1978sc bucking problem?
 

when my car isn't driven hard it bucks. When I have the rpms low and driving in traffic say in forth gear and the rpms are around 2000 to 2600 the car will buck if it has any slight hill to climb or if I try to accelerate. If I down shift and accelerate no problem. Engine dosn't seem to be lugging so I guess it has to be something else. This is a engine that has been rebuilt with a few tweeks 964 cams and back dated exhaust system. All new engine mounts clutch and throw out bearing. So maybe some thing isn't quite right. I think I could replace one of the cv joints in left rear. It has a slight click!

Sounds like the normal "in-between" state of acceleration when you are at low RPMs and the engine is in-between acceleration and decelarating. Maybe your mods changed the location (i.e. RPMs / load) of this state, so it seems new to you. Try shifting more often, as the engine needs it, and either accelerate or decelerate and low RMPs, so as not to get caught in the middle.

Just my $.02

Doug

Crashmy911,

Try disconnecting the vacum line off the WUR (warm up regulator) an plugging the line. Somtimes the new cam grind creates a different vacum that the cis can't handle.

When I had my engine rebuilt they used SC cam grinds and RS pistons. I had this problem and everything was brand new. JW had suggested this mod and it worked perfect.

Let me know if it works for you.

Warm up regulator is on the left when looking in engine bay. Correct? Which line is the vaccume off of wur? Will this have any adverse reacctions when starting cold?

Yes the WUR is on the left. I believe the SC WUR has the vacum hose coming out of the top or side. Disconnect and plug the vacum hose only, not the WUR. Use a screw to plug the hose and leave the opening to the wur open.

One of the problems that occured for me is the vacum was leaning out the motor causing the bucking at low rpm's. Once the line was plugged the CO mixture was normal.

I have no problems with cold start. I believe the vacum off the wur was for emissions purpose.

It took me 6 months and much $$$$ after my rebuild to find this solution. Let me know if it is your problem. If not you may want to check your gas tank for rust,

there are two vacume lines that come off of the wur which one should I unplug the one that comes off the top or the one that comes off the side thanks

side. the CO would have to be adjusted again if you do that. it works best on 76/77 units, but if it works on SCs, fine.