What kind of gas should I be using? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Ole Blue 68 · 08-22-2005, 10:18 AM

I've got a rebuilt 283 with no cat. Does it matter what octane rating I use? Also, should I be adding a lead substitute?

**special-K** · 08-22-2005, 10:25 AM

Cheap!!,if it existed.When it was rebuilt it should have had the no-lead valves/seats installed,I would think.Regular works fine in engines under 10:1 compression.

**pjmoreland** · 08-22-2005, 12:13 PM

If you have valve knock when lugging the engine, and can't get rid of it by retarding the timing, then you may need to use a higher octane gas or a lead additive.

mrein3 · 08-22-2005, 12:48 PM

My 383 knocked like crazy on the gas I had in the tank when I put it back together (regular unleaded).

I switched to super, 91 octane, and all my spark knock went away.

YMMV.

Ole Blue 68 · 08-22-2005, 01:19 PM

Thanks for the responses! The engine was just rebuilt so I think its safe to say they went with no-lead. I've put two tanks of regular in so far and it's been fine but if I hear any knocking/pinging, I'll move up.

08-22-2005, 10:18 AM	#1
Ole Blue 68 Registered User Join Date: Aug 2005 Location: Philly Posts: 1,140	What kind of gas should I be using? I've got a rebuilt 283 with no cat. Does it matter what octane rating I use? Also, should I be adding a lead substitute?

08-22-2005, 10:25 AM	#2
special-K Special Order Join Date: Nov 2004 Location: Mt Airy, MD Posts: 85,852	Cheap!!,if it existed.When it was rebuilt it should have had the no-lead valves/seats installed,I would think.Regular works fine in engines under 10:1 compression. __________________ "BUILDING A BETTER WAY TO SERVE THE USA"......67/72......"The New Breed" GMC '67 C1500 Wideside Super Custom SWB: 327/M22/3.42 posi.........."The '67" (project) GMC '72 K2500 Wideside Sierra Custom Camper: 350/TH350/4.10 Power-Lok..."The '72" (rolling) Tim "Don't call me a redneck. I'm a rough cut country gentleman" R.I.P. ~ East Side Low Life ~ El Jay ~ 72BLUZ ~ Fasteddie69 ~ Ron586 ~ 67ChevyRedneck ~ Grumpy Old Man ~

08-22-2005, 12:48 PM	#4
mrein3 Registered User Join Date: Feb 2000 Location: Center City, MN, USA Posts: 3,253	My 383 knocked like crazy on the gas I had in the tank when I put it back together (regular unleaded). I switched to super, 91 octane, and all my spark knock went away. YMMV. __________________ '70 cab, '71 chassis, 383, TH350, NP205. '71 Malibu convertible '72 Malibu hard top Center City, MN

08-22-2005, 12:13 PM	#3
pjmoreland Senior Member Join Date: Jan 2005 Location: CA Posts: 5,796	If you have valve knock when lugging the engine, and can't get rid of it by retarding the timing, then you may need to use a higher octane gas or a lead additive.

08-22-2005, 01:19 PM	#5
Ole Blue 68 Registered User Join Date: Aug 2005 Location: Philly Posts: 1,140	Thanks for the responses! The engine was just rebuilt so I think its safe to say they went with no-lead. I've put two tanks of regular in so far and it's been fine but if I hear any knocking/pinging, I'll move up.



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