if i go with some 5.3s would 11.3-11.5 compression be too much for a street car, running 93 octane all the time? or should i keep it closer to 11.1 (what i got now)? i figure i can get the extra 5hp out of them by the compression <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" /> . currently a 224 cam, may go to a 230 cam soon though <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />

 

On average, 1 full point of CR is worth about 3% power. For a 93 Octane setup, I've run 11.0 on my old 382ci and now have 11.5 on the 434ci and have no problems with 93 Octane. Of course, on the 434ci I have the ignition timing pulled back some (26 degrees max) in order to do so. If I were to run on 104 unleaded, I could probably tune it for 30 degrees and pick up some decent power.

But, 525 rwhp on 93 Octane is just fine <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" />

-Tony

 

It all depends on where you atmospheric(sp) conditions, some sa you cant get away with 12.1 here in houston (I dont really think so in the summer). But if I ever get another F-body im think I would try that 12.1 (but might just keep it at 11.5. Talk to you local speed shop and talk to people with other heavily modified f-bods in your area and see what comp ratio they are running.

 

its chicago, so like 10 degrees one day and 100 the next. its a 346 cui motor fwiw.

 

well...I'm in Phoenix. I just did my head/cam swap and have 11.1:1 on 91 octane (can't get 93 out here <img border="0" title="" alt="[Mad]" src="gr_images/icons/mad.gif" /> ). I am running 26 degrees advace ignition at WOT and thus far have not had any noticable ping. I'll findout if I'm screwed when it gets to be 115 degrees this summer <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" />

 

i'd say 11.0:1 would be the best compromise between compression and maximum timing you could run

 

It all depends upon the rest of the motor. I have seen 17:1 done on pump gas. (odd cam choice with that.) With a tiny cam (214/224 w/ very little overlap) I have run 11.7:1 on pump gas. 12:1 is about the limit normally. It depends upon alot of things, coolant temp, head temps, cam timing, chamber efficentcy.

Bret

 

It has almost everything to do with your location and tuning, as well as cam selection. You could get away with 14:1 if you detuned the car enough, but where is the benefit? The higher your elevation the more compression you can get away with as well. For your location and with fairly aggressive tuning you should have no problems with ~11:1. I personally wouldn't go any higher then ~11.3:1 for 100% pump gas and a 224 cam.

 

ok, thanks guys. i have 11.1 now, and ive had no problems with it. if i go with real heads ill prolly keep 11.1 then <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />

 

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by Paul @ Thunder:
<strong> I personally wouldn't go any higher then ~11.3:1 for 100% pump gas and a 224 cam. </strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">Paul, Please comment on the other TR cam choices. Are there others that you feel are better solutions at 11.3:1 on pump gas [esp. 91]?

thanks