383 Build

[msgdsrf]

Well, It was not a specific goal on my 383 to acheive 11:1, it's the way things came together. Compression itself doesn't add so much but it can make a build work better (i.e. cam).

We ended up spending too much time tracking a misfire (thanks to exhaust guy for breaking plugs) and haven't got everything out of it yet. Carb is dialed but I think the ignition curve could be better. Torque at the rear wheels was very flat, 305 ftlbs. at 3750 (275 from 3000). I have a few hundred miles on the engine, heat wave, traffic and even a load to the dump (That truck doesn't belong here...). No detonation (12.7 air to fuel, full timing, 91 octane pump gas), runs great.

[Captainfab]

If you don't mind, could we get some more info on your engine build that allows you to run the 11-1 static compression?

Originally Posted by msgdsrf

Well, It was not a specific goal on my 383 to acheive 11:1, it's the way things came together. Compression itself doesn't add so much but it can make a build work better (i.e. cam).

We ended up spending too much time tracking a misfire (thanks to exhaust guy for breaking plugs) and haven't got everything out of it yet. Carb is dialed but I think the ignition curve could be better. Torque at the rear wheels was very flat, 305 ftlbs. at 3750 (275 from 3000). I have a few hundred miles on the engine, heat wave, traffic and even a load to the dump (That truck doesn't belong here...). No detonation (12.7 air to fuel, full timing, 91 octane pump gas), runs great.

[msgdsrf]

Originally Posted by Captainfab

If you don't mind, could we get some more info on your engine build that allows you to run the 11-1 static compression?

Nothing real special. I would say the cam intake closing at 67 ABDC keeps cylinder preasures where is runs well (and it really does). Does that take away low end, well not if you have the compression to begin with I'd say.

OEM Roller block .03 over, .015 deck (Yes, I would have perfered zero deck)
Cast 3.75 crank
Flat top Hyper w Moly comp ring
.039 gasket (x4.166 as spec'd by AFR)
AFR 180 street ported, 63cc
Compcams XR282HR-10
1.6 Rockers
Performer Air Gap
Speed Demon 650 Vacuum, Jets .07/.104, 6.5PV (@12.7AFR)

TH400 w/2600 stall, 3.73 gears and 29" tires

I have only limited experience with SBCs but have modified enough Thumpers and Twins to get a handle on four strokes. From the bike world I've always considered cylinder cranking pressure as the measure of how it might operate. Static Compression is only one factor towards what cylinder pressure will be and that is ultimately what will determine how easily compression contributes to detonation, IMHO. Then you have volumetric efficiency, cylinder heat, intake charge temps, and...

[Captainfab]

Thank You

Originally Posted by msgdsrf

Nothing real special. I would say the cam intake closing at 67 ABDC keeps cylinder preasures where is runs well (and it really does). Does that take away low end, well not if you have the compression to begin with I'd say.

OEM Roller block .03 over, .015 deck (Yes, I would have perfered zero deck)
Cast 3.75 crank
Flat top Hyper w Moly comp ring
.039 gasket (x4.166 as spec'd by AFR)
AFR 180 street ported, 63cc
Compcams XR282HR-10
1.6 Rockers
Performer Air Gap
Speed Demon 650 Vacuum, Jets .07/.104, 6.5PV (@12.7AFR)

TH400 w/2600 stall, 3.73 gears and 29" tires

I have only limited experience with SBCs but have modified enough Thumpers and Twins to get a handle on four strokes. From the bike world I've always considered cylinder cranking pressure as the measure of how it might operate. Static Compression is only one factor towards what cylinder pressure will be and that is ultimately what will determine how easily compression contributes to detonation, IMHO. Then you have volumetric efficiency, cylinder heat, intake charge temps, and...