Flat off idle
Thread Starter
Cruising
Joined: Jun 2008
Posts: 10
Likes: 0
Flat off idle
I have a 78 PC with a rebuilt engine. When we did the rebuild (professional shop) we installed a set of vortec heads, new intake, 650 edelbrock carb, and long tube headers - nothing too drastic. Everything runs great and she goes like a bat out of hell if you mush the go peddle 
but if you drive it like you aren't a NASCAR driver it has a definite hesitation off idle. It is like the engine is stumbling just for the first 100-150 feet from the stop light.
I have tried my best tuning it with a vaccum gauge (I can get it to read 18) and I set my timing at idle with vaccum advanced disconnected at 32* but I can't get rid of the darn lag.
I am thinking my distributor could use a rebuild because my timing mark jumps around a little +/- 3*. I am also looking at the msd street fire ignition instead of a rebuild.
This is also the first edelbrock carb I have owned and I miss my holley. I would like to go back to a holly but don't have the $$ right now.
Thanks for the help,
Ryan
but if you drive it like you aren't a NASCAR driver it has a definite hesitation off idle. It is like the engine is stumbling just for the first 100-150 feet from the stop light. I have tried my best tuning it with a vaccum gauge (I can get it to read 18) and I set my timing at idle with vaccum advanced disconnected at 32* but I can't get rid of the darn lag.
I am thinking my distributor could use a rebuild because my timing mark jumps around a little +/- 3*. I am also looking at the msd street fire ignition instead of a rebuild.
This is also the first edelbrock carb I have owned and I miss my holley. I would like to go back to a holly but don't have the $$ right now.
Thanks for the help,
Ryan
Burning Brakes
Joined: Sep 2008
Posts: 805
Likes: 5
From: Naperville Illinois
32 deg advance at idle? You want your initial (idle) timing around 12 - 16 deg with the vac line plugged; your all-in mechanical (centrifugal) advance should be around 36 deg, which will give you approximately 52 deg advance when you have the vac hooked up. Did you adjust the dwell before you set the timing?
Thread Starter
Cruising
Joined: Jun 2008
Posts: 10
Likes: 0
I didn't think you set the dwell on HEI ignitions. How do I do that? When I plug in my vacuum line to the distributor am I supposed to see the timing jump? It doesn't... Do you think I need to rebuild the distributor or buy a new one?
If I set it at 12* I don't think it really wants to run well. It seems happy at 32*.
If I set it at 12* I don't think it really wants to run well. It seems happy at 32*.
Safety Car
Joined: Mar 2007
Posts: 3,652
Likes: 49
From: Bridgewater nj
I didn't think you set the dwell on HEI ignitions. How do I do that? When I plug in my vacuum line to the distributor am I supposed to see the timing jump? It doesn't... Do you think I need to rebuild the distributor or buy a new one?
If I set it at 12* I don't think it really wants to run well. It seems happy at 32*.
If I set it at 12* I don't think it really wants to run well. It seems happy at 32*.
Try a different dist. every garage has a chevy HEI laying around. slip one in and see what happens.
If you still have a timing mark jumping around you will need to get into the balancer, timing chain, cam gear, crank gear ect..
Instructor
Joined: May 2008
Posts: 154
Likes: 3
From: Indiana
Rally and Huggy are correct. I have a 600 edelbrock on my 327 and it runs fine but there are no adjustments other than idle mixture. If you timing seems to jump or move, I would suspect the Dist. My setup is happy with base timing around 14* to 17*. If your engine doesn't run with that initial timing you may have another issue.
Burning Brakes
Joined: Sep 2008
Posts: 805
Likes: 5
From: Naperville Illinois
I didn't think you set the dwell on HEI ignitions. How do I do that? When I plug in my vacuum line to the distributor am I supposed to see the timing jump? It doesn't... Do you think I need to rebuild the distributor or buy a new one?
If I set it at 12* I don't think it really wants to run well. It seems happy at 32*.
If I set it at 12* I don't think it really wants to run well. It seems happy at 32*.
Regardless, I concur with GeorgeS--if your car doesn't run well with 14 - 17 deg initial, you have other issues. Have you verified your damper mark is at TDC for #1?
*IF* you have a manifold vac source (as opposed to ported), when you plug in the vac can, you should notice an increase in idle rpm and smoothness. Timing should advance about 15 deg. If you are running ported vac, you will need part throttle to see the timing advance.
Suggest you read Lars' posts on timing as well as the sticky at the top of this forum... Good luck!
