Can I run 87 octane

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Apr 14, 2025 | 09:26 PM

Papa_TJ

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Can I run 87 octane

I am building an Lm7 5.3 3rd Gen. I have put flat top pistons in it and a BTR Truck Torque cam.

Question is can I still run 87 octane fuel?

Thanks

Apr 14, 2025 | 11:44 PM

G Atsma

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From: Central Cal.

You're compression would be 10.47:1
It would be dicey

Apr 15, 2025 | 02:55 AM

01CamaroSSTx

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Depends on what heads and head gaskets you're going to use. Get it around 10:1 and you could probably run 87 but why not spend the extra $20 or so for the higher octane fuel anyway?

Apr 15, 2025 | 05:01 AM

the_merv

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Depends on how much timing you throw at it.

Apr 15, 2025 | 10:19 AM

CattleAc

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Quote:

Originally Posted by Papa_TJ

Question is can I still run 87 octane fuel?

Better question is, why would you want to...???

Apr 15, 2025 | 10:36 AM

bthomas

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Its been proven several times its false savings. When your building anything performance oriented with higher than stock comp, youll end up backing out pretty much all the timing.
This means your now making barely more power than you did originally, and getting worse mileage.

Running 91-93 and putting the timing back in is a wash. The better mpg offsets the gas cost.

Apr 15, 2025 | 11:02 AM

IGN-1A

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Iran 89

Hi, 89 OR "mid-grade" is the best buy.
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Apr 15, 2025 | 02:25 PM

IGN-1A

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Your Location

What is your Altitude ?
What are the cam specifications ?

Apr 15, 2025 | 05:29 PM

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SparkyJJO

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From: Ohio

CAN you? probably, tuned appropriately.
SHOULD you? probably not.

As said above, by the time you yank enough timing to run 87 why even bother with what you've done to it?

Apr 19, 2025 | 12:56 PM

#11

KarmaKannon

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Quote:

Originally Posted by IGN-1A

What is your Altitude ?
What are the cam specifications ?

This would seem important. Not to mention premium at certain elevations is only 91 or 89 if I recall. I think when I lived at 4,700' we had 85, 87, and 89 was premium. I'm around 2,000 now and I think we have 91 or 92 premium.

My lm7 at 4,700 ran fine on 89 (the area's premium)with flat tops but at 2,000 I'd probably opt for 91. Our 6.2 with 10.5:1 seems fine on mid grade but we usually run premium for the above stated performance, safety, and efficiency reasons.

I'm no pro but above 10:1 I've always heard guys suggest premium. I'm thinking it's about half superstition from carb and distributor stuff and half solid reasoning based on OEM suggestions.