Fuel!

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Aug 24, 2008 | 10:57 AM

Apocolips

Thread Starter

Drifting

Joined: May 2002

Posts: 1,546

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From: Back in Nebraska

Fuel!

I have a rebuilt stock 350/300 in a 1970. I have been using mid grade fuel since the rebuild. I have noticed a slight knock. No one can hear it but me it seems. My question is: does it matter what grade of fuel I use for a completely stock engine? Should I put the highest grade available in? Need to know, it’s a beautiful day and I want to cruise. Thanks!

Aug 24, 2008 | 11:24 AM

mrvette

Team Owner

Joined: Jul 1999

Posts: 65,492

Likes: 230

From: Orange Park Florida

Need know more abut comp ratio, specifically, and cam....but in general you will need high test gas....92+ octane.....I burn 92+ in my DPFI engine....and need to, damnit....

Aug 24, 2008 | 11:48 AM

Eddie 70

Race Director

Joined: Feb 1999

Posts: 19,659

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From: Lenoir City Tennessee

Ci 6, 8 & 10 Veteran

St. Jude Donor '05-'06-'07-'08-'09-'10-'11-'12-'13-'14-'15

If the motor is still stock and has the stock heads without the hardened valve seats in them, you will also need to run some lead substitute to help lubricate the valve seats. It also helps take some of the heat away from the seats. I would use premium if it has any knocking. Its just a weekend cruiser so its not like you will be filling it several times a week. You can also verify timing is set correctly.

Get out there and drive that puppy. Enjoy the day cruising in your vette. I get to go out there and work on mine today.

Aug 24, 2008 | 11:49 AM

dmayhew

Drifting

Joined: Oct 2007

Posts: 1,254

Likes: 5

From: Brown Summit North Carolina

Quote:

Originally Posted by Apocolips

What not just go buy some 92 octane next time you fill up and see what happens.

The price between the 2 grades is just not enough to not at least try it.

If knocking goes away , you have answered the question.

David

Aug 24, 2008 | 12:40 PM

birdsmith

Melting Slicks

Joined: Feb 2006

Posts: 3,428

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From: Japan

When I first purchased my unmodified 350/300 '70 ten years ago it would not run on straight 92 octane without clattering away like crazy. No amount of fiddling with ignition timing, etc. would cure the problem. Bottom line here is that with 10.25:1 CR, iron heads, and that particular cam it's gonna ping on even the best available pump gas. I rebuilt mine with 9.5:1 pistons from a Summit kit, had hard valve seats put in and a slightly larger cam and now all's well- runs all day on 87 octane with little or no knock. You can try aviation gas or race gas ($$$!!) or aluminum heads, but if you continue driving it on pump gas with that combination you're gonna hurt something eventually.....

Aug 24, 2008 | 07:04 PM

70Donnybrooke

Pro

Joined: Mar 2004

Posts: 640

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From: Mertztown Pa

Quote:

Originally Posted by birdsmith

Same thing with my 350/300. I tried everything. The cure was high test with about 2.5 gallons of 110 leaded racing fuel. Never pings at all. Smells great.

Aug 24, 2008 | 09:13 PM

dmayhew

Drifting

Joined: Oct 2007

Posts: 1,254

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From: Brown Summit North Carolina

Quote:

Originally Posted by 70Donnybrooke

Same thing with my 350/300. I tried everything. The cure was high test with about 2.5 gallons of 110 leaded racing fuel. Never pings at all. Smells great.

There is a Sunoco station in my area that sells a 100 octane unleded

You can pump right nto the car at the pump

David

Aug 24, 2008 | 09:22 PM

garretttpe

Intermediate

Joined: Aug 2008

Posts: 42

Likes: 0

From: Delta Ohio

If you live close to an Airport you can talk to the fueling company there and most wil give you there sump fuel (100 ll octane) and that will save you money anf allow the car to run better.