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Friday, November 5, 2010

SBC Dart Iron Eagle 180's

As the title says I am currently working on a set of Dart Iron Eagle 180cc runner heads. This set of heads was actually on a 385 small Chevy and even though coupled with a very mild hydraulic flat tappet cam it produced healthy power. As tested on our SF 902 this engine produced a best of 436 hp @ 5200 rpm and 460 ft/lbs @ 4200 rpm on pump gas of course. Considering how tame (think stock) this engine was on the dyno you wouldn't really think it could make that kind of steam-but it did. So not being able to leave well enough alone we elected to give this engine a kind of EMC treatment. This 385 SBC will retain the same basic short block and intake manifold (RPM Air-Gap) but will receive a roller juice cam and thoroughly worked over cylinder heads. The goals for this engine are heady- 500 hp @ 6000+rpm/ 480 tq @ 4800-4900 rpm, pumpgas, mufflers, 750-830 cfm carb. Camshaft specification will be decidedly mild-duration @ .050" (expressed in degrees) will not exceed 240 and valve lift won't exceed .600" so it will remain a truly driveable and reliable street engine. Flow testing of the heads today revealed that there is much work to be done! All flow testing was done @ 28 inches of water, 4.030" bore, 2.02" valve. Flow built quickly peaking @ 220cfm at a low valve lift of only .400", stalling at higher lifts. After some mild guide profiling and some short side (s.s.) work  flow rates are now 232 cfm @ .500" with flow flat lining. I'm sure that more s.s. work and maybe a 2.055" valve with no back cut (b.c.) are in the cards. Velocity readings reveal that the s.s. is over loaded with readings of 450+ fps (feet per second). No wonder when we tested the engine on the dyno power hit a wall @ 5300 rpm-the heads are choking it. I suspect the runners are much smaller than the 180 cc moniker, probably closer to 170cc. I'll measure them for volume in cc's next, so I know what I'm dealing with. The video is a short clip of a flow test for anyone who has never experienced one. J.Rob

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