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Old 06-13-17, 01:22AM   #1
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Join Date: Oct 2016
Location: Glendale
Posts: 20
Default 350 HO short block

I have a 1969 350 HO short block. I have a set of 1967 670 72cc heads with 2.11/1.77 valves. I was thinking of putting this together and running it in my 65 Lemans. Concerned about valve clearance in regards to the block, keeping in mind it does have the notches for the large valves and the heads that came with it were same valves just smaller combustion chamber.

It's been decked at some point so with the right head gaskets I will have a deck clearance between the piston top and the quench surfaces of .045-.048".

I'm wondering how much valve lift I can get away with on the intake valve, and on the exhaust valve before shrouding makes it useless to have more lift. Pure street, AC, AT (stock converter), PB and 3.0 rear gear.
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Old 06-13-17, 03:32AM   #2
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Join Date: Jul 2002
Location: La Jolla , California
Posts: 3,503

The HO engines were @ 10.25:1 cr and were supposed to run on 96 to 98 octane leaded gasoline.
They made an "advertised horse power" of 325.

In 2002 RRE built a 350 that
used ported Edelbrock 72cc heads that ran on pump gas
750 cfm Mighty Demon
Torker intake
9.55:1 compression ratio
Stock stroke crank
stock length CAT4340 H beam rods
Custom forged pistons & rings
Special checking & clearancing /relieving of the cylinder decks to ensure safe valve clearance.
And lots of other stuff that's necessary to make it all fly right but details to numerous to mention here.

1.5:1 rocker ratio
The build used this cam:
Camshaft Specifications
Manufacturer: Comp Cams
PN: 51-000-9 (custom)
Grind: 288R7/296R7
Type: Mechanical roller
Duration at 0.020-inch tappet lift: 288 int./296 exh.
Duration at 0.050-inch tappet lift: 255 int./260 exh.
Valve lift (1.50:1 rockers): 0.588-in int./0.588-in exh.
Lobe displacement angle (LDA): 108
Installed intake centerline: 100
Engine made
468.9 ft lbs@ 4600 rpm
539.2 hp @ 6500 rpm

w/125hp nitrous hit
625.5 ft lbs@4900
670.0 hp @6200

11.94 sec@116.24 mph
10.65 sec@127.66 (125 shot N2o)
3000 rpm convertor
3.90 gear
28.5" MT/ET Drag slicks
Ladder bar suspension
Engine was in a Ventura/Nova platform

Do you need to go that big?
Naw , probably not for your current gearing/convertor and your intended use.
With current octane of pump grade gasoline the static compression ratio with your iron heads should not surpass 9:1 by much.
Aluminum heads will tolerate more compression.
Depending on what cam you use you may have to open up those valve reliefs a bit to be safe.
Careful checking of the valve train clearances is in order .Mock everything up. If clearancing is required careful/equal material removal on all corresponding reliefs to keep compression ratios for all cylinders equal.
Rotating assembly has to be kept light to run up there.
Stock rods will not last long.
Step Away From The KOOL AID !
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Old 08-12-17, 03:03AM   #3
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Location: Glendale
Posts: 20

Thanks. I don't plan to exceed .455" lift on the exhaust or .430" lift on the intake and intend to keep it below 5,000. I noticed the stock cams were only like .410"ish lift the 067 and the 068. For the future when the 326 comes out.
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