Dyno results / ? fuel-octane - Team Camaro Tech
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post #1 of 8 (permalink) Old Apr 27th, 11, 06:58 PM Thread Starter
John sr.& jr.
 
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Location: Fitchburg, Ma.
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Dyno results / ? fuel-octane

Re: race gas was used on dyno runs and adjustment; then 93 octane when engine is run in car; will engine run the same and require no changes?
Hi guys; question at hand about octane and dyno runs; we're doing a 69 camaro/4spd/3:73 -12bolt; now and just finished a 383 stroker build with the following build list:

-New GM 1pc main roller block bored .030" over
-internally balanced and blueprinted
-The engine was assembled using only ARP studs and bolts
-Eagle forged crank w/eagle forged H-beam rods
-Mahle forged -16 dish pistons 9.8:1 with file fit rings
-melling select 10% higher volume oil pump and matching 3/4" pick-up
-Dart pro1 platinum 200cc heads w/64cc chambers
-Dart dual plane intake port matched to heads
-Holley 650 HP/Street / double pumper / mech. secondaries
-Comp cams pro magnum rocker arms, pushrods, and hydraulic roller lifters
-Cloyes aluminum timing cover with true roller timing chain
-Comp Cams XR282 Roller cam for 87 and up blocks. .510/.520 lift 230* 236* Duration
-Powermaster high torque mini starter
- Holley #HLY-12-327-11 (110 gph) mechanical fuel pump w/bronze tip pushrod
-ATi super damper
-Ram Clutches: #1531 billet steel flywheel 1-pc. inter. bal. to nuetral / 168 th.
-CenterForce II pressure plate #CFT165552 / CF. #383735 (11") disc / CF. #N1716 throwout brg.
-The block, valve covers and intake are powder coated satin black
Note: machine/speed shop; balanced rotating assembly to "0" neutral; and require a (1-pc. internal balanced to "0" nuetral 168 th. flywheel )

Just had it dynoed; full day; made 12 to 15 pulls through out; with changes of jets, adding 1" spacer, timing changes; etc, to get good air-fuel ratios and even hp / torq. curves; finally pulled 443hp and 465 torq. at 4600rpm and that thing sounded a bit "nasty" My only concern is dyno; all timing and adjustments were made with racing fuel and 1 3/4" headers; 38 deg. total timing; I'll be running 92-93 pump gas with 1 5/8" headers; will all the jet changes, adustments and timing be off when I run it in the car? thanks imput appreciated. John sr&jr
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post #2 of 8 (permalink) Old Apr 27th, 11, 07:08 PM
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Steiner
 
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Re: Dyno results / ? fuel-octane

Your setup is well within the range of 91 octane. The race gas shouldn't have had any effect on the tune other than maybe allowing you to run a couple degrees more timing. It shouldn't have had any effect on the fueling. I run a smaller cam and a bit more static compression which pushes the dynamic compression up (which will have a direct effect on octane requirment) but only 30 degrees timing. It may take more but it's plenty right now and they set it up on the dyno that way.

'69 Camaro
Dart 400-AFR 195-224/224 HR-Powerjection III TB with F.A.S.T. Sportsman XFI
TKO 600-Moser 3.42-Detroit Truetrac
500hp/538lbft

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'69 Camaro Beater-SFT 327-M20-Moser 4.10-sold
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post #3 of 8 (permalink) Old Apr 27th, 11, 07:25 PM Thread Starter
John sr.& jr.
 
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Re: Dyno results / ? fuel-octane

Steiner; thanks for reply; your eng.build sounds pretty stout!! Johns
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post #4 of 8 (permalink) Old Apr 27th, 11, 10:14 PM
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AJ
 
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Re: Dyno results / ? fuel-octane

I agree with Steiner, he knows his stuff.
For internal combustion engines running regular fuel you should run just about the minimum octane rating you can at the pumps which is 85 if your dynamic compression ratio is low enough to run it. You have only 9:1 static with a 383, the stroke does bump up your dynamic, larger cams do "act" smaller in larger ci motors because of the stroke, but even with a 282 and a 9:1 383 assuming the ABDC on the card is around say 67-69 you should be at or around 7.99:1-8:1 (with your aluminum heads you can actually run more dynamic and not be affected as much since they get rid of heat) dynamic which is well below needing even 93 and especially higher octane race fuels. It may not hurt to add 91-93 if you can find it, but if it runs fine on 87, it should make more power since it takes less power to ignite, which is why higher compression ratio motors need higher octane fuels because the lower the octane, the easier it is to ignite.
Race gas may be cool to buy, and smell cool coming out, but if your dynamic is low enough, you're only wasting money, and actually losing power.
Hope this helps.
Also, 465 hp is plenty to be happy with, and more than enough to power the car up steep grades in high gear.
Happy motoring.

The only Mustang I'd ever own is a Fender.

'68 333" Camaro
'14 5.0 Mustang
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post #5 of 8 (permalink) Old Apr 27th, 11, 10:55 PM
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Steps
 
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Re: Dyno results / ? fuel-octane

Basically as the fuel octane increases the length of time to reach max cylinger pressure increases...or it burns slower..
So a little less advance for lower octane 2 or 3 degs
Also increase octane and the specific gravity lowers....more volume of fuel per energy...
So need less fuel....slightly smaller jetting
This assumes the racing fuel octane is reached by solvents and not lead additives.
The "little" and "slightly" mean exactly that..

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post #6 of 8 (permalink) Old Apr 28th, 11, 12:40 AM
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darrell
 
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Re: Dyno results / ? fuel-octane

they are all perty right --and you got a very nice build--i would go back 3 or 4 deg for street driving and the fuel ur using--no reason to have it on kill when your just driving-jettings will probably be fine -jettings are not the same season round--if there is a big change barometric pressure or humidity, the jetting is gonna be off by 2 or 3 jet sizes--
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post #7 of 8 (permalink) Old Apr 28th, 11, 06:16 PM Thread Starter
John sr.& jr.
 
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Re: Dyno results / ? fuel-octane

Thanks for replys / input; I was running a autolite ar3934 race plug with cut electrode (only .022 gap; but autolite tech said that's what they should be?) they we're burning a little rich (maybe due to high oct. fuel not burning completely; with lower comp. engine; like some have aluded to) the dyno tech, decided to lean out some; 650dp / hp-street carb. orignal 69prim. and 75sec. went to 68prim. and 73sec. hopefully these changes won't be wrong; when I step down from race fuel to pump gas; maybe just pull a litlle timing; like you've mentioned. Watching plugs while I make transition to lesser oct. ? may need range change?? I was running a Melling 10% hv / 3/4" pickup; that they said; was running high 80-90pisg and robing maybe 4hp. thanks again Johns
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post #8 of 8 (permalink) Old Apr 28th, 11, 10:37 PM
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Steps
 
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Re: Dyno results / ? fuel-octane

Quote:
maybe just pull a litlle timing
yeah that will be pretty definate....changing jets...hell i wouldnt bother
Plugs..Start with 4 std plugs, NGK autolite what ever..keep thre race plugs for race day...they are not cheap.... basically go as cold as possible, maybe warmer on the 4 cnrs or just the 2 front cnrs maybe.

My Spelling is not incorrect...it is creative

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