Pro Flo 4 Timing

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JD Erisman

JD Erisman

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I know some of this issue has been covered in tangent discussions about Edelbrock's Pro Flo 4 and I've read where some people have had a similar issue but I'm going to ask definitively if anyone has had the problem of not being able to set Advance Timing to greater than an 20 degrees with a Pro Flo 4 on a small block? I have a stroker 408, Hughes Hydrualic lifter flatappet 228/232 @ 50 cam, 727 with a 9' convertor and 3000 stall and I'm running Trick Flow 190 heads. No matter where I try to set the timing, if it is above 20 degrees the car stumbles, backfires and vibrates horribly, especially when accelerating hard, with the worst vibrating beginning about 3000. I have adjusted the fuel via Fuel Modifiers to compensate thinking it might be a fuel issue, but that had no effect. I have varied the Idle Timing from 12 to 18 degrees. I've adjusted the vacuum advance from 0 to 10 and if I go above 5 the engine has a similar reaction: it misfires, stumbles and causes the car to vibrate. I'm running Mag 5028 but I've had the same issues with Maps 5029 and 5030. The engine should be making considerably more power than it does and I blame that on the low timing it will accept without the vibrations. Any input would be appreciated, especially if you've had a similar issue and you were able to resolve it.
 
Another reason I'll stick to carbs. I had one problem with Fi Tech and after getting stuck with no start I went back to carbs on a gen 2 hemi.
 
JD Erisman said:
I know some of this issue has been covered in tangent discussions about Edelbrock's Pro Flo 4 and I've read where some people have had a similar issue but I'm going to ask definitively if anyone has had the problem of not being able to set Advance Timing to greater than an 20 degrees with a Pro Flo 4 on a small block? I have a stroker 408, Hughes Hydrualic lifter flatappet 228/232 @ 50 cam, 727 with a 9' convertor and 3000 stall and I'm running Trick Flow 190 heads. No matter where I try to set the timing, if it is above 20 degrees the car stumbles, backfires and vibrates horribly, especially when accelerating hard, with the worst vibrating beginning about 3000. I have adjusted the fuel via Fuel Modifiers to compensate thinking it might be a fuel issue, but that had no effect. I have varied the Idle Timing from 12 to 18 degrees. I've adjusted the vacuum advance from 0 to 10 and if I go above 5 the engine has a similar reaction: it misfires, stumbles and causes the car to vibrate. I'm running Mag 5028 but I've had the same issues with Maps 5029 and 5030. The engine should be making considerably more power than it does and I blame that on the low timing it will accept without the vibrations. Any input would be appreciated, especially if you've had a similar issue and you were able to resolve it.
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How's your rotor phasing? I don't have a pro Flo, but systems that vary timing rely on good phasing.
 
I checked the phasing, seems to be in line with Edelbrock’s instructions, though they spend more time explaining how to install an intake manifold than anything else.
 
I’d be interested to know your compression ratio and see exactly what your advertised cam specs are - that is Advertised (.004-.006”) in & exh opening and closing degrees but I guess Hughes aren’t that helpful with providing those figures.
 
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Saw you’d posted something on the Edelbrock forum, have you seen this posting?
Timing question - Edelbrock Community Forum
Might also be worth thinking about checking balancer marks, vacuum leaks and possibly valve timing as well?
One last thing, that’s a fairly healthy engine you’ve got and I saw that your AFR was very high at 22.8 I’d recommend going at least another size larger on your fuel map to 5030 (as long as your O2 sensor is ok) and see how that works out, I can’t help thinking that it’s looking for more fuel.
 
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JD Erisman said:
I know some of this issue has been covered in tangent discussions about Edelbrock's Pro Flo 4 and I've read where some people have had a similar issue but I'm going to ask definitively if anyone has had the problem of not being able to set Advance Timing to greater than an 20 degrees with a Pro Flo 4 on a small block? I have a stroker 408, Hughes Hydrualic lifter flatappet 228/232 @ 50 cam, 727 with a 9' convertor and 3000 stall and I'm running Trick Flow 190 heads. No matter where I try to set the timing, if it is above 20 degrees the car stumbles, backfires and vibrates horribly, especially when accelerating hard, with the worst vibrating beginning about 3000. I have adjusted the fuel via Fuel Modifiers to compensate thinking it might be a fuel issue, but that had no effect. I have varied the Idle Timing from 12 to 18 degrees. I've adjusted the vacuum advance from 0 to 10 and if I go above 5 the engine has a similar reaction: it misfires, stumbles and causes the car to vibrate. I'm running Mag 5028 but I've had the same issues with Maps 5029 and 5030. The engine should be making considerably more power than it does and I blame that on the low timing it will accept without the vibrations. Any input would be appreciated, especially if you've had a similar issue and you were able to resolve it.
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JD,
I have the same engine with same problem!
After carefully checking the ignition, I’ve determined the rotor phasing is off enough to cause the misfire when the timing advances. I’m going to pick up an MSD 8421 adjustable rotor which should do the trick.
If you haven’t solved your problem by now, check by rotating the engine to 30BTDC and check how far off the rotor tip is to the terminal on the cap. It’s a lot...
 
Please post an update after you get this installed. I have the same issue although not as bad as yours sounds.
 
Mopar73340 said:
Please post an update after you get this installed. I have the same issue although not as bad as yours sounds.
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Fixed. I slotted the reluctor to change the trigger/rotor relationship. Timing is normal now, lots more power. Rough photo attached before final filing of the holes.

CE03E7F2-09BC-4733-B1F7-1207A870F443.jpeg
 
BergmanAutoCraft said:
Fixed. I slotted the reluctor to change the trigger/rotor relationship. Timing is normal now, lots more power. Rough photo attached before final filing of the holes.

View attachment 1715721423
Click to expand...

I'm at work now, so I can't go look at my car currently (but I plan to when I get home).

What about modifying the body to adjust the hall effect switch location vs moving the reluctor? Something that's easier to adjust maybe.
 
You can do that too as it rotates and is only held in place with a simple metal link. Either way, its the same thing and only has to move a little to make a large difference.
 
BergmanAutoCraft said:
You can do that too as it rotates and is only held in place with a simple metal link. Either way, its the same thing and only has to move a little to make a large difference.
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How did you decide on how much of an adjustment to make, keep moving the rotor more until you were able to get the timing you wanted without breakup/power loss? I know you tried the msd rotor with no luck, care to share what the issues were?
 
TurboGLH said:
What about modifying the body to adjust the hall effect switch location vs moving the reluctor? Something that's easier to adjust maybe.
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If you end up going this route please take pictures and post here. I have had this issue and even discussed with Edelbrock tech support a couple years ago but have not got around to messing with the distributor. In my case anything over 28* seems to cause issues. We should be able to run mid 30’s with some vacuum advance thrown in without issue.

BAC, thanks for your efforts and posting your fix.
 
Mopar73340 said:
If you end up going this route please take pictures and post here. I have had this issue and even discussed with Edelbrock tech support a couple years ago but have not got around to messing with the distributor. In my case anything over 28* seems to cause issues. We should be able to run mid 30’s with some vacuum advance thrown in without issue.

BAC, thanks for your efforts and posting your fix.
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I will. I've got less than 50 miles of time on the system, breaking in a new motor. But I have some issues start/cold idle that requires throttle. I've been leaning towards a bad TPS, it floats around from 0-2%, and anything above 1% disables the idle speed motor.

Peter mentioned that his idle/start issues cleared up with less initial timing, so I've told another possible cause to investigate.

I'm going to try a new TPS and redo the idle tuning. If I still have an issue I'll dig deeper.
 
TurboGLH said:
I will. I've got less than 50 miles of time on the system, breaking in a new motor. But I have some issues start/cold idle that requires throttle. I've been leaning towards a bad TPS, it floats around from 0-2%, and anything above 1% disables the idle speed motor.

Peter mentioned that his idle/start issues cleared up with less initial timing, so I've told another possible cause to investigate.

I'm going to try a new TPS and redo the idle tuning. If I still have an issue I'll dig deeper.
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the tps needs to be 0 or 1. That’s where toy have to start.
 
TurboGLH said:
How did you decide on how much of an adjustment to make, keep moving the rotor more until you were able to get the timing you wanted without breakup/power loss? I know you tried the msd rotor with no luck, care to share what the issues were?
Click to expand...

After synching the distributor at 12, I rotated the crank slightly to 30. You’ll notice the rotor as way far from the terminal on the number one on the cap. Essentially, I moved the rotor closer to the terminal on the cap. It’s off to begin with and when the timing advances it’s firing the next cylinder.
 
BergmanAutoCraft said:
the tps needs to be 0 or 1. That’s where toy have to start.
Click to expand...

I understand, the ECU sets TPS Zero at key on, but it'll refuse to return to zero while driving. I've checked for binding or restrictions in the cable and linkage, but haven't found any.

So it will idle properly for a while, then it will float high enough (2%) to disable idle speed control after driving for a bit.

BergmanAutoCraft said:
After synching the distributor at 12, I rotated the crank slightly to 30. You’ll notice the rotor as way far from the terminal on the number one on the cap. Essentially, I moved the rotor closer to the terminal on the cap. It’s off to begin with and when the timing advances it’s firing the next cylinder.
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Good info, once i try a new TPS Ill take a look and see if what you found on yours is also on mine. It's either a design issue or a QC issue.
 
I've noticed my Fitech has the same issue with the TPS. It's 0% at key-on, but after start it likes to settle at 0.5%, rarely going lower again. Luckily it still recognizes that as 'idle'.

I wonder if these systems are being affected by the higher running voltage after-start? 12v vs 13-14v? Might be worth unhooking a field wire while running to see if the TPS goes back to 0?
 
Phreakish said:
I've noticed my Fitech has the same issue with the TPS. It's 0% at key-on, but after start it likes to settle at 0.5%, rarely going lower again. Luckily it still recognizes that as 'idle'.

I wonder if these systems are being affected by the higher running voltage after-start? 12v vs 13-14v? Might be worth unhooking a field wire while running to see if the TPS goes back to 0?
Click to expand...

The sensors are getting 5v nd ground from the ECU, it's supposed to isolate the sensors from power/ground issues, I have a set of back probes for my meter, it's easy enough to check power at the sensor key on vs running
 
TurboGLH said:
it's easy enough to check power at the sensor key on vs running
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I'm sure it is - but I haven't done it myself as I only just had this thought as I read your post (and I'm still at the office for now...).

I know they should be isolated, and shouldn't be affected by minor voltage fluctuations, but now I want to check and see.
 
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