Ramp up RPM's question

[Duke]

I have a 350HO with a Holley Street Avenger 670 CFM Carburetor. I changed the vacuum secondary spring out for a lighter one to get the secondaries to work on the light T-Bucket. Had a stumble coming off of idle and found that moving the accelerator pump cam profile by moving it one screw hole changed the stumble to a very soft momentary hesitation ( hardly noticeable ). I have the timing at 10 BTDC. Thinking about moving to 12 BTDC. What do you all think ? Help or not help. Most people wouldn't even notice, but I do. Is this a don't fix it if it ain't broke type thing ? I have been known to knit pick sometimes.

 

[putz]

Change the 2 degrees It won't cost anything and 2 degrees isn't that radical of a change in ignition timing.

 

[RPM]

Bump that initial timing up to about 18. That will make a big difference.

 

[Duke]

18, doesn't that put one heck of a load on the starter ? I will give it a shot tomorrow to find out. Thanks

 

[RPM]

I run 18 on my motor and have run more. It should start just fine. You are disconnecting the vac advance if it has one?

 

[Duke]

I would like to leave the vac advance hooked up so I don't want to ramp the initial timing to much. Spec on the 350HO is 10 so I can come up some with no problem. Don't really plan on racing, but sometimes people just keep pushing tell ya just have to dust them off - if ya know what I mean.

 

[RPM]

I meant to disconnect the vac advance when you set the timing. Then hook it back up.

 

[Duke]

Oh !!, I am disconnecting the vac adv. for setting the timing - didn't even dawn on me that people do forget to do that. I was thinking that was a strange thing to say. I use to work in the Nat'l Gas industry and a hand would come to me and want to be a mechanic, I would take them out in the shop and hand them a box that had a Briggs & Straton engine in it all tore down. I would tell them to put it together and see me at the end of the day. If they got it together and it ran - I would have them tear it back down for the next guy. Start them as Mechanic trainee.

 

[RPM]

Oh !!, I am disconnecting the vac adv. for setting the timing - didn't even dawn on me that people do forget to do that. I was thinking that was a strange thing to say. I use to work in the Nat'l Gas industry and a hand would come to me and want to be a mechanic, I would take them out in the shop and hand them a box that had a Briggs & Straton engine in it all tore down. I would tell them to put it together and see me at the end of the day. If they got it together and it ran - I would have them tear it back down for the next guy. Start them as Mechanic trainee.

The things we used to do to a Briggs motor.
We used to be big into Jr Dragster racing. We had a SuperFlow flow bench and in house dyno for them. The best we ever ran in a 1/8 mile was 8.0 sec @ 80 mph. That was 10 years ago. They go much faster now with all the billet blocks and stuff.