Thread: Timing
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Old 07/16/2007, 10:41 AM   #9
davidathans
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Best e.t. : 11.042, Fastest speed: 124.08, Best 60' : 1.615, 0 to 100 in 6.98

Location: San Fernando Valley, California
Joined: Jul 04
Posts: 703

Quote:
Originally Posted by robert campbell View Post
As David states he runs fine on 91 octane. And his car is “way” high performance by the times he sets. Its all about setting your car up properly. I have a nearly 12 to one 428 and a 13 to one 289 that both run on today’s gas. There are a lot of wives tales out there on today’s gas. Today’s 91 or 92 octane reacts much the same as yesterdays 99 or Custom Supreme 101. It burns slowly enough without the use of lead to slow down its explosive ability and suppress pinging. Aluminum heads help also. A cam with a lot of overlap helps bleed off low RPM compression that assists in low speed pinging and starter cranking speed overload.

But for stock engines you should be able to run near stock specs with today’s gas. It reacts much in the same way. Lead additives are a bunch of BS unless you are pulling a trailer with a truck or running a boat with car engine with old iron seats. Most Sunday drivers will never put enough miles on their cars in 50 years to notice a difference of valve seat recession. And the miles are usually very easy. Don’t spend money on lead additives!

If you car runs better on Avgas or with a bunch of octane boosters you don’t have it tuned for today’s gas or you like to spend a lot of money. There was an interesting article a year or so ago in Hot Rod Magazine. They took a test mule 360 mopar motor that was worth about 400 HP and ran it on today’s 87, 92, and yesterdays 101 and some Avgas. They made pulls with all sorts of changes to timing and found that motor would run on all the gas and make power, but it did make the most power on the 101 and Avgas/race fuel. Proves that the old gas was much more explosive and produced many more “joules” of energy. Whew, sound like a professor now….. Not!!!!

I have run many a modified engine and many stock ones. I find that most motors like a bit more initial timing than stock specs. But again you have to keep the total in the 36 to 38 range. Arlie had a cool link on how a stock Ford distributor can shorten up the mechanical and let you run more initial. Every car will react differently. Fine tuning is the key. There is no need to run spend money on half an half today’s and high octane gas AVgas. You can tune it to run fine. My GT/CS, 428 Cobra Jet 1957 Wagon, and 13 to one 289 in a 67 Fastback run great on today’s 91 premium. Would they go faster on the old stuff if tuned? Absolutely!!!

By the way, a great article on the new “corn” fuel is in this months “Mustang and Fords”. You want to go fast??? This is the new stuff that burns even more powerful that gas!!! I am waiting for it to come to my local gas station!! Tune it to run on this stuff and YAAAAAAA BAAAABBBBEEEE!!!

Rob
hey rob so your saying your 289 has 13:1 compression and you run it on 92 octane? that blows me away...the first 347 stroker project for my car...we took the original cast iron block, bored and stroked it, had a cast crank, h-beam rods and keith black (10:1) hypereutectic pistons...we were re-using the cast iron cylinder heads but we modified them by installing unleaded valve seats, threaded rocker arm studs, had the exhaust ports ported and polished and we milled the heads .025" for what we calculated was 11.0:1 compression ratio taking into account the compressed gasket thickness and deck height clearance and valve relief in the pistons and of course the combustion chamber cc's(56)....anyways....the cam we were running on that car was hydraulic flat tappet with .480" lift for intake and exhaust and 230 degrees duration at .05" lift for both the intake and exhaust...was also running msd pro-billet distributor and edlebrock performer rpm manifold with a holley 670 street avenger carb...had hooker super comp. headers on it and flowmaster exhaust...

i remember buying NOS black can octane booster and i had a msd timing module mounted on the shifter so i could retard the timing when i heard pinging...(the point)--i detonated the hell out of that motor...when we built the new motor we used aluminum heads and a more radical cam .544" lift intake .560" lift exhaust 232 deg dur at .05" lift intake and 242 deg dur at .05" lift exhaust with 110 degrees lobe seperation...but we built this motor to around 10:1---10.5:1 compression somewhere around there....the guys at B&D considerd 11:1 compression too high to run California 91 octane fuel....CA 91 is much worse than 92 octane in other states is what they tell me...it was shocking to me to hear that you run a 13:1 compr ratio 289 on 92 octane....you run your intial timing at 16 on that car? and you have a total of 40 degres at 3000rpm? have you run your car with a wide-band air fuel meter? if so what were your air-fuel ratio #s? and you must have aluminum heads on that car, right?

a tuner at B&D said that my previous engine pinged so horrible...partially because of that cam i had in there...he spoke of the overlap issue and it is a little over my head, but im guessing that .480" lift cam with 280 degrees advertise duration and 230 degrees at .05" duration just wasnt a good cam design as far as the overlap bleeding off low rpm compression for that particular 347 with those components? i dont recall the lobe seperation on that cam...what cam do you have in your 13:1 289?

thanks,
David
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