C3 Tech/Performance V8 Technical Info, Internal Engine, External Engine, Basic Tech and Maintenance for the C3 Corvette
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Old Mar 24, 2011 | 12:13 AM
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here is my question, does this sound like it should be a descent combination for some power.
in my 74vette i have...a gmpp 350 short block,
edelbrock performer rpm cam
gmpp vortec heads
edelbrock performer rpm air gap
holley 600 street avenger carb
Summit rocker arms
converted heads to screw in studs
hooker super comp long tube header going back to pair of flow master 40 series
B&M 2600 stall
rebuild 400 turbo
4.56 gears

cam specs are
Basic Operating RPM Range 1,500-6,500
Intake Duration at 050 inch Lift 234
Exhaust Duration at 050 inch Lift 244
Duration at 050 inch Lift 234 int./244 exh.
Advertised Intake Duration 308
Advertised Exhaust Duration 318
Advertised Duration 308 int./318 exh.
Intake Valve Lift with Factory Rocker Arm Ratio 0.488 in.


Cylinder Head Style Assembled
Cylinder Head Material Cast iron
Cylinder Head Finish Natural
Combustion Chamber Volume (cc) 64
CNC-Machined Combustion Chamber No
Intake Runner Volume (cc) 170cc

I had this engine built last fall by local shop and it never seemed to have have power at all so i went and got some new scorpian full roller rocker arms from summit. but for some reason i cant seem to set them correctly started at 8am this morning and watched every youtube video as well as searched forum but nothing seems to work. Just me by self without helper so it takes a little more time. All issues seem to be on passenger side.

I will bump the engine a litle at a time until vale just starts to go down and i will tighten the one next to it by SLOWLY tightening the nut until i can no longer spin the push rod. then i will turn the nut another 1/2 turn(as recomended by edelbrock - i called them). Then i will tighten the allen screw all the way down. I will repaeat this for each valve when done i leave a sheet of cardboard in front of heads. upon startup the clicking sound is very loud and pronounced i have tried to bump the nut on the rocker arm to quite it down but to no success(maybe 1/16 to 1/8 turn)......

I guess my question is since i have repeated multiple this times to the same result did i smoke the engine and my $5000?
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Old Mar 24, 2011 | 08:08 AM
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Try adjusting the valves while the engine is running. If they are all clacking it may take some concentration to hear each valve until some get quiet.
While running if the rocker is quiet, back off the nut until it clacks tighten until quiet add a half turn. If the rockers is clacking tighten until it stops and add a half turn. Continue through the rest of them. As you move along it sould become more quiet.
It is a Hydraulic cam and lifters correct? Screw in studs?
I'm not sure about your cam profile, That is a long power range for some reason, and it begins early just off idle.
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Old Mar 24, 2011 | 08:10 AM
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I just re read the scre in stud statement in your fist post. Disregard the stud question.
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Old Mar 24, 2011 | 04:12 PM
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You shouldn't tighten the nut until you can't spin the pushrod. Something is getting jammed pretty tight if you do that. Since it is sitting in cups both top and bottom, tightening on it until the pushrod can't spin means you could possibly be bottoming out the lifter and forcing the valve slightly open.

When adjusting, you want to move the pushrod up and down. Turn the adjustment nut until there is no more vertical movement, then tighten it 1/2 to 3/4 turn and lock it down.
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Old Mar 25, 2011 | 06:57 PM
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2025 C2 of the Year ('63 and '67) Finalist - Unmodified
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If you adjust the valves with the motor running, listen to Indiancreek.
If you would like to set them with the motor off, here is a great site:
http://www.centuryperformance.com/ad...h-spg-149.html
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Old Mar 25, 2011 | 10:20 PM
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If you want to adjust them while running and don't want a 20w 50 bath, you can get clips that attach to the rocker arms that block the thrown oil from the arms. Some of the exsisting oil may flip out, but a few shop towels will catch that.
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Old Mar 26, 2011 | 03:03 AM
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Cam seems a little mild. I would check the compression, in order to find out if the compression is sufficient. I assume GMPP is a Gm performance engine, what compression ratio is it suppose to be? As far as adjusting the valves, adjust your valve when the matching valve is compressed, not just when the rocker just starts to compress the valve. Your perception of rotating the pushrod until it binds, and adding an additional 1/2 turn of the rocker nut/adjustment, then tighten the lock/jamb nut.
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