High Compression & Pump Gas??

[NightStalker496]

I've been told many times that a high compression engine (12-13:1) can be driven on pump gas as long as it does not have a heavy load on it, i.e. it's just driven normally down the street. I'm planning a 13:1 BBC project with aluminum heads and now I'm wondering if there is any truth to this? Also, if this is true what would be the max dynamic compression ratio or cranking psi, I should aim for so if I had to drive it on pump gas for a few miles it would be ok. Thanks

[bjuice]

NOT TRUE......
12:13 to 1 you better have race gas,,,or you will detonate and kill it.

[sc4405]

bjuice is right - that thing's gonna hammer even under the lightest acceleration. And of course pump gas ain't what it used to be..... 8) JB

[v8Fiero]

I agree with everyting said above. why do you want high compression if your not going to use it?

if you just want that little extra at the track, you can use pump gas compression (9 or 10-1 comp) and throw some nitrous at it to bring it up to the race track performance that you want.

[edvancedengines]

The problem is not if it can do full throttle acceleration. The problem is when trying to do small part throttle acceleration at lower rpms like as in normal driving.

I am a big compression on the street freak, but this is beyond me with current available pump gasolines. I would be scared to build it knowing this.

If this is what you are determined to do, I strongly suggest to use E-85 Fuel which is available in some places at the pump.

Also follow Big Joe's advice about killing it in gear with foot on the brake.

Ed

[a13badazztoys]

If your max DCR is over 8.75.. I sure would not try and run any
pump gas!! :cry:

[NightStalker496]

Thanks everyone, I was planning to run race fuel all the time but it's a streetcar and I was worried that I might want to drive it futher than my fuel cell would allow. I think I'm going to lower the compression to 11 - 11.5:1 and run a good head so I can have the best of both worlds. The combo is gonna be a BBC 496 (4.31x4.25), 11 - 11.5:1, 280/284@50 .722"/.722" cam. I think that cam will put me around 175psi cranking with 11.5:1 static. What heads would you reccomend for best performance and will this be ok for pumpgas?

[bjuice]

your still too border line for pump gas in my book at 11;5;1 ...10:1 max is where i would want to come in...plus you cannot guarantee the quality of fuel you are gettting from the pump ( someone might have mentioned earlier)...

as far as the heads are concerned..there are many more qualified people to answer this..but what i will say is stay away from any heavy port work with the heads or intake for street use..a good bowl blend is about it..

Brian

[hammertime]

your still too border line for pump gas in my book at 11;5;1 ...10:1 max is where i would want to come in...plus you cannot guarantee the quality of fuel you are gettting from the pump ( someone might have mentioned earlier)..

Brian

I agree with Brian for sure 11.5 in my book is to high also. I'd go with a Brodix BB2 head if it were mine.

[nofear57]

Ya 10:1 maybe 10.5:1 Forged pistons max but check the plugs. Brodix or AFR alum. heads and I would have a real good bottom end so NOS can be added for that "Ka-Pow" factor :wink:

[cncmotorsports]

Do you self a favor, stay unnder 10:1, most guys don't tune the engine proper, such as a colder spark plug, less timming. You can curve to compression with a larger cam to bleed off cylinder pressure.
Most people that want to run 11 or 12 to 1 on the street, we end up selling them 2 set's of pistons cause the break the first set.

[triniemi]

How much DCR this calculator gives you?: http://kb-silvolite.com/calc.php?action=comp2

With that cam, good quench (0.040"-0.050") and efficient coolant system (try to keep it under 200), I don't see a problem running 11.5:1 compression on pump gas.

Or you could run 13:1 or even more with E85, especially with that big cam.

[cncmotorsports]

We have tuned 13.0:1 using
E85 , this biggest thing we find with E85 is inconstancy in the octane, from pump to pump

[Pwmax]

I have ran as much as 11.8 on a 383 L-t1 fuel injected combo, that was tuned. It also had enough cam, enough gear, and a stick, with a sharp owner, that understood how to drive it. Which means, don;t lug the engine. Light cars, loose converter, steep gears, all help. More cam, that reduces cylinder pressure, all help. The biggest killer, is if you lug the engine at low rpm. Depending on the application, aluminumn heads, 10.5:1 is no porblem at all. 11.5 is about max, for a car thats a but more radical, if the owner understands a few rules, and, might add a bit of race gas, or low lead 100 octane aviation fuel at certain times. If its a "true" street car, where you never plan to race it, then, I would actualy run less compression, say 9.5:1, and tune it on 87 or 89 octane. That way you can run any fuel you may come across.

I have ran E-85 on 13.5:1, with no issues. Typicaly, the difference in octane, rating, or, the amount of ethanol, in the fuel, is less only in the winter, when its cold, and no one is driving their race/street cars anyhow. Its typicaly around 70% then. If you set your tune up a bit on the fat side, which, doesn;t hurt power nearly as bad as gas, then, when you have a batch that might be a bit lower in ethanol, you have a safety factor built in. Or, buy it in barrells. I know racers who do that. They just buy drums.

Frank
Advanced Performance
www.get-ap.com

[v8Fiero]

how much does barrels of e85 or e98 cost? and where can you buy them? sorry to hijack NightStalker.

[cncmotorsports]

not sure if they sell it by the barrel, we have it at most every pump, about $2.20 a gallon

[signsbyesa]

i going to run around 10:50 and the car will see little street time
mostly strip and the machine shop suggested always using
racing gas to be on the safe side, can you add octane booster
to the 95 octane or does that not work? going with a EFI system :shock:

[v8Fiero]

that octane booster doesnt add much, your better off mixing race gas with the pump gas.

[poncholvr]

new bikes are high compression-
time it the best to avoid the pre detonation
use good gas stations -
some stations fuel- wouldn't run my mower!!!

[edvancedengines]

i going to run around 10:50 and the car will see little street time
mostly strip and the machine shop suggested always using
racing gas to be on the safe side, can you add octane booster
to the 95 octane or does that not work? going with a EFI system

Where are you living that you have to use race gas for 10.50 -1? Or maybe I should say soemthing against the advice you were given but he built your engine so he may know lots about it that I don't.

I don't have a street performance engine out there running on 92 octane from gas pump that is not at least 10.50 -1 and a few that are 11.25 -1 compression. Iron Head BB Chevys, Mopars, and Fords that are 10.60 -1 compression. Iron Head SB Chevys at 11.00 -1 compression and aluminum head SB Chevys at 11.30 -1 compression that work just fine with 92 octane gas pump gas.

Of cource there is more to it than just compression ratio. The complete combination needs to be built for it and be compatable. If you have hot spots in chamber or on piston, or a tight low overlap cam or extremely heavy vehicle, That could all make a big difference as well as if you have a large quench distance clearance. I have SB engines with 11.00-1 compression driven on 92 octane that go for 100,000 miles and farther with good gas mileage on the road.

You can do much more in camshaft with an EFI engine too.

Ed

[Pwmax]

You can buy E-98 in barrells. I know a few guys that will then play chemist, and mix their own batches of E-85. I said, just tune it on E-98, and say its E-85, duh, lol. That way, the compression is basicaly unlimited, like methanol, as it almost pure alchohol. You can;t actualy get 100% Ethanol, then it gets hit with a liquor tax, and you wouldn;t be able to buy it anyhow, without a license, as, it is basicaly moonshine.

E-98, last time I checked, was about $125 for 55 gallons. They mix 2% 87 octane, so it can be shipped as engine fuel. Try drinking it, even with only 2% gas in it, and get sick as hell, or die, lol. Sorta like sniffing NOS that is used for cars, with the sulfer Dioxide in it. Years ago, I had a few buddies, that tried it. I told them, no, you can;t do that. They said, yah, its nos, like at the dentist. I said, its not medicale grade, its industrial grade, with Sulfer dioxide, so you can;t sniff it. No No they said. I wish I had a video camera rolling when they did it. It was funny

Frank
Advanced Performance
www.get-ap.com

[henny]

Hello
How effective is octane boost? I used some charts (program) to figure out my compression ratio and it is going to be around 11.3:1
I have a old mech Crane Compu cam 256/264 @.050 and we don;t have E-85 in our area yet
I was just hoping to get by with the cam and octane boost
Tom
427 5 speed with 4.56's

[engineaction]

High compression pump gas engines, I wouldn't be afraid to run 11.5-12:1 on pump gas with an EFI Alum. headed engine. I would do it with a carb as long as it was a good carb, with the proper fuel curve. There is a secret persay to running that kind of compression with pump gas. Must use an Alum head with proper combustion chamber design. Combustion chamber design includes the piston dish/dome, and the quench area. And the proper camshaft (Int. valve timing) Think in terms of all the pump gas turbo/super-charged engines. Some one mentioned all the new bikes with hi compression. Lots of R&D behind those designs. It is easily accomplished.
E-85 is a great performance fuel, Only a hand full of engine builders actually know anything about it, and the rest think they do. E-85 is an organic fuel, everybody thinks it is made of corn, but it can also be made out of wheat, sage, bean stalks, ditch weed, and any other dry flammable grasses. This is why E-85 is so inconsistant when it comes to octane rating. Know your fuel company, Heck I talked with the fuel truck driver at an E-85 gas station and learned more info/contacts than you can anywhere in regards to E-85. Working for my previous employer, we spent a great deal of time on E-85 fuels, This was when it first came out in early 2001.

11.5 on 92 octane pump gas.........I'm not scared.

[superstreeter]

I`m building right now, a BBC 588 with 11-1 for street and track for pump gas,going to dyno in a month or so,,,so I will post results, DCR shud be under 8-1

[GLADIATORINC]

http://www.e85performance.net/forums/

Check out this website for more info on E-85. Several guys running it but I am not chancin my engine. I am running leaded racing gas in my pro street. In my opinion, it's uncharted waters. Some say you must change fuel cells to stainless and convert carb to alcohol. the website is very informative on E-85. Plenty of E-85 and racing gas in Illinois at Gas City.

[bakerboys]

what type or octane fuel would i have to run bbc just over 500 cubic inches with 13.0 to 13.5 compression

[promod45]

E85 is found at pumps at gas stations here in North Dakota and it cost about 2.60 a gallon but it varies with the price of gas, there is a web site that lists all places that sells it but im not sure where its at so try a little searching you might find it, it was posted i think by our Govenor...

[cepx111]

what type or octane fuel would i have to run bbc just over 500 cubic inches with 13.0 to 13.5 compression !!) 110 race fuel or higher.
Cp

[bakerboys]

can i drive a bbc with about 13.2 to 13.5 compression on the street.

[dcarr511]

This thread falls right in line with my project ... a 1986 Monte Carlo 100% stock bodied , 383 cid approx. 10.5 -1 and 3.42 gears for now ... will be going into the 2 series when I get serious. This will be a LSR ( Land Speed Racing ) car so accelertion in a 1/4 mile isnt my goal, ... right now I am looking at a 1 mile course and in the future a 3 mile and 5 mile.

I'm running flat tap pistons with alum heads. I havent picked out a cam yet but will be going with a hydraulic roller. I'm hoping to get away with 92 oct. and being able to use it as a daily driver .... even though it wont be. Its purpose will be for a cruise every so often and some LSR racing with the first event planned for June with the stock 305 for a baseline and then this fall to try it out with the 383 in it.

To be on topic I have always heard that for pump gas a BB needs to stay at 10.0-1 or below to work out.

[olds48]

My 496 is 11.5:1.Canfields and I race with 93 octane :shock: No problems yet.Plugs look good and have seen a speckle.Motor never goes over 145 degrees water temp though.But my GMPP Fastburn (aluminum headed ZZ4,basically)in my Impala is only 9.5:1 and will not run on 91 octane without rattling,gotta use 93 in it.But it is also 4200 lbs with a 4-speed and 2.73 rear gears.Talk about a load taking off on a hill!!Especailly if my woman's with me :shock: Don't tell her I said that :oops:

[procitation]

I've been told many times that a high compression engine (12-13:1) can be driven on pump gas as long as it does not have a heavy load on it, i.e. it's just driven normally down the street. I'm planning a 13:1 BBC project with aluminum heads and now I'm wondering if there is any truth to this? Also, if this is true what would be the max dynamic compression ratio or cranking psi, I should aim for so if I had to drive it on pump gas for a few miles it would be ok. Thanks


Hey just a note before you start that BBC project- We have a 604 BBC pump gas motor 900 hp ready to rock with all brand new parts- interested? Let me know, Ill post it back on Racing Junk
www.worldsfastestorganization.com

[oncearacer52]

I see people saying that build lower compression engines and spray to get the HP you want. Well just what does Nitrous do? It raises cylinder pressure ......what is the difference?????? What is the first thing that must be done to use Nitrous? You HAVE to RETARD the timing. In my opinion timing is the single largest contributor to detonation. You can detonate an engine just as bad with an 11-1 motor as you can an 13-1 and use the same gas due to timing. You cannot run the same timing at 11-1 that you can at 13-1. On the same motor. Matter of fact you WILL slow down by switching to racing gas if you have your 11-1 tuned properly. I hear people saying that their 10-1 engines will not run on pump gas. Well give me your 10-1 engine and I will save 4.00 a gallon and probably run faster.

[olds48]

:D Good answer,plus the guys at NOS always tell you to up the octane when you spray,anyways :?

[peewee101]

I run 11.5 compression on the street with 93 octane but I have a digital rpm switch with a timming retard adjustment on the dash. This is my setup in case I want to use the spray. Must have the octane if you want to spray.

[Scooterz]

I run 12.5 pistons in a 427 BBC all roller & Lunatti (healthy cam). I am certainly no expert, but here is what I DO know... With extensive port & polish, my comp is about 10.2 now. I run 50/50 93 & 110 leaded... occasionally straght up 93 & ZERO problems at low & high RPM's. It has 488's & 3500 stall. No pings, hestitaions, etc... again, I am not an expert. I will say I have over 100 hours on this motor w/ fuel above. It's a hell of a topic that everyone has thier opinions on though!! Good luck.