Retro-fitting roller lifters in 2 piece rear main seal blocks...

[chevybuilder18]

this is for those who didnt know about the bowtie vortecs, this article is an older one but now i have the latest revised ports to 225 cc's and D shaped exh port. this zz4355 was to small to get the heads to perform better.... but this is an example of how streetable the bowtie iron vortecs perform
http://www.superchevy.com/technical/...c/viewall.html if my 406 took complete advantage of the heads, we should see 450 hp and still a good amount of torque up to 480+ with the right roller cam.

"When it came to the best performance with the Vortec Bow-Tie heads, the results included 391 hp with the small-port heads and 386 hp for the large-port heads. The engine power curve peaked at 6,000 rpm with the Vortec Bow-Tie heads.The 391 hp average peak achieved with the small-port heads included the engine equipped with the single-plane Vortec intake, 1.6 rockers, the hot cam, and a 2-inch carb spacer. The same configuration was used with the large-port heads to achieve their 386 hp average.

So, why the 5hp difference with the smaller-port heads? Displacement, mostly. The large-port heads could use a larger-cube engine to make the most of their capability. Regardless, the new iron heads showed that they had the flow to keep up with--and surpass--aluminum heads.

The test session didn't compare aftermarket heads with the new Vortec Bow-Ties, nor were the iron heads ported or machined in any way. They were out-of-the box examples. We're interested to see how these low-cost alternative heads would fare against the competition, as well how airflow will improve with a little careful grinding.

The initial impression is not only encouraging, but downright impressive - especially for those of us on a tight engine-building budget. And for "spec-head" circle track engines, this latest version of the famed Bow-Tie iron head family seems just about perfect." These words came from the author and those are his words, not mine.



Read more: http://www.superchevy.com/technical/...#ixzz2BSfogKNU