What octane fuel are you using in your Hot Rod ?

[rick 36dodge]

What octane fuel are you using and what is your compression ratio ?
What is the highest compression ratio you can run regular, mid-grade and 93 ?
The average fuel price here in Columbus, GA  is  regular is $2.70 , $2.80 mid and $2.90 for 93.
Thanks, Rick Harris.

[blksheep]

350 RamJet injected 350, 350hp, 9:4 compresson, 93 octane.
Will it run on 87 or 89???      I'll never know.

blksheep....directly injected....in Charlotte

[1FATGMC]

I run the lowest cheapest I can find.  Sometimes 85 oct. with no problem even pulling the trailer.

The trick is not so much "static" compression ratio, but "dynamic" compression ratio which is effected greatly by the intake valve closing point and how much compression bleeds off before closes.  One other thing that really helps is keeping the "quench" distance (distance between the top of the piston - flat part - and the flat part of the head above the piston) around .040 inch.

Here is a good site that explains it better:

http://cochise.uia.net/pkelley2/

Also I started a few pages on my site that shows different engine combos that have worked with different octane ratings.  If you have your data send it to me and I'll add it to the list.  This info will help others build motors that will live with different octane ratings.

http://purplesagetradingpost.com/sumner/techinfo/tech--dcr%20combinations-1.html

I'm building a 383 for Julie's truck now and I'm trying to do everything I can do to make sure it runs the cheapest gas out there and does it will.  It should be about 330 HP and have aroung 420 lb/ft torque from under 2000 to close to 4000 rpm.  It has vortec heads, and 28 cc dish pistons and a extreme energy 256 cam.  Hope to let you know how it works in a month or so.

c ya, Sum

[Charlie Chops 1940]

The engine in the '40 convert is a ZZ4 alum. head crate engine with. 10:1 advertised compression. I generally run it on regular which is 87 octane here in Michigan but on the Western Sweep ran 85, 85.5 and 87. It is fine unless I'm in the throttle too deep at the 3 to 4 gear change, at which time it will rattle a little and I back out of it. Otherwise I can't seem to make it rattle under load. 4th gear (OD) worked fine on all but the very steepest grades with the car at about 3600 pounfds and the Mullins trailer weighing in at around 1000 pounds ( a SWAG). I'm running the HEI that came with the engine with 12 degrees initil, full vacumn advance and 36  degrees total - which comes in fairly early. I didn't back off the initial for the trip and it worked fine. I'm running a 600 vac. scondary Holley which seems unaffected by the altitudes encounted on last years (Pikes Peak @ 14,000+) and a few passes at 12,000 this year. Mileage from 15 to 25 on this trip. I haven't had a chance to calculate the trip average yet

Charlie.

[rick 36dodge]

The engine I am running is a 68 327 Chevy 300 HP. I have put a 350 crank in and bored .030. I have the camel hump heads with the small valves and flat top pistons.  
I think my compression ratio is about 10 to 1. I am not sure. I run 93 because I have tried 87 and had a lot of ping. I run as much timing as I can , about 10 initial with a total of about 38 plus 10 vacuum. It also comes in very early. My biggest thing is I want as much power and gas milage as I can get.  
Thanks for the link I will read it all. No matter how much we know there is still a lot to learn !  
Thanks, Rick Harris

[C9]

87 octane summer and winter.

462" Buick engine.

9.0/1 CR.

Mild cam.

3.70 gears.

30 1/2" tall rear tires.

2400# roadster.

It don't lug much and it don't ping....

[Dave]

87 here also.. dunno what my milage actually is but its pretty good far as i can tell.  I guess if i was really worried about it id buy a toyota or sumpin  
Dave (

[Bib_Overalls]

I run 87 octane in my 32 Ford roadster.  SBC with Vortec heads and a mild Edelbrock Performer cam.  My Keith Black pistons have a "D" cup dish that works with the heart shaped combustion chamber to provide a good quench area.  According to Keith Black my compression ratio is about 9.2/1.

[1FATGMC]

If you guys know the cam timing, the piston dish/valve relief volume, bore size, deck height I can figure the DCR (dynamic compression ratio) and put it on my site.

That way someone that is building a different combo just has to arrive at the same DCR if they want to run the same octane.  Go to my site:

http://purplesagetradingpost.com/sumner/techinfo/tech--dcr%20combinations-1.html

Try and give me as much info as possible that is in the boxes and I'll put your combo there.

Remember a mild cam will make more DCR as the intake closes sooner, so you might need a lower static compression.  A head such as the vortec that burns better than older heads can get away with more static compression ratio.  Also an aluminum head can usually get away with .5 to 1 point higher compression than an iron head.  There are a lot of varibles.

c ya, Sum

[EMSjunkie]

350 chevy .030 over
flat top pistons
fairly mild cam
600 cfm Holley
12 degree initial
40 total

83 and 85 octane work real good
no knocks, pings, rattles.

elevation = 3407 feet

Vance

[CruZer]

Ford 351W crate motor w/ 10 to 1. and a Comp cam. I always run 93.Never tried lower octane.
Heck my v6 S 10 pick up pings on 87 octane but runs great on 89.Go figure....

[BFS57]

Hello;
After reading the posts here, I didn't see much about where you all are purchasing your gas (what brand). I have a buddy of mine that is a Corvette kind of guy. He states that the method of how various gas producers make the gas they have varies from company to company.
Not only that, he claims that some of the newer additives being used are really hard on  the gaskets used in our engines. case in point, I already had to replace my intake gaskets not even two months after I installed a new intake manifold. He claims that the reason is that auto parts stores have "old stock" gaskets and the ones you get to do a job may have been "laying around" for a long time! He also claims that using cheaper gas can lead to "cloged arteries" in your carburetor or fuel system.
As for me, I try not to use anything less than 87 octane as the price of 93 octane is really high! But when I can find the 93 cheaper, I buy it! I only try to use BP gas or Chevron, usually!
I haven't tried running un-leaded regular yet and don't plan on it unless the prices get so high that it is prohibitive. Hell, I used to fly model airplanes and a gallon of fuel with nitro and methanol only costs $10.00! Sometimes, I put a couple ounces in my weed eater gas and LOOK OUT!

Bruce

[Mikej]

I can run 91 and above. BBC with about 10.7 to 1.  I have the timing at 32 + 10 on the vaccum. It is about 75 HP short of what it should be but after 4 years of piddling it doesn't ping anymore unless it gets hot. I have found that you can't always get above 91 octane. That is why I have tuned it to run on 91.  When it gets cold out side I can run 89 but the engine temp has to stay around 160*

[docchevy]

I can run the 87 in my small block without any problem.  The advances in swirl technology are amazing!
As far as ping goes ... look out!  30 years ago I had a 327 that had rebuilt with about 10 to 1.  I ran too much advance and it would ping when I hit it hard.  Being so smart , I thought, "this won't hurt the engine much, I just won't stay on it too long."  In less than 30 K she completely came unglued.  Nothing in the block was salvagable!  That includes the cam and lifters.  God bless the knock sensors that turn us back from too much ADV on rash impluses.  Beware the PING!