360 9:1 on 87 octane?

[crazycanuck]

alright i want to double check that i understand this all first

My goal is to have an engine to produce 300+ ft/lbs at 200 rpm and still be able to produce good high hp numbers at 5-5500 rpm(350-400) from what i understand 87 ocante is capable of an effective compression ratio of 7.5:1, if this is correct and the effective CR calculator says that i would need intake valve close time of 43d after bottom dead center or later(as close as possible in order to maintain as much fuel economy as possible because compression is important for that...not going for honda just want to be able to afford to drive it)

if my understanding is correct iused desktop dyno2k to create a cam that is able to produce 400ftlbs of torque form 2-5k and 380hp(.49 lift, 218 intake, 247 exhaust, 116 degrees seperation)is my understanding correct? are the numbers correct (7.5:1 on 87?)

[jeepsr4ever]

What elevation are you in? Here in MN we run 87 octane to 9-1 compression. Donwag had a really low end grunt engine you can check it out in the general chat section...probly at the second page now

[crazycanuck]

thx i dunno my altitude i assume at least 1-2 thousand but have no clue whats ohio at?
CCA-10-215-5 COMP Cams Xtreme Energy Camshaft form summit matches similar goals to mine...it detunes it to aroun 350 ft/lbs, does anyone have any experience with this cam?

[Holeshot]

You did know that you can run much more compression if you maintain .045" piston to head clearance & use a radical cam to bleed off some of the CR. The more efficient your porting & chamber (as well as intake & exhaust sys) is the better for performance & anti knock. I never considerd building a hipo engine but limiting it to 87 octane. The AM V8 is quite tolerant to high CR but you may need to mix some good gas in with the weaker stuff. Spending more on gas is not that big of a deal if you want over 500 hp & tq. 7.5 to 1 is what you want for a turbo engine, I'd never go that low w/o forced induction.

[crazycanuck]

im in Canada and fuel is a lot more expensive here i think $1.20+/litre for premium in the summer*3.8 = $4.60 a gallon *.7 for exchange(varies not sure right now)= USD 350+ a gallon and i have seen premium for as high as $1.35 Canadian so that would be over 4$US a gallon at times and if i build for 87 and need to run 89 its no big deal $wise but if i must run 91-94 it would be murder even on my medium miles vehicle( iknow poeple who make weekly trips across the border with vehicles modified to carry a weeks supply to avoid the tax

what i am trying to do is push the torque limits with an economical (10-15mpg setup) 87 prefered but if i have to 89 is doable

$4000 will pay for itself in acouple of years if a manage to get 15mpg on 87 or 9 instead of 10 on 91-4

when i say 7.5 compression i mean dynamic after the camshaft is positioned to reduce the effective compression from nine just to clarify if i were going to boost and use premium i agree this would be a good place to start if 5-7 psi of intercooled boost were used.


about the .045" clearance i think that it would only be possible if i raised the static compression to the range of 10 or more now this should still be possible to run on "poorer" fuel if the intake valve closing point where to be delayed even farther...to 50degrees after bottom dead centre this would require that with 58 cc chambers .03" head gasket 4.2" diameter would leave 17cc to removed from the piston (and more to accomodate adding material to combustion chamber i dont know much about this work?)and at 9:1 it would be 28cc, am i on the right track

what would be the best way to properly quench the engine in the 9-10 or slightly more, compression? custom pistons? head work? are there any good pistons available.

Thx for any help, sorry for the long posts i just want to be sure about these things

[crazycanuck]

considering limiting to 6500...either of the small edelbrocks or the Offenhauser Dual Port Intake Manifold...i know about the edelbrock but whaat power range does the offy operate in
is it any good for my 2000-5or6000 rpm build? does anyone have any experience with any others or the offy?

[Holeshot]

Ya need to use flattops with valve reliefs cut specifically for the AM V8. That way the combustion chamber is mostly in the head instead of being in the dish of the piston. .045" clearance is required to get the most EFFICIENT quench, better efficiency yields better mpg & power, & it is impossible to get .045" from dished pistons. That is why so many AM V8s ping, even with 8 or 9 to one compression.

If ya use the flattops (Ross pistons direct from Ross have the correct reliefs, Maddog's do NOT), you can open-chamber the combustion chamber to lower the compression some & flycut the valve reliefs to get even less. AM V8s with flattops, ported chambers, some healthy cam & efficient exhaust can run 10 to 11 to one without race gas. If ping is encountered, adding a little extra fuel can help & water injection has been used effectively for decades. You could also install 1.7~1 SBF rockers to add cam & bleed off more compression.

The BEST dual plane intakes for up to 6500 are the Edelbrock R4B and the AM "Machine" intake.

[crazycanuck]

thx for your help...the piston advice is awesome thx