468 BBC with aluminum heads, 11.6 CR. What is the minimum octane it could run. I'm willing to back the timing down and limit the rpms I spin it for normal driving. Would a good Octane booster be enough, or does it need more? We have 93 Octane at the pump here in Gulfport.
Octane for 11.6 compression
seabees72ss
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468 BBC with aluminum heads, 11.6 CR. What is the minimum octane it could run. I'm willing to back the timing down and limit the rpms I spin it for normal driving. Would a good Octane booster be enough, or does it need more? We have 93 Octane at the pump here in Gulfport.
I am running 11.2:1 on aluminum heads with 93 octane and knock on wood runs great with no signs of a problem...
Depends totally on the specific cam(short or long duration)/heads(AL/Cast iron)/pistons /timing curve (aggresive or conservative) etc being run so with that said if it detonates on 93 fuel then dont fret & simply try some Kemco supreme 130 real lead (like used 30 yrs ago in premiunm fuel) octane booster.
1qt kemco with 18 gals 93 = 97.5 octane,but you can mix to over 100 octane if needed.
You get best price when buying 2 case at discount inc free shipping.
This is much cheaper and easier to deal with then going out special to get race gas and the Kemco has worked well for me in the comp ratio that your running.
You just keep a few qts Kemco in the trunk of the car and add at fillup time.
Costs approx 55 cents per gal to treat 93 fuel to 97.5 octane with the Kemco booster.
2 cases (12qts per case) Kemco @ discount costs approx $210 with free shipping so split cost with a buddy and get 1 case each for 12 tank fulls of higher octane fuel.
It has an 18 month shelf life so keep that in mind.
This is a great way to fix a detonation problem with a limited/wk end use only vehicle because it only costs approx $100-$200 yrly to retain the ability to run full timing etc for full power/perf on pump fuel treated with the Kemco without the hastle and expence of having to drive miles from home to get race fuel at a substantially higher cost.
I have personally had gret results using Kemco in my BBC's and also in other people SBC/BBC motors i work on too that had detonation issues when running the proper timing ign curves for the setups they were running and they didnt want to back off the timing to stop the ping loosing power and the Kemco fit eliminating the detonation.
But i have no esp with the Kemco in a very hi perf hi comp 12.5-14.0 motors ,the ones i have exp with are motors with 12.0 comp or lower when it comes to my exp with the Kemco stopping detination .
So with that said be carfull if anyone tries the Kemco with over 12.0 comp esp if cam timing is a little short creating hi cyl/cranking compression,may need real race fuel for those apps.
Scott
1qt kemco with 18 gals 93 = 97.5 octane,but you can mix to over 100 octane if needed.
You get best price when buying 2 case at discount inc free shipping.
This is much cheaper and easier to deal with then going out special to get race gas and the Kemco has worked well for me in the comp ratio that your running.
You just keep a few qts Kemco in the trunk of the car and add at fillup time.
Costs approx 55 cents per gal to treat 93 fuel to 97.5 octane with the Kemco booster.
2 cases (12qts per case) Kemco @ discount costs approx $210 with free shipping so split cost with a buddy and get 1 case each for 12 tank fulls of higher octane fuel.
It has an 18 month shelf life so keep that in mind.
This is a great way to fix a detonation problem with a limited/wk end use only vehicle because it only costs approx $100-$200 yrly to retain the ability to run full timing etc for full power/perf on pump fuel treated with the Kemco without the hastle and expence of having to drive miles from home to get race fuel at a substantially higher cost.
I have personally had gret results using Kemco in my BBC's and also in other people SBC/BBC motors i work on too that had detonation issues when running the proper timing ign curves for the setups they were running and they didnt want to back off the timing to stop the ping loosing power and the Kemco fit eliminating the detonation.
But i have no esp with the Kemco in a very hi perf hi comp 12.5-14.0 motors ,the ones i have exp with are motors with 12.0 comp or lower when it comes to my exp with the Kemco stopping detination .
So with that said be carfull if anyone tries the Kemco with over 12.0 comp esp if cam timing is a little short creating hi cyl/cranking compression,may need real race fuel for those apps.
Scott
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I will keep the Kemco in mind. I think I just need to try it with 93 and see what it does, I may be ok. I'm waiting on the specs for the cam now.
Thanks!
think about it, Chevy sold 11:1 engines, they required premium fuel. In those days premium was about 100 octane.
Way more people now have Aluminum heads compared to back in the day and few run the 'smallish' factory performance cams any more. The cam for the combo in question will need to be considerable indeed to run on pump gas.
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Why was the engine built that way if pump gas was the goal?I have ran out of fuel in the race engine when it was on the street (not fun at all) and had to put 93 in it to make it back to the shop,,,, Well with a huge converter back then (6000rpm stall) and 5.38 gears the engine was not loaded driving in back but it was driven back like a baby,,, 13:1 engine (pump fuel foul plugs on this engine before we made it back to the shop)
Want to play, you got to pay,,,,, Needless to say we now have a "street" engine in there which is high compresson "but" it will run on pump gas with octane boost due to the cam lobe center and duration and all,, that engine is 12.9:1
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bought the car with this motor.
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I'm wating on the guy I bought the car from to send me all the info.
I know it is a 468, Dart aluminum Heads, Dart Intake, Reher Morrison Custom grind solid roller camshaft .740 lift, all forged internals from Reher Morrison, 1050 Dominator. It was dynoed using 105 octane and made 750HP/ 8** ftlbs to the crank.
Tim,not all is lost by any means,as i suggested before if it detonates on 93 which it likely will if the timing isnt already retartded as heck to run on pump fuel when you got the car which it very well may be just use the Kemco real lead booster at the 1qt to 18 gals mix for 97.8 to see if that stops the ping .
But if it runs on 93 with no ping its either got a very lrg cam,doesnt really have 11:0 comp,or the base timing is retartded along with total too to run on the 93 fuel.
If you suspect retarded timing if runs on 93 with no ping a good base timing setup with perf cam is approx 18 deg base + 18 deg mech in dist in by 2800 rpms for 36 total,hotter cams may like 20 deg base + 18 deg mech for 38 total.
If it runs on 97.5 octane fuel mix with no ping great but if not simply mix more of the Kemco to get approx 99-100 octane (see info on container for mix inst),i know from 1st hand exp with the kemco it works well for motors in the 10-11:0 comp range .
If this is a limited use wk end runner the additional $100-150 cost for fuel yrly to run the motor is not that big of a deal when you take into consideration what it takes $ wise to be in this hobby in the 1st place. Thats approx $8-12 monthly so cut back a few coffee's & donuts over the yr and you have that made right there.(LOL!!!!)
Also,think of all the $ /time/effort it would take to diasasemble the motor to change heads /pistons/and or cam etc & re-assemble to lower the comp and or cyl pressure enough to get it to run on pump fuel & not detonate which would be a real waste if the motor runs well as is with no leaks and it not using oil either.
In 10 yrs the cost for the Kemco would be approx $1000 and just to revamp the motor to run on pump in 1 shot could cost over that and you would maybe have sold the car by 10 yrs down the road etc avoiding the hastle and cost of revising the motor setup/configuration to run on pump fuel at this time,see what i am getting at here?
Scott
But if it runs on 93 with no ping its either got a very lrg cam,doesnt really have 11:0 comp,or the base timing is retartded along with total too to run on the 93 fuel.
If you suspect retarded timing if runs on 93 with no ping a good base timing setup with perf cam is approx 18 deg base + 18 deg mech in dist in by 2800 rpms for 36 total,hotter cams may like 20 deg base + 18 deg mech for 38 total.
If it runs on 97.5 octane fuel mix with no ping great but if not simply mix more of the Kemco to get approx 99-100 octane (see info on container for mix inst),i know from 1st hand exp with the kemco it works well for motors in the 10-11:0 comp range .
If this is a limited use wk end runner the additional $100-150 cost for fuel yrly to run the motor is not that big of a deal when you take into consideration what it takes $ wise to be in this hobby in the 1st place. Thats approx $8-12 monthly so cut back a few coffee's & donuts over the yr and you have that made right there.(LOL!!!!)
Also,think of all the $ /time/effort it would take to diasasemble the motor to change heads /pistons/and or cam etc & re-assemble to lower the comp and or cyl pressure enough to get it to run on pump fuel & not detonate which would be a real waste if the motor runs well as is with no leaks and it not using oil either.
In 10 yrs the cost for the Kemco would be approx $1000 and just to revamp the motor to run on pump in 1 shot could cost over that and you would maybe have sold the car by 10 yrs down the road etc avoiding the hastle and cost of revising the motor setup/configuration to run on pump fuel at this time,see what i am getting at here?
Scott
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673 Posts
I agree with the cost of Kemco vs new heads, cam... I'll be back from deployment real soon and will do some testing with 93 and such. I'm suppose to get the engine build sheet with all the specs from the builder. The engine doesn't even have 2000 miles on it, prior owner never attempted to put pump gas in it. I would suspect that the camshaft is pretty darn big and has enough duration along with the aluminum heads to run lower than 105 octane. I remember my last race engine dynoed with 107, running 11.1 compression. It was a 383 with aluminum heads, crower circle track mechanical camshaft. I ran a total of 39 degrees of timing on 93 and it ran fine on the street. The 383 made 615 Hp/ 598 fltbs all under 6200 rpms. Anyway, I will scan and post the build sheet when I get it. I'm sure that the sheet will answer the question.
>> "prior owner never attempted to put pump gas in it."
smart guy.
wonder if there might be a reason R-M dyno'd it on 105? they've built a few engines over the years, might be the voice of experience.
If you get the build sheet call up R-M with it in hand and ask them if it's OK to run 93 in it.
smart guy.
wonder if there might be a reason R-M dyno'd it on 105? they've built a few engines over the years, might be the voice of experience.
If you get the build sheet call up R-M with it in hand and ask them if it's OK to run 93 in it.
G
Guest
·Fwiw, back then SONOCO 260 Ethyl was about 97 octane and was used in the 13.5 to 1 Max Wedge MOPAR's and the 12.5 and 12.0 L-88 BB's!
Mix some E85 in but be sure and jet your carb so you can run it!!!!
E85 is like 105 or so octane.
pdq67
Best Car Insurance | Auto Protection Today | FREE Trade-In Quote
Mix some E85 in but be sure and jet your carb so you can run it!!!!
E85 is like 105 or so octane.
pdq67
Best Car Insurance | Auto Protection Today | FREE Trade-In Quote
Paul i repsectfully disagree that the majority of those 12:0-13:1 comp IRON HEAD hi perf muscle car motors of yesteryear ran ok on 97 octane fuel. They didnt and i know because i grew up in that era with the muscle cars with my father in the car buisness from 1959 thru 1982 where i worked on many muscle cars/drove them/still work on them to this day on the side for extra $/& also still own one too/BBC.
BTW,its Sunoco and their top Sunoco 260 fuel back 35-40 yrs ago was not 97 octane,it was much higher @ 102 octane for 400hp + motors and thats what the hemi's & hot BBC's and such with hi comp were running on back then,not 97 fuel that would ping like hell in most of them.
Even the brand new bone stock 396/325 & 350hp motors with 10:25:1 comp had tags (from GM)in the new cars stating to use 98 or higher octane leaded fuel for those motors and you think 12:0-13:0 is running on 97 fuel esp the way different blend fuel we have today,not likely in stock form with that HI COMP and IRON HEADS. Even those mild 396's would detonate once in a while on hot day with the 98 fuel but they generally ran good on the 98 fuel.
I am not trying to bust your chops but just want to keep the record staright here for all the youngin's that attend this board.(LOL!!!)
Here's statement directly from Sunoco its self (pasted below) stating what octane their 260 premium fuel was back in the day 40 yrs ago:
" Sunoco stations offered as many as eight grades of "Custom Blended" gasolines from its "Dial A Grade" pumps ranging from subregular Sunoco 190 to Sunoco 260, the latter a super-premium grade of 102 octane that was advertised as the "highest octane pump gas" and very popular with the 400 horsepower (298 kW) musclecars of that era. "
Scott
BTW,its Sunoco and their top Sunoco 260 fuel back 35-40 yrs ago was not 97 octane,it was much higher @ 102 octane for 400hp + motors and thats what the hemi's & hot BBC's and such with hi comp were running on back then,not 97 fuel that would ping like hell in most of them.
Even the brand new bone stock 396/325 & 350hp motors with 10:25:1 comp had tags (from GM)in the new cars stating to use 98 or higher octane leaded fuel for those motors and you think 12:0-13:0 is running on 97 fuel esp the way different blend fuel we have today,not likely in stock form with that HI COMP and IRON HEADS. Even those mild 396's would detonate once in a while on hot day with the 98 fuel but they generally ran good on the 98 fuel.
I am not trying to bust your chops but just want to keep the record staright here for all the youngin's that attend this board.(LOL!!!)
Here's statement directly from Sunoco its self (pasted below) stating what octane their 260 premium fuel was back in the day 40 yrs ago:
" Sunoco stations offered as many as eight grades of "Custom Blended" gasolines from its "Dial A Grade" pumps ranging from subregular Sunoco 190 to Sunoco 260, the latter a super-premium grade of 102 octane that was advertised as the "highest octane pump gas" and very popular with the 400 horsepower (298 kW) musclecars of that era. "
Scott
That's what I'm talkin about. 102. Some of are old enough to remember it.
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Tim,thats true about the octane rating system,i am not 100% sure but from what i understand you can generally add a couple points to todays octane rating to = that of 40yrs ago so 93 fuel now = 95,still not close to what he needs.
Or if you wanted to go another route you could maybe subtract a few points octane from the 40 yr old rating iof for ex Sunoco's 260 102 fuel would now be 100,still looks good to me.
anf one huge factor more people dont think about here when talking fuelsis.
SUNOCO'S 102 OCTANE FUEL OF 40 YRS AGO WAS A LEADED TOO BUT TODAYS FUELS ARE A VERY DIFFERENT FORMULATION THAT ARE :
SIG LOWER OCTANE/NON LEADED/OXYGENATED/HAVE EHTENOLE TOO .
THE FUEL'S OF 40 YRS AGO DID NOT HAVE THOSES ADDITIVES OR THINGS/CHEMICALS REMOVED FROM IT MAKING IT A VERY DIFFERENT FORMULATION FUEL THEN TODAYS FUELS.
OUR IRON HEAD 35-40 YR OLD MUSCLE CAR MOTORS WERE NEVER DESIGNED TO RUN ON IT EITHER UNLKIKE TODAYS COMPUTER CONT MOTORS WITH EFI & PISTON/HEAD/CAM DESIGNS WITH YES 10:0 COMP BUILT SPEFICIALLY TO RUN ON TODAYS CRAPPY 93 FUEL THAT MAY = 95 OCTANE WHEN COMPAIRED TO THE OLD RATING SYSETM.
SCOTT
Or if you wanted to go another route you could maybe subtract a few points octane from the 40 yr old rating iof for ex Sunoco's 260 102 fuel would now be 100,still looks good to me.
anf one huge factor more people dont think about here when talking fuelsis.
SUNOCO'S 102 OCTANE FUEL OF 40 YRS AGO WAS A LEADED TOO BUT TODAYS FUELS ARE A VERY DIFFERENT FORMULATION THAT ARE :
SIG LOWER OCTANE/NON LEADED/OXYGENATED/HAVE EHTENOLE TOO .
THE FUEL'S OF 40 YRS AGO DID NOT HAVE THOSES ADDITIVES OR THINGS/CHEMICALS REMOVED FROM IT MAKING IT A VERY DIFFERENT FORMULATION FUEL THEN TODAYS FUELS.
OUR IRON HEAD 35-40 YR OLD MUSCLE CAR MOTORS WERE NEVER DESIGNED TO RUN ON IT EITHER UNLKIKE TODAYS COMPUTER CONT MOTORS WITH EFI & PISTON/HEAD/CAM DESIGNS WITH YES 10:0 COMP BUILT SPEFICIALLY TO RUN ON TODAYS CRAPPY 93 FUEL THAT MAY = 95 OCTANE WHEN COMPAIRED TO THE OLD RATING SYSETM.
SCOTT
G
Guest
·I thought I got that info from a fuels site, but may be off b/c I was like you, I always thought SONOCO 260 was above 100 octane?? I want to say the site said something about octane being calculated differently back then, but again, I may be off???
I wanna say from "Gasoline FAQ" ????....
Anyway, thanks for the insight b/c I sure the heck, DON'T want to spread bad info around!
Now, bttt, please consider water/alcohol injecting it or even injecting it w/ straight E85 right down the throat at WOT.
We used to buy kits that mounted on the air cleaner top that did this from places like good old W/JCW back then. Worked like a charm.
Like hooking up your windshield washer sorta deal here is all.
pdq67
Best Car Insurance | Auto Protection Today | FREE Trade-In Quote
I wanna say from "Gasoline FAQ" ????....
Anyway, thanks for the insight b/c I sure the heck, DON'T want to spread bad info around!
Now, bttt, please consider water/alcohol injecting it or even injecting it w/ straight E85 right down the throat at WOT.
We used to buy kits that mounted on the air cleaner top that did this from places like good old W/JCW back then. Worked like a charm.
Like hooking up your windshield washer sorta deal here is all.
pdq67
Best Car Insurance | Auto Protection Today | FREE Trade-In Quote
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