73-87chevytrucks.com
73-87 Chevy _ GMC Trucks => Performance => Topic started by: BoobZ on January 04, 2009, 10:39:27 pm
-
alright so heres the low down..
whenever i floor it, it runs good but whenever i slightly lift the throttle (still accellerating) it runs rough.. (almost like a bog)
it never did this with my Edelbrock Performer intake, but it does it with my Weiand Stealth intake..
its a 350 bored .060 over with flat top pistons with 76cc 882 heads.
edelbrock 1406 600 cfm elect. choke.
1 5/8 long tube headers with 2.5" dual exhaust all the way back
stock cam, valves, and rockers
built 55k V ignition system with R44t delco spark plugs.
surely im not undercarbing it that much, but i dont really know. i wouldnt think it..
it is also harder starting when the engine is warm for some reason, this also was apparent after the intake swap..
my question is, why does it run rough (bog) when i slightly lift the throttle?
so do i have too much intake and not enough carb or cam or what?
any incite would me greatly appreciated
-bobby
-
Maybe the timing is a little too advanced?
-
i understand that would make it harder to start but does that make it bog when i lift a little after full throttle?
i can ease the throttle on and itll run like a raped ape but when i hammer down then slightly let off is when it does it.
-bobby
-
Question: did you lose EGR when you went from one intake to the other?
-
never had egr.. the performer had an egr blockoff plate..
HOWEVER, that brings to mind, the perfomer had the heat riser port from head to head but the new stealth doesnt have them..
-
The heat riser just helps cold engine operability, once the engine temp is up it is only a hinderance.
Sounds like a vacuum leak to me. Have you put a vacuum gauge to it yet?
The hard starting is most likely a separate timing issue.
-
yes it has 19" of vacuum with the carb set.. i have the timing advanced to just where it doesnt ping and the adjustable vacuum advance is all the way out.. im also using 91 octane instead of 87 or 89 because it pings like crazy and runs like crap if i dont, even if i set the timing..
good vacuum readings but could that mean i still have a vacuum leak? all vacuum lines are new, including the vacuum modulator on the tranny. PCV is hooked up properly. idk.. ill retard the timing and see if that helps any.