Unleaded or premium?

[fins&chrome]

When I ask about what fuel is best — I get 50%/50% responses for either keep regular unleaded OR go with high octane premium. What do most of you out there use for your stock engine? Mine is a 283 4BBL.

Thanks!

[carls 56]

use reg. 87 in all my v-8's! 350, 327 and (hate to say this) ram hemi :eek:. they all run great :tu:);):D

[Gregs210]

I've always heard if it doesn't ping on regular unleaded, then you don't need premium.


Greg

[ETriggs]

If you are running under 9.0:1 compression you are wasting your money on premium.

The rule of thumb I was taught years ago (not sure if it is completely accurate) is
1. 7-9:1 - regular unleaded
2. 9-9.5:1 - midgrade
3. 9.5-higher - premium

[auggie56]

When I ask about what fuel is best — I get 50%/50% responses for either keep regular unleaded OR go with high octane premium. What do most of you out there use for your stock engine? Mine is a 283 4BBL.

Thanks!

Do you have harded valves and seats ?

[fins&chrome]

They are not hardened, not to my knowledge anyways. The car is stock all the way thru. BTW I really love the color combo on your ’56.

[RichP]

Is a lead additive suggested in a stock car?

[56 2x4]

A factory stock 4bbl needs premium but will run on regular if you can tolerate the occasional pinging uphill and the occasional vapor lock on hot days. A factory stock 2bbl needs regular. If the combustion chambers have alot of carbon buildup it will run better on premium until you can burn the carbon out.

You probably do not need leaded gas on factory seats if they have already been work-hardened on leaded gas, maybe 10K-20K miles. You do have a small risk of a sunken valve over time.

[Watchdog]

I run premium. I use the lead additive every other fill-up. I may be wasting my money, but it runs good and I don't drive it enough to hurt my wallet too bad by paying the extra few cents a gallon. Premium is 93-94 octane here in SC. In some parts of the country, my regular unleaded may be your premium.

[CRUZZA]

Here our Regular is 91 octane. Super is 95 and you can also buy 98 octane from selected gas stations. They are all unleaded. The 57 runs like c**p on 91. I always use 95 with an additive and treat it to a tankful of 98 every now and then.

[CJS57]

87 low octane fuel works perfectly in my bone stock 283 245hp engine with 60,000 original miles on it. Never rebuilt short block, it had a valve job at about 45,000 miles with hardened seats added. Timing is 36 degrees total mechanical with 12 degrees initial. About 54 degrees with the vacuum advance. No pinging at all! Excellent power, when I mash it at 20mph in low gear, it just throws you back against the seat!
The previous owner ran 93 octane with an additive too. Total waste of money in my view, but doesn't hurt anthing. The lowest octane fuel that works in your engine is just fine and technically it will give a hair more power than high octane in this situation. This is because low octane burns faster and gives a little harder push on the piston. High octane burns slower to prevent knock. The power increase is tiny, maybe 1/10th of 1 percent or so.

[Rick_L]

The octane requirement is independent of the need (or lack of need) for lead or some other lubricant for the exhaust valve seats.

You'll get the most power and economy from a fuel that just meets but doesn't exceed your octane requirements. 87 octane fuel has more heating value than higher octane fuels.

For the most part you don't need hardened valve seats or lead compounds to avoid exhaust valve seat problems. If the engine works very hard all the time (like in a truck that's always loaded) then you would have much greater risk. Having said that, I did lose an exhaust seat to recession on a 67 model 283. I really don't know why it did it - it didn't overheat.

[Chevy57Ray]

Hi, I run my '57 engine on regular octane gaz, even with my engine design for performance and HI octane. Once in a while, I fuel on HI, but I tried different test and setup and for the road economy, there is no saving. For performance with the accurate setup, Higher Octane will give much better result for race. On street, don't waste your money unless your engine give you sign of that need. M2C

[LorenB]

WOW! This is some really good information guys. Guess I don't need to waste my money on additives any more.

[bill57]

I use premium with the lead substitute every other tankful.
I waste money on other things, too.

[Black56]

My bone stock power pak 265 runs like a top on 87 octane.

[Bob W]

I've run my 57 on regular fuel for 40,000 miles and no problems at all. 283 with dual 4s and 327/350hp cam , 4 speed. I just added a set of 461 heads and it still runs good on regular fuel.

Bob :)

[CJS57]

Bob, How does your 283 run with the cam and 461 heads? I mean does it still have all the low end torque and driveability of the 245hp with stock 9.5 compression (powerpack) 283 heads? I am sure your top end power above 4,000 rpm is a lot better! I have been thinking of going to a similar setup with aftermarket cam, not as agressive as the 350hp cam and maybe some aftermarket small valve (1.94) heads designed for the smaller 283.

[Bob W]

Bob, How does your 283 run with the cam and 461 heads? I mean does it still have all the low end torque and driveability of the 245hp with stock 9.5 compression (powerpack) 283 heads? I am sure your top end power above 4,000 rpm is a lot better! I have been thinking of going to a similar setup with aftermarket cam, not as agressive as the 350hp cam and maybe some aftermarket small valve (1.94) heads designed for the smaller 283.

My car works great with the 461s. My low end torque is a kinda mushy but that's my fault. I have a high first gear trans and then I put 3.08s behind them. If you had 3.55s in the rear or a low first gear to get you rolling the 461s are fine. 461s are an original 283 head anyway.

This is sure alot different than when I had a 66 Biscayne with a 283/220hp, 2.88 first gear 4 speed and a 5.86 rear. It broke lotsa stuff. Then there was the 65 Chevelle with a 2.20 first and the 6.14 tail ...................................

Bob

[CJS57]

Bob, Thanks for that! Sounds like you have a great combo going. Mine has a 5-speed with 2.87 1st gear and 3.70's rear. But I am going with 4.11's eventually, for even more dig off the line and highway rpm's will still be fine.

[Bob W]

Some guys get all bent out shape about putting 461s on a 283, but what people never stop to think of is that Chevrolet first put them on the 1961 Corvette 315HP FI 283s and then in 62 used them on the 327s.

Bob :)