What octane for a 77’ 351
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Category: Repairs and Maintenance
Forum Name: Boat Maintenance
Forum Discription: Discuss maintenance of your Correct Craft
URL: http://www.CorrectCraftFan.com/forum/forum_posts.asp?TID=863
Printed Date: January-15-2025 at 2:54pm
Topic: What octane for a 77’ 351
Posted By: veedub88
Subject: What octane for a 77’ 351
Date Posted: September-27-2004 at 3:56pm
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I noticed on the sticker on the manifold of my 1977 martinique w/351w it says to use 94 octane leaded gasoline. What octane would be the best since leaded isn't an option?
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Replies:
Posted By: mrese
Date Posted: September-27-2004 at 6:55pm
Lead additive can be added to the gas since only unleaded gas is readily sold at the pump.
Many opinions out there about the need to run high octane gas. If you can run 87 octane and your engine doens't knock or sound other than optimum, I would continue to run 87 and spend the money on something else.
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Posted By: Guests
Date Posted: September-29-2004 at 4:27pm
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My 94, sport with 351, throttle body injection would not run smoothly on the fuel available at the marina on my lake, but when I would fill with cans from the local gas station, it would run like a top. Is this a case of the octane being too low in the marina fuel? Would an octane booster additive help the situation and save me filling cans. etc. Any ideas would help.
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Posted By: mrese
Date Posted: September-29-2004 at 5:47pm
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What octane are you putting in the refuel cans? If the octane is the same in the cans as well as the marina, it may be an issue of water in the fuel at the dock. Yes, there is a seperator in your fuel line, but sometimes, the marinas have more water in the fuel than the seperator can handle. Drain your fuel/water seperator and see what it looks like.
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Posted By: SS 201
Date Posted: September-29-2004 at 7:54pm
Octane normaly goes as the the engine rated
IE 8.6.1 uses 87 octane 9.1.1 93 octane and so on.
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Posted By: reidp
Date Posted: October-04-2004 at 3:18am
I've seen this questioned for some time now and there's someone out there who can probably tell us THE YEAR THE CHANGE(? Later) took place, but here's some background info. This info, by the way, is available on numerous sites by doing a query on octane rating methods. Gasoline for a long time was rated by two separate methods: Motor Method - the early and more conservative and typically lower rating, and the Research Method, which most oil/gas companies years ago posted on their pumps and which many engine/car companies showed as requirements. Today however and for X number of years, and as you may have noticed on the pumps, (in the U.S, and not necessarily the rest of the world), they show the Motor + Research / 2 method as the means for rating the octane. This is simply an average of the two previously used. Now if you have any interest or give a crap, look in the reference section in the Chrysler 1967 engine brochure on pages 34-35 where it shows the fuel octane requirements of most all of their engines, except the top dog, being rated by the motor method, with min requirements all the way down to 80-82 octane. Notice the high compression 415-HP/426-CI engine required 102 octane "research method" fuel. You can find the respective/comparitive Compression Ratios on pages 4-5.
One point and related to veedub88's question of the 94 octane required for his '77, it's not apples to apples with the 94 octane of 2004. In fact, for those who remember 94 octane in 1977, it was low to mid grade fuel, and all that was required for sub-9:1 compression autos. Everyday high test was typically 98 octane with the Sunoco 260 up there at 100 or better. That same fuel today is somewhere in the 92-94 range. The fuel didn't get ALL that crappier, the rating system just changed. I've heard that today's premium 93 fuel is not good enough for hi-po 11+:1 CR engines, but it's certainly more than adequate for the ever increasing number of 10+:1 factory cars being produced today.
So I'm still interested in when the pumps changed, going to the MON+RON/2 method. I found this item which may amount to good bathroom reading: http://web.ask.com/redir?bpg=http%3a%2f%2fweb.ask.com%2fweb%3fq%3dwhat%2bis%2bthe%2bdifference%2bbetween%2b93%2boctane%2bgasoline%2btoday%2band%2b100%2boctane%2bof%2b1970%253f%26o%3d0%26page%3d2&q=what+is+the+difference+between+93+octane+gasoline+today+and+100+octane+of+1970%3f&u=http%3a%2f%2ftm.wc.ask.com%2fr%3ft%3dan%26s%3da%26uid%3d0EF2E89A502C65A04%26sid%3d15B9DEF27688C0614%26qid%3d4EA355A1DA520846A8D22169E78289A3%26io%3d7%26sv%3dza5cb0db5%26o%3d0%26ask%3dwhat%2bis%2bthe%2bdifference%2bbetween%2b93%2boctane%2bgasoline%2btoday%2band%2b100%2boctane%2bof%2b1970%253f%26uip%3d438cf569%26en%3dte%26eo%3d-100%26pt%3dGasoline%2bFAQ%2b-%2bPart%2b3%2bof%2b4%26ac%3d24%26qs%3d0%26pg%3d2%26ep%3d1%26te_par%3d101%26te_id%3d%26u%3dhttp%3a%2f%2fwww.aquamist.co.uk%2fdc%2freference%2fpart3.html&s=a&bu=http%3a%2f%2fwww.aquamist.co.uk%2fdc%2freference%2fpart3.html&qte=0&o=0
Sorry for another long post.
Reid
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ReidP
/diaries/details.asp?ID=231&yrstart=1971&yrend=1975 - 1973 Mustang
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Posted By: kenny g
Date Posted: October-04-2004 at 5:23pm
what da hell u been smokin reid ?
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kenny g
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Posted By: reidp
Date Posted: October-05-2004 at 9:38am
cannabis 104+
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ReidP
/diaries/details.asp?ID=231&yrstart=1971&yrend=1975 - 1973 Mustang
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Posted By: Rick
Date Posted: October-05-2004 at 2:30pm
Motor or Reseach method?
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http://www.correctcraftfan.com/diaries/details.asp?ID=250&yrstart=1996&yrend=2000%20" rel="nofollow - 2000 Ski
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Posted By: IrishFooter
Date Posted: October-11-2004 at 5:07pm
Has anyone ever done any work on the heads to beef ot up to handle unleaded gas? Is the engine running poorly? This should determine what you need to do ie if the engine has never been rebuilt I would use a lead additive and if it is running poorly then I would try a higher octane gas. But as Reid said and the sticker on my engine alludes to the recommended 94 octane gas was in the 70s a mid grade octane. Further do not be fooled by what the pump says- a family friend that drove truck for BP(which is considered by most to supply "good gas") was routinely instructed to mix lower grade fuel with the better grade fuel to top off the truck or tanks at the station. So you may well not get what you pay for in this situation.
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1979 Ski Nautique
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