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Vortec or Summit SUM-152123 for '75 daily driver?

 
G20camperman
I love my Chevy Chevette!
Posts: 1
Joined: 11/17
Posted: 11/09/17 11:21 AM

Hi.  I'm trying to decide between this Summit head and the Chevy Performance Vortec head (12558060).  I know the Vortec is hard to beat, but the heads won't be used for racing or towing.  I almost always stay out of the Thermoquad secondaries and drive smoothly for high MPG (low highway speeds, too).  I'd be happy with 20 more HP over my stock motor, just to help maintain speed on steep mountain highways.  Otherwise, it's all about improving MPG's and having nice starting and idling, with no warm-up needed before driving.  The heads will be replacing the stock heads in a '75 G20 camper van with the original 165hp LS9 350 (the 70's LS9) with stock heads (GM #14034811).  I am now leaning towards these Summit heads over the Vortecs because they have a heat passage for a nicer-running cold engine, and I have a heat riser choke as well (so, less mods needed).  Do these heads make more sense for me?  What compression should I be targeting?  These Summit heads are 72cc chamber, the Vortecs are 64cc, my stock head chamber volume can’t be found anywhere.  Are there flow numbers available for the Summit heads at .05” - .5” of lift?  Will the style of stock piston I have (GM #3991488, see photos)  match one head much better than the other, or is it not much of a factor for a daily driver?  Is quench an issue with either head?  My stock piston # matches to a 1476H or 1470 in this catalog:  http://www.uempistons.com/catalogs/uem_catalog_web.pdf.  I’ll be replacing the stock cam with a suitable high-MPG cam from Summit, Crane, Comp, or Lunati.  I’ll likely also replace the stock intake manifold, as needed (suggestions?).  My motor has GM H.E.I., EVAP, and AIR, but no EGR.  Thanks for any and all advice!  

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