Thread: Performance Issue

Tweet

Hello To All,i Have A Few Questions I Hope Someone Might Answer. The First Is,my 350sbc,at Around 5200rpm The Engine Stumbles Very Bad.as Soon As I Upshift It Pulls Super Hard Until 5200,then Starts Again.everything Is New On The Engine,carb,heads,dist,coil,wires,plugs Gapped .035. Next Is My Car. Its A 78 Nova 2 Door.on The Pass Side Rear On The Bottom Of The Leaf Spring Pack There Is A Piece Of Metal With 4 Holes In It.the Lower End Of The Shock Bolts To It Also.i Was Told It Is Called A Shock Plate.my Question Is Where Can I Buy A New One? Gm Told Me They Were Discontinued.i Would Like A New One If Possible,but If This Is Not Possible Any Ideas Would Be Greatly Appreciated. Thanks In Advance For Any Help! Nick

as for the engine it might be your timing, its really hard to tell whats going on without hearing it in person. mhh thats really werid that it stumbles at such high rpms but not a lower ones maybe your not getting enough fuel at hig rpms. as for the shock plate try Year One....they may be able to help you out...GM really doesnt offer many replacement parts for older cars. you have to go to a place like Year One for stuff like that

Valve float? Spark scatter? Fuel delivery issues? Restricted exhaust? A whole miriad of things can cause this. Valve springs in good shape? Exhaust flowing freely? Step by step. Try one thing at a time. Check the fuel flow, do you have a gauge hooked up? Then move on to valve springs if that's not the problem. Timing advance checks. Spark delivery. Coil strong enough? Distributor cap replacement possibly? Points or HEI? Points could be bouncing. Condensor could have weak capacity. HEI module not getting proper trigger signals. Pick up coil inside the distributor. Shaft worn out and not happy with rpm's. Like I said, a bunch of things can cause this.

Thanks For The Help,i Will Try Year One For The Shock Plate.as Far As The Engine,i Was Thinking Fuel Starvation Also As A Possibility Because From Idle To 5200 It Keeps You Planted.i Will Also Check The Hei Electronics,even Though Everything Is New,we All Know How That Goes.thanks For Pointing Me In A Good Direction,your Help Is Greatly Appreciated!!! Nick

You said new heads.....which springs did they come with and are they a match for the cam?With fuel sometimes it will happen at different rpms,depending on how much got back in the bowls between hard runs.
Spark and springs seem to act up at the same rpms ,over and over.
Whats the exact sound it makes???????Does it seem like its bogging,making tons of noise with the carb ,but no go,a good steady tone when it bogs?
Or does it make a gargle sound,the gargle sound is valves ,the big one tone bog is fuel and a highly variable surging bog is usually spark related.
Does it make the same engine sound when it does this every time?

If that's a stock HEI setup with a stock coil you may be pushing it as far as it can go. You should look into an MSD coil for it and a high energy Ignition Module, you'll get more spark energy and be able to run higher RPM's.

You Guys Are Right On It! Fuel Starvation Aint It.i Think It Is Surely In The Ignition.shaunlee28 Nailed It With His Sound Descriptions.its The Same Pa,paa Pa Papa Paa,shift,5200,starts Again.i Bought This "super Hei Racing Distributor" On E-bay And Dropped It In.looks Like I Got What I Paid 4.unless This Thing Can Be Adjusted I Will Get A Msd,like I Probably Should Have From Jump Street.thanks Again!!!!!

If its a "good" distributor just get the coil and module and you'll be ok. I ran a stock hei that way on a 406 sbc that ran 6.50's in the 1/8 on nitrous....