 1972 - not long before the first gas crisis!

All of the stop-and-rob (convenience store) places which sold gas along a section of Westheimer were competing for gas business. 21.9 cents for regular, and 23.9 for 100 octane premium. Being that I had just started driving, and my first car was a '69 GTO - I thought that I had died and gone to heaven, LOL!

This is when I was used to paying 37.9 for Gulf No-Nox.

[ITSBACK]

E heads win!