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Discussion Starter · #1 · (Edited)
J&M Machine is a lot closer to finishing the heads on my Chevelle. After the last machinist unfortunate work (being very nice) my new guys started from the ground up removing all the guides new and old along with all the substandard parts used previously including the spring that were causing coil bind with my current cam, cheap umbrella seals with crap valves and their hardware. The new swirl polished SS with undercut stems along with all new intake and exhaust hardened seats to allow for all specs to be brought back to new. Their work is impeccable right down to the 5 angle valve job. Still need to unshroud one head and start installing all quality new parts. Oh the new guides are machined for positive seals. The machinist expects I will see over 50hp because how poorly these heads were done initially.
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1968 Malibu sport coupe, 489 ci. 590 hp 600 tq, RV T-400 Freakshow 3200 stall, 3.73 12 bolt posi
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Bill how long before the "Seat of the Pants" dyno test do you think?
 

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Discussion Starter · #3 ·
Bill how long before the "Seat of the Pants" dyno test do you think?
It depends Rick. I think I will have the heads back next week but then I have to put it back together and then weather can affect my pants dyno test. Hopefully mid December if the roads let me take Murphy out.
 

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Discussion Starter · #8 · (Edited)
The 65 L79 used 461 double hump, 2.02 with partially machined chamber to unshroud the intake valve.
Does the 291 have a larger chamber?
The 291 was a 68 version of the 64cc double hump heads (461, 462 and 2.91). The big difference is the addition of the temp sender in the head itself. All factory 2.02 heads were factory unshrouded. If you look at my pics you will see my original 2.02 that is unshrouded and a 1.94 291 replacement head that I had converted to 2.02 by the previous machinist. He said he unshrouded it, he lied. The new machinist is unshrouding my new head Friday. Quickest way to see the difference is to look at the amount of casting between the chambers with adjacent 2.02 valves. A 1.94 head upgraded to a 2.02 that is not unshrouded actually makes less HP compared to the original 1.94. BTW I am having the chambers cc to be even between heads. I will know the actual cc then and will update. Machinist thinks the bigger valves compensates for the metal removed by the unshroud and suspects it will be in the 64 cc range.
 

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Discussion Starter · #10 ·
Is coil bind the thing that killed your Howards FT cam?
No and that was my wife's 71 Camaro 350 that had correct DART heads and springs. The springs removed on my L79 with the Elgin 151 cam (327/350) did coil bind with the .447 lift and did some damage to the tops of the valve stems. One or two things took out the Howard, first some lifters did get out of inventory that lets say underperformed or I had a lift rotation issue but I really doubt that. My L79 cam and lifters look good with a visual check and I do not think I even need to check for proper lift, but I might.
 
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