Home page
SPONSOR AD

Topic: power surging at cruise speeds

in Forum: C3 Fuel, Emission Control, and Exhaust Systems

power surging at cruise speeds

Posted: 2/5/07 3:26pm Message 1 of 4
Former Member
Send PM
Austin, TX - USA
Joined: 12/15/2006
Posts: 4
Vette(s): 1973 L-82 4-speed Blue Green Metallic Original paint and drive train
Hey guys, been reading for a while and now have a question.  I have a 73 4-speed coupe that I just finished an engine swap and now have a couple of issues.  I put in a new GMPP 290HP 350 long block with Edelbrock performer intake and a Holley 670 Street Avenger carb.  I also switched to a HEI ignition set up with the gear driven tach.  My exhaust is Headman headers and the under car chambered exhaust from MA motorworks.  The car is now complete and I am trying to tune it in just right.  The car is hard to start when cold, sometimes and other times starts right up.  It also has a very noticible surg at cruising speeds and on medium throttle accelerations.  The idle speed is also hard to set.  I can get the car warm and set it to 900, then after driving the car it will idle at 1500.  Every part on the engine is also brand new, nothing reused or salvaged.  Any advice you guys have would be very appreciated.  Thanks.
 



SPONSOR AD:: (Our Sponsors help support C3VR)

power surging at cruise speeds

Posted: 2/5/07 5:26pm Message 2 of 4
Former Member
Send PM
Australia
Joined: 5/6/2004
Posts: 535
Vette(s): 71 Coupe Black on Black
Sounds like a vacuum leak somewhere to me.  Check your vacuum take off to the headlight/wiper door system.  Manifold leak?  Power valve in the Holley?  Auto Choke? 


power surging at cruise speeds

Posted: 2/5/07 7:14pm Message 3 of 4
Profile Pic
Lifetime MemberLifetime Member
Moderator
Send PM
Duncanville, TX - USA
Joined: 11/8/2003
Posts: 20214
Vette(s): #1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas
Chips is right where I was goin...sounds like a vac. leak to me, also.
It could also be an issue with the carb. Check to see that the linkage is functioning correctly, and will open fully, and close fully, with no "binding". Sometimes, the base gasket for the carb will have holes that are too small, or off-set a bit, and the throttle blades will hang/stick on it. Make sure the secondary throttle blades are closing completely.
I'd start by verifying there are no vacuum leaks, tho. That be what it sounds like.


Joel Adams
C3VR Lifetime Member #56    

My Link


(click for Texas-sized view!)
             NCRS

"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"

power surging at cruise speeds

Posted: 2/6/07 10:04am Message 4 of 4
Former Member
Send PM
Austin, TX - USA
Joined: 12/15/2006
Posts: 4
Vette(s): 1973 L-82 4-speed Blue Green Metallic Original paint and drive train
Thanks for the advice guys.  I will check for leaks this evening. 
Chuck



in Forum: C3 Fuel, Emission Control, and Exhaust Systems


SPONSOR AD: (Our Sponsors help support C3VR)