Thread: sluggish down low! help!

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Another handy thing to keep in you toolbox is a couple of golf tees; use them to plug vacuum hoses or other things that need temporary plugging.

Originally Posted by Rrumbler

Another handy thing to keep in you toolbox is a couple of golf tees; use them to plug vacuum hoses or other things that need temporary plugging.

Also good to keep extras around if you should decide to slide out for the afternoon and shoot a round!!!!!

Hey guys stupid question but could it be total advanced timing? Or would that not matter since its vacuum advanced?

Originally Posted by t.thompson259

Hey guys stupid question but could it be total advanced timing? Or would that not matter since its vacuum advanced?

Like Glenn said immediately above, your total advance should be in the 34 degree range and will be all in by 2000 to 2200rpm. It builds on your base timing, so if you set the base timing (no vacuum at idle) to 8 degrees your total timing might be 30, but if you set your base to 12 it would then be 34. If your base is now at 16 then your total may be up in the 40 range which is pretty tall, but might still be OK depending on your piston choice and cam.

Originally Posted by rspears

Like Glenn said immediately above, your total advance should be in the 34 degree range and will be all in by 2000 to 2200rpm. It builds on your base timing, so if you set the base timing (no vacuum at idle) to 8 degrees your total timing might be 30, but if you set your base to 12 it would then be 34. If your base is now at 16 then your total may be up in the 40 range which is pretty tall, but might still be OK depending on your piston choice and cam.

Okay thanks. I set the timing with the vacuum advanced hooked up (rookie move) so imma redo the timing this weekend and take it around the block and see what it does then. Hope for no cops cause she ain't got plates on her yet!

Originally Posted by t.thompson259

Okay thanks. I set the timing with the vacuum advanced hooked up (rookie move) so imma redo the timing this weekend and take it around the block and see what it does then. Hope for no cops cause she ain't got plates on her yet!

You want to unhook the vacuum line from the advance can, but plug the line. A sharpened pencil or piece of dowel rod works great.

You might also check the vacuum source the line comes off. Best bet is to use a source directly off the intake. If you are using a source off the carb base, it may or may not have vacuum at idle. The carb nipple which has vacuum at idle is the one you want, and is referred to as 'ported'.

At some point in this process, someone is going to point out that at wide open throttle (wot) you loose vacuum, and you centrifugal advance is in control, and you can swap springs for controlling the centrifugal curve, but first let's nail down your base setting.

Originally Posted by firebird77clone

You might also check the vacuum source the line comes off. Best bet is to use a source directly off the intake. If you are using a source off the carb base, it may or may not have vacuum at idle. The carb nipple which has vacuum at idle is the one you want, and is referred to as 'ported'.

firebird, your theory is correct, but you have the incorrect term. Ported or "timed" vacuum ports are above the throttle plates and have no vacuum at idle.

Originally Posted by Henry Rifle

firebird, your theory is correct, but you have the incorrect term. Ported or "timed" vacuum ports are above the throttle plates and have no vacuum at idle.

Not always the case Jack, some carbs have internal passages that allow manifold vacuum to be seen with a port that is above the throttle blades. Idle the motor. Place a small piece of paper on the port. If it gets sucked down against the port, it's origin is manifold vacuum. If it will not stick to the port, it is a ported vacuum source.

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And lastly, don't forget to test that the vacuum advance chamber isn't leaking. The simple way to test is to apply vacuum and see that it holds that setting while you have the light hooked up. I have a little vacuum pump I use sometimes, but my cheapy way is use a new long piece of hose and "pull" a vacuum with my mouth and place my tongue over the hose while the other end is connected to the vacuum can. If it bleeds off vacuum, you can see it and feel it! Change the can and retest.

Thx Henry, I dunno how I got it backwards.

Well did some research and found out that the carb isn't a 750. It is a 650 double pumper. A Holley 4150. I ran the list number on it and its a 80777. So that's plus in my favor as to not over fueling. But we are inching closer to the weekend and time to get my hands dirty!

Ok guys. So I set my timing light at 36 degrees. Cranked her up to 3k. And check the timing. (all the vac lines off this time. :P) and well she was at 10 advanced. So I'm guessing that means it was at 46 all in? Yes I know I suck. Lmao. Sooo anyway. I set it at 36. Tightened the distributor. And double, cripple and quadrupled checked it. And it didn't move! So out of curiosity. I put my t light back to zero and checked it at idle. And its at 8 degrees. I haven't got a chance to road test it yet. I had some other projects to button up. But it ideas better. Down around the range of 950rpm. I haven't played with the carb yet. But it's coming. Anything else you guys think I should check? I'll also keep you guys in the loop when I road test it.

Also do you guys know a efficient way to check to see if your v belts are lined up properly? The machinist side came out in me and I had to modify my alt bracket to work with my heads since there is no holes in them. Every once in a while when you goose it. You get a quick belt squeal.