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Running High Compression on Street, Mixing Gas, Timing Etc (Big Block Chevy)

Discussion in 'The Hokey Ass Message Board' started by BOSTONCAMARO, Jun 20, 2012.

  1. What about checking at Beverly Airport? They should be able to supply what you need in the way of avgas but it might be pricey.
    Here in Tecumseh we not only have three airports albeit small ones we also have a station that sells race gas but it is VERY pricey(last I heard about $7 a gallon).E85 stations while not on every corner are pretty much available and last week I went by one that was selling it for $3.16 per gallon.
    One guy I know has a 41 Willys that is running a slightly detuned 525 cu.in. Donovan and it runs fine on 94 octane even with the BDS blower.
     
  2. Blower engines don't run high CR's.
     
  3. Funny, I have some friends near the Beverly Airport but never thought of them as a source...I will look into that
     
  4. Boston, check these guys out from a guy that knows, www.snowperformance.net, they have water-methanol injection systems that WORK!!! This system and company I HIGHLY recommend for exactly what you are looking for, one of these set-ups and premium pump gas is all you will ever need, all the best, TR
     

  5. Yea like 8:1 and a lot of fellas don't run much boost in the street either like about 3-5 psi. Up around 8-12 psi and most engines won't run on the street without a little help at the very least water spraying them.
     
  6. Cerberus
    Joined: May 24, 2010
    Posts: 1,381

    Cerberus
    Member

    Bostoncamaro, There is a Sunoco station about 16 miles from you in Weymouth, MA. They sell 98 octane racing fuel. Back in the 70's Sunoco offered 101 octane at the pump. We have Union 76 at certain locations out here that sell 100 octane.
     

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  7. fiveohnick2932
    Joined: Mar 29, 2006
    Posts: 889

    fiveohnick2932
    Member
    from Napa, Ca.

    First off are you having pre ignition problerms?

    If not then dont worry about it.

    just because a engine has high compression doesnt mean you cant drive it on the street. You need to know your cam. Your cam works closely with your compression. If you have a 12:1 motor and a late intake valve closing then you have bleed off enough material by hanging that valve open while the piston is on its way up and now are compressing the same amount as your grandmas 68 plymouth. But if you have 12:1 motor with early intake closing cam then you are going to be compressing most of that 12:1 and with street fuel you will have problems. What kind of cam do you have???
     
  8. 57JoeFoMoPar
    Joined: Sep 14, 2004
    Posts: 4,916

    57JoeFoMoPar
    Member

  9. falcongeorge
    Joined: Aug 26, 2010
    Posts: 18,341

    falcongeorge
    Member
    from BC

    Yes, but I wont post about that kind of stuff on here anymore. Bottom line is, if you have the technical chops to do it, you dont have to ask permission from the HAMB. But you probably already know that.
     
  10. 57JoeFoMoPar
    Joined: Sep 14, 2004
    Posts: 4,916

    57JoeFoMoPar
    Member

    E85 equates to approximately 106 octane. It also produces less power by volume, so you'll consume about 20% more of it than gas.
     
  11. Stukka
    Joined: Feb 13, 2007
    Posts: 64

    Stukka
    Member
    from SoCal

    Math time. 1 to 1 ratio of 91 pump gas and 101 race gas, if my math is right, gives you a theoretical octane rating of 96. Assuming cost of 91 pump gas there is $3.83 and race gas in 5 gal can is $8.50 then the mix would be $6.22 per gal. 1 to 2 ratio pump to race gives you 97.6 octane at a cost of $6.98 per gal.

    Personally I went the E85 route in my high compress motor. That stuff is brilliant. Recommend it highly. Used it for 5 years no problems.
     
  12. C10Barnfind
    Joined: Sep 30, 2010
    Posts: 17

    C10Barnfind
    Member

    I run a aluminum headed 427 (sbc) with 12.5 to 1 on the street all the time. Here in Ca. we can only get 91 out of the pump. I run a total of 35 degrees of timing and have made several plug checks with no sign of detonation. Once in awhile I will mix 50/50 with 110 race gas and run it up to 39 total. It definitely smells better and the throttle seams to be a little crispier but, as far as seat of the pants performance, I cant tell the difference.
     
  13. Aluminum heads are a game changer. I am @ 11.5:1 in my small block and run on pump gas as well. I can actully run on mid grade here in the winter when the ambient is down around 25 degrees. The deal is that if you can keep combustion chamber temps down you have less chance of pre detonation, with aluminum heads it is easier to keep combustion chamber temps down.

    Your quench area is also a determining factor, if you keep your quench @.040 your octain requirements are less as well.

    One of the things I am working on for my monster is my deck height, that along with the thickness if my head gaskets is critical to making it live on the street. @ 13:1 with the old iron heads it is not likely that it is going to survive pump gas alone, but every little bit helps. Keeping your operating temps down also helps.

    Pretty easy on my small block it runs real cool all the time. On an all iron big block it is sometimes a problem. Engine bay size and a way to let hot air out as well as running cool air to the carbs also helps.

    Look at the Ford Thunderbolt, it had that big assed knarly tear drop, most people think it is a scoop. The Bolt ran a big engine in a constricted engine bay. They pulled cool air to the carbs with ducting that had nothing to do with the tear drop, that tear drop was an effort to keep engine bay temps down as much as possible.

    The older cars had louvers for the same reason, they didn't let air in they let (or pulled) air out.
     
  14. You may want to go to the TORCO Racing Fuels web site. They have a product that is a true octane booster that works. It actually cools the combustion temperature and will not attack aluminum like E 85 and does not contain all the additives that aviation gasoline's are required to have, it's called Accelerator. I'm in California and I've noticed that race gas suppliers come and go and are very few and far between. May be worth checking out, it comes with a blend chart that shows 32 oz (one can) will raise 10 gallons of 91 octane to 102 octane. I use it and have not had to pull any timing out of my engine.
     
  15. fiveohnick2932
    Joined: Mar 29, 2006
    Posts: 889

    fiveohnick2932
    Member
    from Napa, Ca.

    Tell me more about this quench distance and octane...
     
    Last edited: Jun 21, 2012

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