87 octane? Is it the truth or a myth that a stock TBI camaro will run better and faster using only 87 octane rather than premium? I am switching over to the holley 670. Do I have to bore the manifold to 2"? I just don't want to tear the whole car apart to do so. Thanks and have a great afternoon everyone.

Bob

 

I dont know about the holley TBI but if the bores are 2's in dia, and the manifold is not then you arent gaining anything by not boring it, you are esentialy choking the engine at the manifold, it creates an air restriction. taking the manifold off the engine is not a big task, i can have mine off in a few minutes.

 

Well I guess I am just paranoid. I've never had good luck with removing distributors and having the car fire up after re-installation. I'm very **** about the procedure while doing it too. I get the wifes finger nail polish so that I put it back in exactly as removed and I still have to start all over again with the timing etc. They never seem to fire up for me. But, it sounds like I need to remove the manifold anyway then. I guess it would be better to purchase the edelbrock performer TBI intake over simply boring out the stock one. Thanks for the info my friend. Have a great afternoon!

Bob

 

You will still have to bore out the edelbrock TBI intake as well. Unforntunatly it comes with the small stock bore sizes. No big deal. I bored mine to 2" with ease. You only need 87 octane if you have no timing advance and have everything else stock. To much octane can delay ingnition causing a loss of power and throttle repsonse. You only need 890 or higher if you run more than 0* advance on your base timing and or you have a high mileage motor with carbon deposits that are causing ping.

 

I'm wanting to get the same holley tbi for my car (and the edle intake to go with it) how do you bore an intake though? just take it to a machine shop? I'd like to know how that setup works out for you. be sure to post back w/the results.

 

See my mod's.......run's on 87 and has 180K on the shortblock.

 

The octance debate has been going on longer then the different octanes have been around. Personally for my car, I use 91, for when I use anything else my gas miles just goes to all hell. It's really not even a performance issue for me. I average right about ~20mpg and have hit 30 with 91, and my last tank of 87 brought a wopping 14mpg. As far as bolt ons and timing advances or the like, though, yeah upping your octane is deff. a good idea...

Bruce (90RS305)

 

MPG avg's 20 in mixed driving with the usual "play time" mixed in.

Wonder what it "could" get with some real tuning, not my lazy get it running approach.

 

i have stock timing, and only a cat back exhaust, and cant get my car to run good at all with 87, 89 is even sometimes touchy, all ive used the 2 yrs ive had it has been 93 on east coast, and now 91 that im west coast, any ideas on this, its got a newer fuel filter

 

for what i remember from Internal Engine class years back.. octane boosts are only required for higher compression ratio motors. threoretically: if your working a high milage motor with CC carbon buildup / or modded motors (specifically ported intakes, heads, or dometops) you're prolly looking at a motor that is 1/2 psi or more over factory compression, hence needing higher octane.
93 is "more explosive" then 87 basically. this would explain better mpg and performance. but if the motor isnt built for dynamite then you're gonna be fixin some stuff eventually.

I COULD BE WRONG:hail:

 

My car runs like crap on anything less than 92 octane. I dont know why, but it goes way down on power and loses what little get up and go it has left.

 

Close but a little off. Gasoline doesn't explode (in the combustion chamber) at all and octane ratings have nothing to do with "power units" of the fuel. Meaning, a higher number does not mean it has more chemical energy. What it does mean in a non-nerd way of explaing it is that it can take more compression before it ignites. If you use fuel that does not have a high enough octance rating in a motor that needs it that the compression stroke will add enough heat to the mxutre to pre-ignite it before the spark does. That is knock. On the other hand, if you use to high of an octane the compression stroke does not add enough heat/compression to the mix so that it is properly set off by the spark. As stated above carbon deposits can cause pre-ignition because they heat up and act like little spark plugs setting off the mix pre-maturely.

 

:werd:

 

i dropped from 92 to 89 and found no reduction in performance. no KC(yet).