Intake runner question

plemon61

Member
I've just started disassembling my Chevy 383. I noticed that the intake manifold runners for cylinders 1&2 are discolored as are the same two runners in the head. Any thoughts as to what might have caused this ? 3,5,7 & 4,6,8 all shiny clean but 1&2 are dark. Thanks
 
since the intake manifold runners and head intake ports are not ALL equally dark its unlikely to be REVERSION related, but the simple fact that its only the front two locations on two different cylinder heads,that are directly , adjacent, cylinder locations makes me suspect the intake manifold gaskets , are not 100% sealed and/or the intake was poorly machined or the front clamping bolts were loose, thus it was sucking oil mist from the lifter gallery, if it was fuel distribution related the results would tend to be related to the plenum design , and either all four front runners or a staggered pattern related to the plenums would be indicated. so ID suggest checking the valve seals, re-adjusting the valves in case the two front cylinders were adjusted too tightly, and valve guides and doing a compression test comparison to help locate the cause!
as usual ..USE LOGIC, THINK IT THROUGH!
ISOLATE AND TEST, DEAL IN FACTS
http://garage.grumpysperformance.co...ads-tuned-intake-turbulence.12998/#post-67611


ede7501-manifold.jpg
 
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Thanks for your thoughts. I will post any subsequent findings. I'm a bit surprised that there is not evidence of reversion in all cylinders as the cam used was Comp Magnum 292. Maybe because of the fact that the motor only had a few hundred miles ? Anyway, I'll be checking all components as I disassemble the motor and be back with more info. And questions I'm sure. Thanks again.
 
http://www.superchevy.com/how-to/engines-drivetrain/1703-efi-versus-carb-dyno-test/

heres a link to a test where they compare EFI in both a single plane and dual plane manifold configuration,
(notice this is NOT a separate dedicated individual injector per cylinder)
which has a further control advantage

look very carefully at the results,
and if you think about whats going on,
its rather obvious that EFI, which controls the individual cylinder to cylinder fuel distribution a bit more precisely,
has an advantage, but its also obvious the guys doing the test can,t tune that well,
as the fuel/air ratio from either intake and its fuel supply source,
should have been closer to 13.9:1 below 3000 rpm and steadily gotten richer,
as the rpms increased, but never gotten richer than about 12.4:1, where either system would have produced a bit more torque.
USE THE CALCULATORS to match port size to intended rpm levels... but keep in mind valve lift and port flow limitations
http://www.wallaceracing.com/runnertorquecalc.php
http://www.wallaceracing.com/ca-calc.php
http://www.wallaceracing.com/area-under-curve.php
http://www.wallaceracing.com/chokepoint.php
http://www.wallaceracing.com/header_length.php
http://www.circletrack.com/enginetech/1 ... ch_engine/


251.gif

carbvefit1.png

carbvefit2.png

carbvefit3.png


Stoich.gif

AFR_Torque.gif

an engines Torque peak is almost always very closely related to the point in the rpm curve where the most effective/efficient cylinder fill, cylinder fill is related to both intake port cross sectional area and exhaust scavenging,efficiency, and is limited by port stall, and cam duration in relation to displacement, compression and valve train stability, ...all factors are easily calculated
links below

volumetric.gif


useful RELATED INFO you might want to read

http://www.wallaceracing.com/runnertorquecalc.php

http://www.pontiacracing.net/js_header_length1.htm

http://www.superchevy.com/how-to/en...-0902-chevy-engine-port-variations-measuring/

http://garage.grumpysperformance.com/index.php?threads/port-speeds-and-area.333/

http://garage.grumpysperformance.com/index.php?threads/calculating-ideal-port-size.624/

http://garage.grumpysperformance.com/index.php?threads/sellecting-cylinder-heads.796/

http://garage.grumpysperformance.co...e-stock-tpi-engine-components.1509/#post-3459

http://garage.grumpysperformance.co...ting-a-port-size-and-intake-for-nitrous.4930/

http://garage.grumpysperformance.com/index.php?threads/semi-fool-proof-cam-sellection.82/

http://garage.grumpysperformance.co...ir-ratios-that-gets-ignored.15506/#post-92064

http://garage.grumpysperformance.co...velocity-heads-tuned-intake-turbulence.12998/

http://garage.grumpysperformance.com/index.php?threads/calculating-header-design.185/
 
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