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1965 2+2 Vintage Burgundy A-code C4
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I have a set of 65 model 289 heads that have new springs and a valve job. I may have a set of roller tip rockers lined up, leaving me needing only pushrods. I plan to port/polish/gasket match them for use on my 65 289 w/Performer/Holley 600/Tri-y/Pertronix setup. The car is a daily driver and I only want to add some extra oooomph to it, nothing radical. I currently get 18 mpg. My question is, will I still be able to use 87 octane with these heads? If not, what can I do to them to be able to? Two head gaskets? I would appreciate any help on this matter....I would like to use the heads, but don't want to have to buy gas that is even MORE expensive than it already is.

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No problem....just get ready for the rattle, rattle....*G*

The more performance you get from your stocker, the more cylinder pressure it makes and the more likely it is for you to run into detonation...

You'd likely have no problems on premium.....I'd just pay the extra .20....maybe .50 this summer...per gallon...

As an alternative, you could bolt on some later 302 or 351W heads with larger chambers to lower your compression...the head gaskets today are pretty thick as it is....no, you can't run two..*G*

Life is full of compromises, yes?

Pat
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Hi russ,

It's hard to say with out knowing if you have decked the block or milled the heads, or if your pistons are stock. If I was to guess I would think you would be ok with 87. You can simply do a search on the web for compression calculators and plug in what you can and get a ball park comp ratio. Gaskets can be bought in different compressed heights to manipulate comp ratio.
 

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Detonation will start at a hot spot within the combustion chamber. This most often occurs at sharp edges along the combustion pocket of the head and the valve reliefs of the pistons. To prevent this take a dremel/drill/other and provide a little radius- 1/32 to 1/16th of an inch is fine- so the edges aren't sharp to the touch. With this, you'll be able to run pump gas with out any difficulties in the mid 9 and in some cases into the upper 9 range.

Tom Kubler, Long-time Mustang Enthusiast & San Antonio Mustang Club Founder
 
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