Replaced my old Dremel with a Black & Decker RTX Rotary tool. Half the cost of Dremel Plenty of power and quality easy to change bits. The Valve guide bosses are good for 3-5cfm. I'm trying to clean up the passages and maintain higher velocity by keeping the ports smaller. Going to let the porting help top end and cam for bottom and midrange. Want a street car with maximum driveability and mileage while maintaining low costs. Trying to get the heads to flow somewhat like early LS1s 230cfm LT1s flow 206-212 intake and 157 exhaust stock. Just polishing (80-120grit intake) is good for 7% improvement in flow. +7% is 220cfm I've cleaned and blended all casting circles and flash out of roofs floors and walls, gasket matched the opening to slow down the flow at the intake to reduce port stall, Cleaned and blended the bowls into the seats and port walls, and behived the guide bosses. Also massaged the roof and pushrod pinch but not to the extent most race porters do.
One thread needs tapped and a broken bolt removed from heads and intake manifold area milled then I can do lap valves or 3 angle valve job clean and install my springs.
Exhaust ports opening up improves top end power.
Cleaning and blending the intake bowls or pockets to the valve seat removes factory machining ridge. This is the biggest blemish in the intake ports. As cast these look lots better stock than the old chevy heads and aluminum is easier to work than cast iron.
Used this as a guide along with David Vizard and Lloyd Elliot information and pictures.
LT1 vs LT4
The roof and pushrod pinch are controversial but areas for improved flow on LT1's my knowledge tells me grinding through the guide boss on the roof adds volume and HP but unless filled with epoxy the hole makes turbulence reducing flow so a smaller faster port biased to the siamesed wall was my choice to widen side opposite pushrod pinch more and just square slightly while maintaining 3/8 to 1/4" thickness at the pushrod pinch curve.
I used a hand drill instead of my die grinders and compressor no power unless use generator in the shed. My old 1/4" carbides are for cast iron and would clog even with ATF fluid dip as cutting oil. Takes me 2hrs to clean up blend and polish 1 intake bowl and blend to port called deep pocket porting. Or is this the term they charge for porting to people with DEEP POCKETS as refered to in college?
The exhaust picture is terrrible I'll see if I can get some better ones soon as the dremel does a nice job on the exhaust ports and intake bowls.
Interested to see the results of the better DA and Elgin 1.6s. I might try rocker arms heads and stock manifolds ported before camming it.
I still say its possible to get high 12's on stock manifolds no ewp and milder 3.23 gears that hookup better on street tires with better MPG. I could be wrong but I've seen it done especially on LT1 Vettes 300hp opposed to 275HP Camaro/Firebirds difference being better exhaust manifolds and duals.
Anyone mod suspension first eg stock car with LCA's what kind of ET reduction or does this pay off only at higher power levels preventing wheel hop breakage etc. Read about a car that hooked up with stock lower control arms but aftermarkets planted the back too well and raised 60ft times.