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Topic: New engine question...

in Forum: C3 Engines


New engine question...

Posted: 10/12/04 3:32am Message 1 of 6
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Marion, IA - USA
Joined: 4/24/2004
Posts: 317
Vette(s): 1969 Corvette Stingray Convertible. Just bought it from my uncle who owned it since 1971. Fathom green, green interior. 350/300, T400.
Still playing with the new engine. It has no low end power/torque. the rebuilder says it needs a new vac advance, it'll be in tomorrow. The other question I have is about valve adjustment. The valve train doesn't seem to make noise, but it'll idles rough like it has a miss. I hooked up a vac gauge. It reads 12-15, but the needle bounces so fast you can hardly see it. Is this normal or should it be more steady? (And yes it does it with the vac advance line plugged off too).
Thanks,
Matt


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New engine question...

Posted: 10/12/04 6:31am Message 2 of 6
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Frederick, MD - USA
Joined: 9/8/2003
Posts: 3398
Vette(s): 1969 convertible L71 427/435 4-speed black interior
The engine vacuum should be steady in the 17-21 area, unless you have a bigger than stock cam in the motor. High lift cams, while increasing horsepower, also lower engine vacuum due to their increasing valve overlap in staying open. My '69 427/435 has an L88 cam installed...much more radical than the oe spec camshaft. Due to that it has much lower vacuum than original.

Yours sound like you may have a vacuum leak somewhere and/or a misadjusted carburetor. Even with a bigger than stock cam profile, you should have a more even vacuum reading and little to no needle flutter.


New engine question...

Posted: 10/12/04 10:54am Message 3 of 6
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CUYAHOGA FALLS, OH - USA
Joined: 12/2/2003
Posts: 6424
Vette(s): 1975 C3 Red, T-Tops, Black Interior. All I need is time and money! Getting there!
You may want to double check the valve adjustment.


New engine question...

Posted: 10/12/04 10:58am Message 4 of 6
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Hot Springs, AR - USA
Joined: 4/24/2004
Posts: 3236
Vette(s): 69 Conv #'s match 427, TKO-600/.64, 3.36HD-Posi, HT, T/T, PS, PB, PW, SP, Leather, Comp XE264HR & Roller Rockers & Lifters, Air-Gap RPM intake, Holley St Av 770 VS, MSD 6AL+Dist+Blaster SS, K&N, Jet-Hot Hooker Side-Pipes, Steeroids, Al Rad, Spal Fans
 kstyer said: You may want to double check the valve adjustment. 


I would go even further and suggest you use the dynamic method of adjustment.

this is exactly the same problem tumarr had after static adjustment.


New engine question...

Posted: 10/12/04 3:52pm Message 5 of 6
Former Member
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Marion, IA - USA
Joined: 4/24/2004
Posts: 317
Vette(s): 1969 Corvette Stingray Convertible. Just bought it from my uncle who owned it since 1971. Fathom green, green interior. 350/300, T400.
Please expalin the method of dynamic adjustment again.

Thanks,
Matt


New engine question...

Posted: 10/13/04 10:55am Message 6 of 6
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CUYAHOGA FALLS, OH - USA
Joined: 12/2/2003
Posts: 6424
Vette(s): 1975 C3 Red, T-Tops, Black Interior. All I need is time and money! Getting there!
Look in the thread "More Issues" It gives the procedure.

|UPDATED|10/13/2004 10:55:39 AM (AZT)|/UPDATED|



in Forum: C3 Engines


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