A few questions

[mrhollywood]

1. Why is my 1920 holley backfiring in park when I try to rev it?

2. When I'm driving down the road it barely accelerates ,top speed is 40 mph even if I have my foot in the floor it just revs up but doesn't really go any faster. Any ideas? It does seem to shift when it suppose to.

I just rebuilt the carb and it was doing this before too....got rid of a fuel leak in the carb though.

 

[jhdeval]

Let me double check what you are calling backfiring. Are you saying that it is firing from the carburetor or backfiring through the exhaust?

If it is from the carburetor you are seeing the exhaust and intake open at the same time. There are several things to start with. First is your timing with 8-14 degrees before top dead center? Also check the valve spacing intake .0010 and .0020 on exhaust. While under the valve cover check and make sure there is no play in any of the push rods. If you see any you will need to replace the seats.

 

[caferacerx]

could be timing chain

 

[805moparkid]

Let me double check what you are calling backfiring. Are you saying that it is firing from the carburetor or backfiring through the exhaust?

If it is from the carburetor you are seeing the exhaust and intake open at the same time. There are several things to start with. First is your timing with 8-14 degrees before top dead center? Also check the valve spacing intake .0010 and .0020 on exhaust. While under the valve cover check and make sure there is no play in any of the push rods. If you see any you will need to replace the seats.

one to many zero's... you want .010 and .020 lash...

and what do you mean by the second part lol... on a mech cam that has a lash setting of anything besides .000 will have play because there is clearance...

what i think you ment is valves but you have to pull the springs to test that...

to op...
how many miles are on you engine? i bet your engine wont rev very high?? maybe 3500 or so? your valve springs might be toast...

but as stated check timing, make sure your fuel filter is clean, and re-lash all the valves to .010 on the intake and .020 on the exhaust...

 

[mrhollywood]

The "backfiring" is coming up the the carb. I think the car has 150,000 miles. I figured the timing was the next thing I needed to check....wanted a second opinion.

 

[cudamark]

Start by making sure the accelerator pump is working, check the initial timing, and that the mechanical and vacuum advance are working. If those are all correct, pull the plugs and do a compression test and valve adjustment to see if there are any leaky valves.

 

[jhdeval]

one to many zero's... you want .010 and .020 lash...

and what do you mean by the second part lol... on a mech cam that has a lash setting of anything besides .000 will have play because there is clearance...

what i think you ment is valves but you have to pull the springs to test that...

to op...
how many miles are on you engine? i bet your engine wont rev very high?? maybe 3500 or so? your valve springs might be toast...

but as stated check timing, make sure your fuel filter is clean, and re-lash all the valves to .010 on the intake and .020 on the exhaust...

I did mean to pull the springs. I have learned a lot but sometimes I don't spew back in the same order. Glad to see though that most people concur with my initial post.

 

[jhdeval]

Start by making sure the accelerator pump is working, check the initial timing, and that the mechanical and vacuum advance are working. If those are all correct, pull the plugs and do a compression test and valve adjustment to see if there are any leaky valves.

cudamark why do you think it may be related to the accelerator pump? Wouldn't the backfiring through the carb indicate more a valve/timing issue? Not trying to start anything just curious.

 

[mrfttmuscle]

could be timing chain

With the information I have read I would have to say the timing chain has slipped a tooth and it is way out of time, replacing the chain and gears isn't a big expensive deal you might even want to replace the water pump at the same time if has a bunch of miles on it 2.

 

[RustyRatRod]

cudamark why do you think it may be related to the accelerator pump? Wouldn't the backfiring through the carb indicate more a valve/timing issue? Not trying to start anything just curious.

The accel pump would be my first look. If the throttle is opened with no enrichment of fuel, it'll pop in a heartbeat. Make sure there is a good strong squirt of fuel in the carb throat when you open the throttle.

 

[green1]

With the information I have read I would have to say the timing chain has slipped a tooth and it is way out of time, replacing the chain and gears isn't a big expensive deal you might even want to replace the water pump at the same time if has a bunch of miles on it 2.

Make sure it is'nt the carb, before going there.

 

[mrhollywood]

Quick question about the timing ..what will the mark on the main pulley look like?

 

[cudamark]

Quick question about the timing ..what will the mark on the main pulley look like?

The timing mark on the balancer is just a tiny slot cut into the outer ring. The guage is attached to the timing cover.

 

[cudamark]

The accel pump would be my first look. If the throttle is opened with no enrichment of fuel, it'll pop in a heartbeat. Make sure there is a good strong squirt of fuel in the carb throat when you open the throttle.

You beat me to it!

 

[TrailBeast]

None of the carb stuff he is explaining would count for a 40 top speed though.
I bet it's cam and lifters, timing chain or Valves.

x2 on the compression test, as it sure would narrow things down fast.

 

[cudamark]

Could be a plugged exhaust too.......I've seen mashed pipes cause that problem.

 

[mrhollywood]

I checked the timing.... it was way off. The dist wasn't even close to tdc.

With the dist all way counterclockwise in adjustment the timing is tdc after I turned the dist a tooth or two.
Which direction is advance when you turn the dist? And my timing tab says before and after tdc... which way is advance? It runs better now but still lacks power/acceleration when "flooring" it. I still need to do a tuneup. The carb is squirting pretty good out of the top jet but the carb/ intake sounds like its own motor when revving it up. This my first time dealing with timing

 

[cudamark]

The normal rotation of a slant 6 distributor is clockwise so, to advance the timing, you need to turn the distributor counter-clockwise. If you've turned the distributor as far counter-clockwise as you can with the normal method and you still need more, you may have to loosen the bolt holding the distributor bracket to the distributor. It will give you a little more adjustment. You may have to remove the distributor to do this as it can be a bit hard to access sometimes. If you still can't get enough advance, you'll have to pull the distributor out and rotate the shaft one cog and reinstall. Do any distributor work it may need while it's out. It's best if you set the timing so the #1 piston is at TDC before you pull the distributor so you will have a good reference point when you reinstall it. This way you can rotate the distributor until the points just open (with the rotor pointing at the #1 terminal on the distributor cap) to get the timing close enough to start the engine. Then readjust once you have it running again. If you can run it at 10-12 degrees BTDC without it pinging, do so. You'll get the best performance and mileage out of it there.