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I have a 489 BBC iron block with aluminum heads, full roller, decent cam with a Full MSD ignition and adjustable timing retard controller. I just got my motor in my car and have only fired it up to get on and off the trailer and into my garage. My buddy was at my engine builders shop the other day and asked him what compression my motor was running and he told him 13:1. I was always told that when running pump gas it's pushing it to go over 12. Do you think I will be ok driving this on the street with 93 octane?
 

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Unless the e85 or race gas is available is available at your local pump I don't think that is going to work very well :no:
 

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My daughters motor we built has 12:2-1 in a sbc. Dome pistons and we run 93 with about 2 gallons of 112 race fuel per tank. And it runs fine. But a BBC might be a little different. Probably due to the heat.
 

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The three biggest tricks to making high compression live with pump gas.....
1. LOTS of cam!!!! Whatever you think it should be plus 10 degrees.

2. LOTS of gear!!!! Whatever you do, you don't want the engine trying to lug at a low RPM under load....

3. LOTS of STALL/LOOSE converter. 5000-5500 stall isn't unheard of in that world.....same reason as #2

For those reasons 99% of the people who attempt these kinds of builds aren't happy with the final result.....Which is the same reason 99% of the professional builders don't recommend it!!!

I've done it as have several others but it's not for the faint-at-heart. Street manors SUCK, drivability SUCKS, efficiency SUCKS, and the maintenance schedule is STUPID...

I found years ago that it was WAY easier to knock some of the domes off (as long as they weren't hollow domes), rebalance, reassemble and set up a nitrous system with a completely independent fuel system to spray the hell out of it. That way it was easier to drive, easier on fuel (only needed to put the expensive stuff in the 1 gallon cell for the nitrous/fuel system), and in the end.....faster. Easier to sucker in races too since the car sounded tamer and they had NO clue how much or when the juice was flowing......because it was "Always on the bottle. Was never built to run on motor alone."......Suckers.:devil:

But, different strokes for different folks.
Good luck!!
 

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efficiency SUCKS
I would have to disagree with that. On the Power Tour, my 14.5-1, iron headed, 10 second small block, got 10.5-11 MPG while spinning 35-3700 RPM most of the time, trying to keep up. Some of the 300 H.P. cars on this site get worse mileage.
 

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I have 11.5 to 1 compression and in my 408 sbc and I need to mix race fuel and super unleaded. After running the car hot I shut it off it wants to keep running ... embarrassing.
mine does that also. I use the highest octane fuel I can get at the pumps. I may try a mixture as well
 

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There's a lot of expensive solutions to doing this. High octane fuel is no exactly economical. Just buy (or make) a water/ methanol kit. The mixture will increase your pump gas' resistance to volatility, which is a fancy way of saying your fuel will behave like a higher octane rated fuel.
 

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For a good street motor with good street manors, I would limit it to 10 to 1. Just my opinion though. You will find a lot of different opinions on SNS.
 
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I ran a 12.8-1 355 last year on 94 octane pumpgas. Timing was locked at 28-30ish and was never a problem. When I wanted to flog on it hard it got 112 octane and a crank on the dizzy.
 

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CR and pump gas..

For a good street motor with good street manors, I would limit it to 10 to 1. Just my opinion though. You will find a lot of different opinions on SNS.
I would agree that 10 to 1 is the practical limit for an engine with old style cam technology and iron heads...if you have a modern cam design and aluminum heads there is room to increase the CR. With the right cam you can "bleed off" some of the cylinder pressure and get away with more CR.

**some of the older BB motors..eg; 396/325hp had very high cylinder pressure and a very small cam with not much duration...that is a recipe for spark knock if you aren't using good fuel.

There are lots more tricks available today with engine building to help utilize today's pump gas.
 

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If you think it's going to be an issue, it probably will, why chance it. I say bite the bullet and spend the money for good fuel. I also run 13:1 in my small block but run 110 or 112 in it only. I've never had any issues. I'm not saying it can't be done but if you've invested that much, no backing out now. And besides, everyone loves the smell of race fuel :yes: Good luck.
 

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If you think it's going to be an issue, it probably will, why chance it. I say bite the bullet and spend the money for good fuel. I also run 13:1 in my small block but run 110 or 112 in it only. I've never had any issues. I'm not saying it can't be done but if you've invested that much, no backing out now. And besides, everyone loves the smell of race fuel :yes: Good luck.
Hello I just Inherented a 1981 gmc Caballero it has a 396 13-1 compression I know very little about the old-school upkeep on something like this any advice you can give me
 

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I have a 489 BBC iron block with aluminum heads, full roller, decent cam with a Full MSD ignition and adjustable timing retard controller. I just got my motor in my car and have only fired it up to get on and off the trailer and into my garage. My buddy was at my engine builders shop the other day and asked him what compression my motor was running and he told him 13:1. I was always told that when running pump gas it's pushing it to go over 12. Do you think I will be ok driving this on the street with 93 octane?
Way too much compression. Guaranteed detonation with 93 octane.
 

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Boostane works good. I run race fuel now because pump gas in AZ is California crap gas and eats carb parts like it's cool. I don't drive during the summer though. Too dang hot lol.

Sent from my SM-G975U using Tapatalk
 
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