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| matts85vet | dynamic compression question | ||
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Guru
 
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finally have everything back and ready to assemble for my 383 miniram build. my question is the final DCR. i was shooting for 9.
my options: 1. assemble as is: static = 11.96 DCR = 9.21 2. retard the cam 2 degrees so it is 2 deg advanced (cam is ground w/ 4degrees advance): static= 11.96 DCR = 9.05 3. thick head gasket (.050"): static 11.69 DCR = 9.01 i'm leaning toward choice #2 what do you recommend? i will use 93 octane, street only thanks in advance! |
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Posted on: 2014/2/11 22:44
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85 coupe, 383, TPIS Miniram, auto 700R4, 3.75 gears, afr 180 eliminator heads 58cc, 12:1 compression ratio, comp cams 280XFI hydraulic roller cam, 1.65 roller rockers, 52mm throttle body, c5 calipers, hedman elite longtube headers, pypes dual exhaust w/x- |
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| rklessdriver | Re: dynamic compression question | ||
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I personally wouldn't do anything based on DCR number alone.
Whats the Intake Valve Closing point in choices 1 and 2? Will |
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Posted on: 2014/2/12 1:16
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1984 Corvette. 434 SBC with a Powerglide. Best pass - 8.48@160MPH 1.23 60ft on MT 275/60R15 Radials. 1972 Corvette. LS5 454 BBC with M20 4 speed. Best Pass - Doing good to just pass a gas station. |
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| matts85vet | Re: dynamic compression question | ||
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choice 1 (install as is) 69 deg abdc
choice 2 (2 deg retarded) 71 deg abdc cam is comp cams 280xfi 280/288 113/109 230/236 @.05 heads afr180 eliminator 57cc pistons srp 5cc flat top |
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Posted on: 2014/2/12 2:47
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85 coupe, 383, TPIS Miniram, auto 700R4, 3.75 gears, afr 180 eliminator heads 58cc, 12:1 compression ratio, comp cams 280XFI hydraulic roller cam, 1.65 roller rockers, 52mm throttle body, c5 calipers, hedman elite longtube headers, pypes dual exhaust w/x- |
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| rklessdriver | Re: dynamic compression question | ||
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Choice 2, is what I would do, as long as you have 2800-3200 stall.
I would also caution you about the engine coolant temp. Do not go out driving it around in traffic and then beat on it with high coolant temps and lots of underhood heat/heat soaked. Try to keep it around 160-180*F coolant temps at the start of a run. What is really important is the cyl head temps around the chamber - but all we can actually monitor is the coolant temps. Will |
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Posted on: 2014/2/12 13:39
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1984 Corvette. 434 SBC with a Powerglide. Best pass - 8.48@160MPH 1.23 60ft on MT 275/60R15 Radials. 1972 Corvette. LS5 454 BBC with M20 4 speed. Best Pass - Doing good to just pass a gas station. |
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| Schrade | Re: dynamic compression question | ||
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Elite Guru
 
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Quote:
Yup - lower squeeze Matt, not just for lower running temps, but motor last longer with lower compression (all else equal). And remember rkless; 'stat rating is only the temp at which stat opens - it doesn't keep the motor running at that temp... 160' coolant temp is too low for good burn. 180' is borderline. 195' - 200' is optimum. I don't know why anyone would want their mill to NOT go Closed Loop til later... |
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Posted on: 2014/2/14 19:10
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LT5, Marc Haibeck ECM module, AUTOMATIC!!! 
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| rklessdriver | Re: dynamic compression question | ||
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I'm not interested in emissions and I'm not talking about thermostat temp ratings.
Every engine I have ever dyno'd made considerablly more HP with the coolant temp ice cold (and the oil temp boiling hot). Everytime I race my 84 I use an oil heater to make sure the oil temp is over 200F and I tow it to the lanes or crank and coast it - so to keep the coolant temp as low as I can. Cool cyl head temps make more HP. They are also more detonation resistant. Thats why I told hm what I did in reguard to coolant temps and running it hard. When your dealing with nearly 12.1 compression on pump gas using a wedge chamber and a relitivley small camshaft, the motor is going to have a bunch of cyl pressure. You need all the help you can get to make it not detonate and coolant temp is all he can control to help. If you heat soak an engine like he is building and then go make a few full power WOT pulls - it's gonna burn a piston in no time. Will Quote:
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Posted on: 2014/2/14 20:26
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1984 Corvette. 434 SBC with a Powerglide. Best pass - 8.48@160MPH 1.23 60ft on MT 275/60R15 Radials. 1972 Corvette. LS5 454 BBC with M20 4 speed. Best Pass - Doing good to just pass a gas station. |
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