Hey guys The title is programm... How to make this 76 heads kinda performing? I think they have the bigger valves from the fac. already right?? Does porting help this heads at all? Milling? What CR would be needed to squeeze a bit out of them.?
Bigger exhaust valves but not blended in vary well. Mike Phillips said head flow on these heads are not desirable shaving heads helps raise compression but piston depth is going to be biggest factor
Yes, basically. Power in 350 Buicks is all in the heads. Torque, shove in the 10:1 pistons, square up the decks and heads, and a crower levvel 3 cam and a good qjet. iirc 74+ heads wont bolt on 70-73 blocks, water jacket differences I think.
Good info as always. Yes the heads wont bolt on to a earlier block. The 76 block is actualy my backup block...lol I was mainly looking into the heads info.
If in you want to use them for boost then they'll be fine. The later heads are supposed to be less prone to cracking as well. The later heads will work on the earlier blocks if they have the scallop coolant ports NPT tapped and plugged. IIRC AM&P did a sbb 350 with the later heads and did some basic port work to them an again IIRC they flowed around 240 CFM on the in. side, so not to shabby for the basic port work they did. Switching to 8mm valves, 1.94" intake and 1.550" ex. and paying more attention on the valve job and un-shrouding with a bit more material removal and that 240 number could maybe be 20 or 30 CFM of more flow? But not to many shops want to mess with cast iron heads nowadays so we may never know? GL
240 not being shabby is showing more power potential than the majority of mild builds happening (450-500hp).
Some of us would actually prefer the later, thicker heads. How good would a set of paper thin fully ported early heads be if they cracked under mild duress? Thinner material would also exacerbate the thermal dissipation capabilities with higher power builds, making disaster almost inevitable given enough time/opportunity. How much power would be lost with a set of thinner, fully ported heads that were hotter than thicker heads flowing slightly less? Maybe even adding to detonation issues? I wouldn't want to take that chance at wasting all that port work/time/money to create a very expensive boat anchor. Besides, for the vast majority of builds here (street/strip), 215-230 CFM is plenty of flow for the target goal, with 200-210 (basic clean up) being capable of respectable power for a mild Buick 350. Of course, for the balls-out crowd, bigger/more is always better. A member here on the boards (I won't mention any names unless they decide for themselves to chime in) using a set of heads flowing 235 CFM intake has a N/A 350 making close to 400 hp. If the '76+ heads can flow 240+ CFM, I see no problems whatsoever using a set of those. Jut another point of view.
240 is really good. Putting things in perspective, many of the aftermarket sbc heads I've flowed claiming 250-260+ cfm actually flow much less than 240 without serious work.
My '76. Was about 250+hp and 350+ torque. 7.8:1, comp 268 cam kit, stock intake, manifolds, downpipes from TA, two 8" cherry bombs, 800cfm qjet, TA HEI, accel wires, R45tsx plugs, etc. Ran great. 15.0 @ 90 according to an app on my phone. it uses gps to sense when you start moving. it works when walking too lol.
Numbers get tossed around the net so easily, and when people try to relate what they see elsewhere and from other brands they don't see the full story. There's some really fast cars outlined here with little work to the heads, so apples/oranges applies more than anything. No doubt about aftermarket heads making power and that there can be a lot of work involved in irons. Even a legit 200 cfm iron Buick head is a much better piece than a similar sbc if comparing only cfm's . There are other characteristics that contribute to power, and the Buick in many ways is a superior engine. The sbc smog heads are good for appx 165-180, legendary (larger port) camelbacks 180-190+- and all still require serious work...to work. Very few of those exceed 240 cfm from a home porter and along with those wild claims, performance numbers to match.
That perspective makes the Buick 350 heads with 198 CFM untouched look pretty good, and Buick's heads achieve that CFM @.350-.400 lift, where it peaks out to max flow.
It's rather difficult to see that kind of flow at a similar lift on an sbc iron head without a lot of work. Any time spent lifted past that point is a gift to the engine.
