334 fire in the hole
10-29-2015, 09:56 PM
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Car: 91 ws6
Engine: Carb'd 334 stroker
Transmission: T5
334 fire in the hole
Right, so this is driving me bananas. Firstly, motor specs.. Bought this car with the motor already in, so can't confirm any inside specs..
305 block (told 334..doubt it though)
993 heads
CP pistons, unknown further info
Unknown cam, sounds slightly loped/pulls like a freight train till 3500-4000
Eddy performer EPS intake
Holley 600 VS
Shorty headers, half *** welded y-pipe dumping out side of car
T5 trans.
This thing has a seemingly random misfire, audible through the exhaust and can be felt driving. No smoke or anything.
It's my DD, so still driving alright.
Will idle around 700 but fluctuates by 20-30ish rpm.
Timing set at 18°.
No known vacuum leaks
Adjusting carb does nothing. I don't believe carb to be the issue.
Plug wires look new-ish.
New plugs (as of 3 hours ago)
New MSD cap and rotor as of 2 days ago, had very light carbon tracking
#5 and 7 wires aren't crossed nor touching
Dizzy is getting 13.7v constantly, no drops.
Fuel pressure constant 6psi
Adjusted valves recently
Vacuum gauge at baseplate of carb gave..interesting..readings..
VERY rapidly bounced between 9ish and 16, almost instantly. The higher the rpm, the wider the boucning got. No backfires out carb or exhaust, no flames, no smoke..
Which if I remember correctly is indicative of ignition misfire. That, or weak valve springs?
Only thing I haven't replaced is the module, coil, pickup and wires. Rather not just throw parts at it..
I unhooked my drivers side VC breather and did notice a substantial amount of suction..enough to make the engine buck when I covered it.
When I was adjusting valves, I fired it up without covers, all rockers moved about the same. None had any give on the lifter or had bent pushrods. This motor supposedly has around 80k miles.
So. ANY ideas or tests to narrow it down?
305 block (told 334..doubt it though)
993 heads
CP pistons, unknown further info
Unknown cam, sounds slightly loped/pulls like a freight train till 3500-4000
Eddy performer EPS intake
Holley 600 VS
Shorty headers, half *** welded y-pipe dumping out side of car
T5 trans.
This thing has a seemingly random misfire, audible through the exhaust and can be felt driving. No smoke or anything.
It's my DD, so still driving alright.
Will idle around 700 but fluctuates by 20-30ish rpm.
Timing set at 18°.
No known vacuum leaks
Adjusting carb does nothing. I don't believe carb to be the issue.
Plug wires look new-ish.
New plugs (as of 3 hours ago)
New MSD cap and rotor as of 2 days ago, had very light carbon tracking
#5 and 7 wires aren't crossed nor touching
Dizzy is getting 13.7v constantly, no drops.
Fuel pressure constant 6psi
Adjusted valves recently
Vacuum gauge at baseplate of carb gave..interesting..readings..
VERY rapidly bounced between 9ish and 16, almost instantly. The higher the rpm, the wider the boucning got. No backfires out carb or exhaust, no flames, no smoke..
Which if I remember correctly is indicative of ignition misfire. That, or weak valve springs?
Only thing I haven't replaced is the module, coil, pickup and wires. Rather not just throw parts at it..
I unhooked my drivers side VC breather and did notice a substantial amount of suction..enough to make the engine buck when I covered it.
When I was adjusting valves, I fired it up without covers, all rockers moved about the same. None had any give on the lifter or had bent pushrods. This motor supposedly has around 80k miles.
So. ANY ideas or tests to narrow it down?
10-30-2015, 08:11 AM
#2
Re: 334 fire in the hole
If it's a miss and adjusting the carb does NOTHING then it sounds electrical.
Pull your plugs and see what they look like. If they look good do a spark test, make sure the spark is bright and blue.
If you have a multimeter you can bench test your Ignition Coil for proper resistance.
You could also bench test the pick-up coil but that's a rarer failure.
My money would be on the ignition control module, last time I had a miss like this it was the culprit. You'll know when it up and totally fails because the car will just crank and refuse to start. I carry a spare in my console.
Pull your plugs and see what they look like. If they look good do a spark test, make sure the spark is bright and blue.
If you have a multimeter you can bench test your Ignition Coil for proper resistance.
You could also bench test the pick-up coil but that's a rarer failure.
My money would be on the ignition control module, last time I had a miss like this it was the culprit. You'll know when it up and totally fails because the car will just crank and refuse to start. I carry a spare in my console.
10-30-2015, 12:30 PM
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Car: 91 ws6
Engine: Carb'd 334 stroker
Transmission: T5
Re: 334 fire in the hole
If it's a miss and adjusting the carb does NOTHING then it sounds electrical.
Pull your plugs and see what they look like. If they look good do a spark test, make sure the spark is bright and blue.
If you have a multimeter you can bench test your Ignition Coil for proper resistance.
You could also bench test the pick-up coil but that's a rarer failure.
My money would be on the ignition control module, last time I had a miss like this it was the culprit. You'll know when it up and totally fails because the car will just crank and refuse to start. I carry a spare in my console.
Pull your plugs and see what they look like. If they look good do a spark test, make sure the spark is bright and blue.
If you have a multimeter you can bench test your Ignition Coil for proper resistance.
You could also bench test the pick-up coil but that's a rarer failure.
My money would be on the ignition control module, last time I had a miss like this it was the culprit. You'll know when it up and totally fails because the car will just crank and refuse to start. I carry a spare in my console.
It's indeed electrical, of some sort. Was running lean..went from 66 jets to 73 (lost my 70s ha-haha) and no change in the miss. Definitely not running lean anymore lol.
I just changed my plugs 3 hrs before the first post, they looked good. Great actually.
Was a nice tan color all gapped at .40, but I switched to NGK's to be safe. No change.
Have not done a spark test yet, somehow that totally slipped my mind.
Strangely, in the 4 birds I've owned, I've lost a pickup coil within months of getting them all! Must be cursed
Huh, I was under the impression that modules on these buggers either work, of they don't.
No idea if it's a GM part or aftermarket, betting on an aftermarket, based on how clean everything inside the dizzy was.
However, time to test it!!
This car reeks of "wired by a 16 ear old", so tracing down and redoing all of this persons.." Fixes" has been just a lovely experience.
10-30-2015, 12:50 PM
#4
Re: 334 fire in the hole
Ha, nice. Yeah, I've had two give me gremlins before that point that magically dissapeared with the new part, and 1 that was a "work or didn't work" piece (the GM original). So maybe it's something with the aftermarket ones that cause them to slowly die. . .no clue.
Reason I always jump to that is because it's a $15 part vs the coil which is way more, and a faulty ICM can fry the coil as well (ask me how I know. . . .ugh).
Anyways, hope you can track it down soon!
10-30-2015, 01:18 PM
#5
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Re: 334 fire in the hole
Vacuum gauge tells it all. Rapid needle bounce is a burnt vlv or u didnt adj the lifters correctly and a vlv is held open.
U need to inspect the vlv train for bent p-rods and broken parts now. Then do a compression test and a leakdown test.
Very common for someone to adj the vlvs/lifters and over adj leaving the vlvs open. U have to know - not guess - what "base circle" and "zero lash" mean. If u dont u will learn the hard way as the engine begins to eat itself.
Not trying to rub this in but its obvious u have cyl leakage w/erratic vac readings.
U need to inspect the vlv train for bent p-rods and broken parts now. Then do a compression test and a leakdown test.
Very common for someone to adj the vlvs/lifters and over adj leaving the vlvs open. U have to know - not guess - what "base circle" and "zero lash" mean. If u dont u will learn the hard way as the engine begins to eat itself.
Not trying to rub this in but its obvious u have cyl leakage w/erratic vac readings.
10-30-2015, 03:57 PM
#6
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Car: 91 ws6
Engine: Carb'd 334 stroker
Transmission: T5
Re: 334 fire in the hole
Vacuum gauge tells it all. Rapid needle bounce is a burnt vlv or u didnt adj the lifters correctly and a vlv is held open.
U need to inspect the vlv train for bent p-rods and broken parts now. Then do a compression test and a leakdown test.
Very common for someone to adj the vlvs/lifters and over adj leaving the vlvs open. U have to know - not guess - what "base circle" and "zero lash" mean. If u dont u will learn the hard way as the engine begins to eat itself.
Not trying to rub this in but its obvious u have cyl leakage w/erratic vac readings.
U need to inspect the vlv train for bent p-rods and broken parts now. Then do a compression test and a leakdown test.
Very common for someone to adj the vlvs/lifters and over adj leaving the vlvs open. U have to know - not guess - what "base circle" and "zero lash" mean. If u dont u will learn the hard way as the engine begins to eat itself.
Not trying to rub this in but its obvious u have cyl leakage w/erratic vac readings.
Same symptoms before and after valves. Zero change. Compression 187-193 lbs across all cyls. Don't have a leakdown tester. Nothing is bent, I've driven 500 miles since and nothing is damaged. Rockers have zero give, pushrods are good to go, and valves are at zero lash. It's not my first rodeo. Only thing I can't test is the valve springs-i don't have a tester, but all rockers move about the same distance.
I learned by having the first 383 i built lose compression on 4 cyls, two each bank within minutes of each other with no warning. Talk about heart breaking..
When I say rapid, I mean the needle instantly moves from 16-10lbs, and gets even wider/more erratic as rpms go up, yet the motor only still sounds like it has a slight miss.
My process for valves has been the same for years, so this would be the second time (first being the first motor I ever built) I've ever had issues.
Rotate motor till cyl 1 TDC, rotate until intake valve closes/both valves are closed. Adjust to zero lash, zero lash being spinning the p-rod in my fingers until it just started to catch, then back off just a nut hair, maybe 1/52 of a turn. Then tighten 1/4 turn to preload. Rotate motor till #8 intake closes, so on and so forth for the firing order, then repeat for exhaust.
Last edited by dixie wrecked; 10-30-2015 at 04:17 PM.
10-30-2015, 04:04 PM
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Car: 91 ws6
Engine: Carb'd 334 stroker
Transmission: T5
Re: 334 fire in the hole
Ha, nice. Yeah, I've had two give me gremlins before that point that magically dissapeared with the new part, and 1 that was a "work or didn't work" piece (the GM original). So maybe it's something with the aftermarket ones that cause them to slowly die. . .no clue.
Reason I always jump to that is because it's a $15 part vs the coil which is way more, and a faulty ICM can fry the coil as well (ask me how I know. . . .ugh).
Anyways, hope you can track it down soon!
Reason I always jump to that is because it's a $15 part vs the coil which is way more, and a faulty ICM can fry the coil as well (ask me how I know. . . .ugh).
Anyways, hope you can track it down soon!
Such as having my alternator sense wire tapped to the cigarette lighter. I mean..technically its 12 volts lol!
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10-30-2015, 04:16 PM
#8
Member
Re: 334 fire in the hole
Yes i learned the hard way to from adj vlvs. Thats why i dont forget it.
Well something curious is many times the rocker arms are not rigid when the lobe is on base circle. Cant explain why compression is high w/bad vlvs and that doesnt add up but compression does increase when the lope wears as in wiped. Maybe measure vac at another location like out on the intake runner? For a leakdown test u need an air compressor also and lock the crank at TDC for that cyl. Any small AC should do the job though as it doesnt take much airflow for the leakdown test. I use the cheap Summit tester for like $50.
What im saying is your not going to get anything to run well with fluctuating vac. Find that problem first. BTW i think u mean 16-10"Hg. Bad timing or bad vlv springs dont do that.
Well something curious is many times the rocker arms are not rigid when the lobe is on base circle. Cant explain why compression is high w/bad vlvs and that doesnt add up but compression does increase when the lope wears as in wiped. Maybe measure vac at another location like out on the intake runner? For a leakdown test u need an air compressor also and lock the crank at TDC for that cyl. Any small AC should do the job though as it doesnt take much airflow for the leakdown test. I use the cheap Summit tester for like $50.
What im saying is your not going to get anything to run well with fluctuating vac. Find that problem first. BTW i think u mean 16-10"Hg. Bad timing or bad vlv springs dont do that.
10-30-2015, 04:25 PM
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Car: 91 ws6
Engine: Carb'd 334 stroker
Transmission: T5
Re: 334 fire in the hole
Yes i learned the hard way to from adj vlvs. Thats why i dont forget it.
Well something curious is many times the rocker arms are not rigid when the lobe is on base circle. Cant explain why compression is high w/bad vlvs and that doesnt add up but compression does increase when the lope wears as in wiped. Maybe measure vac at another location like out on the intake runner? For a leakdown test u need an air compressor also and lock the crank at TDC for that cyl. Any small AC should do the job though as it doesnt take much airflow for the leakdown test. I use the cheap Summit tester for like $50.
What im saying is your not going to get anything to run well with fluctuating vac. Find that problem first. BTW i think u mean 16-10"Hg. Bad timing or bad vlv springs dont do that.
Well something curious is many times the rocker arms are not rigid when the lobe is on base circle. Cant explain why compression is high w/bad vlvs and that doesnt add up but compression does increase when the lope wears as in wiped. Maybe measure vac at another location like out on the intake runner? For a leakdown test u need an air compressor also and lock the crank at TDC for that cyl. Any small AC should do the job though as it doesnt take much airflow for the leakdown test. I use the cheap Summit tester for like $50.
What im saying is your not going to get anything to run well with fluctuating vac. Find that problem first. BTW i think u mean 16-10"Hg. Bad timing or bad vlv springs dont do that.
My brake booster is tapped in to the manifold right behind the carb, I can try testing there.
Yep, I meant Hg lol!
This thing actually doesn't run bad, if I'm honest. The misfire is..more of a neusence if I'm honest, though it's certainly doing me no good. Still getting 17.6-18.3mpg, pulls like a Saturn V till 4000 (well, pulls for a 305, erm "334"
D)All my rockers moved about the same distance, so if I have a wiped lobe then its too small to see by eye. Or they're all wiped! My oil isn't sparkly though.
10-30-2015, 08:30 PM
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Car: 91 ws6
Engine: Carb'd 334 stroker
Transmission: T5
Re: 334 fire in the hole
Not the module. No change at all.
Multimeter on the coil suggests it may be the culprit. Testing each prong, going from prong to ground showed infinite resistance, which is good. Going from point to point showed 2.5, moved to 2.6 when I opened vac advance. If that's the case then..wow..I would be 4 for 4
I grabbed vacuum reading from behind the manifold, its even more erratic after the new module. Instantly fluctuating between 15-3Hg, revving it just widens it to, oh, 25-6Hg.
Whilst I adjusted my valves fine, no idea what some Dingus before me did.. If worse comes to worse, it runs good enough, may as well just run her till she dies/the 5.3 is built.
Multimeter on the coil suggests it may be the culprit. Testing each prong, going from prong to ground showed infinite resistance, which is good. Going from point to point showed 2.5, moved to 2.6 when I opened vac advance. If that's the case then..wow..I would be 4 for 4
I grabbed vacuum reading from behind the manifold, its even more erratic after the new module. Instantly fluctuating between 15-3Hg, revving it just widens it to, oh, 25-6Hg.
Whilst I adjusted my valves fine, no idea what some Dingus before me did.. If worse comes to worse, it runs good enough, may as well just run her till she dies/the 5.3 is built.
Last edited by dixie wrecked; 10-30-2015 at 11:44 PM.
11-02-2015, 07:18 AM
#11
Re: 334 fire in the hole
Sounds like you may have found the issue!
Is the button underneath your coil in good shape? Mine had gotten pinched in a sideways position at some point which caused the coil to short out. Just want to make sure, if you are going to replace the coil, that there's nothing other than old age that caused it to fail.
Is the button underneath your coil in good shape? Mine had gotten pinched in a sideways position at some point which caused the coil to short out. Just want to make sure, if you are going to replace the coil, that there's nothing other than old age that caused it to fail.
11-02-2015, 01:12 PM
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Car: 91 ws6
Engine: Carb'd 334 stroker
Transmission: T5
Re: 334 fire in the hole
Sounds like you may have found the issue!
Is the button underneath your coil in good shape? Mine had gotten pinched in a sideways position at some point which caused the coil to short out. Just want to make sure, if you are going to replace the coil, that there's nothing other than old age that caused it to fail.
Is the button underneath your coil in good shape? Mine had gotten pinched in a sideways position at some point which caused the coil to short out. Just want to make sure, if you are going to replace the coil, that there's nothing other than old age that caused it to fail.
Went and got one from Orileys, of course it would test bad out of the box, and the only other one in town is 20 miles the opposite direction. Their house brand really sucks, not only did it test bad, but it didnt fit. So, old one went back in..
Yep, the button is good to go.
The cap and rotor are brand new MSD, and everything else inside looks pretty new as well, which is weird. It looks like this dizzy was bought perhaps a year ago and just sat.
Pickup looked nice and relatively new as well, but we all know that means Nada lol.
Edit: answered my own question. Was measured on the 200 setting and showing 2.4. Which would come out to 240 ohms, and they're supposed to read 500-1500 ohms.
Last edited by dixie wrecked; 11-02-2015 at 01:22 PM.
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