Fuel Octane Question

zreg · May 31st, 2006, 10:12 PM

I have a 1973 Mustang Convertible and it starts and runs fairly well. I just bought the car and it needs some work, but it is a running project car. I put 93 Octane unleaded in the car and am concerned that I may need to to perform some modifications to run this fuel. Right now, the car hesitates when accelerated from a stop and also from low speeds, but I have not floored the engine. The exhaust is clear, but after driving on the highway for 30 minutes I noted some black soot on the rear bumper, so I think the engine is running rich. I plan on replacing the plugs and points, but I am not sure if I can use 93 octane unleaded. The engine is a 351 4V (4Barrel). I don't think the engine has been modified. Any tips would be greatly appreciated. Thanks

Darrell · May 31st, 2006, 10:53 PM

Sounds like you need a tune up and carburetor rebuild. 93 octane will be fine in that engine. You could probably get away with 89 octane.

Twist 2 Go · May 31st, 2006, 11:14 PM

also ck the dist. vacuum advance diapragm and make sure it's working correctly.

68 Coop · November 14th, 2006, 07:53 PM

I think the octane grade is OK, but it sounds like you might re-jet your carb. What size jets and needles are you running now?

My67_fastback · December 1st, 2006, 06:13 PM

dont run higher octane if u dont need it. its highly possile that the engine is due for a rebuild, so the compression has lowered, causing the engine not to like that 93 octane fuel you're using. do a compression test.

Clutch · December 1st, 2006, 08:36 PM

I'd also say to give it an "Italian Tune-up"

You know, where you go out to the highway and get into it a little bit. Helps flush out residual gas and other junk from the intake planes before they turn into power robbers.

I also agree, regardless, a tune up is most definatly in order. No matter what anyone tells me when I buy a car (except brand new

), the first thing I do is a tune up.

Cleaning and rebuliding the carb is another plus.

May 31st, 2006, 10:12 PM	#1
zreg Newbie Join Date: May 2006 Posts: 15	Fuel Octane Question I have a 1973 Mustang Convertible and it starts and runs fairly well. I just bought the car and it needs some work, but it is a running project car. I put 93 Octane unleaded in the car and am concerned that I may need to to perform some modifications to run this fuel. Right now, the car hesitates when accelerated from a stop and also from low speeds, but I have not floored the engine. The exhaust is clear, but after driving on the highway for 30 minutes I noted some black soot on the rear bumper, so I think the engine is running rich. I plan on replacing the plugs and points, but I am not sure if I can use 93 octane unleaded. The engine is a 351 4V (4Barrel). I don't think the engine has been modified. Any tips would be greatly appreciated. Thanks

May 31st, 2006, 10:53 PM	#2
Darrell MM Ninjas! 1990 Mustang LX 9.36@143 mph Join Date: Jan 2006 Location: Fond du Lac, Wisconsin Posts: 6,507	Sounds like you need a tune up and carburetor rebuild. 93 octane will be fine in that engine. You could probably get away with 89 octane. __________________ Racing in memory of Dave Bandt 11/19/69 - 3/23/08 "he's traded his wheels for wings" Professor of Natural Aspiration Thanks to: Artie at Trick Flow, Dave at Team Z Motorsports, Brian at Total Engine Airflow and Harold at Furo Racecraft

May 31st, 2006, 11:14 PM	#3
Twist 2 Go Hardcore Enthusiast Join Date: Aug 2005 Location: Chesapeake, Virginia Posts: 1,716	also ck the dist. vacuum advance diapragm and make sure it's working correctly. __________________ 88 Mustang Coupe 2006 FFW Richmond True Street Runner-Up www.rickscarcare.net http://img146.imageshack.us/img146/2158/ricksadql2.jpg

November 14th, 2006, 07:53 PM	#4
68 Coop Newbie Join Date: Nov 2006 Location: Mesquite, NV Posts: 19	I think the octane grade is OK, but it sounds like you might re-jet your carb. What size jets and needles are you running now? __________________ William 68 Coupe 289 C4 3:55's/Trac-Lok

December 1st, 2006, 06:13 PM	#5
My67_fastback Regular Join Date: Dec 2006 Location: oklahoma Posts: 196	dont run higher octane if u dont need it. its highly possile that the engine is due for a rebuild, so the compression has lowered, causing the engine not to like that 93 octane fuel you're using. do a compression test. __________________ TO: Ricers- 1) there's no replacement for displacement 2) my lug nuts require more torque than your engine makes 3) a light car doesn't excuse a weak engine 4) a bottle of pepsi has more liters than your car eating rice builds muscle

December 1st, 2006, 08:36 PM	#6
Clutch Regular Join Date: Nov 2006 Posts: 66	I'd also say to give it an "Italian Tune-up" You know, where you go out to the highway and get into it a little bit. Helps flush out residual gas and other junk from the intake planes before they turn into power robbers. I also agree, regardless, a tune up is most definatly in order. No matter what anyone tells me when I buy a car (except brand new ), the first thing I do is a tune up. Cleaning and rebuliding the carb is another plus. __________________ Getting a new computer . . . . $1500 Restoring a 40 year old Mustang . . . . $50K~ Building a business . . . . $Don't go there. Being this damn broke . . . . Priceless!

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