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 aftermarket igniton module causing bog?
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69warbird
Tribal Scout

USA
22 Posts

Posted - 13 Jun 2012 :  02:24:08 AM  Show Profile  Reply with Quote
without going into too much detail off the bat...I've got an aftermkaret low-buck performance HEI, the 50k coil just never seemed to work at all so im currently running a stock coil which works pretty well. Will an aftermarket 4 pin module designed to work with a 50k volt coil cause problems when used with a stock coil? In particular, off idle bogging and stuttering/jolting when you apply throttle from coasting.

I have heard many people swear by the stock module, for example:

"Stock modules incorporate what they call a "variable dwell" circuit that reduces dwell at lower RPM to keep the coil from over saturating. This is good for sharp performance and long coil life. Some parts store modules don't have this circuitry in them."

should i try a stock module and trash the aftermarket high output module or stick with it and just get a hotter coil?

cortcomp
Coyote

USA
5335 Posts

Posted - 13 Jun 2012 :  09:15:18 AM  Show Profile  Visit cortcomp's Homepage  Reply with Quote
Are you 100% sure this isn't carb related? What carb you running?

I can't answer the module part, but i can attest that i've chased a couple bogs and hesitations back and forth between the fuel system and the ignition system. Just when i think i'm on the right track, that's when i discover something saying it's the other system
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cortcomp
Coyote

USA
5335 Posts

Posted - 13 Jun 2012 :  09:15:50 AM  Show Profile  Visit cortcomp's Homepage  Reply with Quote
Also, have you tried switching vacuum advance to ported if it's on manifold, or to manifold if it's on ported?
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69warbird
Tribal Scout

USA
22 Posts

Posted - 13 Jun 2012 :  11:16:20 AM  Show Profile  Reply with Quote
Its entirely possible that the carb is part of the problem (it is a holley 4150 700cfm mech. secondaries, bought new, still has stock components)...the motor revs up without as much of a pronounced bog in neutral and this very noticeable bog only happens under load. It could be a wrong sized powervalve contributing to the problem...engine vaccuum is only about 8in hg at idle and the carb probably has a # 8 or 10PV.

I have tried running it on both ported and full manifold vaccuum. However full manifold could use some additional testing, with the current vac canister which advances about 16 deg, i would need only a few degrees of initial timing to help avoid detonation. From what i have read, the camshaft isnt really radical enough to need full manifold vac. However full manifold vac. would probably help the car run a bit cooler.

my theory is that the improper dwell time in the module, wrong powervalve, and overly advanced iginition timing due to the HEI's vac. advance canister are causing this problem. Also the xtreme energy 268H cam just might not be capable of producing ideal low rpm acceleration, that cam starts really making power at 1600rpm.

I am going to get the car up to the shop ive been around for years to get some expert help with this before i go get it professionally tuned...problem is i really dont like having to pull out in traffic with this bog. Would be great to make some progress before all that street driving.
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GtoGuy32
Cochise

USA
842 Posts

Posted - 13 Jun 2012 :  6:41:19 PM  Show Profile  Reply with Quote
Does the car momentarily bog or does it last long enough that the car almost goes into a stalling state?

If it is instant, try switching your discharge nozzle on the primary side. Buy the size up and down from stock, which is likely somewhere around 31.

Another problem I had a long time ago with a serious "bog" turned out to be a bad metering block. I was able to mask about 90% of it out by jetting the crap out of the primaries. This was a band aide. I never realized it until I sold the carb cheap to another local guy and his car had the same bog (I returned the carb to stock jetting before selling to him). He had some extra parts kicking around and discovered that the metering block was bad from the factory. It apparently was not metering

also, with 8 inches of vacuum at idle, I think you want a power valve that reads 50% of that value. A 4.5 should do it
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69warbird
Tribal Scout

USA
22 Posts

Posted - 13 Jun 2012 :  8:02:28 PM  Show Profile  Reply with Quote
it's usually a momentary bog as you let the clutch out at normal street rpms. At higher rpm launches there isnt as much of hesitation. If you drive off and the motor has not warmed up the bog is to the point of stalling. and like i said the coasting issue which is always a brief hesitation. Seems like it is a lean spot. I will try stepping up to an .031" primary nozzle.

Is 8in hg on the low side? there is a good bit of overlap in the cam, 56 degs if im not mistaken. even if more vacuum was acheivable with ideal air/fuel ratio, 13in or more seems out of reach so i will likely have to change out the powervalve...

also, according to holley you should go through this checklist before going into the carb.
-contamination in the fuel(not likely-rockett 100, just ran a little sea foam through just in case)
-improper ignition timing/advance (12 intial is correct, advance curve might be advancing the timing too quickly-need to check further)
-improper alt. voltage output (new 100 amp alt, good according to my gauge, will double check with multimeter)
-fouled/improperly gapped plugs (plugs are clean, need to re-gap to .045"






Edited by - 69warbird on 13 Jun 2012 9:22:54 PM
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GtoGuy32
Cochise

USA
842 Posts

Posted - 13 Jun 2012 :  9:09:51 PM  Show Profile  Reply with Quote
8 inches seems pretty low. I did a Bonneville for a guy. He had the engine built at some "local shop". The car only made 9 inches at idle.

The car had a dual diaphram 8" brake booster in it. I actually wound up putting a vacuum pump in just to get the brakes to work at low RPM.

The more vacuum you have, the better the engine should run, especially in the idle range. Are you sure you didn't wipe a cam lobe at one point or another?

Sounds like a lot of your issue is right off idle. Does the engine have good power once you get into it a bit?

What happens when you lightly roll into the throttle?

One other thought. Check to make sure that when you move the throttle lever on your carb, the slightest movement should begin to depress the accelerator pump. If not, you need to make an adjustment. You may be leaning out momentarily.

Edited by - GtoGuy32 on 13 Jun 2012 9:27:39 PM
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69warbird
Tribal Scout

USA
22 Posts

Posted - 13 Jun 2012 :  9:31:24 PM  Show Profile  Reply with Quote
i agree 8 seems low. i think 10-12in is possible for this motor. The car has manual brakes and no vacuum lines other than the vac.adv. Pretty sure the cam is fine, once you get into the powerband the car pulls good, plenty of power through the gears. When you lightly roll into the throttle the transition is a bit smoother, that's how i have been dealing with this for awhile. Really hoping that a .031 nozzle will do the trick.

Edited by - 69warbird on 13 Jun 2012 9:35:17 PM
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GtoGuy32
Cochise

USA
842 Posts

Posted - 13 Jun 2012 :  10:22:30 PM  Show Profile  Reply with Quote


look at the accelerator pump adjustment first, if that is good. Increase your nozzle size 3-5 sizes. I think Pump cams are a last resort. Holley usually get's that right.

When I had my 750DP on my 400, I found that that a 31/35 discharge nozzle worked the best for me. I don't remember what is the stock nozzle....every car may be a little different. Since you are low on vacuum, your primaries might want more or less fuel off idle.

Good luck!

--Dave
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clintww
Cochise

USA
582 Posts

Posted - 13 Jun 2012 :  11:07:11 PM  Show Profile  Reply with Quote
Unless this is a full race engine, 8" of vacuum is way to low. I would be looking hard at that. I get 14 on my 461 with almost 600 lift and 240 duration. Are you sure 8 will work for you.
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69warbird
Tribal Scout

USA
22 Posts

Posted - 14 Jun 2012 :  12:00:14 PM  Show Profile  Reply with Quote
i will check vaccuum readings again. A vaccuum leak seems unlikely, everything is new. float level is right, fuel pressure is constant 6psi from an electric pump, idle mix screws are within spec (about 1 and 3/4 turns out).

would mis-adjusted valves cause low engine vaccuum? i heard a very slight bit of chatter when the car was warming up yesterday. could have been an oil temp issue, oil might be a bit too thick (base oil is royal purple 10w-30 w/lucas oil hd oil stabilizer, and i just added stp for the additional zddp). after the car warms up the noise dissipates and the throttle response issue seems more like a pump nozzle being too small. the primary is an .028 which seems pretty small for this car. its not a super heavy car and the gears are 3.73 posi...

Edited by - 69warbird on 14 Jun 2012 12:15:41 PM
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Blued and Painted
Chief PONTIAC

USA
3405 Posts

Posted - 14 Jun 2012 :  1:06:40 PM  Show Profile  Reply with Quote
quote:
Originally posted by 69warbird

everything is new.

Welcome Alex to PSP. Yes, tight valve adjustment would drop engine vacuum. I think we need more info. Is this a fresh engine and what is the CID. What intake manifold, adapter, or spacer is being used. What cylinder heads and are thay modified. What cam timing components were used and is the cam installed straight up.


Bull Nose Formula/ 461/ Q-Jet/
TH400/ 3.08 8.5 / R44TS.

Edited by - Blued and Painted on 14 Jun 2012 1:09:02 PM
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69warbird
Tribal Scout

USA
22 Posts

Posted - 14 Jun 2012 :  7:20:20 PM  Show Profile  Reply with Quote
thanks, im happy to have found this forum.

the motor is a 69 400. it was rebuilt back in 2005 and only has maybe a few hundred miles on it. details on the engine:

.030 overbore, stock crank/rods, aluminum pistons, #62 72cc heads. 3 angle valve cut, stainless steel ferrea valves. xe 268 cam and lifters http://www.compcams.com/Company/CC/cam-specs/Details.aspx?csid=1203&sb=2 crower springs, comp chrome-moly pushrods, comp double roller timing chain, 1.5 scorpion roller rockers. Performer rpm manifold, no carb spacer. dougs headers, 3in exhaust w/xpipe and classic chambered powerstick mufflers.

its been years but i am pretty sure the cam was installed straight up and the timing chain was installed in the right orientation, but there is always room for human error. if this were a late valve timing/cam issue, wouldn't there be major idling problems?

so today i gapped the plugs to .045 and installed a .032 main nozzle. Throttle response in neutral was more crisp, idling strong with a nice lope, thought i was making progress.. however the stumble when you accelerate from coasting seemed worse. now it's showing rich symptoms-initial response good, then an abrupt bog/misfire, then it picks back up.

vaccuum readings were steady at 9in hg, little bit of drifting due to the cam. should re-adjust the valves or advance initial timing to 14? pay up for a professional tune???


Edited by - 69warbird on 14 Jun 2012 7:35:25 PM
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clintww
Cochise

USA
582 Posts

Posted - 14 Jun 2012 :  7:39:41 PM  Show Profile  Reply with Quote
You have a big vacuum problem. Should be at least 13 with that combo. Many things can cause low vacuum.
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Blued and Painted
Chief PONTIAC

USA
3405 Posts

Posted - 14 Jun 2012 :  10:28:58 PM  Show Profile  Reply with Quote
Thanks for the info. Only one more question. At idle is there fuel dripping from the primary main discharge nozzles? With the air cleaner on, take some throttle cleaner and sparingly spray around the intake manifold gasket and carb base areas. A noticable increase in idle speed will indicate a vaccuum leak in that area. Vapors entering the top of the carb can give you a false indication. Avoid a flash fire. Stay away from plug wires. A cool engine is safer. Repair any leak. I'm not a holley guy but here we go. Make sure the secondaries will fully close. You may have to remove the carb to check. Back off both pump adjustment until you get a very small gap. We want to insure a full pump stroke. Hopfully you will find something. Keep us posted.


Bull Nose Formula/ 461/ Q-Jet/
TH400/ 3.08 8.5 / R44TS.

Edited by - Blued and Painted on 14 Jun 2012 10:35:19 PM
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69warbird
Tribal Scout

USA
22 Posts

Posted - 15 Jun 2012 :  12:58:04 PM  Show Profile  Reply with Quote
i will check for leaks at the nozzle and vac. leaks around the carb base later today.

would an exhaust leak cause low engine vacuum? no.8 cylinder has always had a noticeable leak. Im planning to pull the motor out this winter and fix a number of issues with the engine...also if the idle mix is off would these two factors result in 4 inches less of vaccuum?


Edited by - 69warbird on 15 Jun 2012 12:58:56 PM
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cortcomp
Coyote

USA
5335 Posts

Posted - 15 Jun 2012 :  1:53:05 PM  Show Profile  Visit cortcomp's Homepage  Reply with Quote
I thinl that the mixture alone could get you 2 or so off.
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Blued and Painted
Chief PONTIAC

USA
3405 Posts

Posted - 15 Jun 2012 :  2:05:33 PM  Show Profile  Reply with Quote
Dripping from the nozzles is a simptom. If you must use extra throtle angle to get the car to idle fuel will drip from main metering.


Bull Nose Formula/ 461/ Q-Jet/
TH400/ 3.08 8.5 / R44TS.
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bnorris_74
Crazy Horse

USA
1442 Posts

Posted - 15 Jun 2012 :  2:07:20 PM  Show Profile  Reply with Quote
quote:
Originally posted by 69warbird

i will check for leaks at the nozzle and vac. leaks around the carb base later today.

would an exhaust leak cause low engine vacuum? no.8 cylinder has always had a noticeable leak. Im planning to pull the motor out this winter and fix a number of issues with the engine...also if the idle mix is off would these two factors result in 4 inches less of vaccuum?





I vote no on the exhaust leak.

I also agree with others that you should see more vacuum than what you have.
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69warbird
Tribal Scout

USA
22 Posts

Posted - 27 Jun 2012 :  11:22:13 AM  Show Profile  Reply with Quote
quick update, i drove the car all the way to the shop and right about the time i pulled in, the holley red fuel pump started making a bad grinding noise...lost 1-2psi of pressure (down to 5psi) which would not allow the car to idle properly. Had to Order a rotor/vane kit to rebuild this pump which is only about 5 years old. Is it just me or does holley expect you to have to rebuild everything every few years?
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bnorris_74
Crazy Horse

USA
1442 Posts

Posted - 27 Jun 2012 :  11:43:51 AM  Show Profile  Reply with Quote
I read a discussion yesterday at another website that talked about a failure on a Holley Blue. The discussion centered around failures caused by ethanol in the fuels available today.

If you look at the application info for the Blue and Red at the Summit site, they both list for gasoline only where the Holley Black is good for gasoline, methanol and alcohol. The reasoning of the posters was that the Black has hard anodized guts and the red and blue do not. The anodizing cuts down on corrosion.
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Blued and Painted
Chief PONTIAC

USA
3405 Posts

Posted - 27 Jun 2012 :  12:36:19 PM  Show Profile  Reply with Quote
What's the best mechanical pump for hot street application?


Bull Nose Formula/ 461/ Q-Jet/
TH400/ 3.08 8.5 / R44TS.
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Phil
The Great White Buffalo

USA
7215 Posts

Posted - 27 Jun 2012 :  12:45:13 PM  Show Profile  Reply with Quote
quote:
Originally posted by 69warbird

Is it just me or does holley expect you to have to rebuild everything every few years?



Now you're catching on!

Bowties are for Pee-wee Herman. "Chevy": even the name sounds cheap, but not as cheap as your Pontiac will be with an LS transplant.
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69warbird
Tribal Scout

USA
22 Posts

Posted - 27 Jun 2012 :  1:23:04 PM  Show Profile  Reply with Quote
Ive been running rockett 100 octane almost exclusively, that is good gas so i dont think that is what caused the failure. Probably lack of use throughout the years (partially due to fuel cost).

Maybe i could find a local place to anodize the guts of the rebuild kit just in case...thoughts?

Edited by - 69warbird on 27 Jun 2012 1:30:09 PM
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cortcomp
Coyote

USA
5335 Posts

Posted - 27 Jun 2012 :  2:21:30 PM  Show Profile  Visit cortcomp's Homepage  Reply with Quote
This is why i like mechanical pumps.
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ledhed76
Cochise

USA
304 Posts

Posted - 27 Jun 2012 :  2:40:38 PM  Show Profile  Reply with Quote
<- Carter M6122
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Phil
The Great White Buffalo

USA
7215 Posts

Posted - 27 Jun 2012 :  7:29:40 PM  Show Profile  Reply with Quote
Robbmc.

Bowties are for Pee-wee Herman. "Chevy": even the name sounds cheap, but not as cheap as your Pontiac will be with an LS transplant.
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BearGFR
Bear

USA
580 Posts

Posted - 28 Jun 2012 :  12:55:45 PM  Show Profile  Visit BearGFR's Homepage  Reply with Quote
+1 for RobbMC. High quality stuff and exceptional customer service.

Bear
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69warbird
Tribal Scout

USA
22 Posts

Posted - 10 Jul 2012 :  11:19:03 AM  Show Profile  Reply with Quote
a quick update on the whole situation: I ended up borrowing and rebuilding a coworker's holley blue pump which worked great when we dialed down the pressure to a bit less than 7psi. reset the timing to about 10btdc and adjusted the idle speed (850) and mixture and viola, the bog was not nearly as pronounced as it had been. Constant fuel pressure really made a difference.

Before that I tried using a new carter p4594 which didnt work hardly at all, it wouldn't pull more than 3 psi...junk!!!

so now i still need another fuel pump. converting to mechanical would be great but it's out of my price range and the car is already set up for electic pumps.

lost 65$ on the carter so im probably going to settle for a jegs or summit holley style 13.5 psi blue/black knock off. it might last another 5 years which is fine for 80$.

Does anyone know if you can still rebuild the electric motor in holley blue/black style pumps? If im not mistaken the off brand versions are just old holley designs, which at one time were fully rebuildable.

Edited by - 69warbird on 10 Jul 2012 11:21:12 AM
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69warbird
Tribal Scout

USA
22 Posts

Posted - 19 Jan 2014 :  3:36:15 PM  Show Profile  Reply with Quote
It's been forever since i have really messed with the car, i've been busy at work with customer's restorations ranging from a complete restoration on a 93 mustang 5.0 conversion to a 68 firebird with a 455 stroker from butler and a tci race th400...great times...anyway, i have made some progress on solving the bog.

I found several issues with the carb. First was the fact that the secondary accel pump check valve had ripped in half...replaced that.

the secondary accelerator pump also was not within .015 at WOT, it was quite difficult to get the gauge in at all, this may have been why the check valve failed and i think the secondary accel pump may have been dumping a bit of fuel at all times which is why the car ran very rich at idle and the mix screws were producing no change.

The idle mix screws were also a full turn past where they should have been.

I also changed the power valve to a 5.0, checked the float levels and primary accel pump adjustment, and swapped the original .028 nozzle in place of the .032 that was in place.

The car immediately responded favorably. Idles strong at 750 rpm at 14 initial advance (using a crane cam vacuum limiter plate). I now have about 12-13in hg at idle and lower egt's. It still has a slight bog on initial acceleration which i should be able to tune out with accel pump adjustments or maybe jetting. Even with the bog, there's a noticeable improvement in low end torque thanks to the improved vacuum signals at the carb. Also going to put the 6.5 PV back in. From there i will probably try 02 sensor tuning of some sort, either at a dyno or through an aftermarket kit. Probably will invest in a more adjustable distributor as well from pertronix, msd, etc.
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69warbird
Tribal Scout

USA
22 Posts

Posted - 20 Jan 2014 :  6:15:41 PM  Show Profile  Reply with Quote
Working off the momentum from yesterday and some unseasonably good weather, I have finally solved the bog as far as i can tell so far. I realized the primary accel pump had the pink cam, which delivers the most fuel volume of any of the cams...swapped for the blue cam and acceleration was much smoother! That made me real happy. It was the carb all along. Thanks for all the advice, it has been spot on and I have learned a lot in the process.
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bnorris_74
Crazy Horse

USA
1442 Posts

Posted - 20 Jan 2014 :  6:40:01 PM  Show Profile  Reply with Quote
And thanks for updating your post which could help someone else with this same problem/

Too many times the issue is resolved and the poster never updates the thread or creates a new thread to point out that he had figured out the problem.

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